Blackpoll warblers’ breeding range extends from the southern two-thirds of Alaska, eastward through nearly the entirety of Canada to the central Hudson Bay. Their range continues eastward to the Atlantic coast of Canada, as far north as the Torngat Mountains National Park Reserve. They breed as far south as Quebec, Montreal, and northern Maine (United States). They have disjunct breeding populations in central New York State and in Vermont along the Green Mountains. They do not breed in the southern half of western Canada.
Blackpoll warblers migrate south across the eastern United States and through the Caribbean. When migrating through the Caribbean, they may over-winter in Costa Rica. These warblers spend the winter in South America, primarily in the Amazon basin of Brazil, to the east of Peru. Their range extends to Columbia, Venezuela, Guyana, and east Ecuador. Blackpoll warblers have the longest migratory path of any New World land bird and the southernmost wintering habitat of any North American warbler. Small quantities were detected as far south as 40 degrees south in Chile and Argentina. A few of these warblers were recorded wintering in Panama, Costa Rica, and Trinidad and Tobago. (Davis, 2001; DeLuca, et al., 2020; Dunn and Garrett, 1997; Weber, 2000)
Blackpoll warblers breed in cool, wet forests of low conifers. Their breeding range includes habitats such as boreal wetlands, black spruce (Picea mariana), fir (Abies), and red spruce (Picea rubens). They’re also found in high-moisture shrubby habitats. Their range extends in the overlap zone of taiga and tundra, and far into northeastern North America in thickets on mountain peaks. These warblers range between sub-montane and subalpine habitats, where they typically nest in red spruce, coastal white spruce (Picea glauca), balsam fir (Abies balsamea), and mountain ash (Sorbus americana). These spruce bogs, conifer swamps, and groves in which they breed are at elevations of 700m-760m; these warblers rarely breed at elevations below 460m.
During migration, blackpoll warblers use deciduous and coniferous wooded habitats. They have a wide variety of habitats, ranging broadly in spruce and tamarack (Larix laricina) regions. These regions include wet thickets, oak-hickory forests, dry forests, and mangrove forests. They’re also found in any vegetated habitats and are more common in alpine habitats. Throughout their migratory routes, blackpoll warblers typically reach a maximum elevation of 3,000m. These warblers utilize cloud forests, edges of lowland forests, and deciduous forests in wooded habitats during the winter. They’re also found in mangroves, cloud forests, rain forests, and coffee plantations.
Blackpoll warblers roost in compact, cup-shaped nests on spruce and other tree branches, and occasionally on the ground. Their nests are usually located near the trunk of the tree ranging between 1.0 to 10.7m above ground. These concealed nests are made from grapevine (Vitis), bark strips, weed stems, twigs, pine needles (Pinus), and bristles lined with materials such as feathers they find, hair, and plant fibers. (Baicich and Harrison, 2005; DeLuca, et al., 2020; Dunn and Garrett, 1997; Headstrom, 1970; Smetzer, et al., 2017; Weber, 2000)
Blackpoll warblers are approximately 14cm in length and body masses are 7.8 to 22.1g. Their wingspan is 18 to 26mm. These warblers are endothermic and have bilateral symmetry.
There is little information about sexual dimorphism in size for blackpoll warblers. However, their sexual dimorphism in plumage is well known. Adult males in the spring have an olive-gray back, with black streaks over the nape, forehead, and lores. Their white cheeks feature a black malar stripe and they have a black crown. Their belly, breast, and throat are white, while the flanks have prominent black streaks. These warblers have two bold white wing bars and olive-gray upper tail coverts with black stripes. Adult females in the spring may have variable plumage, but they are mostly olive-gray. Females lack a malar stripe and black cap like the males. Their dorsal side has dark stripes, and the crown may have streaks as well. They are white with a yellow wash and have some streaks on their belly and breast. They possess a grayish-white eye-ring, and their cheeks have black striping. They have faintly-streaked flanks, while upper tail coverts are less prominently streaked. Adults of both sexes in the fall are drab, like females in the spring.
Immatures have a brownish olive nape, back, and rump. These warblers have a grayish-white belly, throat, and breast speckled with blackish brown, similar to fall adults. However, their flanks are less streaked. As immatures, sexes look similar; females may be duller and males may be whiter. Both sexes have dark brown eyes. First feathers appear on the wings of blackpoll warblers three days after hatching. Within 6 to 7 days, body feathers are apparent.
Blackpoll warblers look similar to black-and-white warblers (Mniotilta varia), but the latter lack the black crown and white cheeks described above. Bay-breasted warblers (Dendroica castanea) are similar, as well - but bay-breasted warblers have brown patterns on their flanks and, their facial plumage lacks the eyeline, and primary feathers lack the white tips that blackpoll warblers possess. Further, blackpoll warbler bills are slightly thinner than those of bay-breasted warblers and pine warblers (Dendroica pinus), about 9 to 11mm in length. (Alderfer, 2006; DeLuca, et al., 2020; Dunn and Garrett, 1997)
Blackpoll warblers are primarily monogamous, though males have been known to be polygynous on rare occasions when these warblers have greater fitness. These warblers may arrive on breeding grounds as early as May until June. Males arrive on breeding grounds first to select their territories, and they sing a high-pitched song once territories are identified. These warblers are territorial and may interact with other males, attacking and striking each other with their beaks. Yearling males arrive days later than older males due to their lack of experience competing for territory. They arrive shortly after the older male has shifted his focus from territorial defense to mating. Females arrive over a longer period and may be seen 2 to 3 days after males.
Breeding takes place in cool, wet forests in low conifers or mixed woodlands generally 1.0 to 10.7m above ground, or occasionally on the ground. Females are cryptic and choose the nest site in males' territories, and after finding a location, these warblers flutter their wings. Females may build the nest with overhanging foliage, lichens, fibers, small twigs, and feathers they find. Males do not help build nests. However, they assist by feeding their mates and singing nearby. Shortly after nests are built, mating occurs. (Baicich and Harrison, 2005; DeLuca, et al., 2020; Eliason, 1986; Hauber, 2014; Pough, 1953)
Blackpoll warblers breed seasonally from mid-May to mid-June, and females may have second broods in a single season in July. Female clutch sizes range from 3 to 7 eggs, most often in the range of 3 to 5 eggs. The eggs are oval-shaped, white, pale to grayish-yellow, or greenish. They are speckled with brown spots or blotched with brown markings typically at the blunt end of the eggs. The eggs are smooth and slightly glossy, measuring about 18mm in length and 13mm in width. Females incubate the eggs for 11 to 12 days while males provide food for the offspring and sing nearby. Close to the end of brooding, females often stand over eggs and poke them with their beaks, sometimes eating eggshell fragments to quicken hatching.
Hatchlings have an average weight of 1.5 grams. During the nestling period, they are fed by both parents. Their eyes open between 4 to 5 days, and feathers are visible in 5 to 8 days. Hatchlings typically fledge in 8 to 11 days, and fledglings are independent at approximately 35 days post-hatching. Both sexes reach sexual maturity at approximately 1 year old. (Baicich and Harrison, 2005; Baughman, 2003; DeLuca, et al., 2020; Hauber, 2014)
Hatchlings are altricial and are fed by both parents after hatching. Males frequently sing nearby, just as they do during incubation to alert mates and other birds. Females will depart from the nest while males are nearby to watch. Males will sometimes guard their mates while the female forages and will return to the nest briefly after the female returns. The nest is protected by both parents; females will chase away other birds that approach the nest by making a loud chip. The male mainly protects the territory by approaching other males with alarm calls and beak snapping.
Even after fledging, baby birds will remain close to their parents until the time for independence at approximately 35 days. Some females begin their second brood soon after the first brood fledges. Males tend to the fledglings while females begin building a second nest. Males that are polygynous at times focus more on one nest than the other to maximize their fitness. Hauber (2014) reported in some cases, males feed nestlings equally at one nest but only feed approximately 20% at the second nest. (Baicich and Harrison, 2005; DeLuca, et al., 2020; Eliason, 1986; Hauber, 2014)
Little information is known about the lifespan of blackpoll warblers. However, the oldest-recorded bird was at least 8.1 years old when it was released alive. Predation is common for eggs and nestlings. As of spring and fall migration, respectively, blackpoll warblers ranked 8th and 9th most commonly-killed migrant. These birds are not kept in captivity. (USGS, 2021)
Blackpoll warblers are a migratory species that migrate at night, but during longer flights, migration also occurs during the day. During migration, they will join mixed flocks of species to avoid predation from larger birds and to maximize feeding success. They forage faster during spring migration due to less resource availability in the fall.
Throughout the spring in May, male warblers sing to attract mates and defend territories. Males are territorial and may sing while drooping their wings to warn each other. They aggressively fly towards one another while attacking and chasing other males from territories. This often leads to physical contact in the air and involves striking with their beaks. Females will also chase other birds to protect the nest and when the female is not incubating the eggs, she is foraging. During the spring, these warblers forage mainly on the ground. They tend to feed in the middle and upper layers of conifers, and males will spend much of their time singing in treetops to let their mates know they’re nearby and to alert other males. While molting, they typically preen and scratch their heads using their legs. These warblers are diurnal and may jump, hop, and fly throughout their territories. (DeLuca, et al., 2020; Dunn and Garrett, 1997)
Home ranges are 0.2 to 1.85 hectares during the breeding season and may decrease with increasing elevations. They defend the nest during breeding season, but this territory size has not been quantified. (DeLuca, et al., 2020)
Like most warblers, only male blackpoll warblers sing. Females, on the other hand, use a variety of vocalizations to communicate, including brief and rapid chips. Coughing is a sound made by both males and females. These warblers are visual and see in color.
Male songs are short series of 12 or more single or double high-pitched notes. Their song steadily builds in loudness until it repeats a "tsit tsit tsit" (Alderfer, 2006) sound, then it fades to the end. Blackpoll warblers sing at a rate of 5 to 12 notes per second, with an average frequency of 8,050 to 10,225 Hz. These warblers also have a second form of song that is faster and has fewer pauses between notes. Their call is a sharp chip and a loud squeaking sound, while their flight call is a loud, sharp, buzzy "zeet" (Dunn & Garrett, 1997). Only used during migration, blackpoll warblers’ flight calls consist of 3 to 5 undulations of sound with a frequency range of 1 to 8 kHz and a length of 80 to 100 milliseconds. These warblers sing frequently in the spring, but less commonly in the fall. Males sing primarily during the day. They also sing from the tops of conifers on breeding territory, as well as from mid-canopy while foraging. Bill snaps, which are commonly audible between interactions, are also employed as non-verbal messages.
Like all birds, blackpoll warblers communicate with tactile efforts, using this sense for mating, feeding and protecting young, and for foraging. (Alderfer, 2006; DeLuca, et al., 2020; Dunn and Garrett, 1997; Eliason, 1986; Pough, 1953)
Blackpoll warblers eat almost entirely insects and non-insect invertebrates, with some fruit consumed during fall migration. Invertebrates consumed include lice (order Phthiraptera), migrating locusts (Locusta migratoria), cankerworms (Alsophila pometaria), caterpillars (order Lepidoptera), webworms (Hyphantria cunea), ants (family Formicidae), termites (order Isoptera), gnats (order Diptera), and spiders (order Araneae). These warblers also eat fruits of honeysuckle (Lonicera), yew (Taxus), and pokeberry (Phytolacca decandra). During the breeding season, these warblers forage mainly in conifers, on inner portions of the limbs. They also forage on dead or deciduous trees, where foraging is focused on the outer portions of limbs. Blackpoll warblers forage at mid-canopy in conifers up to 10m tall.
During migration, they are not constrained to certain tree heights or foraging locales. In winter months, these warblers primarily foraged in the mid-to-upper canopies of taller trees. Most prey is found on leaves and twigs, but individuals can sometimes capture items by hawking and hovering. In fall migration, they concentrated on caterpillars that were inside needles and closed buds. There are no dietary differences between males, females, or juveniles.
Weber (2000) documented 121 male blackpoll warblers feeding on 382 prey items. These items included caterpillars (56.5%), adult dipterans (36.6%), adult moths (6.5%), and arachnids (0.3%). Prey with a length of 0-5mm had an average handling time of 1.0 sec, while prey with a length of 16-20mm had an average handling time of > 10.0 sec. Given this holding discrepancy, larger prey had a higher chance of escaping. (DeLuca, et al., 2020; Eliason, 1986; Weber, 2000)
Little information is known about predators of blackpoll warblers. However, sharp-shinned hawks (Accipiter striatus) and cattle egrets (Bubulcus ibis) are predators of adult blackpoll warblers and nests. There are a variety of eggs and nestling predators such as blue jays (Cyanocitta cristata) and gray jays (Perisoreus canadensis). Small rodents (order Rodentia) are also suggested to be predators of eggs and nestlings.
Humans benefit economically from the ecotourism of Neotropical migratory birds. In the United States, tens of millions of birders spend at least $20 billion per year on observations, equipment, traveling, and seeding. The average yearly spending of birders is between $1,500 and $3,400. ("Birding economics and birder demographics studies conservation tools", 1993)
Blackpoll warblers have no reported negative economic impacts on humans.
Blackpoll warblers are listed as “Near Threatened” on the IUCN Red List. This species is protected under the US Migratory Bird Act. However, they have no special status on the US Federal List, CITES appendices, or the State of Michigan List.
Forest loss and degradation are unlikely threats in the non-breeding range. In the breeding range, these warblers breed in remote areas. Logging is an uncommon threat. However, these warblers are thought to be most affected by climate change in the breeding range. As other species shift northwards with a warming climate, they compete more often with blackpoll warblers. As result, this transforms lower-elevational limits of spruce-fir forests (Picea, Abies) into population sinks. Mortality also is due to birds colliding with towers, lighthouses, wind energy facilities, and other large structures during migration.
Despite their listing on the IUCN Red List, blackpoll warblers have few conservation efforts because their populations are considered fairly stable. If there are regions that are in decline, researchers should study these warblers to determine why they are in decline. Because they are protected under the US Migratory Bird Act, they are prohibited from being captured, killed, transported, sold, or traded unless authorized by the U.S. Fish and Wildlife Service. (DeLuca, et al., 2020)
Ty'Nasia Hairston (author), Radford University, Sierra Felty (editor), Radford University, Bianca Plowman (editor), Radford University, Karen Powers (editor), Radford University, Victoria Raulerson (editor), Radford University, Christopher Wozniak (editor), Radford University, Genevieve Barnett (editor), Colorado State University.
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.
a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.
an animal that mainly eats meat
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
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.
parental care is carried out by females
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.
the area in which the animal is naturally found, the region in which it is endemic.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
having more than one female as a mate at one time
specialized for leaping or bounding locomotion; jumps or hops.
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
Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short.
uses sight to communicate
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