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.