Species of bird in North and Central America
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The red-winged blackbird (Agelaius phoeniceus) is a passerine bird of the family Icteridae found in most of North America and much of Central America. It breeds from Alaska and Newfoundland south to Florida, the Gulf of Mexico, Mexico, and Guatemala, with isolated populations in western El Salvador, northwestern Honduras, and northwestern Costa Rica. It may winter as far north as Pennsylvania and British Columbia, but northern populations are generally migratory, moving south to Mexico and the Southern United States. Claims have been made that it is the most abundant living land bird in North America, as bird-counting censuses of wintering red-winged blackbirds sometimes show that loose flocks can number in excess of a million birds per flock and the full number of breeding pairs across North and Central America may exceed 250 million in peak years. It also ranks among the best-studied wild bird species in the world. The red-winged blackbird is sexually dimorphic; the male is all black with a red shoulder and yellow wing bar, while the female is a nondescript dark brown. Seeds and insects make up the bulk of the red-winged blackbird's diet.
Taxonomy.
The red-winged blackbird is one of five species in the genus "Agelaius" and is included in the family Icteridae, which is made up of passerine birds found in North and South America. The red-winged blackbird was formally described as "Oriolus phoeniceus" by Carl Linnaeus in 1766 in the twelfth edition of his "Systema Naturae", but was later moved with the other American blackbirds to the genus "Agelaius" by Louis Pierre Vieillot in 1816. Linnaeus specified the type location as "America" but this was restricted to Charleston, South Carolina in 1928. The genus name is derived from Ancient Greek , meaning "gregarious". The specific epithet, , is Latin meaning "crimson" or "red". The red-winged blackbird is a sister species to the red-shouldered blackbird ("Agelaius assimilis") that is endemic to Cuba. These two species are together sister to the tricolored blackbird ("Agelaius tricolor") that is found on the Pacific coast region of the California and upper Baja California in Mexico.
Depending on the authority, between 20 and 24 subspecies are recognised which are mostly quite similar in appearance. However, there are two isolated populations of bicolored blackbirds that are quite distinctive: "A. p. californicus" of California and "A. p. gubernator" of central Mexico. The taxonomy and relationships between these two populations and with red-winged blackbirds is still unclear. Despite the similarities in most forms of the red-winged blackbird, in the subspecies of Mexican Plateau, "A. p. gubernator", the female's veining is greatly reduced and restricted to the throat; the rest of the plumage is very dark brown, and also in a different family from the European redwing and the Old World common blackbird, which are thrushes (Turdidae). In the California subspecies, "A. p. californicus" and "A. p. mailliardorum", the veining of the female specimens also covers a smaller surface and the plumage is dark brown, although not in the "gubernator" grade; and also its superciliary list is absent or poorly developed. The male subspecies "mailliardorum", "californicus", "aciculatus", "neutralis", and "gubernator" lack the yellow band on the wing that is present in most male members of the other subspecies. The red-shouldered blackbird was formerly considered as a subspecies of red-winged blackbird. They were split by the American Ornithologists' Union in 1997.
Listed below are the red-winged blackbird subspecies and groups of subspecies recognized as of January 2014 with their respective distribution areas and the location of their wintering quarters:
Description.
The common name for the red-winged blackbird is taken from the mainly black adult male's distinctive red shoulder patches, or "epaulets", which are visible when the bird is flying or displaying. At rest, the male also shows a pale yellow wingbar. The spots of males less than one year old, generally subordinate, are smaller and more orange than those of adults. The female is blackish-brown and paler below. The female is smaller than the male, at long and weighing , against his length of and weight of . The smallest females may weigh as little as whereas the largest males can weigh up to . Each wing can range from , the tail measures , the culmen measures and the tarsus measures . The upper parts of the female are brown, while the lower parts are covered by an intense white and dark veining; also presents a whitish superciliary list. According to Crawford (1977), females exhibit a salmon-pink stain on the shoulders and a light pink color on the face and below this when they are a year old, while older females show a stain usually more crimson on the shoulders and a darker pink hue on and under the face. Observations in females in captivity indicate that small amounts of yellow pigment are present on the shoulders of these after leaving the nest, that the concentration of the pigment increases with the first winter plumage after the change of the feathers and that the passage from yellow to orange generally takes place in the second summer with the acquisition of the second winter plumage, after which no further changes in feather color occur. The colored area on the wing increases in surface with the age of the female, and varies in intensity from brown to a bright red-orange similar to that of the males in their first year.
Young birds resemble the female, but are paler below and have buff feather fringes. Both sexes have a sharply pointed bill. The tail is of medium length and is rounded. The eyes, bill, and feet are all black. Unlike most North American passerines which develop their adult plumage in their first year of life so that the one-year-old and the oldest individual are indistinguishable in the breeding season, the red-winged blackbird does not. It acquires its adult plumage only after the breeding season of the year following its birth when it is between thirteen and fifteen months of age. Young males go through a transition stage in which the wing spots have an orange coloration before acquiring the most intense tone typical of adults.
The male measures between in length, while the female measures . Its wingspan is between approximately. Both the peak male and the legs, the claws and the eyes are black; in the female beak is dark brown and clear in the upper half at the bottom, and the tail is medium in length and rounded. As in other species polygyny exists, the red-winged blackbird exhibit considerable sexual dimorphism both in plumage and size, males weighing between 65 and 80g the females about 35g. Males are 50% heavier than females, 20% larger in its linear dimensions, and 20% larger compared to the length of their wings. The trend towards greater dimorphism in the size of non-monogamous ichterid species indicates that the larger size of males has evolved due to sexual selection.
The male is unmistakable except in the far west of the US, where the tricolored blackbird occurs. Males of that species have a darker red epaulet edged with white, not yellow. Females of tricolored, bicolored, red-shouldered and red-winged blackbirds can be difficult to identify in areas where more than one form occurs. In flight, when the field marks are not easily seen, the red-winged blackbird can be distinguished from less closely related icterids such as common grackle and brown-headed cowbird by its different silhouette and undulating flight.
Staining of red spots and yellow bands.
Two keto-carotenoids – carotenoid with a ketone group – reds synthesized by the birds themselves – namely astaxanthin and canthaxanthin – are responsible for the bright red color of the wing spots, but two yellow dietary precursor pigments – lutein and zeaxanthin – are also present in moderately high concentrations in red feathers. Astaxanthin is the carotenoid more abundant (35% of the total), followed by lutein (28%), canthaxanthin (23%) and zeaxanthin (12%). Such a balanced combination of dietary precursors and metabolic derivatives in colored feathers is quite unusual, not only within a species as a whole but also in individuals and particular feathers.
After removing the carotenoids in an experiment, the red feathers acquired a deep brown coloration. This is because the feather barbles of the colored spot contain melanin pigments – mainly eumelanin, which was equivalent to 83% of all melanins, but also pheomelanin at a concentration approximately equal to that of carotenoids, which seems to be a rare trait for carotenoid-based ornamental plumage. On the other hand, the feathers of the yellow stripes of the males are devoid of carotenoids —except occasionally when they appear tinged with a pink coloration derived from small amounts of said pigments— and present high concentrations of pheomelanin —82% of all melanins. Melanin concentrations in the yellow band are even higher than in the red spot.
Role of wing spots.
These markings are vital in the defense of the territory. Males with larger spots are more effective at chasing away their non-territorial rivals and are more successful in contests within aviaries. When the red shoulder patches were dyed black as part of an experiment, 64% of males lost their territories, while only 8% of control subjects did. However, males whose wings had been dyed before they had mated could still attract females and successfully reproduce. In the red-winged blackbird, the spots on the wings are a sign of threat among males and have an unimportant role, if any, in intersex encounters. Therefore, the spots are likely to have evolved in response to pressures linked to intrasexual selection. Additionally, neither the size nor the coloration of the same are linked to the reproductive success of the males with those females that are not their mates, that is, those with which they eventually mate. It has been suggested that also in the case of females, the best explanation for the evolution of a variable coloration in the shoulder spots is that their intensity indicates their physical condition in aggressive encounters between them.
The fact that female red-winged blackbirds do not appear to consistently use variability in the size and color of male wing spots when choosing a mate runs counter to the classic role of carotenoid pigmentation ornamental feathers, mostly used in the attraction of a couple. In turn, its use as a sign of aggressiveness and social status against rival males is not a common trait in carotenoid ornaments. On the other hand, ornaments with a preponderance of melanin do tend to have an important role as an indicator of status in avian populations, so the spots of red-winged blackbirds seem to work more as melanin ornaments than as carotenoids.
Vocalizations.
The calls of the red-winged blackbird are a throaty "check" and a high slurred whistle, "terrr-eeee". The male's song, accompanied by a display of his red shoulder patches, is a scratchy "oak-a-lee", except that in many western birds, including bicolored blackbirds, it is "ooPREEEEEom". The female also sings, typically a scolding chatter "chit chit chit chit chit chit cheer teer teer teerr".
Feather molt.
The most critical period of feather molting runs from late August to early September. When viewed in flight, they have a misaligned or "moth-eaten" appearance and generally slower and more laborious travel. Their mobility is reduced due to the lack of several remiges or rectrices or these are not entirely renewed. Most of the red-winged blackbirds have moved almost entirely by October. By then, some birds have not completed the molt of the feathers of the capital region and the helmsmen of the center of the tail and the internal secondary sprouts have only partially emerged from the pod. Virtually all individuals have completed their molts by mid-October.
Birds do not begin their migration to wintering quarters until the two outer primary sprouts and the two inner or central rectrices have completed at least two-thirds of their development. Therefore, there is a correlation between molting, particularly replacement of the remiges and rectrices, and fall migration in red-winged blackbirds.
Females are dark above with feathers bordered with beige or rust. The lower part shows black and white streaks, but with more beige on the chest and sometimes on the flanks than in the reproductive plumage. The medium and secondary major cover feathers are noticeably bordered with beige. They generally lack the pink coloration on the chin and throat – which may be beige, yellow, or light