Bird feeding and biodiversity: The decline of the Willow Tit

Abstract

Monitoring data from the British Trust for Ornithology document a decline in United Kingdom (UK) Willow Tit (Poecile montanus kleinschmidti) abundance that has been abrupt enough to be characterized by a catastrophe theoretic model. The reasons for the decline are thought to be some combination of increased nest competition and predation by the beneficiaries of a bird-feeder food subsidy, and habitat loss. A statistically estimated predator-prey catastrophe model is useful in illustrating how habitat loss and species interactions could combine to cause a precipitous population decline, and showing that, if the UK Willow Tit population is to recover, it will likely require both reversals of habitat loss and reductions in food subsidies to its competitors and predators. To achieve the latter, humans may have to collectively introduce rules that reduce the private enjoyment of backyard bird feeding to preserve broader ecological integrity.