Neotropical songbird chick predation by an invasive wasp, the German yellowjacket (Vespula germanica)

Abstract

Social wasps (Family: Vespidae) are opportunistic and generalist feeders, which can occasionally feed on live vertebrates. The German yellowjacket (Vespula germanica) is native to Eurasia and Northern Africa, and has invaded many countries around the world, producing several environmental, economic and social impacts. Here we report the first video- recorded evidence that this wasp species preys on chicks. Over six breeding seasons, we studied the parental care behaviour of the Chilean Elaenia (Elaenia chilensis), a long- distance migratory bird that breeds in the Andean- Patagonian Forest. We filmed 59 nests when chicks were 2–3 and 10–11 days old, and recorded in a nest containing two 10- day- old nestlings the predation of one of them by German yellowjackets. The other chick was found alive on the ground, indicating that it escaped from the wasps. Parents did not defend offspring against wasp attacks. The rarity of this observation may suggest either that this insect is not yet a significant nest predator or that it is difficult to obtain a record of predation by wasps, because birds may remove dead nestlings from the nests (i.e. nest sanitation). Although Chilean Elaenia is not threatened, 41% of bird species in the Andean- Patagonian Forest are endemic, and this new nest predator may potentially become a threat to the conservation of any of those species, which deserves further research. Hence, to evaluate the German yellowjacket impact on bird populations, it is imperative to conduct videotaped nest monitoring in order to remove the masking effect of nest sanitation on predator identity, which will allow to determine how much this wasp contributes to nest failure in the invaded zone of the Neotropical region.