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Figure 7-36. Bald eagle ( Haliaeetus leucocephalus )
dries its feathers on a utility pole, Kodiak, Alaska,
United States. Modii ed from original photograph by
M.L. Stephenson; obtained from Wikimedia Commons
<
http://commons.wikimedia.org/
>
.
motorboats, low-l ying airplanes, and walking
too close to nesting sites. Raptors and other
i shing birds are at the top of the food chain in
many wetland ecosystems, and the i sh they
consume may have accumulated heavy metals
and other toxic compounds derived from human
pollution. Widespread use of pesticides has
caused thinning of egg shells for many bird
species, as documented by Rachael Carson in
her inl uential topic Silent Spring (1962). A com-
bination of these factors brought many wetland
bird species to the brink of extinction in the
mid-twentieth century. Increased public aware-
ness and conservation efforts since then have
led to remarkable recovery for some species,
most notably the bald eagle (Fig. 7-36).
Figure 7-35. Snail kite ( Rostrhamus sociabilis ) holding
a snail shell. Photo adapted from Everglades NPS
<
http://www.nps.gov/ever/naturescience/Snail-Kite.
htm > .
7-1). Among the most specialized is the snail
kite ( Rostrhamus sociabilis ). It is widespread in
Central and South America, Mexico and Cuba,
but is found only in vicinity of the Everglades
and Lake Okeechobee, Florida in the United
States (Tyson 2009). This kite feeds almost
exclusively on apple snails ( Pomacea paludosa ),
which it catches in shallow water and extracts
from shells with its slender, hooked beak (Fig.
7-35). The brightly colored snails are heavily
collected by shell hunters; the snails are further
limited by loss of fresh-water habitats. Thus, the
snail kite is listed as endangered in the United
States, but is not considered threatened for the
rest of its range.
Continuing loss of wetland habitat is the
single greatest threat to wetland birds. Many
are especially sensitive to any kind of human
disturbance, such as nearby airboats and
7.3.4 Mammals
Mammals, like other animals, have adapted to
diverse niches throughout the Earth's biosphere.
Several familiar mammals are specialized for
wetland habitats; for example, beaver, otter,
muskrat, mink, moose (Fig. 7-37), hippopota-
mus (see Fig. 1-2), and seals (Fig. 7-38). These
animals spend most, if not all, their life cycles
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