There has been a recent article in the New Scientist 9 August 2014 entitled:
“Songbirds really do fly south for the winter”
Scientists had postulated that intercontinental migratory songbirds flew north for the summer to breed in order to escape overcrowding and intense competition in the tropics. Most of us had always though that the flew south to avoid hard winters.
Ben Winger of the University of Chicago has now done some research. He suggests that there is strong evidence that songbirds are actually driven to fly south to avoid harsh northern winters. Winger’s team studied 800 species of North American sparrows, warblers and blackbirds and looked at the present distribution of each species and then inferred where the species had once lived and discovered that birds who carried out long distance migration were twice as likely to come from temperate ancestors than tropical ones.
This leads to the supposition that if Climate Change is leading to warmer winters we will see more birds staying put for the winter. This indeed is what we already find with birds changing their strategies and becoming resident where the climate allows this.
This piece of work just underlines what I think we all knew all along –birds migrate to avoid harsh winters.