Blue Tits Cyanistes caeruleus Laying Smaller Eggs after a Decline in Snail Numbers: An Indirect Effect of Slug Control in a City Park

Egg size is a basic species-specific life-history trait in birds which influences offspring performance through the nestling stage and, therefore, fitness. Shells of snails are the principal source of calcium for female parids and some other passerines during egg formation. Shortages in the availability of snail shells may lead to laying smaller eggs with thinner shells. In urban green spaces that require protection against pests, the numbers of...