Fun with Science Club®


			Does the dominant bird always get the worm? Carrie Straight 05.14.01 Carolina chickadees (Poecile carolinensis) are birds native to the southeastern United States. They eat a variety of foods including seeds, insects, and spiders. With chickadees, it is very common for the biggest, strongest bird (the most dominant) to get the food first. The weaker, smaller birds (the subordinates) usually have to wait for the dominants to finish before they eat. This system is very common in the animal world. If the subordinates have to wait for the food, it could mean that the dominant birds would eat all of the food and leave none for the subordinates. Because the subordinates cannot always know if the dominants will leave food, some scientists hypothesized that subordinates would eat a lot early in the day, when they could add on weight. Then, if not as much food is around later in the day, they won’t be as hungry. A group of scientists in Indiana wanted to test this prediction, so they captured some chickadees and took them to an aviary (a large cage for birds). They put two chickadees into each cage, one that was larger and dominant over the other, smaller bird. They set up a feeder to drop one seed at a time so that the dominant bird would get the first chance to get the seed. Then they set up perches, which are places where the birds sit while they crack open their seeds. The perches had scales hooked up to them, so that each time a bird landed on one it recorded their weight into a computer. They tested the differences in weight gain for dominants and subordinates, but the data did not follow their prediction. Both subordinate and dominant chickadees gained weight during the day. Actually, dominant birds gained more weight than the subordinates, exactly the opposite of their prediction. Many times in science predictions are not supported by observations, so that the scientists must figure out whether the experiment was faulty and did not test the prediction properly, or whether their prediction was wrong to begin with.


			Pravosudov, Vladimir V. and Jeffrey R. Lucas. 2000. The effect of social dominance on fattening and food-caching behavior in Carolina chickadees, Poecile carolinensis. Animal Behaviour 60: 483-493.