During the non-breeding season, blue-headed vireos can be found in thickets, coastal/floodplain swamps, and dense forests. They tend to inhabit areas with elevations as low as sea level and as high as 300 m in various types of forests. They are known to build nests in evergreen trees, such as pines. Farther south in Mexico to Costa Rica, blue-headed vireos tend to inhabit arbutus (Arbutus menziesii) forests in coastal lowlands and rainforests with elevations between sea level to 2700 m. During breeding season, they have most commonly been found in mountains that consist of mixed coniferous-hardwood forests across Canada and the United States. The elevation at which blue-headed vireos have been seen in these forests has been as low as sea level and as high as 1200 m. (Baicich, 2005; Hamel, 1992; Morton and James, 2014)
Blue-headed vireos have a grayish blue plumage on their cranium and an olive-green hue on their dorsal side. Their wings and tail feathers have a gray, white, and yellow pinstripe. Their ventral side tends to be bright white with a yellowish green plumage flowing upward toward their wings. These birds also have a white supraloral line, a stripe that forms between the eye and bill on the side of the cranium and extends to the eye. Males and females look alike. While adults and juveniles differ in the appearance of their plumages, with that of juveniles being slightly duller and more brown. Morton and James (2014) report blue-headed vireos to have lengths between 126 and 148 mm, a mass between 13 and 19 g, and a wingspan between 138.4 and 155.6 mm. (Johnson, 1995; Morton and James, 2014; Ryan, 2008)
Blue-headed vireos have monogamous mating systems. One of the females mates with one the males in a population to form a bonded pair. Unmated males select multiple nesting sites and may have some nesting materials gather on one main site within their territories. Once females have found unmated males, the females quiver their wings and wait for the males to sing and quiver back, signaling acceptance. The bonded pairs proceed to the selected nesting sites where they begin building nests. The males lower their heads and proceed to display motions of nest-building until the females acknowledge them. It is currently unclearly how females display their communication of acceptance to the males. They proceed to gather materials needed for the nests, which is mostly organic material (such as bark strips, spiderwebs, insect silk, twigs, grass, and feathers). The females are protective of their potential mates at this point. They will chase off other females and males wanting to intrude. It takes about 8 days to finish the nests. Once the nests are completed, the females will start displaying signs that they are ready to copulate by quivering their wings and positioning their bodies in a horizontal position. The females does not vocalize. The males response by singing, quivering wings, and hopping towards the females until they are able to mount. The males bodies are at a-45 degree tilt and their eye-ring, lores, and sides are ruffled while the belly feathers are flattened. The males perform a kind of song and dance by swaying their bodies from side to side and arc at 90 degrees as they approach the females. The pairs usually copulate about 15 to 50 meters away from their nests. When the eggs are laid, the males and females have equal brood incubation periods during the day. The females take over the brooding at night. If intruders are heard while the males are brooding, the females will end their hunt for food early so that the males can protect the territories. When the offsprings hatch, both male and female parents keep sharing the responsibilities of caring for the nests. However, about 1 to 4 days prior to the offsprings becoming fledglings (12 to 13 days after birth), the females desert them to find other mates in different territories. This leaves the males with all the parental duties while the offsprings are in the fledging stage until they reach the independence stage. (Baicich, 2005; Morton and James, 2014; Morton, et al., 2010)
Blue-headed vireos' breeding season occurs once a year between April and August. They are iteroparous, breeding multiple times during that season and across multiple years. There are typically 4 eggs per brood (range 3-5). The males and females divide the brooding time of eggs equally during the day and the females takes over the night incubation. It takes about 13 to 15 days for the eggs to hatch. There has not been any reports regarding a particular range of mass at birth. Morton and James (2014) mentioned some weights gathered from four different nestlings, prior to fledging: 4.6 g at 3.5 days for the first individual, 8.4 g at 5.5 days for the second individual, 17 g at 8.5 days for the third individual, and 13.8 g at 12 days for the fourth individual. Young fledge about 12 to 13 days after hatching. The females desert the nest 1 to 4 days prior to finding a new mate, leaving the parental care to the males. The fledglings depend on the male parents to provide food and protection for at least 1 month. The offspring have shown sexual maturity by the next spring, at about 1 year old. (Baicich, 2005; Morton and James, 2014; Morton, et al., 2010)
Female blue-headed vireos will chase off invading females and males from their selected mates before they have copulated. After the eggs have been laid, the females and the males divide the time of incubation equally during the day but the females are solely responsible for night incubation. If an intruder is heard around the nesting territory while the males are incubating, the females will end their hunt for food early to relieve the males so they can protect the territories. The eggs hatch and the males and females still perform their parental duties until about 1 to 4 days before their offspring become fledglings and the female deserts to find a new mate. Hereafter, the males take over all the parental responsibilities of feeding and protection. The fledglings continue to rely on the male parents for about one month, until they are fully independent. (Baicich, 2005; Morton and James, 2014; Morton, et al., 2010)
The maximum lifespan to be reported for blue-headed vireos was 7.4 years in the wild. These birds are not kept in captivity. (Klimkiewicz, et al., 1983)
Blue-headed vireos are migratory birds and are solitary for the most part (hence, their scientific name,). During the non-breeding season, they migrate to habitats within the southern coastal regions of the United States, Mexico, Guatemala, Honduras, Nicaragua and Costa Rica. During the breeding season, the males select a nesting sites and establish territories and the females will nest with mated males until the point of desertion. This is the only time males stay in one place for an extended period.
This species has been seen with the most activity during the day meaning that they are diurnal. Not much has been reported with their sleeping patterns except from what has been seen by the females when brooding at night. Males are not typically visible near the nest at night.
The range of territory for blue-headed vireos during the breeding season is is about 3 hectares (30,000 square meters), although the same report states that they rarely travel more than 100m away from the nest. (Morton and James, 2014)
Blue-headed vireos have various calls and songs that they use to communicate. Both sexes use calls for reproduction, nest building, distress, contact, and alarm whereas only the males have been known to use primary song. Duration, pitch, and volume variations contribute to the differences in the calls along with pauses between certain trills and tweets.
Primary song consists of many phrases of which have been described as teeyay, tayah, taweeto, teeaytoay, toowip sounds. Each phrase is separated by pauses and usually low pitched. The males displays anywhere from 6 to 22 of these phrases at a rate of 20 to 30 per minute as reported by Morton and James (2014). Primary song is used most often when looking for females. Once mated the males use this song to display territory, contact with young, and nest construction.
When the males and females are ready to mate, the females will start displaying signs that they are ready to copulate by quivering their wings and positioning their bodies in a horizontal position. The females do not vocalize. The males response by singing, quivering wings, and hopping towards the females until they are able to mount. The males bodies are at a-45 degree tilt and their eye-ring, lores, and sides are ruffled while the belly feathers are flattened. The males perform a kind of song and dance by swaying their bodies from side to side and arc at 90 degrees as they approach the females.
If intruders are present, males and females will display alarm and scolding calls. The alarm calls consists of a meeer or ti-ti-ti-ti depending on how big the threat is. The scolding calls consists of a cha-cha-cha-cha and usually males will also display bill snaps, dives, and chases the intruders. The females will have a whinny sound in their scolding calls.
Contact calls are described as pleasant-sounding calls, by Morton and James (2014), and used after a pair bond has been formed. The males and females will use this call when nest-building. These calls consists of repeated syllables in a range of 1,500 to 4,000 Hz. Distress calls are used by nestlings to communicate to parents that they may be in danger or hungry. These calls consists of a high pitched ceeeee sound. (Morton and James, 2014)
Blue-headed vireos are insectivores throughout the year. Their diet includes a variety of insects and insect larvae that they find in trees near their nests. Specific groups include caterpillars, adult moths and butterflies, true bugs (especially stinkbugs in the fall months), and beetles. Uncommonly, they will consume bees, ants, spiders, and snails.
They have adapted over time to eating fruits in the winter months due to low insect activity on their winter grounds. Wheelwright et al. (1984) observed that the fruit of Florida toadwood, Cupania glabra, was the only fruit to be eaten by the blue-headed vireos in their study. (Hamel, 1992; Morton and James, 2014; Wheelwright, et al., 1984)
The predators of blue-headed vireos are barred owls (Strix varia), masked shrews (Sorex cinereus), American crows (Corvus brachyrhynchos), and brown-headed cowbirds (Molothrus ater). Barred owls usually attack female blue-headed vireos at night when brooding. Morton and James (2014) reported that female brown-headed cowbirds prey on unattended nestlings. Nestlings being unattended makes them easy prey because they are not strong enough to fend off predators without parents. Horvath (1965) reported one case of a few individuals of masked shrews in a blue-headed vireo nest. The nest and its contents were destroyed by the shrews. It is rare that nests are left unattended, as males and females share brooding efforts. Morton and James (2014) reported that when predators are heard or seen approaching the nest, blue-headed vireos attempt to appear bigger and more aggressive. They ruffle their feathers and make loud snapping noises with their bills. Predators are then chased about 50 meters away from the nest by a swift diving motions and bill snapping. Blue-headed vireos also make loud scolding alarm calls to communicate to their mates and nestlings there is a predator. If predators or other males intrude while males are brooding, males give an alarm call to communicate to females that there is an intruder. Females return to nests and relieve the males of brooding so they can defend their territories. Most songbirds have the ability to hear the song of another bird and determine the intruder's location. (Horvath, 1965; Morton and James, 2014; Morton, et al., 2010)
During the non-breeding season, insects may be scarce so blue-headed vireos feed on fleshy fruits. The seeds will be expelled via feces or carried in their plumage to different locations. The seeds get dropped and grow into mature plants in these new locations. In the breeding season blue-headed vireos prey on insects of various species, such as bees, ants, and grasshoppers. Blue-headed vireos also provide food for their predators. Brown-headed cowbirds are brood parasites of blue-headed vireos. Brown-headed cowbirds try to lay eggs in the nest of blue-headed vireos before vireos have a chance to lay their own. If eggs or nestlings are already present brown-headed cowbirds will rid the nest of the blue-headed vireos eggs/nestlings and will place their own eggs in the nest for the blue-headed vireos to raise. Morton and James (2014) reported sixty-five cases with nests containing brown-headed cowbirds eggs were accepted by blue-headed vireos, if no blue-headed vireos eggs were present. Two cases reported that the blue-headed vireos abandoned the nests with cowbirds eggs. Rabbit ticks (Haemaphysalis leporispalustris) and feather mites (Proctophyllodes breviquadratus) are parasites of blue-headed vireos. (Atyeo and Braasch, 1966; Goguen and Mathews, 1998; Morton and James, 2014; Peters, 1936)
Birdwatching for blue-headed vireos and other songbirds has been a source of ecotourism for Mexico. "A Bird-finding Guide to Mexico" is one bird finding guide that mentions blue-headed vireos. (Howell, 1999)
There are no known adverse effects of blue-headed vireos on humans.
Blue-headed vireos are a protected species under the US Migratory Act, which means they cannot be hunted or collected without a permit. They are listed as "Least Concern" on the IUCN Red List. There is no special status listed for blue-headed vireos on the US Federal List, CITES, or State of Michigan List.
Humans have impacted blue-headed vireos in a negative way. Blue-headed vireos are sensitive to human presence while mating and nest-building. Females abandon their nests and mates quicker in the presence of humans, but show more tolerance to humans when brooding eggs. The tall structures, such as TV towers, that humans have built in the forest have killed birds of this species in the United States and Toronto, Ontario. One case in Wisconsin had reported that three separate TV towers had collectively killed 175 blue-headed vireos in one night in September of 1963. Forest degradation due to woolly adelgids (Adelges tsugae), acid precipitation on clear cut land, and fragmentation/clear cutting has reduced the range and quantity of blue-headed vireos habitat. This species needs an extensive forest to expand their numbers. The overall loss of trees disrupts the behavior of the blue-headed vireos mating season. If the females do not have sufficient forested tracts to find new mates, they will only be able to mate with available males in the sectioned forests. This limits the amount of offspring that will be produce that season. Morton and James (2014) reported in a two year study, less than 50% individuals were able to find a mate after a group selection harvest in Virginia. Whereas, a three year study showed more than 80% mated in the unharvested area. Fortunately the forests have been able to regenerate from the presence of humans, and has not needed any management techniques so far. (BirdLife International, 2016; Frank and Lebude, 2011; Morton and James, 2014; U.S. Fish and Wildlife Service, 2016)
Kayla Hiatt (author), Radford University, Alex Atwood (editor), Radford University, Karen Powers (editor), Radford University, Joshua Turner (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the southern part of the New World. In other words, Central and South America.
uses sound to communicate
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
Referring to an animal that lives in trees; tree-climbing.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
union of egg and spermatozoan
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
An animal that eats mainly insects or spiders.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
parental care is carried out by males
makes seasonal movements between breeding and wintering grounds
Having one mate at a time.
having the capacity to move from one place to another.
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.
scrub forests develop in areas that experience dry seasons.
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
uses sight to communicate
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