The
first two attempts to introduce the European Starling into
North America failed. The third did not, and what has
followed since those 60 starlings were released in 1890 in
New York City's Central Park has kept ornithologists
alternately astounded, puzzled, and infuriated. Much as
European human settlers did in the preceding years, the
invading birds pushed their way across the continent, taking
advantage of its riches and, where necessary, usurping the
habitat of residents. What enabled the starling to advance
all the way to the Pacific within a mere 60
years? Starlings were not always
pests, although, according to historical records, they have
associated with people since the advent of agriculture. They
were described in detail by Aristotle and Pliny, and the
Romans taught them to mimic human speech. The meager mention
of starlings by European chroniclers before 1830 is thought
to indicate rather limited numbers. After 1830, however,
milder European winters eliminated starlings' need to
migrate or shortened the migration route, and the conversion
of forest into farms created more favorable open habitats
and provided cereal grains for food. These concurrent
changes are thought to have favored double-brooding,
breeding at an earlier age, and formation of ever larger
starling colonies (which probably have higher breeding
success than small ones) and led to a rapid increase in
those populations. Before the turn of the century, the
species was brought to our shores. Few people like starlings.
But disdain of the species may be tempered by knowledge of
its biology. Take, for example, its bill. Unlike most of the
130-member starling family, Sturnidae, the European Starling
has jaw muscles that work "backward." Instead of using most
of their power to clamp the bill shut, these muscles use it
to spring the bill open. Thus the bill functions not just to
grip prey but also to pry apart obscuring plants. The closed
bill is inserted between blades of grass in thick turf or
other cover, and then sprung open to expose hidden prey. As
the bill opens, the eyes move forward toward each other,
permitting binocular vision. This readily observed foraging
technique enables the starling to detect not only active
prey but also dormant or stationary prey, as well. William
Beecher, who made this discovery during a seven-year study
of songbird head musculature and skull adaptations, suggests
that this unique hunting maneuver was also key to the high
rate of survival of starlings during winter. Consider, as well,
starlings' housekeeping. Even more than most cavity nesters,
starlings use a wide array of sites and an endless variety
of human-built structures. Typically cavity nesters lay
their eggs on nothing more than a bed of chips or feathers,
but starlings build nests inside their chambers. In addition
to gathering dead grasses for those nests, starlings
carefully select fresh green vegetation rich in chemicals
that act as fumigants against parasites and pathogens. Green
sprigs are added to the nest until the eggs hatch. To
maintain its insulating properties the nest is kept dry by
removing the fecal sacs of the nestlings. Once the chicks
are feathered, nest insulation becomes superfluous, the
fecal sacs are no longer removed, and fresh anti-parasite
greenery is no longer added. Thus, even before fledging,
starling nests resemble a pest-ridden compost. But starlings
are hardier than many other cavity nesters. They can, for
example, withstand the infestation of tens of thousands of
mites per nest hole without an increase in mortality.
Therefore nest construction includes early (but not late)
incorporation of leaves containing fumigants, and minimal,
but precisely timed, efforts in nest sanitation, the
starling has reduced the energy costs of housekeeping while
decreasing the value of its hole for reuse by its
competitors. Starlings are colonial
breeders. There are reports of bachelor males feeding the
young and, along with the male parent, guarding the nest
tree after the fledglings and female parent depart to
forage. There may thus be a tendency toward cooperative
breeding (which has been found in some tropical members of
the starling family) in European Starlings. Observers should
be alert for signs of such behavior. Breeding males may attempt
to father a second and even third brood. Their fidelity to
mates depends, in part, on the success of the previous
brood, but apparently it is not uncommon for males to select
a new female for a second brood, perhaps on the basis of her
previous success. A family unit usually forages within
200-500 yards of its nest. During nest building and egg
laying, unit members make, on average, 30 visits a day to
the nest; during incubation this decreases to 18, but when
young are being fed, visits jump to 260. Also, visits to the
nest may not be restricted to members of a unit. Evidence
points to intraspecific nest parasitism -- visiting female
starlings are known to dump their eggs in the active nests
of other females. In the winter, starlings
become somewhat nomadic but are able to find dormant insects
under snow wherever it is not too deep. They show a marked
preference for foraging for insects in short grass but are
extremely opportunistic and will even rely on fungus to get
by in the absence of preferred foods. Exotic "weeds" often escape
the natural controls that limit their numbers at home and
may, quite quickly, become pests. Is it possible to control
our weed-like starlings? Some think starlings could serve
humanity well by ridding pastures of insect infestations,
although benefits have been demonstrated under only very
special conditions. Nonetheless, a reputation for
controlling pests has apparently paved the way for starlings
in New Zealand, where nest boxes for them can be found atop
many pastureland fence posts. The use of starlings to
suppress North American insect outbreaks, however, is
unlikely. Instead, programs to control starlings probably
will become more common. Starlings form aggregations
with other species which may reach 10 million birds and can
be astonishingly difficult to control. Congregations on
trees have been discouraged by thinning the canopy.
Loudspeakers have been wired throughout vineyards and
orchards to broadcast distress calls, which may be effective
under some conditions in keeping the birds from roosting.
During the past 15 years, where massive winter roosts have
occurred, a million or more individuals have been killed at
one time by spraying with detergent (which destroys the
insulating properties of the plumage). But even these local
losses have not put a significant dent in starling
populations. Human modification of North
American habitats permitted rapid colonization of the entire
continent. Starlings are now ubiquitous, out-competing other
such cavity nesters as Eastern Bluebirds, Red-headed
Woodpeckers, Northern Flickers, and Great Crested
Flycatchers. Within one century, 60 starlings introduced to
North America have increased to over 200,000,000 (one-third
of the world's European Starling population). How fast and
for how long their numbers will continue to grow is
uncertain, but it is likely that managing the consequences
of their introduction will continue to be difficult,
expensive, and (considering the nature of the foe) often
unsuccessful. SEE: Avian
Invaders;
Range
Expansion;
Communal
Roosting;
Mixed-Species
Flocking;
Vocal
Copying;
Cooperative
Breeding;
Brood
Parasitism. Copyright
® 1988 by Paul R. Ehrlich, David S. Dobkin, and Darryl
Wheye.