Dendroica palmarum are average sized wood warblers (12.5 to 14.5 cm of length). In their basic plumage they present grayish-brown to olive-brown upperparts and yellowish to off-whitish underparts. Their have a long pale supercilium and bright lemony-yellow undertail-coverts. They present blurry brown streaking on breast and flanks and pale wing-bars. While in alternate plumage they present a rufous crown. Legs are blackish, eyes are small and black, and their bills are short and pointy, varying in color from black to pale.
There are two subspecies: 1) Yellow Palm Warbler in the east and 2) Western Palm Warbler. The Yellow Palm Warbler has underparts that are entirely yellow in all plumages. Western Palm Warbler only have deep yellow color in their undertail-coverts and throat, contrasting with a whitish or slightly yellow breast and belly. Sexes are very similar in both subspecies, and are often indistinguishable in the field (Pyle 1997; Wilson 1996).
Dendroica palmarum breeds in the boreal forests of North America. This species breeds from northern Canada south through the northern United States. It is also classified as a neotropical migrant. On the East Coast, this species winters regularly from southern Delaware south through Florida and along the Gulf Coast through southern Texas. This species also winters throughout the West Indies, along the Yucatan Peninsula through Belize, and along coastal Honduras (Dunn and Garrett 1997; Wilson 1996).
On the breeding grounds, Palm Warblers prefer open bogs with a wooded border of spruces and tamaracks. The bog cover is preferably Sphagnum moss, sedges, or other damp ground plants. On the wintering grounds, Palm Warblers prefer a variety of habitats including open and weedy fields, forest edges, second-growth, thickets, savannas, and mangroves (Dunn and Garrett 1997; Wilson 1996).
Palm warblers are monogamous. However, there are two examples of bigamous males, where a second female was sometimes noted on territory. Pair formation in Palm Warblers begins shortly after arrival on breeding grounds, from late April until mid-May, where the male sings frequently upon arrival on breeding grounds.
Nest-building apparently begins in early to mid-May. The nest is usually located in Sphagnum of peat bog at the base of a small conifer on the ground. Site characteristics include nests closely located to the margins of heath bogs with scattered tall trees and small saplings, in addition to very dense shrub cover. The nest itself is cup-shaped and is comprised of weed stalks, grass and sedges, shreds of bark, rootlets, woody stems of Labrador tea, and bracken fern.
Palm Warbler is known to produce only 1 clutch/season which consists of 4 to 5 eggs. Egg dates are from mid-May to late June, mid-July. The incubation period for this species is 12 days. During incubation, the male feeds the incubating female. Both parents feed the young in the nest and through fledging after 12 days of age (Wilson 1996).
Upon hatching, Palm Warblers are altricial and don't leave the nest for nearly a couple weeks. From juvenal plumage, Palm Warblers molt into their first basic plumage from July through September before winter sets in (Wilson 1996).
The oldest recorded age for Palm Warbler is 6 years 7 months. There is no data on life span and survivorship.
Some body parasites found on Palm Warblers include ticks, mites, and Hippoboscid flies, which may affect their lifespan (Wilson 1996).
Some common observed locomotion behaviors is that Palm Warbler commonly walks on the ground, wagging its tail.
Palm Warbler has also been observed behaving in an agonistic manner. Males chase and fight intruding males during breeding season and on wintering grounds. In a breeding territory, intruding males announce their presence by singing, but territory owners chase away the intruder and sing from a post to proclaim ownership (Wilson 1996).
On the breeding grounds, Palm Warblers are mainly insectivorous, taking food from the ground, from shrubs and scattered trees in the territory, and in the air by means of sallying from the ground or from a perch. In open areas, the majority of insects are caught from the ground or from low shrubs. Common insect prey include: grasshoppers (Odonata), beetles (Coleoptera), true files (Diptera), true bugs (Hemiptera), butterflies and moths(Lepidoptera) and wasp, bee and ant larvae (Hymenoptera). During the fall and winter, Palm Warblers feast on seeds, insects, and berries, including bayberries, in addition to nectar from century plants, sea grapes, hawthorns, and tiger claw trees (Wilson 1996).
Palm Warblers are diurnal visual foragers. Prey is captured by gleaning from leaves and cones, on the ground, and by hawking. Palm Warblers actively forage by flitting from branch to branch, as well as to the ground pursuing flying insects. Foraging methods are described as opportunistic, often switching between predation and nectivory.
Gray Jays, Short-tailed Weasels and Garter Snakes have been reported as possible nest predators of Palm Warblers
Palm Warblers have very important roles in their boreal bog habitat. One of their most important roles in the ecosystem is by controling insect populations through feeding (Wilson 1996).
Only known beneficial aspect of this species to humans is that Palm Warblers eat insects, thus may control the insect populations (Wilson 1996).
Palm Warblers are tolerant of human activity, occurring in winter in residential areas.
One threat to Palm Warbler is the presence of TV towers and other tall structures. Palm Warbler is one of the most common victims to illuminated TV towers.
There seems to be no suggestion of degradation of habitat except for some evidence of bog drainage and peat-harvesting which may harm habitat (Wilson 1996).
Within the genus Dendroica, Palm warblers have been considered most closely related to Prairie, Kirtland's, and Pine Warblers, but more study is needed.
Palm Warbler is actually a misnomer, due to the fact that this species shows no inclination to use palms. Palms do dominate portions of where they overwinter (Dunn and Garrett 1997).
Nicholas Laviola (author), University of Arizona, Jorge Schondube (editor), University of Arizona.
Dunn, J., K. Garrett. 1997. Warblers. New York: Houghton Mifflin.
Pyle, P. 1997. Identification Guide to North American Birds. Bolinas, California: Slate Creek Press.
Williams, W. 1996. Palm warbler. Pp. 1-20 in F Gill, A Poole, eds. The Birds of North America, No. 238. Washington, D.C.: Academy of Natural Sciences, Philadelphia, PA , and American Ornithologists Union.