Laboratory Exercises in Animal Behavior - Interspecific Flocking in Birds

Interspecific Flocking in Birds

Each of our exercises thus far have examined the behavior of a single species. It is clear, however, that animals in the real world interact with individuals of other species. In some cases the interactions involve hunting for food or avoiding becoming food (prey-predator interactions) and in others they involve interactions of species on the same "trophic level," that is animals that use the same sources of food. We have all observed interspecific interactions of this sort, but probably without realizing it.

One of the most common ways that people in North American interact with animals is by providing food for birds. Bird feeding has become a major industry, with specialty shops catering to feeding enthusiasts by providing an amazing variety of feeders and feed. There is even a coordinated research project (Project FeederWatch, coordinated by the Laboratory of Ornithology at Cornell University) that uses bird feeders to gather data about the behavior of birds at feeders. If you maintain bird feeders at home, you know that one of the goals of the activity is to attract a variety of species. One way to do this is to use several different kinds of feeders and different kinds of feed, each with a particular set of species of birds in mind. Most feeders and feed are designed to appeal to certain types of birds. For example, thistle feeders are highly specialized to provide food for certain finches, and some sunflower feeders are made for chickadees and nuthatches.

If you are a bird feeder, you also know that the other goal of the activity is to attract birds to your house so you can watch them. For this reason, feeders or feeding stations are usually placed where people can watch the birds from the comfort of their homes. Anyone who has watched birds at a feeder, especially in winter, has noticed that the interactions among the birds are not always peaceful. On the contrary, some species of birds seem to "bully" other species. The ability of one species to dominate another means that members of the dominant species have priority of access to the food. Subordinate species must wait until the dominants are finished eating, or are forced for forage on the spillage left by the dominant species.

In this exercise we will study the behavior of different species of birds at a feeding station. Our goal will be to describe the "dominance hierarchy" of the species we see, and to propose explanations for that hierarchy. In this exercise you will be responsible for all aspects of the study, from posing questions and proposing hypotheses, to interpreting the results of your study. You will also choose the method by which you will present your study to the class.

Things to Think about

One of your first decisions will be how and where to conduct your study. If one of you has a feeding station at home, you could gather data there. If not, you could establish a feeding station at your school. It need not be elaborate. You could use a large board (such as a sheet of plywood) or even a big piece of cardboard (with weights so it won't blow away) to provide a smooth feeding surface, and you could simply spread bird seed on that surface.

Tips for Teachers

Although birds will use feeders throughout the year, winter tends to concentrate foraging activity around feeders. Snow cover helps even more. Let your students design everything from beginning to end, but encourage them to investigate different phenomena. You will need to provide a bird identification guide if your students don't own their own (but many will have one at home, especially if they have a feeding station at home).

We have mentioned Project FeederWatch above. You may want to contact them for information about the project prior to the start of the semester, so you can tell your students about methods used by "FeederWatchers," as the participants are called, and the goals of the project. You can get information by writing to Project FeederWatch, Cornell Laboratory of Ornithology, 159 Sapsucker Woods Road, Ithaca, New York, 14850. Note, however, that FeederWatchers pay a fee and agree to keep careful records according to the Project's specifications.