Fun with Science Club®


			Birds just know when its time to leave for winter “vacation” Carrie Straight 05.18.01 In response to global warming (the average temperature increase on Earth), plant species are changing worldwide, and so is the behavior of different animal species. Ranges of some species are expanding into new areas; others' ranges are decreasing because of the change in temperature and changing habitats. Some migratory bird species are spending more time on the breeding grounds, migrating shorter distances, and expanding their ranges. Most people believe global warming is causing these changes, but scientists want to know how these changes happen. Some scientists wanted to look specifically at how the timing of the fall migration changes. Other scientists have shown that the time to leave for migration is heritable (a mother bird leaves at a certain time and she passes that information to her young through her genes or her example from which her youngsters learn). So a mother bird’s young will leave at approximately the same time she does. But, when does a bird know it is time to leave the breeding grounds? To look at this question, researchers collected over 500 blackcaps (Sylvia atricapilla) and took them back to a laboratory. They chose some birds to put in an outdoor aviary, where they let them nest and raise young. Using these young birds produced in the outdoor aviary, the researchers recorded the behavior of the birds. Specifically, the researchers recorded “restless” activities that indicate the birds are ready to migrate, called zugunruhe. For blackcaps, activities indicating restlessness included hopping or flying around in their cages during the evening and at night. Normally these birds sleep or rest at night. Because the researchers knew the kin relationship between all of the birds, they could estimate the heritability of timing of migration by comparing the mother’s zugunruhe to her offspring’s zugunruhe. The date that the young started their migratory restlessness was similar to when the mother started her zugunruhe. German blackcaps do inherit their timing of migration.


			Pulido, Francisco, Peter Berthold, Gabriele Mohr, and Ulrich Querner. 2001. Heritability of the timing of autumn migration in a natural bird population. Proceedings of the Royal Society of London. Biological Sciences Series. 268: 953-959.