Diet and Foraging

Based on species-typical foraging tactics and guild classification, animal matter should be dominant in the overall diet of adults, especially during the breeding season, while fruits evidently are taken opportunistically (Skutch 1969, de Graaf et al. 1985). Limited direct information on foods identified in the stomachs of specimens during preparation supports this view. Foods consumed include large and small caterpillars (Lepidoptera), a larval beetle and adult beetles (Coleoptera), grasshoppers (Orthoptera), spiders (Araneida), and a nematode (Nematoda) (Runnels 1975). The specimen on which this list is based was taken in Jeff Davis County, Texas, well outside its normal range either in the United States or Mexico in a Quercus gravesii community on the bottom of a canyon. No other information on foods consumed are known to me, apart from a few observations on individual birds in the field that took larger, conspicuous prey. For example, one large insect thought to be a dragonfly was noted because of its size—it took time for the bird to swallow (I. Davis in Bent 1942). Skutch (1969) identified small, green larvae, and small moths and butterflies with wings still attached, as adults brought food to nestlings.

Evidence indicates that the Rose-throated Becard is a facultative frugivore. Focal observations on fruiting trees in Mexico and Guatemala (Scott and Martin 1984, Wendelken and Martin 1987), involving Bursera simaruba (Burseraceae), Ficus cotinifolia (Moraceae), Ehretia tinifolia (Boraginaceae), and Guaiacum sanctum (Zygophyllaceae), indicated that fruits may be taken infrequently in some places (the status of becards near the focal trees was unknown), while they can be important in other places or times ("berry seeds and fruit pulp" reported in 9 of 10 stomachs examined in El Salvador; Dickey and van Rossem 1938). Mobley (2004) said the species can take "considerable quantities of small fruits and arillate seeds (e.g. Stemmadenia [Apocynaceae])," in addition to insects.

de Graaf et al. (1985) classified Rose-throated Becard in two foraging guilds, based on food, food substrate, and foraging technique, defined as "Insectivore: air sallier" and "Frugivore: lower-canopy gleaner" . Only a few observers describe foraging behavior. Skutch (1969) characterized becards as sit-and-watch foragers (Huey and Pianka 1981). They take adult and larval insects by sighting their prey from perches and sallying and snatching from foliage without alighting, or by hawking in the air. Even before Skutch prepared his life history account, Pough (1953) noted that becards sit quietly, often inconspicuously on leafy branches, and make forays after the manner of a "typical flycatcher". Dearborn (1907) also described the behavior similarly (of birds in Guatemala), as hawking from perches in isolated trees and along woodland margins "very like flycatchers (Tyrannidae)". Oberholser (1974) mentioned the importance of fruiting Ficus in Texas and neighboring Tamaulipas, and remarked that becards take insects from foliage and by hawking insects in the air. The importance of foliage sallying is implied by the presence of non-flying larval forms of insects, and a spider, in Runnel’s (1975) stomach contents list (above). Only one source (Wendelken and Martin 1987) mentions fruit handling: a single becard visited a Guaiacum sanctum tree under observation, perched above a ripe, open fruit capsule and removed an arillate seed from its locule and swallowed it whole without carrying it away from its perch. In this plant, the aril is bright red and fleshy, and covers the seed, while the seed (about 10 mm long on average) is hard and may not be digestible.

Nonbreeding becards singly or in pairs often join mixed species foraging flocks. In the highlands of Guatemala, Skutch (1969) noted that becards often attached themselves to such flocks during the northern winter, but each flock contained only a single becard, usually a female or a young male. Along the Río Corona, Tamaulipas, Mexico, winter mixed species foraging occurred in association with jays, orioles, and tanagers (Gehlbach 1987). In the only study that provided quantitative details, Hutto (1994) observed Rose-throated Becards in 5 out of 57 (9%) mixed flocks (averaging 1.60 individuals per occupied flock) that he studied in western Mexico in November and December. The species was censused and found to be uncommon in the study area. The foraging style of becards associated with continuously moving mixed species flocks remains to be described.