City life may help Darwin's finches survive bloodsucking flies

A small-billed ground finch on Española Island

Krystyna Szulecka/Alamy

Finches found only in the Galapagos Islands are under attack from bloodsucking fly larvae, but those that live in cities may have an edge compared with their countryside counterparts: they lose less blood and have higher rates of survival during infestations.

The avian vampire fly (Philornis downsi) was accidentally introduced to the Galapagos archipelago a few decades ago. The flies lay eggs in bird nests, where maggots that hatch later burrow into nestlings’ skin and drink their blood. Infestations of the invasive parasites …