22 July 2011
Widespread declines in house martin numbers have been reported from central and northern Europe since 1970.
House martin populations are affected greatly by weather. They require rain to produce wet mud for nest building and for encouraging the abundance of insect prey, but cold wet weather prevents them feeding.
Large-scale mortality is regularly recorded during and after periods of bad weather, during both breeding and migration. On the other hand, hot and dry weather can result in mortality through dehydration and heat stress.