Diet and Foraging

Adelaide’s Warblers are generalist insectivores, consuming arthropods of many taxa. Wetmore (1916a) found they consumed 60% Hemiptera (true bugs, mostly lantern flies Fulgoridae), 14% Coleoptera (beetles) and 11% Lepidoptera (moths and butterflies). Other diet items recorded include spiders, ant pupae, leafhoppers, aphids, flies, insect eggs and moth eggs (Bowdish 1903, Danforth 1926, 1931, 1937, Wetmore 1927). There is also one record of an Adelaide’s Warbler consuming a coqui frog (Eleutherodactylus sp.; Wetmore 1916a).

Adelaide’s Warblers are also generalists in foraging substrates used, actively searching for food from ground level to over 10 m in height, and searching all types of vegetation. In Guánica Dry Forest, southwest Puerto Rico, females tend to forage at lower heights than males, and both sexes forage at lower heights during the dry season (J. Toms, unpub. data). In a savanna-like habitat (Cabo Rojo Wildlife Refuge, south west Puerto Rico), they spent almost 50% of their time foraging in Prosopis trees, and almost 25% of their time in shrubs; however, they used trees in nearly the proportions available, with a slight preference for Prosopis spp. and Tamarindus spp. (Staicer 1992).

Adelaide’s Warblers mostly capture their prey by gleaning from leaves (50-58%), but also commonly sally glean, glean from other surfaces, flycatch and hover (Kepler 1977, Post 1978). They frequently chase insects that were missed in another foraging maneuver, rapidly changing direction and speed while attempting to catch the insect in mid-air (Wetmore 1916a, pers. obs.).

In some parts of the island, they join in mixed-species foraging flocks; other flock members include Puerto Rican Tody (Todus mexicanus), Lesser Antillean Pewee (Contopus latirostris), Puerto Rican Vireo (Vireo latimeri), Black-whiskered Vireo (Vireo altiloquus), and Elfin-woods Warbler (D. angelae) (Curson et al. 1984). They have a 23.6% foraging niche overlap with Puerto Rican Tody (Kepler 1977).