Migratory bird numbers fall in Britain despite last year’s warm spring

Despite one of the warmest and driest springs on record in the UK during 2025, numbers of several migratory warbler species fell significantly, according to data from the British Trust for Ornithology (BTO). The breeding season proved especially poor for four species: willow warbler, blackcap, garden warbler, and common whitethroat, all showing marked declines. Three other warblers—sedge warbler, reed warbler, and lesser whitethroat—also experienced decreases, though less severe. Only the chiffchaff, which winters closer to Britain, recorded an increase in numbers. The BTO’s breeding bird survey revealed mixed trends among other bird species as well. While populations of woodpigeon and stock dove continued to grow, the smaller collared and turtle doves faced ongoing rapid declines. These contrasting patterns highlight the complex factors influencing bird populations beyond weather alone. Habitat loss both in the UK and in wintering grounds abroad, alongside climate change, are likely contributors to these shifts. Experts caution against attributing changes in bird numbers solely to weather conditions in any given year, emphasizing the multifaceted pressures migratory birds face. However, the increasing frequency of extreme weather events linked to the climate crisis underscores the need for continued monitoring and conservation efforts. The work of BTO staff and volunteers remains vital in tracking these trends and informing strategies to protect vulnerable species. The decline in migratory warblers and other birds raises concerns about broader ecosystem health and biodiversity in the UK. As climate change accelerates, understanding how species respond to shifting environmental conditions will be crucial for conservation planning. The BTO’s findings serve as a reminder that warm weather alone does not guarantee positive outcomes for wildlife, and that sustained vigilance is essential to safeguard Britain’s avian populations.