14
15
Figure 7. Breeding Bird Survey trend map (average percent population change per year) for long-billed curlew from
1966 to 2003.
southwestern Idaho (Dugger and Dugger 2002), and
the last week of March for Kansas (Thompson and Ely
1989), South Dakota (South Dakota Ornithologists’
Union 1991), Utah (Paton et al. 1992), and Oregon
(Gilligan et al. 1994). The spring migration peak occurs
in mid-March in Texas and in mid-April in Utah (Paton
et al. 1992). Curlews arrive in Colorado in mid- to
late-March (King 1978), and in Wyoming from mid- to
late-April (Salt and Wilk 1966). Early arrival dates in
Canada are the first week in April in British Columbia
(Campbell et al. 1990), 8 April in Saskatchewan
(Renaud 1980), and 16 April in Alberta (Salt and Wilk
1966). Peak arrival occurs in British Columbia from
late March to early April (Campbell et al. 1990), and in
Saskatchewan and Alberta from mid- to late-April (Salt
and Wilk 1966, Renaud 1980).
Long-billed curlews arrive on breeding areas
in small, heterosexual groups (Jenni et al. 1981),
averaging two or three individuals (Saskatchewan)
(Renaud 1980), but flocks of 50 have been reported
in British Columbia. Some non-breeders summer on
coastal wintering areas (Colwell and Mathis 2001), and
small flocks of apparent non-breeders occur on breeding
areas in southeastern Washington (Allen 1980) and
British Columbia (Campbell et al. 1990).
The breeding season for long-billed curlews in
most areas is from early April through June, extending
into July in some areas (Dugger and Dugger 2002).
Median clutch-completion dates for 3 years in Idaho
were 14, 19, and 24 April (Redmond 1986), but late
egg-laying dates include the end of May in Colorado
and Utah, 4 June in British Columbia (Campbell et
al. 1990), and early July in Saskatchewan and Idaho
(Dugger and Dugger 2002). Egg hatching normally
occurs from May through June (Oregon, Idaho,
Washington, Utah, and Colorado) to early to mid-July
(Wyoming) (Dugger and Dugger 2002).
Curlews periodically depart the breeding grounds
in small flocks, with no real evidence of fall staging
(Campbell et al. 1990). During late summer and
migration, flocks of 10 to 50 birds are common (range =
100 to 500; Allen 1980, Renaud 1980, Pampush 1981,
Campbell et al. 1990, Roy 1996). Small migratory flocks
in Utah during fall contain one or two adults and two to
four juveniles, suggesting that family groups sometimes
migrate together (Paton and Dalton 1994).
Long-billed curlews depart their breeding
grounds relatively early. In Saskatchewan and British
Columbia, most birds depart by late August (Renaud
1980, Campbell et al. 1990); early August is believed
to be the peak of fall migration in South Dakota (South
Dakota Ornithologists’ Union 1991). In Utah, the
number of breeders on areas around Great Salt Lake
declines after the first week of June (Paton and Dalton
16
17
1994). In Kansas, fall migrants are commonly seen
from 21 August to 25 September (Thompson and Ely
1989). Curlews first arrive in the Playa Lakes region,
Texas, between 28 July and 13 August, and in Sonora,
Mexico, most curlews pass through in August and
September (Russell and Monson 1998). In the southern-
most portion of their winter range (Costa Rica), curlews
have been recorded beginning in mid-December (Stiles
and Skutch 1989).
Habitat
Habitat associations
Long-billed curlews are native prairie specialists,
nesting primarily in shortgrass or mixed-grass prairie
habitat with flat to rolling topography (King 1978,
Pampush 1980, Jenni et al. 1981, Pampush and
Anthony 1993, Hooper and Pitt 1996). They prefer short
vegetation, generally less than 30 cm tall (often less than
10 cm), and generally avoid habitats with trees, a high
density of shrubs (e.g., sagebrush [Artemisia spp.]), and
tall, dense grass (Pampush 1981, Campbell et al. 1990,
Pampush and Anthony 1993). Open, sparse grassland
habitats may facilitate predator detection, and foraging
with such a long bill may be difficult or inefficient
in tall, dense habitats (Redmond 1986). Curlews use
taller, denser grass during brood rearing when shade
and camouflage from predators are presumably more
important for chicks (Jenni et al. 1981), but this may
also reflect a decline in the availability of shorter
habitats later in the season. Curlews will also nest
in croplands if vegetation is of the correct height.
Climate modeling indicates that the limits of curlew
breeding distribution are correlated with high summer
precipitation (average >68.1 mm) in the east, high
winter precipitation (average >89.5 mm) in the west,
low winter temperatures (average <-12.2 °C) in the
north, and high summer temperatures (average >24.9
°C) in the south (Price 1995).
Long-billed curlews in Colorado used shortgrass,
mixed-grass, and weedy areas more than expected
based on the availability of those habitats (King 1978).
They used agricultural areas (i.e., cropland, stubble
fields, bare ground) less than expected based on
availability and did not use areas dominated by sand
sagebrush (Artemisia filifolia). In the Platte River Valley
of Nebraska, curlews nested at higher densities in wet
meadows than in upland prairie (Faanes and Lingle
1995). Within the sandhill grasslands of Nebraska,
proximity of mixed-grass uplands to wet meadows
was the most important criterion in nest-site selection
(Bicak 1977). In north-central Oregon, areas of shrubs
or areas of downy brome (Bromus tectorum) intermixed
with patches of Sandberg’s bluegrass (Poa sandbergii)
were preferred or used in proportion to availability
(Pampush 1980, Pampush and Anthony 1993). Areas of
dense forbs, antelope bitterbrush (Purshia tridentata),
and bunchgrasses were used in proportion to their
availability or were avoided.
In winter along the Pacific Coast, curlews use
tidal estuaries, wet pasture habitats, and sandy beaches;
unlike willets (Catoptrophorus semipalmatus) and
marbled godwits (Limosa fedoa), curlews use beach
habitat infrequently (Stenzel et al. 1976, Colwell and
Sundeen 2000). They commonly roost in high-elevation
salt marsh during high tide (Page et al. 1979, Danufsky
2000). In California (Humboldt Bay), wintering curlews
regularly occur only in tidal mudflats (27 percent of
surveys) and salt marshes (37 percent) (Gerstenberg
1979) or use flooded and unflooded cultivated rice
(Oryza spp.), managed wetlands, evaporation ponds,
sewage ponds, and grassland habitats (Central Valley)
(Day and Colwell 1998, Shuford et al. 1998, Elphick
2000). Along the Gulf Coast of southeastern Texas,
long-billed curlews almost exclusively use shallowly
inundated mudflats (Brush 1995) but frequently move
between intertidal flats and inland areas (Brush 1995).
Of the shallow-water habitats, curlews use
flooded agricultural fields most in winter and managed
wetlands most in spring; in late summer/fall, most
were reported in pastures, drainage ditches, sloughs,
streams, farm ponds, and reservoirs (Shuford et al.
1998). Curlews used flooded rice fields more during
dry versus wet years. Use was independent of harvest
practices (i.e., conventional vs. stripper-header),
winter hydroperiods (i.e., dry, puddled, intentionally
flooded), and post harvest treatment of stubble (i.e.,
none, burned, chopped, rolled, plowed) (Elphick and
Oring 1998, Shuford et al. 1998). Curlews occurred
more frequently in fields flooded <16 cm deep, where
median water depth was approximately 5 cm (Elphick
and Oring 1998).
Long-billed curlews favor a wide range of
habitats during migration, including dry short-grass
prairie, wetlands associated with alkali lakes, playa
lakes, wet coastal pasture, tidal mudflats, salt marsh,
alfalfa fields, barley fields, fallow agriculture fields, and
harvested rice fields (Colwell and Dodd 1995, Davis
1996, Warnock et al. 1998, Manzano-Fischer et al.
1999, Danufsky 2000). In northern Chihuahua, Mexico,
curlews occur in association with prairie dog colonies in
fall (Manzano-Fischer et al. 1999). In the Playa Lakes
region of Texas, at least 95 percent of flocks during