Biology Reference
In-Depth Information
But they don't re-nest, so when the babies at long last fledge and the families move on,
your dog will be left in peace.
WHAT'S IN A TERRITORY?
A bird's diet and nesting habits determine what kind of territory it will defend. A sub-
urban robin prefers moist lawns with earthworms and berry-bearing plants to provide
food, and good tree limbs or house eaves for a secure nest site. A Barn Swallow looks
for a bridge, culvert, barn, or other building that provides struts, eaves, or other supports
for its heavy mud nest, near a pond or open field rich with flying insects.
Both species require mud for nest construction, so the best territories for each will
also contain wet, muddy shorelines or good puddles. In good swallow areas, insects are
far more abundant than the birds require, so many may nest close to one another without
it hurting each other's ability to find food for their own young. Robins could much more
easily deplete the supply of worms and other food on their territories if other robins nes-
ted too closely, so they defend their territories far more vigorously than do swallows.
Most hummingbirds seem to prefer territories with plenty of spider webs and lichens
becausetheyusethesematerialstobuildtheirnests.Anidealterritorymightalsoinclude
nesting sapsuckers. Before flowers open and produce nectar in spring, Ruby-throated
Hummingbirds can drink sap from wells in trees drilled by Yellow-bellied Sapsuckers.
Birds that nest in cavities but do not excavate their own, such as bluebirds and wrens,
search out these structures in suitable habitat that will supply their food needs.
Males of a few species, including tropical manakins, birds-of-paradise, bowerbirds,
andcocks-of-the-rock,defendterritoriesjustsotheycandisplaytofemalesthere.Dozens
or even hundreds of male Sharp-tailed Grouse or other grassland grouse species, includ-
ing prairie-chickens, gather on large display areas called leks. These spots may look like
any others to the human eye, but the grouse may return to them year after year, ignoring
other similar-looking spots nearby.
At the lek, males display by inflating colorful air sacs, erecting their tails, and stomp-
ing their feet. Competing males, especially those on the periphery of the lek, may come
to blows, pecking, biting, feather-pulling, wing-beating, and clawing at one another, es-
pecially when females enter the lek. Females may visit a lek several times during the
early nesting stages, but they build their nest and raise their chicks completely independ-
ently of the males, sometimes more than a mile from the lek.
SEE ALSO : page 238 for more on lek displays.
 
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