Understanding how habitat quality, insect abundance and aquatic subsidies impact population change in a rapidly declining bird

Global declines in migrant bird populations are a major threat to the world's ecosystems. Long-distance migrants travel in vast numbers between temperate breeding regions and tropical wintering grounds, providing energy transfer and ecosystem services at large spatial scales. Furthermore, avian population trends are key indicators of environmental change, so migrant declines are concerning for scientists and policymakers alike. Migrants are particularly susceptible to environmental change because of their multistage lifecycle, and research increasingly implicates climate change in their decline. However, focusing on the climate has meant that other aspects of environmental change have received far less attention.

Recent high profile studies have reported a catastrophic collapse in insect numbers around the world. While the generality of these findings is contentious, most researchers agree that rapid declines of key groups have worrying implications for ecosystem functioning. For example, insects are a critical component of the diet of many migrant birds, yet the interplay between the population trends of insects and their avian predators is poorly understood.

The spotted flycatcher Muscicapa striata is one of the UK's most rapidly declining birds, but the underlying causes are unclear. As an obligate insectivore, this species is an important indicator of environmental health and an ideal model for studying the link between declines in insects and migrant birds. The Biodiversity Action Plan for this 'Priority Species' highlights knowledge gaps regarding breeding ecology and habitat use. This project addresses these by combining analyses of long-term data with fieldwork, spatial analysis, cutting-edge laboratory techniques and population modelling in order to: (1) investigate the impact of habitat change and invertebrate abundance on national population trends; (2) determine how habitat quality and food availability affect breeding success in a local population; and (3) use the results from (1) and (2) to develop an integrated model of population change.