Bird Predation on Gypsy Moth (Lepidoptera: Lymantriidae) Larvae: An Aviary Study

Using captive birds, two aspects of bird predation on gypsy moth, Lymantria dispar (L.), larvae were examined: whether birds are more likely to attack and consume early rather than late larval instars, and whether birds will attack gypsy moth larvae in the presence of alternative prey. Of 37 individuals of nine passerine bird species offered second-instar gypsy moth larvae, 27 individuals of seven species accepted them. Of 22 individual birds of six species offered third- to sixth-instar larvae, 15 individuals of five species accepted them. Birds given a simultaneous choice between gypsy moth larvae and alternative prey (two nonhairy types and one hairy type) preferred the nonhairy alternatives. We conclude that birds may be important sources of mortality for early (first and second) as well as late (third to sixth) instars. Most field studies of gypsy moth population dynamics have documented bird predation primarily on the latter, but our results indicate that bird predation on early instars must also be taken into account in analyses of gypsy moth population dynamics.