Feeding Birds

Where's the Seed?, pencil drawing of House Sparrows
by Terry Miller
Feeding backyard birds began in earnest in the 1950s. Today, at an estimated expenditure of more than one-half billion dollars, one in three North American households makes available an average of 60 pounds of supplemental seed each year. New Englanders are our most dedicated providers. In the city of Amherst, Massachusetts, for example, more than 40 percent of the households provide winter feed. The effect that this artificial resource may have on the survival, population stability, and migration patterns of our birds is uncertain, but ornithologists speculate that if handouts were to stop tomorrow, there would be neither species extinctions nor major population declines, although some recently enlarged ranges would contract and there might be detectable decreases in some regions.

Recent range expansion thought to be related to supplemental feeding is evident among finches, especially the House Finch, which has spread from Long Island to the Mississippi River within the past 45 years. Several other beneficiaries of feeding (Northern Cardinal, Tufted Titmouse, Red-bellied Woodpecker, and Mourning Dove) are working their way northward. In a number of areas where supplemental food is plentiful, some species, such as the Mourning Dove, no longer migrate.
Feeding may pull many birds, especially weak individuals, through the extremes of winter. Birds increase their visits to feeders in harsh weather, particularly after snowfalls and ice storms that make natural foods inaccessible. Small species, which are more constrained energetically, benefit greatly from feeding. In one experiment, chickadees raised their daily fat deposits by about 4 percent of their body weight when offered sunflower seeds in place of their normal diet of conifer seeds, berries, etc. During extreme cold spells, juncos, finches, and other winter residents unable to find sufficient food before sunset often will not survive the night.

In some circumstances, however, taking advantage of handouts may be a mistake. Feeding stations may attract weakened or sick individuals and promote the spread of avian diseases. In addition, many birds will readily approach damp grain or bread contaminated with the mold Aspergillus fumigatus, which, if inhaled, can cause a potentially lethal infection, aspergillosis. Irregular feeding can be hazardous to birds which establish habitual foraging patterns; oversupply may attract undesirable species such as pigeons, starlings, and grackles, which crowd out other birds. Feeding on the ground encourages predation by cats and, much more desirable from a birder's viewpoint, as the number of visitors increases, so does the number of hawks that are able to find their food around the station.

The provisions themselves may also cause problems. Beef suet brings 80 species of birds (including woodpeckers, catbirds, mockingbirds, nuthatches, chickadees, titmice, wrens, orioles, shrikes, thrushes, warblers, grackles, and starlings) into backyards. Unfortunately, many feeders are kept stocked as spring advances. Sun-warmed suet mats feathers, which can result in reduced insulation and waterproofing, inflamed or infected follicles, and loss of facial feathers. In Iowa, more suet is taken by birds in May than during the rest of the year. Many Downy Woodpeckers that eat this warm suet become barefaced in the spring. Bird enthusiasts also encourage more than 50 species of birds (mostly hummingbirds, orioles, tanagers, and various warblers) to sip ersatz nectar from backyard feeders. But the liquid ferments within two to three days while continuing to lure birds, resulting in enlarged hummingbird livers.

In addition to seed-, suet- and nectar-eating species (and their predators) that forage at backyard feeders, many other species take advantage of food wastes generated by people and industry. The size of opportunistic Brewer's Blackbird, European Starling, and Rock Dove populations varies as people directly and indirectly alter available food supplies. Similarly, Red-winged Blackbirds have expanded beyond their marshland habitat to cultivated areas where leftover grain is abundant. Profiting from dumped refuse or offal released from fish-processing plants and from boats and ships in sea lanes, local populations of petrels and Herring, Ring-billed, Great Black-backed, and other gulls may build giant colonies.

Today, in spite of the farsighted efforts of many bird enthusiasts, the provision of supplemental food remains somewhat uneven. But this is likely to change. Bird watching has become the second most popular passive sport (after gardening) in North America; with some 30 million participants. As more information about avian nutrition is made available to the well-intentioned public, safer, more effective bird feed will be made available in backyards. This change should not take very long; more farmers have been discovering how to increase their profits (up to five times) by selling their grain as bird feed. In addition many birders are participating in "Project Feederwatch" of the Laboratory of Ornithology of Cornell University, by recording which birds visit their feeders on one of two days of each week in the winter. They will both help the birds and add to knowledge of wintering bird populations.

Along with improvements in feeds, we should see modification of public trash and waste disposal policies, which will influence which species are common in the vicinity of cities and towns. Whereas garbage fosters population growth in some colonial seabirds, oil contamination and chemical pollution remain the major threats to others. As laws controlling refuse dumping and regulating maritime industries become commonplace, the population density and distribution of "garbage birds" and of some species considered more desirable will change. How similar the mix of bird species around centers of human population will be at that point compared to today's avifauna is, in many respects, up to us.
SEE: Irruptions Helping to Conserve Birds -- Local Level; Metallic Poisons; Disease and Parasitism; European Starlings; Urban Birds.
Copyright ® 1988 by Paul R. Ehrlich, David S. Dobkin, and Darryl Wheye.