18
19
within 1 m of an object, and 27 percent were directly
next to an object (e.g., cow pie, rock; Allen 1980).
Such objects are generally limited in curlew territories,
suggesting that individuals may intentionally place
nests near these objects, possibly to provide shade,
increase camouflage, or facilitate nest location by the
breeding pair.
Territoriality
Long-billed curlews are territorial during the
breeding season, defending nesting territories from pre-
laying through hatching of eggs (Allen 1980, Pampush
1980, Jenni et al. 1981). Territory size ranges from 6 to
8 ha (southeastern Washington) to 14 ha (Idaho), with a
buffer of unoccupied habitat 300 to 500 m wide around
the edge of each territory (Allen 1980, Jenni et al.
1981). Nesting territory appears to be primarily related
to the nest site, rather than food resources; adults often
forage outside of territories, and broods leave territories
after hatching.
Spatial patterns,
landscape mosaic,
juxtaposition of habitats
Long-billed curlews prefer large expanses of
mixed-grass or shortgrass prairie. In British Columbia,
breeding curlews used only grassland areas over 250
m across (Ohanjanian 1992). In southwestern Idaho,
curlew densities were positively correlated with size
of the management unit and with amount of area
within the management unit that contained vegetation
under 10 cm tall (Bicak et al. 1982). Area sensitivity
for many avian species has been well established,
and habitat fragmentation is generally thought to
be one of the primary causes of avian population
decline. Small fragments of grasslands cannot support
species that need interior habitats or large expanses
of grasslands (Samson 1980, Johnson and Temple
1986), and grassland birds are more likely to occur on
large patches of grassland than on small ones (Illinois:
Herkert 1994; Maine: Vickery et al. 1994). Herkert et
al. (2003) found higher nest predation in small (under
100 ha) than in large (over 1,000 ha) prairie fragments
in five mid-continental states. O’Connor et al. (1999)
report that grassland bird species are more influenced
by habitat patch variables and less by landscape
composition than other bird species.
Habitat change and causes
Degradation of habitat is the single greatest threat
to the long-billed curlew. The change in the extent of
habitat available to this species over time is mostly
due to losses to agricultural and urban development,
especially the conversion of mixed-grass and shortgrass
prairies to cultivated fields (Stewart 1975). In Canada,
76 to 99 percent of native grasslands have been lost to
agriculture and development (Pitt and Hooper 1994).
Mixed-grass prairie losses to cropland range from 72
to over 99 percent in North Dakota, Nebraska, Alberta,
Saskatchewan, and Manitoba (Samson and Knopf
1994). The extent of the loss of shortgrass prairie to
agriculture (especially to winter wheat on marginally
arable lands) is also significant. In Saskatchewan, for
example, only 17 percent of the original native prairie
remains, and in Wyoming over 20 percent has been
lost (Samson and Knopf 1994). Nearly 32 percent of
the shortgrass prairie region in the southwestern Great
Plains (including 30.7 percent in Colorado, 78 percent
in Kansas, 65.4 percent in Nebraska, and 12.1 percent in
Wyoming) has been converted to cropland (Knopf and
Rupert 1999). By comparison, more recent rangeland
losses to agriculture are smaller but not insignificant.
In Colorado, for example, 3.8 percent of the shortgrass
and mixed-grass prairie east of the Rocky Mountains
was lost to agriculture and urban expansion from 1982
to 1997 (Seidl et al. 2001).
Habitat loss in curlew wintering areas is also a
concern. In California’s Central Valley, 90 percent of
wetlands have been drained, and grassland habitats
are being lost to urban growth or converted to row
crops, vineyards, and orchards. In San Francisco Bay,
80 percent of inter-tidal habitats have been lost, and
changes in sedimentation and flows have changed
existing coastal habitats.
Habitat availability relative to occupied habitat
Annual variation in breeding populations and
habitat availability suggest that nesting habitats are
not always saturated (Bicak 1977, Allen 1980, Jenni et
al. 1981). Winter or migration habitats may also limit
population size, but this has not been investigated.
Food habits
Long-billed curlews are entirely carnivorous.
Their diet consists primarily of terrestrial insects,
marine crustaceans, and benthic invertebrates; some
small vertebrates are also taken (Dugger and Dugger
2002). Curlews use their long, decurved bill to forage
by probing for earthworms or burrow-dwelling
organisms such as shrimp and crabs. Probing is a major
foraging method during winter, whereas pecking may
be the most common foraging method on the breeding
grounds (Dugger and Dugger 2002). Curlews also hawk