American redstarts are smaller warblers measuring 13.3 cm in length and weighing 8.3 g. Adult males have mostly black upperparts with bold patches of orange. The sides of breast, bases of wing feathers, and bases of the outer tail feathers feature large patches of bright orange. The belly and undertail coverts are white. Adult females feature the same pattern, but have mostly gray upperparts with patches of bright yellow or orange in older females. They have olive-colored backs and the wings and tail feathers are a darker gray than the head. Throat, belly, and undertail coverts are pale gray to white. First year males closely resemble females and will obtain adult male plumage after the first breeding season. Females and young males may also feature a slight white eye-ring and pale stripe running above the eye and to the bill. All sexes and ages have black legs, feet and bills. The short bill is very similar to insect-eating flycatchers in being relatively flat and surrounded by tiny bristles. ("National Geographic Complete Birds of North America", 2006; Sherry and Holmes, 1997; Sibley, 2000)
American redstarts are Neotropical migrant warblers that spend portions of the year in North, Central, and South America. During the spring and summer, American redstarts breed across much of Canada and the United States. They inhabit the southern regions of Canada from the east to west coast. In the United States, American redstarts may be found in limited regions of the northern Midwest, and most states east of the Mississippi River. Exclusions include portions of Kentucky, Tennessee, Florida, Georgia, and North and South Carolina. This species migrates twice a year across much of the United States and Central America to and from their wintering grounds in southern Central and northwestern South America. American redstarts also overwinter on many Caribbean islands, including Jamaica and Cuba. (Sherry and Holmes, 1997)
American redstarts select different habitats depending on the season and geographic location. During the breeding season, these warblers inhabit open-canopy, deciduous forests, second growth, and forest edge across much of the United States and southern Canada. This insectivorous (insect-eating) bird shares its foraging habitats with other warblers, and is often found feeding in the mid to lower regions of a tree or shrub. American redstarts prefer to build nests well within dense shrubs or the fork of a low tree, and males will select territories that contain several of these potential nest sites.
During migration, American redstarts stop to rest in dense shrubby habitats where food is abundant. On their wintering grounds in Central and South America, these warblers may be found in nearly all woody habitats but tend to avoid non-forested agricultural areas. They are often found in shade-grown coffee plantations which provide native trees and shrubs, as well as coffee trees. Elevations occupied vary by location, as this species may be found at elevations up to 3,000 m in South America, but only up to 1,500 m in Jamaica. During the non-breeding season, American redstarts are influenced by strong dominance hierarchies that result in males and females being found in different habitats. Older males occupy preferred, resource-abundant habitats (mangroves). Females are restricted to lower quality habitats (scrub), which results in greater mass loss and lower survivorship rates during the non-breeding season. (Ehrlich, et al., 1988; Marra and Holmes, 2001; Sherry and Holmes, 1997)
American redstarts are monogamous, meaning one male and one female pair up each year to breed and raise their young. Courtship often involves males showing interest in and displaying to females. Nest sites are selected by females, and males will closely follow females during this period. Males give two main types of displays during nest-building: fluff displays and bow displays. Fluff displays involve raising the feathers on the head and back, while feathers are sleek for bow displays and the male will lower his body to the ground while keeping his head vertical and tail spread. (Ehrlich, et al., 1988; Ficken, 1963; Sherry and Holmes, 1997)
American redstarts are Neotropical migrants that travel to North America to breed in the spring. Courtship and pair-formation begins within a week of the arrival of females, which occurs from mid to late May. After a pair has formed, the female selects the nest site which is typically up against a tree trunk, hidden in dense vegetation. The cup-shaped nest consists of tightly-woven, fine materials such as grass, feathers, roots, birch bark, or animal hair. Once the nest is complete, the female lays between 2 and 5 white or cream-colored eggs which are speckled with varying amounts of brown. The clutch is incubated by the female for 10 to 13 days. The young fledge after 9 days in the nest and may remain with one parent for up to 3 weeks after fledging. (Ehrlich, et al., 1988; Sherry and Holmes, 1997)
Male American redstarts actively defend their territories, mates, and young. Females select a suitable nesting site and construct the entire nest alone. Once eggs are laid, females also perform all incubation for an average of 12 days. The young are altricial at birth, meaning they are featherless, immobile, and have eyes closed. The helpless chicks require lots of parental care to stay warm and properly fed. The chicks are brooded by the female alone, as she has a patch of bare, featherless skin on her belly that allows her to share her body heat with the young. This bare patch of skin is called a "brood patch". Male American redstarts do not have brood patches and do not incubate eggs or young. Both parents participate equally in feeding the young, and each mate makes between 4 and 13 feeding trips per hour. Both parents also remove fecal sacs from the nest to reduce predation and keep nests clean. After the young fledge at 9 days of age, each parent typically cares for certain offspring only. The two parents often separate with their respective young, although the male typically stays near the nest site with his brood. (Ehrlich, et al., 1988; Sherry and Holmes, 1997)
The oldest American redstart was a male that was at least 10 years old. Many females live to be at least 5. Annual survival rates are estimated to be between 50 and 60%. Females may suffer a slightly higher mortality rate as they spend significantly more time on the nest and are often consumed by nest predators. (Sherry and Holmes, 1997)
American redstarts are Neotropical warblers that travel between Central or South America and the United States or Canada each year. American redstarts are known for their distinctive foraging behavior of flicking their brightly colored tails to stir up insects from foliage. These warblers perform long migrations at night but are usually diurnal. They are highly territorial and will vigorously defend territory during the breeding and even non-breeding seasons. Because of their highly territorial nature, more than 2 American redstarts are rarely seen together. However, during migration one or two will travel together with multi-species groups. (Marra and Holmes, 2001; Sherry and Holmes, 1997)
American redstarts typically defend a breeding territory of less than 1 hectare. Size may vary with habitat quality, population density, and age of defending male. (Sherry and Holmes, 1997)
American redstarts primarily use vocal and visual forms of communication. Males give distinctive songs which are used to defend territory or attract mates. Songs of this species are generally rapid and high pitched. American redstarts use these different song types to communicate in different situations. Like many birds, a significant amount of song variation is due to local dialects. Males of this species can quickly learn the songs of neighboring rivals and incorporate them into their own songs, leading to unique neighborhood dialects.
American redstarts also use body postures and movements as communication. During courtship, males often chase potential mates in a somewhat aggressive manner and interested females will respond by flying a short distance, then giving a tail-spreading display. Males often give two types of displays towards females: fluff displays and bows. Fluff displays consist of fluffing the body feathers, particularly the bright orange flanks. Bow displays are typically given later in courtship, when a male sleeks his feathers, lowers his breast to the ground, and holds his head vertically.
This species is highly territorial year-round and employs song, body postures, and aerial attacks to deter intruders. As discussed above, males often advertise territory boundaries through singing, but females also give a variety of chips and short notes towards intruders. Both males and females assume threatening body postures including head-forward displays with drooping wings and bill agape, and tail-spreading displays with tail held near vertically. Males also give a wings-out display where they raise and spread their wings, likely to display the orange wing patches. Males also make distinctive circling flights during territorial disputes. Two neighboring males (occasionally females) will alternate short, deliberate, circling flights in pursuit of each other.
American redstarts are nearly exclusively insectivorous, but will occasionally consume berries or seeds during the fall when there are fewer insects. American redstarts flick their brightly-patterned tail to flush insects from leaves. They prefer to forage from twigs and branches versus tree trunks or limbs. Overall, these warbler are flexible feeders that can easily adapt to varying habitats, seasons, insect communities, vegetation structures, and time of day. Diet consists largely of caterpillars, moths, flies, leafhoppers and planthoppers, small wasps, beetles, aphids, stoneflies, and spiders. Few berries and seeds are consumed, but are most often from barberry, serviceberry, and magnolia trees. Currently, how these birds obtain water is unknown but they may get most of their water from the juicy insects they consume, dew drops, or small bodies of water. (Ehrlich, et al., 1988; Sherry and Holmes, 1997)
American redstarts are vulnerable to both terrestrial and aerial predators. Highest rates of predation occur during the breeding season when eggs and helpless nestlings are abundant and easy prey for terrestrial predators. Females sit on the nest during this period and may also fall prey to nest predators. Common terrestrial predators include red squirrels, fishers, eastern chipmunks, black bears, flying squirrels, fox snakes, and domestic cats. Aerial predators take nestlings, eggs, or even adults in flight. Possible aerial predators include jaegers, blue jays, common ravens, northern saw-whet owls, common grackles, northern goshawks, and sharp-shinned hawks, and Cooper's hawks. (McCallum and Hannon, 2001; Sherry and Holmes, 1997)
As insectivores, American redstarts consume significant amounts of insects and likely have an impact on local insect communities. This species also consumes small amounts of fruits and seeds during the fall which may contribute to seed dispersal. Eggs, nestlings and adults are consumed by a wide variety of predators. Like many birds, this species is host to several ectoparasites including three lice species and one tick. American redstarts are common hosts for brown-headed cowbirds and currently will accept and successfully raise cowbird chicks. Populations of American redstarts that are exposed to brown-headed cowbirds will react more aggressively to adults than populations that have encountered them less often. (Ehrlich, et al., 1988; Sherry and Holmes, 1997)
There are no known adverse effects of American redstarts on humans.
American redstarts are common visitors to shade-grown coffee plantations in Central and South America. These insectivorous warblers are attracted to the ample vegetation provided on these plantations and will consume large amounts of crop pests. This species along with other insectivores help to reduce farmer reliance on pesticides. (Sherry and Holmes, 1997)
American redstarts are listed as least concern by the International Union for Conservation of Nature and Natural Resources (IUCN) an account of its wide geographic range and relatively stable population size. Recent population data however, has shown this species to be in slight decline and numbers should be monitored closely in the future. Like many declining Neotropical migrants, this species likely suffers from habitat loss on both the wintering and breeding grounds. The main causes for habitat loss is logging for human conversion of land to urban or residential areas. This species also suffers significant fatalities from impacts with man-made structures during night migration. American redstarts are also common hosts for brown-headed cowbirds which decrease the number of young they have. In general, efforts are being made to create sustainable logging practices that support the creation of early-successional habitat. Sustainable farming practices, such as shade-grown coffee, are becoming more prevalent on Central and South American countries that strike a balance between agriculture and providing habitat for songbirds. Many local Audubon chapters are promoting "lights out" campaigns that work with businesses to turn lights off in large skyscrapers during peak migration season, which reduces migrating bird collisions and fatalities. (Sherry and Holmes, 1997)
Rachelle Sterling (author), Special Projects, Tanya Dewey (editor), University of Michigan-Ann Arbor, George Hammond (editor), Animal Diversity Web Staff, Tricia Jones (editor), University of Michigan-Ann Arbor, ADW Zookeeper (editor), University of Michigan-Ann Arbor.
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