Many migratory bird species that spend winters in Africa or Asia are declining because of agricultural intensification in their European and North American breeding grounds, not only on wintering sites.
The welfare of migratory birds is affected not only by conditions on wintering grounds and during migration, but critically by the quality of their breeding habitat. Birds returning from a winter in Africa to find insect-depleted, structurally simplified farmland cannot raise chicks successfully. Female birds that have made a demanding migration and invested in nest building and egg laying experience breeding failure due to inadequate food supply for chick rearing. The chronic failure of breeding attempts across multiple years causes population-level decline that reduces the total welfare of these species across their range. Restoring insect-rich habitat within farmland is the most direct intervention available for breeding bird welfare in agricultural landscapes.