Feeding on migratory butterflies: opportunistic observations of birds preying on the Painted Lady Vanessa cardui

Abstract

Many butterfly species are often seen with severe wing damage, which is regarded as evidence of unsuccessful predation, most likely by insectivorous birds. However, observations of bird predation are rare for the vast majority of butterflies. During a long-term study of the ecology of the Painted Lady Vanessa cardui, a common migratory butterfly, a high frequency of wing damage was noted, especially in North African populations. Attacks by several bird species were confirmed during fieldwork which, along with a number of published and unpublished records from ornithological colleagues, are reported in this note. Twenty-four bird species have been recorded preying on the Painted Lady in the Palaearctic-Afrotropical region. Records from eight additional species from the Nearctic region were obtained from photographs and from the literature. With 16 families (13 passerines and three non-passerines), this bird community embraces a notable diversity of morphologies and prey-capture techniques. The most represented families were the Tyrannidae, the Sylviidae and the Turdidae while the species most frequently recorded as predators were European Bee-eater Merops apiaster, Blue-cheeked Bee-eater Merops persicus, White-crowned Wheater Oenanthe leucopyga, and Cattle Egret Bubulcus ibis. Most observations occurred in March–April and October when the Painted Lady migrates in large numbers, suggesting that a sudden increase in abundance may lead to a regular use of this resource by predators. Moreover, unsuccessful attacks are common, which suggests that butterflies may quite often escape with some form of wing damage. The consequences these interactions have on butterfly populations are speculative but deserve further study.