Cape May warblers (Dendroica tigrina) overwinter in the Neotropical region and spend the summer breeding season in the Nearctic region. More specifically, they spend the winter in parts of Central America, including Nicaragua, Costa Rica, Panama, and the northernmost sections of Colombia and Venezuela. There are also overwintering populations throughout the Caribbean islands. In the summer, Cape May warblers occupy much of southeastern and central Canada, as far west as Alberta and southern parts of the Northwest Territories. There are also summer breeding populations in the Great Lakes region and northern New England, in the United States.
Cape May warblers migrate seasonally between overwintering and breeding areas. They have a wide migratory range that includes the eastern and Midwestern United States, as far west as the Mississippi River and parts of eastern North Dakota. (Mason, 1976; BirdLife International, 2021)
Cape May warblers spend their summer breeding months in boreal forests and other conifer-dominated forests. They spend much of their time high up in the canopy, often building nests between 9.1 and 18.3 m off the ground. Cape May warblers typically select conifers such as spruce trees (genus Picea) and balsam fir (Abies balsamea). There are no reported elevation ranges for Cape May warblers.
Outside of breeding season, Cape May warblers may be found in a variety of habitats in North and Central America. Migration and overwintering habitats include wetlands, scrublands, agricultural fields, cities, and suburban areas. They may also be found in deciduous forests, including dry forests and broadleaf forests, or mixed coniferous-deciduous forests. (Baicich and Harrison, 2005; Baltz and Latta, 2020; Latta and Faaborg, 2002; Stephenson and Whittle, 2013; "The land manager's guide to the birds of the South", 1992)
Cape May warblers are relatively small birds, with body lengths ranging from 10 to 13 cm, wingspans ranging from 20 to 22 cm, and wing chord lengths ranging from 6.3 to 7.2 cm in length. Cape May warblers have yellow breasts and bellies, with narrow stripes of dark brown or black coloration. They have yellow throats and napes, with dark brown or black crowns and eye stripes. Cape May warblers have greenish-brown mantles, yellow rumps and short tails. The coloration on their flight feathers and tail feathers is mostly black, but with yellow or white edges. Cape May warblers have pointed bills that curve downward at the end. Their tongues are thick at the base and narrow at the tip, which is forked slightly and is used to collect nectar.
Cape May warblers exhibit some sexual dimorphism; although males and females are similar in size, males are typically heavier (10.2 to 15.2 g) compared to females (10.0 to 14.2 g). Males also have brighter coloration and more conspicuous patterns than females, especially during the breeding season. Breeding males have chestnut-brown cheek patches, prominent white wing bars, and more olive coloration on their mantles. Males and females are closer in resemblance outside of breeding season. Female Cape May warblers have duller plumage overall and lack any distinctive facial markings, with only greyish cheek patches. Females also white wing bars, but they are thinner than those of males.
Cape May warblers eggs that are roughly 17 mm in length and 13mm in width. Eggs are creamy white with brown, reddish brown, or blackish splotches. Upon hatching, Cape May warblers are pink and mostly featherless with yellow beaks and orange mouths. Juvenile Cape May warblers have light grey and white plumage, and develop more coloration as they approach sexual maturity. Juvenile males have body masses of 10.5 to 14.1 g, whereas juvenile females body masses of 10.0 to 13.5 g. ("Accounts and measures for managing identified wildlife: Northern Interior Forest Region", 2004; Baicich and Harrison, 2005; Baltz and Latta, 2020; "Cape May Warbler", 2023; Lucas, 1894; Stephenson and Whittle, 2013)
Cape May warblers are monogamous and iteroparous. During the breeding season, males produce mating calls to attract females. After pair-bonding, females build nests and males remain nearby, protecting females from potential predators. Males do not assist with any of the nest-building. As females build nests, males court them by flying over the nests with rigid wings.
Cape May warblers build cup-shaped nests between 9.1 and 18.3 m off the ground, often in spruce trees (genus Picea) or balsam firs (Abies balsamea). Common nesting materials include spruce twigs, grasses, pine needles, cedar bark, or other plants. Cape May warblers line their nests with hair, fur, feathers, and rootlets. In many cases, sphagnum moss (genus Sphagnum) grows on the outside of their nests. Nests are an average of 10.4 cm in diameter and 5.3 m tall. Around one day after they finish building their nests, females fly about 3 m above it and indicate they are ready to mate by producing a call and raising their tails. The pair-bonded males then approach and initiate copulation. ("Accounts and measures for managing identified wildlife: Northern Interior Forest Region", 2004; Baicich and Harrison, 2005; Baltz and Latta, 1998; Baltz and Latta, 2020; Chamberlain, 1885; "Cape May Warbler", 2023)
Cape May warblers reproduce once each breeding season with only one mate. During the breeding season, males produce mating calls to attract females. After pair-bonding, females build nests and males remain nearby, protecting females from potential predators. Males do not assist with any of the nest-building. As females build nests, males court them by flying over the nests with rigid wings.
Cape May warblers build cup-shaped nests between 9.1 and 18.3 m off the ground, often in spruce trees or balsam firs. Common nesting materials include spruce twigs, grasses, pine needles, cedar bark, or other plants. Cape May warblers line their nests with hair, fur, feathers, and rootlets. In many cases, sphagnum moss grows on the outside of their nests. Nests are an average of 10.4 cm in diameter and 5.3 m tall. Around one day after they finish building their nests, females fly about 3 m above it and indicate they are ready to mate by producing a call and raising their tails. The pair-bonded males then approach and initiate copulation. ("Accounts and measures for managing identified wildlife: Northern Interior Forest Region", 2004; Baicich and Harrison, 2005; Baltz and Latta, 1998; Baltz and Latta, 2020; Chamberlain, 1885; "Cape May Warbler", 2023)
Cape May warblers are iteroparous and reproduce sexually. They breed seasonally in mid-to-late June, and they typically produce one brood per breeding season, although they occasionally have two broods. Fertilization occurs internally, followed by a six-day gestation period.
Cape May warblers have an average clutch size of 6 eggs, although clutches range in size from 2 to 9 eggs. Clutches are larger on average in seasons where spruce budworms (genus Choristoneura) are more abundant. Eggs are cream-colored with reddish-brown blotches. Eggs are anywhere from 1.50 to 1.84 cm long and 1.15 to 1.40 cm wide. There is no information on incubation time, birth mass, or time until fledging in Cape May warblers. However, other species in the genus Dendroica incubate their eggs for 11 to 13 days and fledge around 9 to 12 days after hatching. In Cape May warblers, both sexes reach sexual maturity at around one year of age. ("Accounts and measures for managing identified wildlife: Northern Interior Forest Region", 2004; Baicich and Harrison, 2005; Baltz and Latta, 1998; Baltz and Latta, 2020; Chamberlain, 1885; "Cape May Warbler", 2023; "Status of the Cape May warbler (Dendroica tigrina) in Alberta", 2001)
Cape May warblers exhibit significant parental investment in their offspring. Prior to fertilization, females build nests while males stay nearby to protect females and, by extension, their eggs. After females mate and lay their eggs, they incubate and protect their eggs until they hatch. Male Cape May warblers are usually absent during incubation, but males and females both care for hatchlings by providing food and protection from predators. Cape May warbler hatchlings likely leave the nest within 9 to 12 days, but remain associated with their parents after leaving the nest. Parents and their young often remain in the same area for several weeks before they migrate together and join mixed-species flocks. ("Accounts and measures for managing identified wildlife: Northern Interior Forest Region", 2004; Baltz and Latta, 1998; Baltz and Latta, 2020; "Cape May Warbler", 2023)
Studies of Cape May warbler longevity are limited to interpretations from banding records. Both sexes reach maturity at 1 year of age, though some do not make it to adulthood due to factors including predation, window collisions, and parasitism.
The maximum recorded lifespan for a wild Cape May warbler is 4 years and 3 months, based on data from a female banded in Ohio and recaptured in Quebec. (Baltz and Latta, 1998; Baltz and Latta, 2020; "Cape May Warbler", 2023; Klimkiewicz, et al., 1983; Powers, et al., 2019; Terres, 1980)
Cape May warblers are arboreal and volant. Their primary flight pattern involves rapid wingbeats, but they will hover briefly to glean insects from vegetation. Although they do not frequently glide, males will do so when competing for mates. Aside from migratory movements, Cape May warblers typically move short distances through the canopy by hopping along tree branches or making short flights between branches. Cape May warblers migrate seasonally between Central America in winter and the boreal forests of North America in summer. Cape May warblers migrate nocturnally, but otherwise they are mostly crepuscular.
Cape May warblers are social during migration, forming interspecific or intraspecific flocks of up to 30 birds. These flocks forage and travel together, although individuals - especially males - may establish short-term territories along migratory routes. When Cape May warblers are at overwintering sites, their level of sociality varies based on habitat; in some cases they are found in mixed-species flocks and in other cases they are solitary.
Male Cape May warblers are especially territorial during the breeding season, establishing territories approximately 0.4 ha in size almost immediately upon arriving to breeding areas. To show aggression, males raise their tails, crouch, and walk rapidly towards competing males. If necessary, they actively chase competing males from their territories. Cape May warblers are silent during chases, but they occasionally make physical contact with their opponents.
Cape May warblers form pair bonds throughout the breeding season. Pair-bonded females construct nests and pair-bonded males remain nearby to protect females from potential predators. Males typically stay within 14.6 m of females while they gather nesting materials. Cape May warblers are solitary during the breeding season, only interacting directly with their mate and their offspring. Females construct cup-shaped nests using twigs, stems, and grasses. They line the interior of their nests with insulating materials, such as hair, fur, feathers, and rootlets. Only females incubate eggs, but both parents contribute to feeding and guarding hatchlings. ("A Beginner's Guide to Fall Warblers", 2020; "Accounts and measures for managing identified wildlife: Northern Interior Forest Region", 2004; Baltz and Latta, 1998; Baltz and Latta, 2020; "Cape May Warbler", 2023)
At the beginning of breeding season, male Cape May warblers establish territories and begin to court females. If males are successful in finding mates, their territories serve as a nesting and foraging area. Males continue to protect their territory while females gather nest supplies and incubate eggs. Studies on Cape May warblers in Ontario reported an average territory size of 0.4 ha (range: 0.2 to 1.0 ha), whereas studies in New Hampshire and Maine reported an average of 7 ha (range: 0.2 to 1.2 ha). During migration, males sometimes establish temporary territories and keep 1.5 to 2 m apart from other males during migration. Overwintering males and females will sometimes establish territories less than 1 ha in size. ("Accounts and measures for managing identified wildlife: Northern Interior Forest Region", 2004; Baltz and Latta, 1998; Baltz and Latta, 2020; "Cape May Warbler", 2023)
Cape May warblers have tetrachromatic vision and rely mostly on visual cues when foraging or watching for predators. They also use tactile cues to catch prey, feed their young, and communicate with mates.
Cape May Warblers primarily communicate using vocalizations and body language. Males produce songs for two main reasons: to attract mates and to defend their territories. For the first two weeks after arriving in breeding areas, males select territories and sing from tall trees (average height: 10.7 m, range: 2.7 to 19.8 m). During the first two weeks, males return to the same tree every time they sing. Territorial songs consist of "tseet" notes at a constant pitch repeated 3 to 8 times. Males also produce songs consisting of multiple consecutive “tsee-tee” notes, again at a constant pitch. Cape May warbler songs closely resemble the songs of bay-breasted warblers (Dendroica castanea).
In addition to the songs that males produce, Cape May warblers of both sexes will make intraspecific calls. These calls are typically singular, high-pitched “tsip” or “chip” sounds. They make similar calls while flying, but their flight calls have a descending “tzee” component that they also make while feeding. Mating pairs frequently vocalize while in their nest or getting food. Cape May Warblers also produce "tzee” or "prspp" calls when chasing away other birds from their territories. Finally, nestlings will produce begging calls when they are hungry. ("Accounts and measures for managing identified wildlife: Northern Interior Forest Region", 2004; Baltz and Latta, 1998; Baltz and Latta, 2020; "Cape May Warbler", 2023)
Cape May warblers are omnivores that exhibit seasonal changes in diet; they mainly eat insects during the breeding season, and eat more fruit and nectar outside of breeding season. During the breeding season they mainly forage for food in the canopy near their nests and they forage closer to the ground during migration and while overwintering.
Cape May warblers rely heavily on spruce budworms (genus Choristoneura) during their breeding season. Although spruce budworms comprise the majority of their diet, Cape May warblers also eat spiders (order Araneae), moths and butterflies (order Lepidoptera), leafhoppers (family Cicadellidae), aphids (superfamily Aphidoidea), and various wasps, ants, and bees (family Hymenoptera). They are also reported to eat spider and insect eggs. Early in the breeding season, Cape May warblers often eat beetles (order Coleoptera) and caterpillars, and in the mid-breeding season they consume flies (order Diptera). A 2020 study from Maine during an outbreak of spruce budworms reported that budworms comprised 33% of Cape May warbler stomach contents and other invertebrates comprised the other 67%. During a non-outbreak season in New Hampshire, spiders made up 60% of Cape May warbler stomach contents, while leafhoppers made up 25%, and beetles made up 15%.
Outside of the breeding season, Cape May warblers eat a combination of arthropods, fruit, and nectar. Along migratory routes in North America they still primarily eat arthropods, but in overwintering habitats they eat more plant material. For example, a 2020 study from Pennsylvania reported that bees and ants were present in 57% of stomachs analyzed, flies were present in 16.7%, beetles were present in 16.7%, and true bugs (order Hemiptera) were present in 17.8%. In comparison, at overwintering grounds in Jamaica, insects were present in 71% of stomachs analyzed, while fruit was present in 17%, and nectar and tree sap collectively were present in 15%. In dry forests in the Dominican Republic, insects were present in 85% of stomachs, nectar was present in 7%, and fruits were present in 4%. Cape May warblers may also eat fruits and nectar while migrating. They are often found eating grapes (family Vitaceae) or drinking from hummingbird feeders. ("Accounts and measures for managing identified wildlife: Northern Interior Forest Region", 2004; Baltz and Latta, 1998; Baltz and Latta, 2020; Burns, 1915; "Cape May Warbler", 2023; McMartin, et al., 2002; Sealy, 1988; Sealy, 1989; "The land manager's guide to the birds of the South", 1992)
There is limited information on common predators of Cape May warblers. Known predators include Chuck-will’s-widows (Caprimulgus carolinensis) and short-eared owls (Asio flammeus). Some corvids (family Corvidae) and small mammals will prey on Cape May warbler eggs and nestlings. As more boreal forest habitat is fragmented into smaller patches, predation from corvids is becoming a larger threat to Cape May warblers. Domestic cats (Felis catus) also kill Cape May warblers and other songbirds. (Baltz and Latta, 1998; Baltz and Latta, 2020; Owre, 1967; "Status of the Cape May warbler (Dendroica tigrina) in Alberta", 2001; "Status of the Cape May warbler in British Colombia", 1997)
Cape May warblers are primarily insectivores and thus likely help control populations of various arthropods, such as spruce budworms (genus Choristoneura). Cape May warblers eat seeds and nectar outside of breeding season, so they may serve as pollinators and seed dispersers for various tropical plants. Cape May warblers also serve as prey for predatory birds and small mammals.
Cape May warblers are victims of nest parasitism by brown-headed cowbirds (Molothrus ater). They are also hosts for endoparasites, such as blood protozoans (genera Leucocytozoon, Haemoproteus, Trypanosoma, and Plasmodium), and endoparasites, such as bird lice (Ricinus picturatus), nasal mites (Ptulonyssus constructus), and hippoboscid flies (genus Ornithomyia). ("Accounts and measures for managing identified wildlife: Northern Interior Forest Region", 2004; Baltz and Latta, 1998; Baltz and Latta, 2020; "Status of the Cape May warbler in British Colombia", 1997)
Cape May warblers have a positive economic impact via birdwatching. During their breeding season, Cape May warblers and other songbirds are estimated to contribute to the 2.4 billion USD brought in from ecotourism in Maine alone. Other U.S. states and Canadian provinces likely also benefit from the presence of songbirds. Countries in Central America also benefit from songbirds, many of which overwinter in tropical areas. For example, Costa Rica brings in around $1.4 billion USD annually from ecotourism, part of which comes from birdwatching. ("About the Maine warden service", 2023; Turcot, 2021)
Cape May warblers have no reported negative economic impacts.
Cape May warblers are listed as a species of “Least Concern" on the IUCN Red List. They have a "Protected” status under the U.S. Migratory Bird Act, which prohibits capturing, trading, or killing migratory birds without the approval of the U.S. Fish and Wildlife Service. Cape May warblers have no special status on the U.S. Federal List, CITES, or the State of Michigan list. They are included on the "D" Yellow Watch List of Partners in Flight, which means their populations are declining with moderate or high threats still present.
Most threats to Cape May warblers occur during migration. Mortalities arise from collisions with cars and building windows, as well as predation by domestic cats (Felis catus). They are also shot in areas where they overwinter. Another cause for population declines is habitat loss and fragmentation due to silviculture. Logging practices not only reduce the amount of available breeding habitat, but also the abundance of important food sources. Logging of spruce trees (genus Picea) and insecticide treatments in boreal forests result in declines of spruce budworms (genus Choristoneura), which comprise a large part of the summer diet of Cape May warblers. Forest fragmentation also increases the threat of predation by species that prefer edge habitats, such as corvids (family Corvidae).
Some conservation efforts have been implemented to protect Cape May warblers. The United States Migratory Bird Act protects migratory birds from being killed, captured, or traded. Canada has implemented the Migratory Birds Convention Act, which has similar restrictions and works together with the US Migratory Bird Act to restore populations of migratory birds. A common bird conservation practice is the use of reflective tape or window decals to reduce bird-window collisions in cities and suburbs. Furthermore, changes to insecticide formulas, such as those used on spruce budworms, have reduced the use of chemicals known to increase bird mortality. Cape May warblers are also indirectly supported by protected lands acts, which preserve forests and other natural areas as parks for public use. Parks and ecological reserves not only enhance forest protection on a large scale, but also improve bird conservation when implemented in breeding habitats, along migration routes, and in overwintering areas. ("Accounts and measures for managing identified wildlife: Northern Interior Forest Region", 2004; Baltz and Latta, 1998; Baltz and Latta, 2020; "Cape May Warbler", 2023; Powers, et al., 2019; "Types of parks and protected areas", 2023; BirdLife International, 2021; "Status of the Cape May warbler (Dendroica tigrina) in Alberta", 2001; "Status of the Cape May warbler in British Colombia", 1997)
Kaitlyn Tracy (author), Radford University, Candice Amick (editor), Radford University, Katherine Gorman (editor), Radford University, Karen Powers (editor), Radford University, Galen Burrell (editor), Special Projects.
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
living in landscapes dominated by human agriculture.
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
active at dawn and dusk
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 mainly eats fruit
An animal that eats mainly plants or parts of plants.
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.
an animal that mainly eats nectar from flowers
active during the night
an animal that mainly eats all kinds of things, including plants and animals
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
specialized for leaping or bounding locomotion; jumps or hops.
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
living in residential areas on the outskirts of large cities or towns.
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.
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).
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
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
living in cities and large towns, landscapes dominated by human structures and activity.
uses sight to communicate
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