Geoscience Reference
In-Depth Information
A
B
Figure 7-18.
Laguna Atascosa National Wildlife Refuge, southern Texas, United States. This refuge is a key site on
the central l yway; migrating birds avoid crossing over the Gulf of Mexico to the east and inland deserts to the
west. A. Overview looking toward the northeast with Lagua Madre, a hypersaline lagoon, on the right and the
mainland on the left (see Color Plate 7-18A). B. Detail view of tiny, crescentic island and shallow shoals within
Laguna Madre. Such islands are important bird sanctuaries, as predators cannot reach them. Kite aerial photographs
by S.W. Aber and J.S. Aber.
and gulls are among the many kinds of shore-
birds. As with other animals, it is most instruc-
tive to consider the beaks and feet to understand
how birds eat and how they move around on
land or in water.
Shorebirds comprise more than 200 species
that have long legs and highly specialized
beaks
-
most are members of the Charadriidae
(lapwing and plover) or Scolopacidae (sand-
piper and snipe) families (Dugan 2005). They
are normally seen wading in shallow water or
walking on mudl ats in which they probe for
various insects, other small animals, and vegeta-
tion. Many species may live and feed together
in these habitats, often in large numbers; each
species is specialized for a particular method of
probing for food in different depths of water or
levels below the mudl at surface (Fig. 7-21).
The black-necked stilt (
Himantopus mexica-
nus
) favors shallow marshes and l ooded i elds
and is found throughout the Great Plains of the
United States. It has a long neck, long legs, and
a straight beak that is needle sharp (Fig. 7-22).
Different races of this species are found around
the world in temperate and tropical environ-
ments (Fellows and Gress 2006). The American
avocet (
Recurvirostra americana
) has quite a
different beak that is slender, long, and curved
