Species that have no long-distance migratory relatives, such as the waxwings Bombycilla, are effectively moving in response to winter weather and the loss of their usual winter food, rather than enhanced breeding opportunities.
As especies que non teñen parentes migradores de longa distancia, como os picoteiros (Bombycilla), móvense en resposta ao tempo invernal e á perda do seu alimento usual invernal, en vez de para mellorar as súas oportunidades de reprodución.