Blue-headed vireo | |
---|---|
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Aves |
Order: | Passeriformes |
Family: | Vireonidae |
Genus: | Vireo |
Species: | V. solitarius |
Binomial name | |
Vireo solitarius (Wilson, 1810) | |
The blue-headed vireo (Vireo solitarius) is a migrating song bird found in North and Central America. There are currently two recognized subspecies that belong to the blue-headed vireo. It has a range that extends across Canada and the eastern coast of the United-States, Mexico and some of Central America. It prefers large temperate forests with a mix of evergreen trees and deciduous under growth.
As the name suggests, the blue-headed vireo is characterized by its blue-grey head and bold yellow wing bars. Both sexes are very similar in plumage and size. Juveniles also have a similar plumage.
Populations of the blue-headed vireo have been steadily increasing since the 1970s. Therefore, in 2004, the species was classified as a "Least Concern" species. [2]
The blue-headed vireo has similar plumage year round and does not drastically change its appearance during the breeding season. It can be characterized by its olive green upper body, two bold yellow wing bars down the edge of its wing, and a deep blue-grey crown from which it gets its name. The juvenile plumage of immature blue-headed vireos is not distinct but very similar to the adult plumage. [3] While this bird's appearance is similar to the closely related Cassin's vireo (Vireo cassinii), the Cassin's vireo can be differentiated by its lighter yellow patches, a smaller, thinner bill, and a brownish-grey crown. [4] There is little to no sexual dimorphism between males and females as both are similar in plumage colouration and size. [5]
Like most Vireos, the blue-headed vireo is a relatively small bird with a length of 126–148 mm (5.0–5.8 in). The wingspan is usually found to be around 200–240 mm (7.9–9.4 in) and their weight is typically 13–19 g (0.46–0.67 oz). There are some subtle differences between the V.s. solitarius and V.s. alticola subspecies. V.s. alticola, the larger of the two subspecies, has a darker back with a larger wing length of 76–83.5 mm (2.99–3.29 in) and a bill length of 11–12 mm (0.43–0.47 in). Conversely, V.s. solitarius is slightly smaller with a wing length of 69.2–77.8 mm (2.72–3.06 in), and a bill length of 8.9–11 mm (0.35–0.43 in). [3]
The average lifespan of the blue-headed vireo in the wild has been measured to be approximately 7 years and 5 months. [3]
The blue-headed vireo is placed in the genus Vireo , a group of small migrating passerine birds that are characterized by their usually dull greenish colouring, and a simple, monotonous song. Members of this group are usually characterized by the presence or absence of eye-rings, eye-strips, and wing bars. There is no sexual dimorphism between sexes in this group. [5]
Though it had been previously classified as a separate species, the blue-headed vireo along with the plumbeous vireo (Vireo plumbeus) and the Cassin's Vireo (V. cassinii) were lumped in the 1950s into a single species, based on morphological data. This group of vireos was collectively known as the "Solitary Vireo" (Vireo solitarius). This taxonomy prevailed until 1997 when new molecular data showed that there were in fact three distinct species. The taxonomy reverted to that prior to the 1950s, and the blue-headed vireo was once again its own species. [6]
There are two recognized subspecies of blue-headed vireo: [6]
Native to North America, the blue-headed vireo enjoys a large breeding range that extends over an immense area of Canada and northern United States. The breeding range of V.s. solitarius extends from northeastern British Columbia across Alberta, Saskatchewan, Manitoba, Ontario and Quebec and down to southern Pennsylvania and New Jersey. V.s. alticola has a distinct breeding range that includes western Maryland and south, mainly in the Appalachian Mountains, to northern Georgia. At the end of the breeding season, the blue-headed vireo migrates south to its overwintering area. V.s. solitarius has the longest migration of the two subspecies and inhabits an overwintering area that includes eastern and southern Mexico to northern Central America. V.s. alticola migrates across a shorter distance to an area that extends from southeastern Virginia to Texas. [3]
Blue-headed vireos prefer to breed in cool temperate forests, which in the southern part of its breeding range are found at higher elevations. Evergreen forests with spruce, fir, hemlock, and pine mixed with deciduous growth such as alder shrubs, willow shrubs, poplar, birch or maple trees are the habitat of choice. [7] During the winter, blue-headed vireos inhabit mixed woods of pines and hardwoods. They are also found in coastal and flood plain swamps and low shrubby thickets. [3]
Year round, even during the breeding season, population density is somewhat low and spread out. Overwintering population densities are usually found to be lower than in the breeding season. [8] The density of the population ultimately depends on the type of forest being inhabited. [3]
During migration, blue-headed vireos are often found to flock with groups of different sparrow species but rarely with members of its own species. [3]
When blue-headed vireos arrive on their breeding grounds, typically in mid-April, many deciduous trees have yet to leaf out, leading them to nest in evergreen trees including hemlocks (Tsuga). Recently, however, many hemlocks in eastern USA have been killed by an invasive Asian insect, the Hemlock woolly adelgid (Adelges tsugae), leaving the vireos with fewer nesting options until spring leaf opening begins for deciduous trees. [9]
The primary song of the blue-headed vireo is a simple, slow, monotonous tune that is often confused with the faster red-eyed vireo (Vireo olivaceus) song. The primary song is sung only by the males and usually only during the breeding season. The males become quite vocal during the breeding season, with the song frequency reaching its height prior to mating and then decreasing after copulation. Both sexes share a series of calls that are used in both defence of nests, interspecies competition, and communication between breeding pairs while foraging. [3]
When foraging during the breeding season, mated pairs constantly communicate with each other using a series of high pitched chirping calls. [3] [10]
Blue-headed vireos are mainly insectivorous birds but are also known to eat fleshy berries and fruit. [11] They are equipped with short, strong bills used for processing insect prey with a tough carapace such as beetles. Foraging usually occurs in the mid level of trees. A foraging blue-headed vireo will hop from branch to branch on the same or to an adjacent tree and will then fly towards its prey to capture it. [3] Typical prey consist mostly of caterpillars, butterflies and moths but may also include tree bugs, stink bugs, beetles, bees, ants, flies, dragonflies, grasshoppers, crickets, spiders and, on some occasions, snails. [3] Fruit feeding occurs primarily during migration and overwintering, especially when overwintering in more tropical regions where fruit is more abundant or if the insect populations are low. This large and varied diet is an example of an opportunistic feeding strategy, allowing the blue-headed vireo to be plastic in its ability to adapt to resource availability. [12]
When arriving to the breeding ground in mid-April, male vireos will hold large, individual territories that can range from 1.5–6.6 hectares (3.7–16.3 acres). Females will choose a male to mate with depending on the male's ability to defend and control a large territory. While defending their territory from other males, the male vireos will sing a primary song to attract females. [13] Undecided females can usually be seen flying along the edges of competing male territories; usually this will force the two males into direct conflict for the right to copulate with the female. [10] [13]
Once a female has approached a suitable mate, the male will perform a series of mating rituals. Typically, these rituals involve the male building a courtship nest for the female. The courtship nest is not a full nest but is most likely an attempt by the male to display his ability to gather resources. [10] [13] Once the pair is established, the courtship nest is abandoned. Mating does not occur for approximately 2 weeks after pair has been established. During this time, the male and the female will cooperatively build a breeding nest which is typically formed between forking mid-level branches of evergreen and deciduous trees and are composed of twigs and foliage. Breeding nests are not reused in following breeding seasons. [3]
In one breeding season, a female will lay 3–5 eggs at a rate of 1 egg per day. Eggs are creamy white with brown or black spots and are 17–23.1 x 13.3–15.8 mm (0.055–0.075 in x 0.04–0.05 in). Eggs are incubated for approximately 14 days after being laid. Once hatched, infants are highly altricial, often having little to no downy feathers. Infants open their eyes during day 5 or 6 and will begin to fledge after 14 days for a total chick-rearing period of 28 days. Once the young are able to leave the nest, the parents will split the juveniles and separate. Juveniles are usually dependent on the parent to provide food for approximately 1 month after leaving the nest. If the nest is destroyed or a mating pair produces a failed brood, an attempt to re-nest may occur but this ultimately depends on when the brood fails. If the brood fails early on in the season, there is a higher chance that the pair will re-nest, if later, the pair will often separate and not attempt a second brood. [3]
Blue-headed vireo's have an atypical breeding strategy when compared to other closely related species. Blue-headed vireo males will assist their mates with daytime incubation of eggs, nest construction, and feeding of the chicks. [10] Also, unlike most bird species, female blue-headed vireos do not attempt any extra-pair copulations with other males. Likewise, males make no attempt to guard females from other males, making blue-headed vireos both socially and genetically monogamous birds. [10]
The increase in male blue-headed vireo parental care is thought to be attributed to the levels of testosterone and prolactin found in the plasma of these birds during the mating season. Testosterone, a steroid hormone that is secreted by the testes, has been found to increase aggressive behaviour in male birds during the breeding season [14] and that these males display less parental care if their testosterone levels are maintained. [15] Conversely, prolactin is a peptide hormone that is regulated by the hypothalamus that has been found at higher levels in birds that do the majority of incubation. [16] It was found that in the early breeding season, male blue-headed vireos have a low testosterone level and will maintain this low level at all stages of the season. [17] This low level does not affect the Vireo's ability to compete with other males for territory however, as a high testosterone level has been found to not be necessary for territory establishment. [18] Prolactin levels of the males were found to be high very early on in the breeding season and are maintained for the duration of the season. This high level of prolactin along with a low testosterone level, explains why male blue-headed vireos are so involved in the construction of the nest, daytime incubation, and feeding of the nestlings. [10] [17]
Blue-headed vireos have a low nesting success rate, with about 10–30% of hatchlings surviving. [3] Common predators of the blue-headed vireo eggs and chicks include blue jays, crows, and squirrels.
Often, when a nest is attacked by a blue jay, the male and female will execute coordinated attacks on the approaching predator. This usually involves one partner swooping towards the blue jay while calling the mate who will then execute a second attack. [10] Blue-headed vireos have also been known to nest close to nesting raptorial birds that do not prey on them. It is thought that they use the raptors as protection from squirrels that are, in turn, hunted by these bird of prey. [3]
The largest contributor to the low nesting success rate of the blue-headed vireo is most likely the parasitic brown-headed cowbird (Molothrus ater). These birds will often lay their large eggs overtop the existing brood, causing the parents to feed the cowbird which will ultimately starve the infant Vireos. [3]
The American goldfinch is a small North American bird in the finch family. It is migratory, ranging from mid-Alberta to North Carolina during the breeding season, and from just south of the Canada–United States border to Mexico during the winter.
The American coot, also known as a mud hen or pouldeau, is a bird of the family Rallidae. Though commonly mistaken for ducks, American coots are only distantly related to ducks, belonging to a separate order. Unlike the webbed feet of ducks, coots have broad, lobed scales on their lower legs and toes that fold back with each step to facilitate walking on dry land. Coots live near water, typically inhabiting wetlands and open water bodies in North America. Groups of coots are called covers or rafts. The oldest known coot lived to be 22 years old.
The chipping sparrow is a species of New World sparrow, a passerine bird in the family Passerellidae. It is widespread, fairly tame, and common across most of its North American range.
The ruff is a medium-sized wading bird that breeds in marshes and wet meadows across northern Eurasia. This highly gregarious sandpiper is migratory and sometimes forms huge flocks in its winter grounds, which include southern and western Europe, Africa, southern Asia and Australia.
Brewer's blackbird is a medium-sized New World blackbird. It is named after the ornithologist Thomas Mayo Brewer.
The scarlet tanager is a medium-sized American songbird. Until recently, it was placed in the tanager family (Thraupidae), but it and other members of its genus are now classified as belonging to the cardinal family (Cardinalidae). The species' plumage and vocalizations are similar to other members of the cardinal family, although the Piranga species lacks the thick conical bill that many cardinals possess. The species resides in thick deciduous woodlands and suburbs.
The buff-bellied pipit or American pipit is a small songbird found on both sides of the northern Pacific. It was first described by Marmaduke Tunstall in his 1771 Ornithologia Britannica. It was formerly classified as a form of the water pipit. It is known as "American pipit" in North America and "buff-bellied pipit" in Eurasia.
The yellow warbler is a New World warbler species. Yellow warblers are the most widespread species in the diverse genus Setophaga, breeding in almost the whole of North America, the Caribbean, and down to northern South America.
The blue-footed booby is a marine bird native to subtropical and tropical regions of the eastern Pacific Ocean. It is one of six species of the genus Sula – known as boobies. It is easily recognizable by its distinctive bright blue feet, which is a sexually selected trait and a product of their diet. Males display their feet in an elaborate mating ritual by lifting them up and down while strutting before the female. The female is slightly larger than the male and can measure up to 90 cm (35 in) long with a wingspan up to 1.5 m (5 ft).
The painted bunting is a species of bird in the cardinal family, Cardinalidae. It is native to North America. The bright plumage of the male only comes in the second year of life; in the first year they can only be distinguished from the female by close inspection.
The shiny cowbird is a passerine bird in the New World family Icteridae. It breeds in most of South America except for dense forests and areas of high altitude such as mountains. Since 1900 the shiny cowbird's range has shifted northward, and it was recorded in the Caribbean islands as well as the United States, where it is found breeding in southern Florida. It is a bird associated with open habitats, including disturbed land from agriculture and deforestation.
The green-rumped parrotlet, also known as the green-rumped parakeet, is a species of parrot in the family Psittacidae that is found in northeastern South America and the Caribbean island of Trinidad. The green-rumped parrotlet occurs from northern Venezuela eastwards to the lower Amazon in Brazil, Also Suriname and has been introduced to Curaçao, Jamaica and Barbados. It prefers semi-open lowland areas and is also sometimes present in city parks. There are five subspecies.
The golden-headed quetzal or corequenque is a strikingly coloured bird in the genus Pharomachrus. It is found in moist mid-elevation forests from eastern Panama to northern Bolivia.
The black-capped vireo is a small bird native to the United States and Mexico. It was listed as an endangered species in the United States in 1987. It is the only Vireo that is sexually dichromatic. Recovery of the species' population contributed to its delisting in 2018. The IUCN lists the species as "near threatened."
The silver-throated tanager is a species of passerine bird in the tanager family Thraupidae. It is found in Costa Rica, Panama, Colombia, Ecuador, and northeastern Peru. It inhabits mossy forests, montane evergreen forests, tropical lowland evergreen forests and forest edges, along with tall secondary forests and disturbed habitat with remnant trees and forest. It is 13 centimetres (5.1 in) long and weighs 22 grams (0.78 oz) on average, and shows slight sexual dimorphism, with duller female plumage. Adult males are mainly bright yellow, with a silvery-white throat bordered above with a black stripe on the cheeks, black streaking on the back, and green edges to the wings and tail. Juveniles are duller and greener.
The Kentish plover is a small wader of the family Charadriidae that breeds on the shores of saline lakes, lagoons, and coasts, populating sand dunes, marshes, semi-arid desert, and tundra. Both male and female birds have pale plumages with a white underside, grey/brown back, dark legs and a dark bill; however, additionally the male birds also exhibit very dark incomplete breast bands, and dark markings either side of their head, therefore the Kentish plover is regarded as sexually dimorphic.
The brown treecreeper is the largest Australasian treecreeper. The bird, endemic to eastern Australia, has a broad distribution, occupying areas from Cape York, Queensland, throughout New South Wales and Victoria to Port Augusta and the Flinders Ranges, South Australia. Prevalent nowadays between 16˚S and 38˚S, the population has contracted from the edges of its pre-European range, declining in Adelaide and Cape York. Found in a diverse range of habitats varying from coastal forests to mallee shrub-lands, the brown treecreeper often occupies eucalypt-dominated woodland habitats up to 1,000 metres (3,300 ft), avoiding areas with a dense shrubby understorey.
The black sparrowhawk, sometimes known as the black goshawk or great sparrowhawk, is a bird of prey belonging to the family Accipitridae. It was formerly placed in the genus Accipiter. It occurs mainly in forest and non-desert areas south of the Sahara, particularly where there are large trees suitable for nesting; favored habitat includes suburban and human-altered landscapes. It preys predominantly on birds of moderate size, such as pigeons and doves, in suburban areas.
The sickle-billed vanga is a species of bird in the vanga family Vangidae. It is monotypic within the genus Falculea. It is endemic to Madagascar. Its natural habitats are tropical dry forests and tropical dry shrubland.
The purple martin is a passerine bird in the swallow family Hirundinidae. It is the largest swallow in North America. Despite its name, the purple martin is not truly purple. The dark blackish-blue feathers have an iridescent sheen caused by the diffraction of incident light giving them a bright blue to navy blue or deep purple appearance. In some light, they may even appear green in color.