Do migratory pathways affect regional abundance of wintering birds?
A test in northern Spain The distribution of organisms at regional scales is commonly interpreted as the result of spatial variation in habitat suitability. However, the possibility that geography itself may affect distribution patterns has received less attention. For example, the abundance of wintering bird populations might be influenced by the cost of reaching areas located far away from the main migratory pathways. To explore this idea, a team from the Universidad Complutense of Madrid studied the abundance distribution of three common migratory passerines (meadow pipits, common chaffinches and European robins) wintering in farmlands located in the 600-km long Cantabrian coastal sector of northern Spain. This is an area roughly perpendicular to the west-Pyrenean migratory pathway, which drives European migrant birds into the Iberian Peninsula. Despite the effects of climate, vegetation structure and local abundance of breeding conspecifics, the winter abundance of all three specie
