Thursday, July 30, 2009

Bird Food

By Susan Benson,
CNHM Director of Education

Earlier this spring, when school groups were visiting the Museum, white boards were set up outdoors to “feed” ants in order to teach about ant intelligence. After two days of feeding the ants, I noticed a robin, almost appearing as if it was trying to run me out of the area. The following day, there were significant scratch marks that were made by a small “implement” that I assume must have been the robin, having eaten the peanut butter. Every day thereafter, I saw the robin, and later, the peanut butter would be scraped clean. This morning after the rain, I was watching five robins in the Museum yard and began thinking about birds and their food.

Natural foods that birds eat include insects, worms, grubs, berries and other fruit, tree sap, buds of trees and shrubs, nectar, nuts and seeds, fish and small animals or other birds, eggs, or dead animals.

Sometimes it is surprising to discover what some birds eat. For example, ruby-throated hummingbirds feed on the nectar of mostly red or orange flowers. However, they will also catch insects in midair such as gnats, mosquitoes, fruit flies, or small bees. Hummers will also pull them out of spider webs, and sometimes eat the spider as well. Hummingbirds also take insects attracted to tree sap or pick small caterpillars and aphids from leaves. A red-winged blackbird is believed to eat a diet of up to fifty-seven percent plant seeds, twenty-six percent insects, thirteen percent grain.

Birds have high body temperatures and high metabolic rates so they eat more food ounce for ounce, in proportion to their weights, than do most other vertebrate animals. Larger birds generally eat less in proportion to their body weight than do smaller birds each day.

The smaller a bird is, the more time it needs to spend feeding. Eagles may go without food for several days without ill effect, but the tiny chickadee needs to feed regularly throughout the day in order to survive. The bird with the widest variety of diet ever recorded is the ruffed grouse. Its food is known to include 518 kinds of animals and 414 different plants.

Birds digest their food very quickly. Some small birds like the chickadee eat almost constantly, especially during the winter. Diurnal birds feed most heavily in the morning and late in the afternoon.

Clues can be taken about what a bird eats by observing the type of beak or bill the bird has. Thin, slender, pointed beaks such as those found in warblers are found mainly in insect eaters that use their beak to pick insects off leaves, twigs, and bark. Beaks which are flat and wide at the base are found in birds such as flycatchers, which catch insects in flight. These birds also often have whiskers at the corners of their beak which widens the mouth opening, allowing more successful capture of prey. Woodpeckers have a chisel like beak for pecking holes in trees. Mergansers, adapted for fish eating, have sharp tooth-like edges on the bill to hold fish tightly. The fringed edges of a mallard bill strain plants, seeds, and small animals from water. Cardinals, grosbeaks, finches, and sparrows have a thick, cone-shaped bill good for cracking seeds all year long. When seeds are scarce they eat insects.

Whatever birds may eat, they continue to be a source of enjoyment for humans. It is estimated that over sixty million people in the United States feed birds in their back yards. Birds play an important role in balancing healthy ecosystems, and certainly contribute to our human economy. Sadly, many people are not aware that ten percent of our 852 bird species of North America are endangered or threatened. It is impossible to imagine what our lives would be like without them.

For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility and exhibits, the Curiosity Center and Brain Teasers 2, in Cable at 13470 County Highway M. Also find us on the web at to learn more about exhibits and programs.

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