FILE under: strange consequences of having sex. The sedentary Audubon鈥檚 warbler is starting to migrate 鈥� possibly because it is mating with a cousin that flies south in the winter.
Audubon鈥檚 warbler () lives in western US and Canada. Some head south for the winter while others don鈥檛. of the University of British Columbia in Vancouver, Canada, and his team decided to investigate why.
When the team looked at the bird鈥檚 mitochondria 鈥� the energy-producing structures within cells 鈥� it found that those in northern birds were unusually energy efficient. This is normally only seen in the myrtle warbler (), a closely related migratory bird whose range overlaps with the Audubon鈥檚 in the north. They also found that northern Audubon鈥檚 warblers were more likely to migrate.
Advertisement
This suggests that interbreeding between the two subspecies has seen more energy-efficient mitochondria pass into some of the Audubon鈥檚 northern population, giving them a boost that allowed them to become migratory (Evolution, ).
This article appeared in print under the headline 鈥淚nterbreeding birds begin to migrate鈥�
