Willet (Catoptrophorus semipalmatus)
Associated Species: Other species that may use habitat in a similar way and/or respond similarly
to threats, management, and conservation activities include Wilson's Phalarope, American
Avocet, Killdeer, and Savannah Sparrow.
Distribution: Willets nest only in North America. Nesting occurs in saltwater marshes of the
Atlantic and Gulf coasts and in the Great Basin and prairies of the western U.S. and Canada. In
Colorado, the species breeds primarily in North Park. A small number (1 or 2 pairs) recently
began breeding at Fruitgrower's Reservoir in Delta County, and there is evidence of breeding at
Antero Reservoir, and in Moffat and Alamosa counties (Kingery 1998).
Habitat Requirements: Willets nest near open water in marshes, wet meadows, and prairies
with short, sparse vegetation. They forage largely in the shallow water of ponds and playas.
Broods need taller, denser vegetation (>15 cm; 6 in) than that found at the nest site. Territory
size is about 44 ha (110 ac), but nesting birds may be area-sensitive--in North Dakota, they are
rarely found in small (<100-ha; 250-ac) wetland/grassland blocks (Ryan and Renken 1987).
Preferred areas are those that provide a mosaic of these habitat types (wet meadows for nesting,
shallow open water for foraging, taller vegetation for brood rearing) within an area large enough
to contain at least one territory (i.e., 40 ha; 100 ac).
Ecology: Colorado's Willets arrive on the breeding grounds in late April and May, lay eggs in
late May, and hatch young by late June. The birds leave for their wintering grounds by
Management Issues and Conservation Recommendations: As with nearly all species of
conservation concern, habitat loss is a consideration. Preserve suitable habitat by protecting it
from conversion to other land cover types (cropland, urbanization) or other development (roads,
trails, recreational sites).
Willets are ground-nesters and therefore highly susceptible to predation. Where land management
encourages proliferation of such species as foxes, coyotes, skunks, and raccoons, there is the
possibility of increased mortality during nesting. In addition, since adults abandon the nests
readily to distract potential predators, frequent human disturbance is likely to have significant
impacts to breeding success. Limit visitor access to known breeding habitat. Maintain trails and
roads away from breeding habitat.
Burning or grazing outside of the nesting season can create the short, sparse vegetation profile
preferred by nesting Willets. However, livestock densities are likely to correlate with the
possibility of nest trampling. Limit stocking rates during nesting season in known Willet breeding
Waterfowl management can maintain or enhance the habitat for this species, such as protection of
taller vegetation for nesting. However, management that maintains deep water with few beaches
or shallow water areas can be detrimental. Waterfowl management plans and activities should
consider impacts on Willet habitat.
Focus conservation efforts on the North Park population (unless additional breeding populations
are discovered). Population increases may be possible by determining the direct causes of
mortality during breeding (e.g., predation by enhanced populations of some carnivores).
Status and Reasons for Concern: This species is on the national Watch List, indicating a high
conservation need throughout its range. Willets are not adequately monitored by the BBS within
Physiographic Area 62, and data collected between 1966 and 1996 are too sparse for meaningful
analysis. This species is monitored by MCB with a statewide census.
Biological Objective: Maintain or increase the species' distribution and abundance, as based
upon results of BBS or MCB monitoring programs.
Selected References: Andrews and Righter 1992, Kantrud and Higgins 1992, Kingery 1998,
Ryan and Renken 1987.