Philadelphia Vireo    Vireo philadelphicus

Migratory Status: Neotropical migrant

PIF Population Estimate: 4 000 000

Percent of western hemisphere population breeding in boreal forest: 86%

BAM Effective Detection Radius (m) : 66.44

PIF Maximum Detection Distance (m) : 125

Canadian BBS Population trend: 2.2 (0.4 to 4.0)

Life History

The Philadelphia Vireo is a small, slow-moving songbird that has one of the most northerly breeding ranges of all North American vireo species. Males and females look alike. Both have gray-olive upperparts and are tinged pale yellow below, which gradually becomes brighter towards the breast and throat. They have a grayish cap, dusky lores, and a dark eyeline that contrasts with a whitish superciliary, or eyebrow stripe.

The Philadelphia Vireo is primarily a boreal forest breeder, occurring in a near continuous band from the border of the Yukon and British Columbia east to New Brunswick, with smaller numbers ranging east to Newfoundland and Nova Scotia. The winter range is mainly in Central America. Philadelphia Vireos prefer deciduous forests, generally utilizing younger stands than the closely-related Red-eyed Vireo (Vireo olivaceus), with which it coexists. In summer, favoured tree species include aspen (Populus), alder (Alnus), birch (Betula) and ash (Fraxinus). Mixed coniferous and deciduous forests are also used. As in the breeding season, Philadelphia Vireos tend to use second-growth forests during migration and on the wintering grounds. Their food consists mainly of insects, particularly caterpillars when available. During migration and in the winter they will also consume small fruits.

Only males sing, producing an array of short two or three syllable phrases. Philadelphia Vireos sing sporadically during spring migration and all day during the breeding season. They typically sing from within the canopy and are difficult to detect among the foliage. There are five different song types, each used in a different context. Their song can be difficult to distinguish from the song of the Red-eyed Vireo, and at times, may attribute to the underestimating of Philadelphia numbers. Both sexes utter a raspy “ehhh” that serves as a location call among family members and between a mated pair. This call is also used during aggressive encounters and when agitated by the presence of intruders.

Males are territorial, and defend an area against other males of their species. Where their habitat overlaps with dense populations of Red-eyed Vireo, the Philadelphia Vireo will often utilize areas higher in the forest canopy. Nevertheless, the Philadelphia Vireo frequently has aggressive territorial disputes with its larger cousin.

Reference(s)

Moskoff, W., and S. K. Robinson. 1996. Philadelphia Vireo (Vireo philadelphicus), The Birds of North America Online, . A. Poole, Ed. Ithaca: Cornell Laboratory of Ornithology; Retrieved from The Birds of North America Online database: http://bna.birds.cornell.edu/bna/species/214