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147-423: The indigo bunting ( Passerina cyanea ) is a small seed -eating bird in the cardinal family, Cardinalidae . It is migratory , ranging from southern Canada to northern Florida during the breeding season, and from southern Florida to northern South America during the winter. It often migrates by night, using the stars to navigate. Its habitat is farmland, brush areas, and open woodland. The indigo bunting

294-489: A coleoptile that forms the first leaf while the radicle is covered with a coleorhiza that connects to the primary root and adventitious roots form the sides. Here the hypocotyl is a rudimentary axis between radicle and plumule. The seeds of corn are constructed with these structures; pericarp, scutellum (single large cotyledon) that absorbs nutrients from the endosperm, plumule, radicle, coleoptile, and coleorhiza – these last two structures are sheath-like and enclose

441-505: A "blue" ( lazuli bunting and blue grosbeak ) and a "painted" ( rose-bellied bunting , orange-breasted bunting , varied bunting , and painted bunting ) clade . This genetic study shows these species diverged between 4.1 and 7.3 million years ago . This timing, which is consistent with fossil evidence, coincides with a late- Miocene cooling, which caused the evolution of a variety of western grassland habitats . Evolving to reduce size may have allowed buntings to exploit grass seeds as

588-421: A "net", helping in the capture of flying prey, although to date, there has been no empirical evidence to support this idea. There is some experimental evidence to suggest that they may prevent particles from striking the eyes if, for example, a prey item is missed or broken apart on contact. They may also help to protect the eyes from particles encountered in flight, or from casual contact from vegetation. There

735-542: A bird; the orangeness of a Montagu's harrier 's cere, for example, correlates to its body mass and physical condition. The cere color of young Eurasian scops-owls has an ultraviolet (UV) component, with a UV peak that correlates to the bird's mass. A chick with a lower body mass has a UV peak at a higher wavelength than a chick with a higher body mass does. Studies have shown that parent owls preferentially feed chicks with ceres that show higher wavelength UV peaks, that is, lighter-weight chicks. The color or appearance of

882-528: A bunting is a male. As indicated by data collected from Charles H. Blake from his banding experiments in Hillsborough, NC, the Indigo Bunting has a weighted annual survival rate of 0.585. Using his own methods (Blake 1967, p. 5) and a pool of 25 indigo buntings captured and observed, it was determined that approximately two out of twenty-five indigo buntings should live up to six years. Using

1029-415: A complex three-dimensional network of bony spicules (or trabeculae ) seated in soft connective tissue and surrounded by the hard outer layers of the beak. The avian jaw apparatus is made up of two units: one four-bar linkage mechanism and one five-bar linkage mechanism. The upper mandible is supported by a three-pronged bone called the intermaxillary. The upper prong of this bone is embedded into

1176-422: A curved megagametophyte often giving the seed a tight "C" shape. The last ovule shape is called amphitropous , where the ovule is partly inverted and turned back 90 degrees on its stalk (the funicle or funiculus ). In the majority of flowering plants, the zygote's first division is transversely oriented in regards to the long axis, and this establishes the polarity of the embryo. The upper or chalazal pole becomes

1323-436: A dozen types of carotenoids are responsible for the coloration of most red, orange, and yellow beaks. The hue of the color is determined by the precise mix of red and yellow pigments, while the saturation is determined by the density of the deposited pigments. For example, bright red is created by dense deposits of mostly red pigments, while dull yellow is created by diffuse deposits of mostly yellow pigments. Bright orange

1470-410: A few days of hatching, though petrels keep theirs for nearly three weeks and marbled murrelets have theirs for up to a month. Generally, the egg tooth drops off, though in songbirds it is resorbed. The color of a bird's beak results from concentrations of pigments — primarily melanins and carotenoids — in the epidermal layers, including the rhamphotheca. Eumelanin , which is found in

1617-411: A few will end in a favorable place for growth. Herbaceous perennials and woody plants often have larger seeds; they can produce seeds over many years, and larger seeds have more energy reserves for germination and seedling growth and produce larger, more established seedlings after germination. Seeds serve several functions for the plants that produce them. Key among these functions are nourishment of

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1764-399: A food source. The indigo bunting is a smallish songbird, around the size of a small sparrow. It measures 11.5–15 cm (4.5–5.9 in) long, with a wingspan of 18–23 cm (7.1–9.1 in). Body mass averages 14.5 g (0.51 oz), with a reported range of 11.2–21.4 g (0.40–0.75 oz). During the breeding season, the adult male appears mostly a vibrant cerulean blue. Only

1911-543: A large hole. The weakened egg eventually shatters under the pressure of the bird's movements. The egg tooth is so critical to a successful escape from the egg that chicks of most species will perish unhatched if they fail to develop one. However, there are a few species which do not have egg teeth. Megapode chicks have an egg tooth while still in the egg but lose it before hatching, while kiwi chicks never develop one; chicks of both families escape their eggs by kicking their way out. Most chicks lose their egg teeth within

2058-513: A large squirming frog) have very wide nails. Certain types of mechanoreceptors , nerve cells that are sensitive to pressure, vibration, or touch, are located under the nail. The shape or color of the nail can sometimes be used to help distinguish between similar-looking species or between various ages of waterfowl. For example, the greater scaup has a wider black nail than does the very similar lesser scaup . Juvenile " grey geese " have dark nails, while most adults have pale nails. The nail gave

2205-512: A less vivid gape. Conversely, the red gape of the common cuckoo ( Cuculus canorus ) did not induce extra feeding in host parents. Some brood parasites , such as the Hodgson's hawk-cuckoo ( C. fugax ), have colored patches on the wing that mimic the gape color of the parasitized species. When born, the chick's gape flanges are fleshy. As it grows into a fledgling , the gape flanges remain somewhat swollen and can thus be used to recognize that

2352-415: A location and be there at a time favorable for germination and growth. When the fruits open and release their seeds in a regular way, it is called dehiscent , which is often distinctive for related groups of plants; these fruits include capsules , follicles , legumes , silicles and siliques . When fruits do not open and release their seeds in a regular fashion, they are called indehiscent, which include

2499-496: A membraneous, horny or cartilaginous flap. In diving birds, the operculum keeps water out of the nasal cavity; when the birds dive, the impact force of the water closes the operculum. Some species which feed on flowers have opercula to help to keep pollen from clogging their nasal passages, while the opercula of the two species of Attagis seedsnipe help to keep dust out. The nares of nestling tawny frogmouths are covered with large dome-shaped opercula, which help to reduce

2646-580: A negative correlation between Zugunruhe and cloud coverage. When in the artificial planetarium scenario and in the presence of a magnetic field similar to Earth's, birds were unable to orientate themselves in a no-star environment, indicating that past hypotheses supporting that birds use geophysical clues as well may be incorrect. Indigo buntings do not rely on individual stars or the general brightness of groups of stars, but instead use them as clues in navigation. Prior experiments removing certain constellations and stars (Big Dipper, Cassiopeia or Polaris) from

2793-492: A part of their partner's beak while others clash their beaks vigorously together. Gannets raise their bills high and repeatedly clatter them, the male puffin nibbles at the female's beak, the male waxwing puts his bill in the female's mouth and ravens hold each other's beaks in a prolonged "kiss". Billing can also be used as a gesture of appeasement or subordination. Subordinate Canada jay routinely bill more dominant birds, lowering their body and quivering their wings in

2940-416: A particular bird is young. By the time it reaches adulthood, the gape flanges will no longer be visible. Most species of birds have external nares ( nostrils ) located somewhere on their beak. The nares are two holes—circular, oval or slit-like in shape—which lead to the nasal cavities within the bird's skull, and thus to the rest of the respiratory system . In most bird species, the nares are located in

3087-404: A reddish or orangish gonydeal spot near the gonydeal expansion. This spot triggers begging behavior in gull chicks. The chick pecks at the spot on its parent's bill, which in turn stimulates the parent to regurgitate food. Depending on its use, commissure may refer to the junction of the upper and lower mandibles, or alternately, to the full-length apposition of the closed mandibles, from

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3234-531: A reduced premaxillary bone due to the overdevelopment of the prenasal cartilage, which takes up more mesenchymal cells for cartilage, instead of bone, formation. Different species' beaks have evolved according to their diet; for example, raptors have sharp-pointed beaks that facilitate dissection and biting off of prey animals ' tissue, whereas passerine birds that specialize in eating seeds with especially tough shells (such as grosbeaks and cardinals ) have large, stout beaks with high compressive power (on

3381-449: A secreted protein also known to be expressed in mammalian craniofacial development. The combination of these signals determines beak growth along the length, depth, and width axes. Reduced expression of TGFβllr significantly decreased the depth and length of chicken embryonic beak due to the underdevelopment of the premaxillary bone. Contrarily, an increase in Bmp4 signaling would result in

3528-766: A small percentage of buntings remain as summer residents instead of migrating (7.2% of banded birds in Burke's observation). The indigo bunting often migrates during the night, using the stars to navigate. This is not an unusual proposal, for many other birds such as the blackcaps or red-backed shrikes were used to test if birds have orientated migratory behavior or Zugunruhe . Research indicates that indigo buntings placed in funnel cages outside on cloudless autumn nights or in artificial planetariums made more southern directional choices. When introduced to increasingly overcast nights, many bunting's abilities to distinctively make southern directional changes decreased, possibly indicating

3675-456: A small sharp, calcified projection on their beak, which they use to chip their way out of their egg . Commonly known as an egg tooth, this white spike is generally near the tip of the upper mandible, though some species have one near the tip of their lower mandible instead, and a few species have one on each mandible. Despite its name, the projection is not an actual tooth , as the similarly-named projections of some reptiles are; instead, it

3822-405: A strong correlation with summer temperatures recorded in the locations where the sparrows breed; latitude alone showed a much weaker correlation. By dumping excess heat through their bills, the sparrows are able to avoid the water loss which would be required by evaporative cooling—an important benefit in a windy habitat where freshwater is scarce. Several ratites , including the common ostrich ,

3969-435: A supply of nutrients for the embryo in most monocotyledons and the endospermic dicotyledons. Seeds have been considered to occur in many structurally different types (Martin 1946). These are based on a number of criteria, of which the dominant one is the embryo-to-seed size ratio. This reflects the degree to which the developing cotyledons absorb the nutrients of the endosperm, and thus obliterate it. Six types occur amongst

4116-550: A tegmen from the inner integument while unitegmic seeds have only one integument. Usually, parts of the testa or tegmen form a hard protective mechanical layer. The mechanical layer may prevent water penetration and germination. Amongst the barriers may be the presence of lignified sclereids . The outer integument has a number of layers, generally between four and eight organised into three layers: (a) outer epidermis, (b) outer pigmented zone of two to five layers containing tannin and starch, and (c) inner epidermis. The endotegmen

4263-463: A waxy structure called a cere (from the Latin cera , which means "wax") or ceroma which covers the base of their bill. This structure typically contains the nares , except in the owls, where the nares are distal to the cere. Although it is sometimes feathered in parrots, the cere is typically bare and often brightly colored. In raptors, the cere is a sexual signal which indicates the "quality" of

4410-405: A way for the species to survive dry or cold seasons. Ephemeral plants are usually annuals that can go from seed to seed in as few as six weeks. Seed germination is a process by which a seed embryo develops into a seedling. It involves the reactivation of the metabolic pathways that lead to growth and the emergence of the radicle or seed root and plumule or shoot. The emergence of the seedling above

4557-404: A woodpecker's nares help to keep wood particles from clogging its nasal passages. Species in the bird order Procellariformes have nostrils enclosed in double tubes which sit atop or along the sides of the upper mandible. These species, which include the albatrosses, petrels, diving petrels, storm petrels, fulmars and shearwaters, are widely known as "tubenoses". A number of species, including

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4704-453: Is a selection pressure for an intermediate amount of overhang. Western Scrub Jays who had more symmetrical bills (i.e. those with less of an overhang), were found to have higher amounts of lice when tested. The same pattern has been seen in surveys of Peruvian birds. Additionally, because of the role beaks play in preening, this is evidence for coevolution of the beak overhang morphology and body morphology of parasites. Artificially removing

4851-487: Is also evidence that the rictal bristles of some species may function tactilely, in a manner similar to that of mammalian whiskers ( vibrissae ). Studies have shown that Herbst corpuscles , mechanoreceptors sensitive to pressure and vibration, are found in association with rictal bristles. They may help with prey detection, with navigation in darkened nest cavities, with the gathering of information during flight or with prey handling. Full-term chicks of most bird species have

4998-541: Is also susceptible to parasitism by louse flies . The criteria for a change in conservation status are a decline of more than 30% in ten years or over three generations. The species is classified as being of least concern according to the International Union for Conservation of Nature , with an estimated range of 5,900,000 km (2,300,000 sq mi) and a population of 28 million individuals. Global population trends have not been quantified, but

5145-509: Is at a suitable temperature with proper soil moisture. This true dormancy or innate dormancy is therefore caused by conditions within the seed that prevent germination. Thus dormancy is a state of the seed, not of the environment. Induced dormancy, enforced dormancy or seed quiescence occurs when a seed fails to germinate because the external environmental conditions are inappropriate for germination, mostly in response to conditions being too dark or light, too cold or hot, or too dry. Seed dormancy

5292-481: Is caused by conditions outside the embryo, including: Endogenous dormancy is caused by conditions within the embryo itself, including: The following types of seed dormancy do not involve seed dormancy, strictly speaking, as lack of germination is prevented by the environment, not by characteristics of the seed itself (see Germination ): Not all seeds undergo a period of dormancy. Seeds of some mangroves are viviparous; they begin to germinate while still attached to

5439-402: Is closely related to the lazuli bunting and interbreeds with the species where their ranges overlap. The indigo bunting is a small bird, measuring 11.5–13 cm (4.5–5.1 in) in length. It displays sexual dimorphism in its coloration; the male is vibrant blue in the summer, with brightly colored plumage during the breeding season to attract a mate. It is brown during the winter months, while

5586-501: Is created by dense deposits of both red and yellow pigments, in roughly equal concentrations. Beak coloration helps to make displays using those beaks more obvious. In general, beak color depends on a combination of the bird's hormonal state and diet . Colors are typically brightest as the breeding season approaches, and palest after breeding. Birds are capable of seeing colors in the ultraviolet range, and some species are known to have ultraviolet peaks of reflectance (indicating

5733-402: Is derived from the inner epidermis of the inner integument, the exotegmen from the outer surface of the inner integument. The endotesta is derived from the inner epidermis of the outer integument, and the outer layer of the testa from the outer surface of the outer integument is referred to as the exotesta . If the exotesta is also the mechanical layer, this is called an exotestal seed, but if

5880-497: Is misleading since most of those birds supporting that study were immature, not having a high body fat content. Since indigo buntings and many other birds are at their lightest after mating season, questions arose whether increases in overall weight were attributed to fat or other factors such as water weight, or carbohydrates . Research indicates that most if not all weight gain is a gain in fat content. Quantitative methods of estimating flight range instead look at metabolic rates of

6027-444: Is not the same as seed persistence in the soil or on the plant, though even in scientific publications dormancy and persistence are often confused or used as synonyms. Often, seed dormancy is divided into four major categories: exogenous; endogenous; combinational; and secondary. A more recent system distinguishes five classes: morphological, physiological, morphophysiological, physical, and combinational dormancy. Exogenous dormancy

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6174-601: Is one of the few species of mammals to use electroreception . The beaks of aquatic birds contain Grandry corpuscles , which assist in velocity detection while filter feeding. The beak of birds plays a role in removing skin parasites ( ectoparasites ) such as lice. It is mainly the tip of the beak that does this. Studies have shown that inserting a bit to stop birds from using the tip results in increased parasite loads in pigeons. Birds that have naturally deformed beaks have also been noted to have higher levels of parasites. It

6321-449: Is part of the integumentary system , as are claws and scales . The hatching chick first uses its egg tooth to break the membrane around an air chamber at the wide end of the egg. Then it pecks at the eggshell while turning slowly within the egg, eventually (over a period of hours or days) creating a series of small circular fractures in the shell. Once it has breached the egg's surface, the chick continues to chip at it until it has made

6468-535: Is protection against disease. Seeds protect and nourish the embryo or young plant. They usually give a seedling a faster start than a sporeling from a spore, because of the larger food reserves in the seed and the multicellularity of the enclosed embryo. Unlike animals, plants are limited in their ability to seek out favorable conditions for life and growth. As a result, plants have evolved many ways to disperse their offspring by dispersing their seeds (see also vegetative reproduction ). A seed must somehow "arrive" at

6615-446: Is the ability of the embryo to germinate and is affected by a number of different conditions. Some plants do not produce seeds that have functional complete embryos, or the seed may have no embryo at all, often called empty seeds. Predators and pathogens can damage or kill the seed while it is still in the fruit or after it is dispersed. Environmental conditions like flooding or heat can kill the seed before or during germination. The age of

6762-411: Is then aborted or absorbed during early development. The seed is composed of the embryo (the result of fertilization) and tissue from the mother plant, which also form a cone around the seed in coniferous plants such as pine and spruce . Seeds are very diverse, and as such there are many terms are used to describe them. A typical seed includes two basic parts: In addition, the endosperm forms

6909-538: Is thought that the overhang at the end of the top portion of the beak (that is the portion that begins to curve downwards) slides against the lower beak to crush parasites. This overhang of the beak is thought to be under stabilising natural selection . Very long beaks are thought to be selected against because they are prone to a higher number of breaks, as has been demonstrated in rock pigeons. Beaks with no overhang would be unable to effectively remove and kill ectoparasites as mentioned above. Studies have supported there

7056-435: Is typically a septum made of bone or cartilage that separates the two nares, but in some families (including gulls, cranes and New World vultures), the septum is missing. While the nares are uncovered in most species, they are covered with feathers in a few groups of birds, including grouse and ptarmigans, crows, and some woodpeckers. The feathers over a ptarmigan's nostrils help to warm the air it inhales, while those over

7203-477: Is used as an alarm call if a nest or chick is threatened. A high-pitched, buzzed zeeep is used as a contact call when the indigo bunting is in flight. The song of the male bird is a high-pitched buzzed sweet-sweet chew-chew sweet-sweet , lasting two to four seconds, sung to mark his territory to other males and to attract females. Each male has a single complex song, which he sings while perched on elevated objects, such as posts, wires, and bush-tops. In areas where

7350-419: Is usually triploid , and is rich in oil or starch , and protein . In gymnosperms, such as conifers , the food storage tissue (also called endosperm) is part of the female gametophyte , a haploid tissue. The endosperm is surrounded by the aleurone layer (peripheral endosperm), filled with proteinaceous aleurone grains. Originally, by analogy with the animal ovum , the outer nucellus layer ( perisperm )

7497-671: The West Indies and Central America to northern South America . It has occurred as a vagrant in Antigua and Barbuda , Barbados , Denmark , Ecuador , Germany , Iceland , Ireland , Netherlands , the Netherlands Antilles , Saint Pierre and Miquelon , Serbia and the United Kingdom . The indigo bunting communicates through vocalizations and visual cues. A sharp chip! call is used by both sexes, and

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7644-417: The cone scales as they develop in some species of conifer . Angiosperm (flowering plants) seeds consist of three genetically distinct constituents: (1) the embryo formed from the zygote, (2) the endosperm, which is normally triploid, (3) the seed coat from tissue derived from the maternal tissue of the ovule. In angiosperms, the process of seed development begins with double fertilization , which involves

7791-412: The embryo , dispersal to a new location, and dormancy during unfavorable conditions. Seeds fundamentally are means of reproduction, and most seeds are the product of sexual reproduction which produces a remixing of genetic material and phenotype variability on which natural selection acts. Plant seeds hold endophytic microorganisms that can perform various functions, the most important of which

7938-701: The emu and the southern cassowary , use various bare parts of their bodies (including their beaks) to dissipate as much as 40% of their metabolic heat production. Alternately, studies have shown that birds from colder climates (higher altitudes or latitudes and lower environmental temperatures) have smaller beaks, lessening heat loss from that structure. During courtship, mated pairs of many bird species touch or clasp each other's bills. Termed billing (also nebbing in British English), this behavior appears to strengthen pair bonding . The amount of contact involved varies among species. Some gently touch only

8085-572: The falcons , have a small bony tubercule which projects from their nares. The function of this tubercule is unknown. Some scientists suggest it may act as a baffle, slowing down or diffusing airflow into the nares (and thus allowing the bird to continue breathing without damaging its respiratory system) during high-speed dives, but this theory has not been proved experimentally. Not all species that fly at high speeds have such tubercules, while some species which fly at low speeds do. The nares of some birds are covered by an operculum (plural opercula ),

8232-421: The flowering plants , the ovary ripens into a fruit which contains the seed and serves to disseminate it. Many structures commonly referred to as "seeds" are actually dry fruits. Sunflower seeds are sometimes sold commercially while still enclosed within the hard wall of the fruit, which must be split open to reach the seed. Different groups of plants have other modifications, the so-called stone fruits (such as

8379-424: The legumes (such as beans and peas ), trees such as the oak and walnut , vegetables such as squash and radish , and sunflowers . According to Bewley and Black (1978), Brazil nut storage is in hypocotyl and this place of storage is uncommon among seeds. All gymnosperm seeds are albuminous. The seed coat develops from the maternal tissue, the integuments , originally surrounding the ovule. The seed coat in

8526-548: The noisy miner , use bill clapping as a form of communication. Some woodpecker species are known to use percussion as a courtship activity, whereas males will get the ( aural ) attention of females from a distance and then impress them with the sound volume and pattern. This explains why humans are sometimes inconvenienced by pecking that clearly has no feeding purpose (such as when the bird pecks on sheet metal repeatedly). Studies have shown that some birds use their beaks to rid themselves of excess heat. The toco toucan , which has

8673-416: The peach ) have a hardened fruit layer (the endocarp ) fused to and surrounding the actual seed. Nuts are the one-seeded, hard-shelled fruit of some plants with an indehiscent seed, such as an acorn or hazelnut . The first land plants evolved around 468 million years ago, and reproduced using spores. The earliest seed bearing plants to appear were the gymnosperms , which have no ovaries to contain

8820-579: The ratites . Here, the vomer is large and connects with premaxillae and maxillopalatine bones in a condition termed as a "paleognathous palate". All other extant birds have a narrow forked vomer that does not connect with other bones and is then termed as neognathous. The shape of these bones varies across the bird families. The lower mandible is supported by a bone known as the inferior maxillary bone—a compound bone composed of two distinct ossified pieces. These ossified plates (or rami ), which can be U-shaped or V-shaped, join distally (the exact location of

8967-548: The 13th century, comes from the Middle English bec (via Anglo French ), which itself comes from the Latin beccus . Although beaks vary significantly in size and shape from species to species, their underlying structures have a similar pattern. All beaks are composed of two jaws, generally known as the maxilla (upper) and mandible (lower). The upper, and in some cases the lower, mandibles are strengthened internally by

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9114-439: The ability to preen in birds, followed by readdition of preening ability was shown to result in changes in body size in lice. Once the ability of the birds to preen was reintroduced, the lice were found to show declines in body size suggesting they may evolve in response to preening pressures from birds who could respond in turn with changes in beak morphology. A number of species, including storks , some owls , frogmouths and

9261-464: The bare parts of many bird species, is responsible for all shades of gray and black; the denser the deposits of pigment found in the epidermis, the darker the resulting color. Phaeomelanin produces "earth tones" ranging from gold and rufous to various shades of brown. Although it is thought to occur in combination with eumelanin in beaks which are buff, tan, or horn-colored, researchers have yet to isolate phaeomelanin from any beak structure. More than

9408-424: The basal third of the upper mandible. Kiwi are a notable exception; their nares are located at the tip of their bills. A handful of species have no external nares. Cormorants and darters have primitive external nares as nestlings, but these close soon after the birds fledge ; adults of these species (and gannets and boobies of all ages, which also lack external nostrils) breathe through their mouths. There

9555-511: The beak. This shield -shaped structure, which sometimes spans the entire width of the beak, is often bent at the tip to form a hook. It serves different purposes depending on the bird's primary food source. Most species use their nails to dig seeds out of mud or vegetation, while diving ducks use theirs to pry molluscs from rocks. There is evidence that the nail may help a bird to grasp objects. Species which use strong grasping motions to secure their food (such as when catching and holding onto

9702-401: The bill" and runs from the point where the upper mandible emerges from the forehead's feathers to its tip. The bill's length along the culmen is one of the regular measurements made during bird banding (ringing) and is particularly useful in feeding studies. There are several standard measurements that can be made—from the beak's tip to the point where feathering starts on the forehead, from

9849-486: The bill, above the nares; though it is sometimes referred to as the cere , this is a different structure. Tapaculos are the only birds known to have the ability to move their opercula. Some species, such as the puffin , have a fleshy rosette, sometimes called a "gape rosette", at the corners of the beak. In the puffin, this is grown as part of its display plumage. Birds from a handful of families—including raptors, owls, skuas, parrots, turkeys and curassows—have

9996-446: The bird to slice through a seed's outer hull . Most falcons have a sharp projection along the upper mandible, with a corresponding notch on the lower mandible. They use this "tooth" to sever their prey's vertebrae fatally or to rip insects apart. Some kites , principally those that prey on insects or lizards, also have one or more of these sharp projections, as do the shrikes . The tomial teeth of falcons are underlain by bone, while

10143-410: The breeding season. While most extant birds have a single seamless rhamphotheca, species in a few families, including the albatrosses and the emu , have compound rhamphothecae that consist of several pieces separated and defined by softer keratinous grooves. Studies have shown that this was the primitive ancestral state of the rhamphotheca, and that the modern simple rhamphotheca resulted from

10290-501: The brush-like projections may help to increase the coefficient of friction between the mandibles, thereby improving the bird's ability to hold hard prey items. Serrations on hummingbird bills, found in 23% of all hummingbird genera, may perform a similar function, allowing the birds to effectively hold insect prey. They may also allow shorter-billed hummingbirds to function as nectar thieves , as they can more effectively hold and cut through long or waxy flower corollas . In some cases,

10437-430: The bunting and how much fat it has to use as fuel. Research indicates that the metabolic rate of a lean 13 g (0.46 oz) indigo bunting is 0.64 kcal/hour. With an average speed of 20 mph, 5 extra grams of fat (47.5 kcal of energy) extends a bunting's range to six hundred and eighty-eight miles (1,107 km). 19 g (0.67 oz) is equivalent to eight hundred and twenty-six miles (1,329 km). Given that

10584-433: The calculated annual rate of six-year-old birds obtained (2/25 = 0.08), an annual rate of 0.656 was calculated, 12% higher than the annual rate of 0.585, leading to the 1 out of 25 statistic. The oldest recorded bunting was at least 13 years and 3 months old. However, not much emphasis should be placed on these values since the pool of individuals is small, where any individual can affect the weighted average . The habitat of

10731-636: The cells are filled with starch , as for instance cereal grains , or not (non-farinaceous). The endosperm may also be referred to as "fleshy" or "cartilaginous" with thicker soft cells such as coconut , but may also be oily as in Ricinus (castor oil), Croton and Poppy . The endosperm is called "horny" when the cell walls are thicker such as date and coffee , or "ruminated" if mottled, as in nutmeg , palms and Annonaceae . In most monocotyledons (such as grasses and palms ) and some ( endospermic or albuminous ) dicotyledons (such as castor beans )

10878-405: The cells of the outer epidermis enlarge radially and their walls thicken, with nucleus and cytoplasm compressed into the outer layer. these cells which are broader on their inner surface are called palisade cells. In the inner epidermis, the cells also enlarge radially with plate like thickening of the walls. The mature inner integument has a palisade layer, a pigmented zone with 15–20 layers, while

11025-401: The cere can be used to distinguish between males and females in some species. For example, the male great curassow has a yellow cere, which the female (and young males) lack. The male budgerigar 's cere is royal blue, while the female's is a very pale blue, white, or brown. All birds of the family Anatidae (ducks, geese, and swans) have a nail , a plate of hard horny tissue at the tip of

11172-556: The chicks are altricial at hatching. Chicks fledge 10 to 12 days after hatching. Most pairs raise two broods per year, and the male may feed newly fledged young while the females incubate the next clutch of eggs. The brown-headed cowbird may parasitize this species. Indigo buntings abandon their nest if a cowbird egg appears before they lay any of their own eggs, but accept the egg after that point. Pairs with parasitized nests have less reproductive success. The bunting chicks hatch, but have lower survival rates as they must compete with

11319-412: The color of a bird's tomia can help to distinguish between similar species. The snow goose , for example, has a reddish-pink bill with black tomia, while the whole beak of the similar Ross's goose is pinkish-red, without darker tomia. The culmen is the dorsal ridge of the upper mandible. Likened by ornithologist E. Coues to the ridge line of a roof, it is the "highest middle lengthwise line of

11466-518: The corners of the mouth to the tip of the beak. In bird anatomy , the gape is the interior of the open mouth of a bird, and the gape flange is the region where the two mandibles join together at the base of the beak. The width of the gape can be a factor in the choice of food. Gapes of juvenile altricial birds are often brightly coloured, sometimes with contrasting spots or other patterns, and these are believed to be an indication of their health, fitness and competitive ability. Based on this,

11613-431: The cowbird chick for food. The indigo bunting forages for food on the ground or in trees or shrubs. In winter, it often feeds in flocks with other indigo buntings, but is a solitary feeder during the breeding season. During the breeding season, the species eats seeds of grasses and herbs , berries , spiders and insects , including caterpillars , grasshoppers , true bugs , and beetles . The seeds of grasses are

11760-410: The culmen can also help with the identification of birds in the field. For example, the culmen of the parrot crossbill is strongly decurved, while that of the very similar red crossbill is more moderately curved. The culmen of a juvenile common loon is all dark, while that of the very similarly plumaged juvenile yellow-billed loon is pale towards the tip. The gonys is the ventral ridge of

11907-407: The early 19th century, influential works being: Angiosperm seeds are "enclosed seeds", produced in a hard or fleshy structure called a fruit that encloses them for protection. Some fruits have layers of both hard and fleshy material. In gymnosperms, no special structure develops to enclose the seeds, which begin their development "naked" on the bracts of cones. However, the seeds do become covered by

12054-440: The elaiosomes are eaten. The remainder of the seed, which is hard and inedible to the ants, then germinates either within the nest or at a removal site where the seed has been discarded by the ants. This dispersal relationship is an example of mutualism , since the plants depend upon the ants to disperse seeds, while the ants depend upon the plants seeds for food. As a result, a drop in numbers of one partner can reduce success of

12201-429: The embryo is embedded in the endosperm (and nucellus), which the seedling will use upon germination . In the non-endospermic dicotyledons the endosperm is absorbed by the embryo as the latter grows within the developing seed, and the cotyledons of the embryo become filled with stored food. At maturity, seeds of these species have no endosperm and are also referred to as exalbuminous seeds. The exalbuminous seeds include

12348-429: The female in coloring, although a male may have hints of blue on the tail and shoulders and have darker streaks on the underside. The beak is short and conical. In the adult female, the beak is light brown tinged with blue, and in the adult male the upper half is brownish-black while the lower is light blue. The feet and legs are black or gray. First years and adult males are distinguishable through close observations of

12495-468: The female is brown year-round. Nest-building and incubation are done solely by the female. The diet of the indigo bunting consists primarily of insects during the summer months and seeds during the winter months. The indigo bunting is included in the family Cardinalidae , which is made up of passerine birds found in North and South America , and is one of seven birds in the genus Passerina . It

12642-452: The fertilised ovule, an immature plant from which a new plant will grow under proper conditions. The embryo has one cotyledon or seed leaf in monocotyledons , two cotyledons in almost all dicotyledons and two or more in gymnosperms. In the fruit of grains (caryopses) the single monocotyledon is shield shaped and hence called a scutellum . The scutellum is pressed closely against the endosperm from which it absorbs food and passes it to

12789-645: The first few years of their lives deriving energy from the fungi and do not produce green leaves. At up to 55 pounds (25 kilograms) the largest seed is the coco de mer (Lodoicea maldivica). This indicates a 25 Billion fold difference in seed weight. Plants that produce smaller seeds can generate many more seeds per flower, while plants with larger seeds invest more resources into those seeds and normally produce fewer seeds. Small seeds are quicker to ripen and can be dispersed sooner, so autumn all blooming plants often have small seeds. Many annual plants produce great quantities of smaller seeds; this helps to ensure at least

12936-404: The forehead, while the two lower prongs attach to the sides of the skull . At the base of the upper mandible a thin sheet of nasal bones is attached to the skull at the nasofrontal hinge, which gives mobility to the upper mandible, allowing it to move upward and downward. The base of the upper mandible, or the roof when seen from the mouth, is the palate, the structure of which differs greatly in

13083-507: The fruits achenes , caryopses , nuts , samaras , and utricles . Other seeds are enclosed in fruit structures that aid wind dispersal in similar ways: Myrmecochory is the dispersal of seeds by ants . Foraging ants disperse seeds which have appendages called elaiosomes (e.g. bloodroot , trilliums , acacias , and many species of Proteaceae ). Elaiosomes are soft, fleshy structures that contain nutrients for animals that eat them. The ants carry such seeds back to their nest, where

13230-408: The fusion of two male gametes with the egg cell and the central cell to form the primary endosperm and the zygote. Right after fertilization, the zygote is mostly inactive, but the primary endosperm divides rapidly to form the endosperm tissue. This tissue becomes the food the young plant will consume until the roots have developed after germination . After fertilization, the ovules develop into

13377-415: The gape coloration, and other factors influencing their decision remain unknown. Red gape color has been shown in several experiments to induce feeding. An experiment in manipulating brood size and immune system with barn swallow nestlings showed the vividness of the gape was positively correlated with T-cell –mediated immunocompetence , and that larger brood size and injection with an antigen led to

13524-403: The gradual loss of the defining grooves through evolution. The tomia (singular tomium ) are the cutting edges of the two mandibles. In most birds, these range from rounded to slightly sharp, but some species have evolved structural modifications that allow them to handle their typical food sources better. Granivorous (seed-eating) birds, for example, have ridges in their tomia, which help

13671-446: The grasses, are not distinct structures, but are fused with the fruit wall to form a pericarp .) The testae of both monocots and dicots are often marked with patterns and textured markings, or have wings or tufts of hair. When the seed coat forms from only one layer, it is also called the testa, though not all such testae are homologous from one species to the next. The funiculus abscisses (detaches at fixed point – abscission zone),

13818-569: The ground, but rarely up to 9 m (30 ft). The nest itself is constructed of leaves, coarse grasses, stems, and strips of bark, lined with soft grass or deer hair and is bound with spider web. It is constructed by the female, who cares for the eggs alone. The clutch consists of one to four eggs , but usually contains three to four. The eggs are white and usually unmarked, though some may be marked with brownish spots, averaging 18.7 mm × 13.7 mm (0.74 in × 0.54 in) in size. The eggs are incubated for 12 to 13 days and

13965-431: The growing parts. Embryo descriptors include small, straight, bent, curved, and curled. Within the seed, there usually is a store of nutrients for the seedling that will grow from the embryo. The form of the stored nutrition varies depending on the kind of plant. In angiosperms, the stored food begins as a tissue called the endosperm , which is derived from the mother plant and the pollen via double fertilization . It

14112-411: The head is indigo . The wings and tail are black with cerulean blue edges. In fall and winter plumage, the male has brown edges to the blue body and head feathers, which overlap to make the bird appear mostly brown. The adult female is brown on the upperparts and lighter brown on the underparts. It has indistinct wing bars and is faintly streaked with darker markings underneath. The immature bird resembles

14259-464: The indigo bunting is brushy forest edges, open deciduous woods, second growth woodland , and farmland . Increases in population size have been seen in the event of forest clearings and development of land into farms. The breeding range stretches from southern Canada to Maine , south to northern Florida and eastern Texas , and westward to southern Nevada . The winter range begins in southern Florida and central Mexico and stretches south through

14406-434: The inner epidermis may remain a single layer, it may also divide to produce two to three layers and accumulates starch, and is referred to as the colourless layer. By contrast, the outer epidermis becomes tanniferous . The inner integument may consist of eight to fifteen layers. As the cells enlarge, and starch is deposited in the outer layers of the pigmented zone below the outer epidermis, this zone begins to lignify, while

14553-444: The innermost layer is known as the fringe layer. In gymnosperms, which do not form ovaries, the ovules and hence the seeds are exposed. This is the basis for their nomenclature – naked seeded plants. Two sperm cells transferred from the pollen do not develop the seed by double fertilization, but one sperm nucleus unites with the egg nucleus and the other sperm is not used. Sometimes each sperm fertilizes an egg cell and one zygote

14700-483: The jaw muscles of similarly sized mammals. The outer surface of the beak consists of a thin sheath of keratin called the rhamphotheca , which can be subdivided into the rhinotheca of the upper mandible and the gnathotheca of the lower mandible. This covering arises from the Malpighian layer of the bird's epidermis , growing from plates at the base of each mandible. There is a vascular layer between

14847-549: The joint depends on the species) but are separated proximally , attaching on either side of the head to the quadrate bone. The jaw muscles, which allow the bird to close its beak, attach to the proximal end of the lower mandible and to the bird's skull. The muscles that depress the lower mandible are usually weak, except in a few birds such as the starlings and the extinct huia , which have well-developed digastric muscles that aid in foraging by prying or gaping actions. In most birds, these muscles are relatively small as compared to

14994-479: The largest beak relative to the size of its body of any bird species, is capable of modifying the blood flow to its beak. This process allows the beak to work as a "transient thermal radiator", reportedly rivaling an elephant's ears in its ability to radiate body heat. Measurements of the bill sizes of several species of American sparrows found in salt marshes along the North American coastlines show

15141-424: The latter example these hairs are the source of the textile crop cotton . Other seed appendages include the raphe (a ridge), wings, caruncles (a soft spongy outgrowth from the outer integument in the vicinity of the micropyle), spines, or tubercles. A scar also may remain on the seed coat, called the hilum , where the seed was attached to the ovary wall by the funicle. Just below it is a small pore, representing

15288-451: The lower mandible, created by the junction of the bone's two rami, or lateral plates. The proximal end of that junction—where the two plates separate—is known as the gonydeal angle or gonydeal expansion . In some gull species, the plates expand slightly at that point, creating a noticeable bulge; the size and shape of the gonydeal angle can be useful in identifying between otherwise similar species. Adults of many species of large gulls have

15435-402: The main area of growth of the embryo, while the lower or micropylar pole produces the stalk-like suspensor that attaches to the micropyle. The suspensor absorbs and manufactures nutrients from the endosperm that are used during the embryo's growth. The main components of the embryo are: Monocotyledonous plants have two additional structures in the form of sheaths. The plumule is covered with

15582-589: The mainstay of its diet during the winter, although buds and insects are eaten when available. The young are fed mainly insects at first, to provide them with protein . The indigo bunting does not drink frequently, generally obtaining sufficient water from its diet. Indigo bunting nests are vulnerable to a variety of climbing and flying predators, including Virginia opossum ( Didelphis virginiana ), red fox ( Vulpes vulpes ), domestic cat ( Felis catus ), blue jay ( Cyanocitta cristata ), eastern racer ( Coluber constrictor ) and raccoon ( Procyon lotor ). The bird

15729-716: The male garganey touches his beak to the blue speculum feathers on his wings in a fake preening display, and the male Mandarin duck does the same with his orange sail feathers. A number of species use a gaping, open beak in their fear and/or threat displays. Some augment the display by hissing or breathing heavily, while others clap their beak. Red-bellied woodpeckers at bird feeders often wave their formidable beaks at competing birds who get too close, clearly signaling "this seed's mine, you can't have it." The platypus uses its bill to navigate underwater, detect food, and dig. The bill contains electroreceptors and mechanoreceptors, causing muscular contractions to help detect prey. It

15876-422: The mature seed can be a paper-thin layer (e.g. peanut ) or something more substantial (e.g. thick and hard in honey locust and coconut ), or fleshy as in the sarcotesta of pomegranate . The seed coat helps protect the embryo from mechanical injury, predators, and drying out. Depending on its development, the seed coat is either bitegmic or unitegmic . Bitegmic seeds form a testa from the outer integument and

16023-514: The mechanical layer is the endotegmen, then the seed is endotestal. The exotesta may consist of one or more rows of cells that are elongated and pallisade like (e.g. Fabaceae ), hence 'palisade exotesta'. In addition to the three basic seed parts, some seeds have an appendage, an aril , a fleshy outgrowth of the funicle ( funiculus ), (as in yew and nutmeg ) or an oily appendage, an elaiosome (as in Corydalis ), or hairs (trichomes). In

16170-456: The micropyle of the ovule. Seeds are very diverse in size. The dust-like orchid seeds are the smallest, with about one million seeds per gram; they are often embryonic seeds with immature embryos and no significant energy reserves. Orchids and a few other groups of plants are mycoheterotrophs which depend on mycorrhizal fungi for nutrition during germination and the early growth of the seedling. Some terrestrial orchid seedlings, in fact, spend

16317-399: The monocotyledons, ten in the dicotyledons, and two in the gymnosperms (linear and spatulate). This classification is based on three characteristics: embryo morphology, amount of endosperm and the position of the embryo relative to the endosperm. In endospermic seeds, there are two distinct regions inside the seed coat, an upper and larger endosperm and a lower smaller embryo. The embryo is

16464-442: The normal seasonal color change in the beaks of male black-headed gulls and indigo buntings . The beak of modern birds has a fused premaxillary bone, which is modulated by the expression of Fgf8 gene in the frontonasal ectodermal zone during embryonic development. The shape of the beak is determined by two modules: the prenasal cartilage during early embryonic stage and the premaxillary bone during later stages. Development of

16611-403: The optimal conditions for survival of the resulting seedling; the second is spreading germination of a batch of seeds over time so a catastrophe (e.g. late frosts, drought, herbivory ) does not result in the death of all offspring of a plant ( bet-hedging ). Seed dormancy is defined as a seed failing to germinate under environmental conditions optimal for germination, normally when the environment

16758-477: The other. In South Africa , the Argentine ant ( Linepithema humile ) has invaded and displaced native species of ants. Unlike the native ant species, Argentine ants do not collect the seeds of Mimetes cucullatus or eat the elaiosomes. In areas where these ants have invaded, the numbers of Mimetes seedlings have dropped. Seed dormancy has two main functions: the first is synchronizing germination with

16905-410: The parent. The large, heavy root allows the seed to penetrate into the ground when it falls. Many garden plant seeds will germinate readily as soon as they have water and are warm enough; though their wild ancestors may have had dormancy, these cultivated plants lack it. After many generations of selective pressure by plant breeders and gardeners, dormancy has been selected out. For annuals , seeds are

17052-485: The parents decide how to distribute food among the chicks in the nest. Some species, especially in the families Viduidae and Estrildidae , have bright spots on the gape known as gape tubercles or gape papillae. These nodular spots are conspicuous even in low light. A study examining the nestling gapes of eight passerine species found that the gapes were conspicuous in the ultraviolet spectrum (visible to birds but not to humans). Parents may, however, not rely solely on

17199-455: The plumule and radicle, acting as a protective covering. The maturing ovule undergoes marked changes in the integuments, generally a reduction and disorganization but occasionally a thickening. The seed coat forms from the two integuments or outer layers of cells of the ovule, which derive from tissue from the mother plant, the inner integument forms the tegmen and the outer forms the testa . (The seed coats of some monocotyledon plants, such as

17346-451: The prenasal cartilage is regulated by genes Bmp4 and CaM , while that of the premaxillary bone is controlled by TGFβllr , β-catenin , and Dickkopf-3. TGFβllr codes for a serine/threonine protein kinase that regulates gene transcription upon ligand binding; previous work has highlighted its role in mammalian craniofacial skeletal development. β-catenin is involved in the differentiation of terminal bone cells. Dickkopf-3 codes for

17493-441: The presence of ultraviolet color) on their beaks. The presence and intensity of these peaks may indicate a bird's fitness, sexual maturity or pair bond status. King and emperor penguins , for example, show spots of ultraviolet reflectance only as adults. These spots are brighter on paired birds than on courting birds. The position of such spots on the beak may be important in allowing birds to identify conspecifics . For instance,

17640-617: The product of the ripened ovule , after the embryo sac is fertilized by sperm from pollen , forming a zygote . The embryo within a seed develops from the zygote and grows within the mother plant to a certain size before growth is halted. The formation of the seed is the defining part of the process of reproduction in seed plants ( spermatophytes ). Other plants such as ferns , mosses and liverworts , do not have seeds and use water-dependent means to propagate themselves. Seed plants now dominate biological niches on land, from forests to grasslands both in hot and cold climates . In

17787-561: The ranges of the lazuli bunting and the indigo bunting overlap, the males defend territories from each another. Migration takes place in April and May and then again in September and October. Previous research indicates that towards the end of August there is a spike in migration, indicated by a rapid surge of captures in the last ten days of August. Migration activities peak in late September and fall off rapidly as October approaches. Only

17934-401: The rapid evaporation of water vapor, and may also help to increase condensation within the nostrils themselves—both critical functions, since the nestlings get fluids only from the food their parents bring them. These opercula shrink as the birds age, disappearing completely by the time they reach adulthood. In pigeons , the operculum has evolved into a soft swollen mass that sits at the base of

18081-405: The rate of germination. This is given as a percent of germination over a certain amount of time, 90% germination in 20 days, for example. 'Dormancy' is covered above; many plants produce seeds with varying degrees of dormancy, and different seeds from the same fruit can have different degrees of dormancy. It's possible to have seeds with no dormancy if they are dispersed right away and do not dry (if

18228-424: The rhamphotheca and the deeper layers of the dermis , which is attached directly to the periosteum of the bones of the beak. The rhamphotheca grows continuously in most birds, and in some species, the color varies seasonally. In some alcids , such as the puffins, parts of the rhamphotheca are shed each year after the breeding season, while some pelicans shed a part of the bill called a "bill horn" that develops in

18375-486: The same principle as a human-devised nutcracker ). Birds that fish for a living have beaks adapted for that pursuit; for example, pelicans ' beaks are well adapted for scooping up and swallowing fish whole. Woodpeckers have beaks well adapted for pecking apart wood while hunting for their meals of arthropods . Birds may bite or stab with their beaks to defend themselves. Some species use their beaks in displays of various sorts. As part of his courtship, for example,

18522-428: The same species, and female American avocets have beaks which are slightly more upturned than those of males. Males of the larger gull species have bigger, stouter beaks than those of females of the same species, and immatures can have smaller, more slender beaks than those of adults. Many hornbills show sexual dimorphism in the size and shape of both beaks and casques , and the female huia 's slim, decurved bill

18669-415: The scar forming an oval depression, the hilum . Anatropous ovules have a portion of the funiculus that is adnate (fused to the seed coat), and which forms a longitudinal ridge, or raphe , just above the hilum. In bitegmic ovules (e.g. Gossypium described here) both inner and outer integuments contribute to the seed coat formation. With continuing maturation the cells enlarge in the outer integument. While

18816-413: The seed affects its health and germination ability: since the seed has a living embryo, over time cells die and cannot be replaced. Some seeds can live for a long time before germination, while others can only survive for a short period after dispersal before they die. Seed vigor is a measure of the quality of seed, and involves the viability of the seed, the germination percentage, germination rate, and

18963-437: The seeds dry they go into physiological dormancy). There is great variation amongst plants and a dormant seed is still a viable seed even though the germination rate might be very low. Environmental conditions affecting seed germination include; water, oxygen, temperature and light. Beak Although beaks vary significantly in size, shape, color and texture, they share a similar underlying structure. Two bony projections –

19110-405: The seeds. The ovule consists of a number of components: The shape of the ovules as they develop often affects the final shape of the seeds. Plants generally produce ovules of four shapes: the most common shape is called anatropous , with a curved shape. Orthotropous ovules are straight with all the parts of the ovule lined up in a long row producing an uncurved seed. Campylotropous ovules have

19257-507: The seeds. They arose during the late Devonian period (416 million to 358 million years ago). From these early gymnosperms, seed ferns evolved during the Carboniferous period (359 to 299 million years ago); they had ovules that were borne in a cupule, which consisted of groups of enclosing branches likely used to protect the developing seed. Published literature about seed storage, viability and its hygrometric dependence began in

19404-428: The shrike tomial teeth are entirely keratinous. Some fish-eating species, e.g., the mergansers , have sawtooth serrations along their tomia, which help them to keep hold of their slippery, wriggling prey. Birds in roughly 30 families have tomia lined with tight bunches of very short bristles along their entire length. Most of these species are either insectivores (preferring hard-shelled prey) or snail eaters, and

19551-484: The skull and its degree of ossification . Juvenile skulls have a slightly pinkish color that gives under pressure due to its singular layer. Adults instead have a double layer skull, which gives more resistance when applying pressure. First year birds also tend to have a fleshy, yellow gape in the corner of the mouth, apparent in all months except October and November. When comparing males to females that both have brown molt, increased wing length and weight typically indicate

19698-466: The sky had minimal effect on Zugunruhe. Indigo buntings do use the northern sky to help navigate both in the fall and in the spring. It was thought that the bunting has an internal clock, being able to compensate for the movement of stars. However, temporal compensation for stellar motion is not a part of their migratory methods. In captivity, since it cannot migrate, it experiences disorientation in April and May and in September and October if it cannot see

19845-420: The soil surface is the next phase of the plant's growth and is called seedling establishment. Three fundamental conditions must exist before germination can occur. (1) The embryo must be alive, called seed viability. (2) Any dormancy requirements that prevent germination must be overcome. (3) The proper environmental conditions must exist for germination. Far red light can prevent germination. Seed viability

19992-401: The species is not believed to approach the thresholds for a population decline warranting an upgrade in conservation status. Seed In botany , a seed is a plant embryo and nutrient reserve enclosed in a seed coat, a protective outer covering called a testa. More generally, the term "seed" means anything that can be sown , which may include seed and husk or tuber . Seeds are

20139-552: The species where their ranges overlap, in the Great Plains . They were declared to form a superspecies by the American Ornithologists' Union in 1983. However, according to sequencing of the mitochondrial cytochrome-b gene of members of the genus Passerina , it was determined that the indigo bunting and lazuli bunting are not, in fact, sister taxa . The indigo bunting is the sister of two sister groups,

20286-522: The stars from its enclosure. While debate has occurred over the years about how birds migrate near the Gulf of Mexico , indigo buntings migrate to South America by flying both over the Gulf of Mexico and around the Gulf of Mexico, with a majority of buntings choosing the trans-Gulf path. Past evidence indicated that indigo buntings did not have a high enough fat content to travel across the Gulf, but that evidence

20433-507: The strength of the seedlings produced. The germination percentage is simply the proportion of seeds that germinate from all seeds subject to the right conditions for growth. The germination rate is the length of time it takes for the seeds to germinate. Germination percentages and rates are affected by seed viability, dormancy and environmental effects that impact on the seed and seedling. In agriculture and horticulture quality seeds have high viability, measured by germination percentage plus

20580-405: The tip to the anterior edge of the nostrils, from the tip to the base of the skull, or from the tip to the cere (for raptors and owls) — and scientists from various parts of the world generally favor one method over another. In all cases, these are chord measurements (measured in a straight line from point to point, ignoring any curve in the culmen) taken with calipers . The shape or color of

20727-444: The trip across the Gulf of Mexico from Florida is approximately six hundred miles (966 km), buntings weighing at least 18 g could make the trip without any stops. These birds are generally monogamous but not always faithful to their partner. In the western part of their range, they often hybridize with the lazuli bunting . Nesting sites are located in dense shrub or a low tree, generally 0.3–1 m (0.98–3.28 ft) above

20874-417: The upper and lower mandibles – are covered with a thin keratinized layer of epidermis known as the rhamphotheca. In most species, two holes called nares lead to the respiratory system. Although the word "beak" was, in the past, generally restricted to the sharpened bills of birds of prey , in modern ornithology , the terms beak and bill are generally considered to be synonymous. The word, which dates from

21021-473: The very similarly-plumaged king and emperor penguins have UV-reflective spots in different positions on their beaks. The size and shape of the beak can vary across species as well as between them; in some species, the size and proportions of the beak vary between males and females. This allows the sexes to utilize different ecological niches, thereby reducing intraspecific competition . For example, females of nearly all shorebirds have longer bills than males of

21168-428: The wildfowl family one of its former names: "Unguirostres" comes from the Latin ungus , meaning "nail" and rostrum , meaning "beak". Rictal bristles are stiff hair-like feathers that arise around the base of the beak. They are common among insectivorous birds, but are also found in some non-insectivorous species. Their function is uncertain, although several possibilities have been proposed. They may function as

21315-399: Was nearly twice as long as the male's straight, thicker one. Color can also differ between sexes or ages within a species. Typically, such a color difference is due to the presence of androgens . For example, in house sparrows , melanins are produced only in the presence of testosterone ; castrated male house sparrows—like female house sparrows—have brown beaks. Castration also prevents

21462-414: Was originally described as Tanagra cyanea by Linnaeus in his 18th-century work, Systema Naturae . The current genus name, Passerina , is derived from the Latin term passer for true sparrows and similar small birds, while the species name, cyanea , is Latin for cyan , the color of the male's breeding plumage. The indigo bunting is a close relative of the lazuli bunting and interbreeds with

21609-426: Was referred to as albumen , and the inner endosperm layer as vitellus. Although misleading, the term began to be applied to all the nutrient matter. This terminology persists in referring to endospermic seeds as "albuminous". The nature of this material is used in both describing and classifying seeds, in addition to the embryo to endosperm size ratio. The endosperm may be considered to be farinaceous (or mealy) in which

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