Il Chirpo Di Tutti Chirpi

Don, er, Avione. Pic lifted here.

Cowbird mob tactics:

The cowbirds are among a range of species, notably cuckoos, that are so-called brood parasites that lay their eggs among unsuspecting hosts. But questions remain as to why the host birds raise chicks that are obviously not their own.

The new study finds that cowbirds are likely to ransack and destroy the nests of warblers that reject mob rule by refusing to raise cowbird eggs. However, by accepting mafia offspring, host birds lose fewer of their own chicks than those that reject the parasites and lay themselves open to retaliatory behaviour.

Today, in the Proceedings of the National Academy of Sciences, Jeff Hoover and Scott Robinson of the Illinois Natural History Survey document how they mounted a surveillance operation in which they interfered with cowbird access to warbler nests in the Cache River watershed of southern Illinois.

The researchers monitored 182 predator-proofed nests over four breeding seasons and found that warbler nests were ransacked 56 per cent of the time when researchers removed the parasitic eggs and cowbirds were allowed into the nests, versus only six per cent when the cowbird eggs were accepted and cowbirds had nest access.

No nests were ransacked when researchers removed cowbird eggs and cowbirds were denied nest access.

Never go against the flock, indeed.

This article grabbed my attention because I was watching a cowbird at our feeder this weekend. It sat there for quite a long time, gobbling food and bullying other birds. Back in the day, Dad used to shoot them (along with grackles) as a matter of policy. From this article, it seems taking up such a practice would actually be an avian public service.