Vermivora pinus

Geographic Range

Blue-winged warblers ( Vermivora pinus ) are native to North America and migrate seasonally between North and South America. During their breeding season, they can be seen in the Midwest, as well as the northeastern and southeastern United States; specifically, as far west as Nebraska and as far south as northern Georgia and northern Alabama. More recently, their geographic range has expanded further north, to southern Maine, as environmental impacts have limited suitable forests. During winter, this species migrates south, where they can be found in Mexico, throughout Central America (but sparingly in Panama), and northern Colombia. While the wintering range of blue-winged warblers seems vast, they are mainly concentrated in a 900 x 500 km range, located between Honduras and the Yucatán Peninsula. The North American range of blue-winged warblers has been steadily expanding northward, with expansion rates estimated between 3 to 6 km per year. Populations reached Ohio in the early 1900s and became well established there, and in Michigan by the 1920s. The species was established in New York between 1950 to 1971. Hitch and Leburg (2007) reported their mean latitudinal shift northward over 26 years to be 85.34 km +/- 18.55 km.

• Biogeographic Regions
• nearctic nearctic
  • native native
• neotropical neotropical
  • native native

Habitat

Blue-winged warblers live in wetlands, shrublands, and early successional forest communities. Generally, blue-winged warblers nest at lower elevations on the edges of successional areas. Breeding grounds tend to be clearings, fields, and stream edges that have undergrowth consisting of forbs, weeds, and brush. In the mid-Atlantic region, they populate low elevations of the Appalachian Mountains (less than 609.6 m). They make use of similar ecological areas during the winter, occupying low elevation areas of foothills, overgrown fields, and mixed forests.

• Habitat Regions
• temperate temperate
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest
• scrub forest scrub forest
• mountains mountains

• Aquatic Biomes
• rivers and streams

Physical Description

Male and female blue-winged warblers exhibit similar coloration patterns, though females tend to be drabber. Their forehead, crown, chin, throat, breast, flanks and belly have a bright yellow coloration that does not change seasonally. Their wing coverts are blue-grey with broad white bars on both the tail and flight feathers. In females, these white bars tend to be thinner. Bill coloration changes seasonally for males: black in spring and summer, and pinkish to light brown in the fall and winter. Blue-winged warblers are recognizable by a black stripe through their eye and white wing bars. Towards the end of the breeding season, typically late June to early August, adults molt. As adults, blue-winged warblers weigh between 7.9 to 10.5 g, with an average of 9.2 g, and they measure 11.4 to 12.7 cm in length, with an average of 12.0 cm. Their wingspan has been reported as 17.15 cm.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes colored or patterned differently
• male more colorful

Reproduction

Pair bonds begin to form within a week of arrival at the breeding grounds. This process involves the male chasing a female, who may or may not choose to mate with him. When she chooses a mate, pair bond formation is initiated by her responding to his chase with “tzip” calls. Bonded pairs may peck at each other or participate in bill dueling. Pairs are monogamous, though extra pair copulations occur within other songbird species and are likely for blue-winged warbler pairs as well. During the egg-laying stage, females solicit to males by extending their neck, raising their tail and fluttering their wings.

• Mating System
• monogamous monogamous

On average, blue-winged warblers arrive at their breeding grounds the first week of May, although their arrival has been significantly altered by a shift towards warmer temperatures in the breeding ground ranges. For long-distance migratory birds, arrival at the breeding grounds averaged 1 day earlier for every 1° C increase in spring temperature. In New York, the mean first arrival date for blue-winged warblers between 1903 to 1950 was May 16, while between 1951 to 1993, it was May 5. Blue-winged warblers in this region arrived an average of 6.9 days sooner in 1993 than they did in 1903, similar to Boston, where they arrived an average of 6.6 days sooner.

After a pair bond forms, nest building begins immediately and is completed almost entirely by the female. A breeding season consists of nest building, egg laying, incubation and nestling stages. Females use thick grass to form a deep, cup-shaped nest that is supported by dead leaves and typically finished within 2 to 4 days. Nests sit close to the ground and their nest material is predominantly vegetation found close to the nesting site, allowing the nest to blend in well with the surroundings. Females have been observed making up to 40 trips per hour bringing nesting material back and forth. Upon completion, nests measure 8.7 to 14.5 cm wide and 7.2 to 12.7 cm deep, with an inner depth of 3.3 to 6.2 cm. After female solicitation and copulation, egg laying begins. Eggs are, on average, 15.66 mm long and 12.33 mm wide and speckled with grey or brown spots against their white color. The female lays 1 egg per day for 3 to 5 days. The incubation period begins immediately after egg laying is completed and lasts 10 to 12 days. During this stage, the female spends a substantial amount of time sitting on the eggs, keeping them warm and leaving only when she needs to feed. Upon hatching, nestlings weigh, on average, 1.5 g. The nestling stage lasts 8 to 10 days, until nestlings fledge. During the nestling stage, both the male and female spend an increased amount of time foraging, and bring food to the nest to sustain nestlings. To feed, the male or female perches on the nest and drops food into the open mouth of a nestling. After fledging, the female and male continue to bring food to the young, who tend to stay within 100 m of the nest for 2 to 5 days. It is unknown how long fledglings remain dependent on parents for food after leaving their home territory. Blue-winged warblers have only been observed with one clutch per season, which typically fledges in late May or early June. Blue-winged warblers occasionally breed with golden-winged warblers in hybrid zones of North America. The resulting offspring are hybrids known as Brewster’s warblers, which may further interbreed with other hybrids, giving rise to Lawrence’s warblers. Hybrid Brewster’s and Lawrence’s warblers are able to produce viable offspring with each other, but most often breed with a parental type, blue-winged or golden-winged warblers.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• oviparous oviparous

During the nest construction process, females are likely to abandon a partial nest if disturbed by predators or intruders. During the incubation period, females infrequently leave the nest, and have been observed allowing people to touch them before flying away and abandoning the eggs momentarily. During the nestling stage, both parents spend time provisioning and keeping the nest clean by removing fecal pellets, which they pick up and carry out of the nest with their beaks. Feeding has been observed at 4 to 6 trips per hour when nestlings hatch, increasing to 12 trips per hour when nestlings are close to fledging age.

• Parental Investment
• altricial altricial
• male parental care male parental care
• female parental care female parental care
• pre-independence
  • provisioning
    • male
    • female
• post-independence association with parents

Lifespan/Longevity

There have been relatively few studies on longevity for blue-winged warblers. Available data are limited to wild banded birds that have been recaptured. There are reports of blue-winged warblers being recaptured at 7 and 9 years of age, though living to these ages in the wild is uncommon. On average, blue-winged warblers live 2.5 years in the wild. Because this species is not kept in captivity, captive lifespans are unknown.

Behavior

Blue-winged warblers interact variably with conspecifics depending on the time of year, sex, and type of encounter. During the breeding season, they are aggressive towards intruders of their established mating ground. When an intruder of the same or different species enters their territory, they respond with displays of tail-spreading and crown-raising. Physical acts of aggression include chasing, flying past, and physically fighting the intruder. Encounters like these may last seconds or several minutes, depending on the persistence of the intruder. Aggressive encounters are most common with conspecifics during the first week of arrival at breeding grounds, when males are vying for a mate and territory. During the winter, because males are not in close proximity to each other, chasing behavior has not been observed. Blue-winged warblers move on the ground by hopping, though spend only brief moments there, normally while foraging. They perch on branches near their nest during the breeding season, and occasionally hang upside down as they explore new areas. Both sexes preen, which occupies 2 to 5% of their time. During the winter, most wood warblers, like blue-winged warblers, live in small groups and sometimes separate into sex-specific groups.

• Key Behaviors
• arboreal arboreal
• flies
• diurnal diurnal
• motile motile
• migratory migratory
• territorial territorial

Home Range

Depending on species density at a particular breeding ground, territory may range from 0.13 to 2 ha. During the breeding season, neither the male or female stray far from their territory, they usually remain within 100 m of the nest.

Communication and Perception

Blue-winged warblers sing two distinct songs that are described as sounding more insect-like than bird-like. Type I songs are sung by males, most often during the first few weeks of the breeding season when they are not paired. It is a simple “bee-bzzz,” and lasts approximately 1.1 to 1.9 seconds. Type II songs are used throughout the breeding season, though more common during egg-laying and incubation phases. This song is highly variable in notes, length, and frequency. Different dialects of the second song exist across geographical regions. Males use the type II song most frequently when interacting with other males, often as a sign of territoriality. Type II songs last approximately 1.04 to 1.97 seconds and are not unique to blue-winged warblers. Golden-winged warblers and hybrids sing nearly identical versions. Female and male call notes are blunt and described as “tzip” or “tsik”.

• Communication Channels
• visual visual
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Blue-winged warblers forage for small insects and vegetation in their surrounding habitat. Their beak is longer than other wood warblers, which allows them to search through and open clusters of leaves to better find the food that could be inside. During the incubation period, females spend 18.6% of their time foraging, compared to males, who forage with 33 to 38% of their time. This is because females are incubating the eggs and are unable to forage for themselves. Because of this, males bring their mates food during the incubation period, so they do not have to leave the nest. After nestlings have hatched, parents spend 73 to 77% of the day foraging.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore
  • eats non-insect arthropods
  • vermivore
• herbivore herbivore
  • frugivore frugivore
  • granivore granivore

• Animal Foods
• insects
• terrestrial worms

• Plant Foods
• seeds, grains, and nuts

Predation

Egg and nestling predation is common, as nests are fairly accessible from the ground. Small animals such as chipmunks , raccoons , opossums , water snakes and black snakes (likely Elaphe obsoleta , also known as Pantherophis alleghaniensis ) are frequently seen removing eggs or nestlings from the nest. Larger birds such as blue jays , American crows and hawks are more common predators of adult blue-winged warblers, though small mammals may also prey upon adults.

Ecosystem Roles

As with many avian species, nestlings are prone to ectoparasite attack. Larvae of avian blowflies , chigger mites , and fowl mites attach and feed from young while they are confined to the nest and unable to escape, though this does not often directly result in the death of nestlings. Instead, blood loss from blowfly predation leaves nestlings immunodeficient and nutrient poor. Together, this can result in a longer time to fledging and more susceptibility to additional disease and predation. Blue-winged warblers participate in "anting," where they "bathe" in ant nests or place ants under their feathers. Some ant species secrete a liquid that contains formic acid, which subsequently covers the bird and may act as an insecticide against ectoparasites that attach and feed on blood from the bird. The relationship between blue-winged warblers and the ants is suggestive of a mutualistic relationship, though no resources have clearly stated this. Brown-headed cowbirds are brood parasites that lay eggs in the nests of other species, is a common parasite of blue-winged warblers. This parasitism results in prolonged nestling periods and reduced reproductive success, as blue-winged warblers feed the brown-headed cowbird nestlings in conjunction with their own. Brown-headed cowbird nestlings also tend to be larger than blue-winged warbler nestlings, and outcompete them for food. Adaptations to these parasites have been less studied in blue-winged warblers.

Economic Importance for Humans: Positive

Blue-winged warblers are tolerant of human activity near their nesting sites, which makes them an easily spotted species for avid bird watchers, a significant source of ecotourism. Some cities host bird watching festivals, a tourist attraction that can bring in revenue and interest for future visits. Throughout the United States in 2006, birders were estimated to make a total economic impact of $82.2 billion, spending $23.7 billion on equipment alone. For example, in Louisiana, 197,000 bird watchers traveled to the state in 2006, illustrating the strong economic impact this industry can have.

• Positive Impacts
• ecotourism ecotourism

Economic Importance for Humans: Negative

There are no negative effects of blue-winged warblers on humans.

Conservation Status

Blue-winged warblers are listed as a species of least concern by the IUCN Red List and do not have special status on US government lists. While their population is reportedly declining, it is not at a rate that would qualify the species as vulnerable. Although it is not a major cause for concern currently, significant decreases in habitat range due to human population expansion may have negative impacts on blue-winged warblers in the future. The recent geographic shift northwards has caused blue-winged warbler territories to overlap with the territories of the related golden-winged warbler , creating hybrid zones occupied by the hybrid Brewster's and Lawrence's warblers. As the prevalence of hybrid zones increase, it has been speculated that blue-winged warblers may rapidly replace golden-winged warblers within 4 to 50 years.

Other Comments

The scientific name for blue-winged warblers was changed in 2010 by the American Ornithologists Union, from Vermivora pinus to Vermivora cyanoptera . The name change was brought about because “pinus” more accurately applies to pine warblers, Setophaga pinus , previously classified as Dendroica pinus .

Additional Links

Encyclopedia of Life

BioKIDS Critter Catalog

Contributors

Fionna Surette (author), Radford University, Karen Powers (editor), Radford University, Leila Siciliano Martina (editor), Texas State University.

References

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