Migrants seek out berry, berry rich food.

For songbirds on the move, berries appear to be more important than resear- chers had thought.

From 1993 to 1995, investigators determined the diet of migratory songbirds making their autumn visit to Block Island, R.I., by analyzing more than 1,500 droppings, reports ecologist Jeffrey D. Parrish.

During their autumn trek, most of the 69 species bound for the island switched from an insect-rich diet to one based on fruit, he explains in a report accepted for publication in The Condor. For several of the breeds, including the hermit thrush, red-eyed vireo, and yellow-rumped warbler, fruit made up 80 percent of their diet, notes Parrish, now with the American Association for the Advancement of Science in Washington, D.C.

A few species, including the American redstart, continued to dine exclusively on insects. However, the insect eaters put on less weight than the others, and the bigger the role fruit played in a species' diet, the greater its weight gain, he asserts.

Fruit has advantages over insects beyond providing lots of energy. Since it is more abundant and easier to grab than insects, hunting it down takes less work, Parrish notes in a separate report accepted for publication in Studies in Avian Biology.

Researchers have known that many songbirds make stops at coastal shrublands, rich with fruit-bearing bushes, during their autumn migration. To test whether the birds select the shrublands for the fruit, Parrish monitored how many birds landed in an area where his group had picked all the berries. Compared to a similar but berry-filled spot, only a third as many birds visited the depleted area, he reports.

Bird-loving landowners should plant shrubs such as northern arrowwood, bayberry, and pokeweed, which produce berries that birds like, he recommends.