Associated Species: Other species that may use habitat in a similar way and/or respond similarly to threats, management, and conservation activities include Red-naped Sapsucker, House Wren, and Western Bluebird.

Distribution: Williamson's Sapsuckers breed in forested regions throughout the western United States, except for the coastal areas and Southwest. In Physiographic Area 62, populations are concentrated along the eastern edge of the Rockies and in the San Juan Mountains in southwestern Colorado, with smaller numbers in appropriate habitat throughout the area. They winter from northern Arizona and northern New Mexico south into central Mexico.

Habitat Requirements: Williamson's Sapsuckers nest primarily in ponderosa pine and in aspen components of mixed-conifer. They often place nest cavities in aspen trees, and often choose nest trees in aspen stands adjacent to open ponderosa pine or mixed-conifer forest. Nest substrate preferences appear to be live aspen (with some decay) or aspen snags, followed by conifer snags.

Ecology: Birds generally arrive in Colorado in early to mid April, and nest cavity excavation begins within three weeks of the females' arrival and lasts 3-4 weeks. They lay eggs in May to early June, and young leave the nest about mid July. Birds leave for wintering grounds in September to mid October. They feed on conifer sap and phloem during the pre-nesting phase, and shift to invertebrates (principally ants, but also beetles, flies, and aphids) after the young have hatched.

Management Issues and Conservation Recommendations: These sapsuckers require large-diameter trees for nesting: in Colorado, mean dbh of ponderosa pine nest trees was 50.8 cm (20 in; Crockett and Hadow 1975). They apparently tolerate some timber harvesting activities, provided aspens and snags are retained for nesting substrate, especially if clusters of large snags are preserved. Fire can create snags for nesting. Large snags created by fire should be retained rather than "salvaged." Retain at least 6 snags per 40 ha (100 ac), each at least 46 cm (18 in) dbh if ponderosa pine or 30 cm (12 in) dbh if aspen or other conifer species (Crockett and Hadow 1975, Raphael and White 1984).

Status and Reasons for Concern: Williamson's Sapsuckers have a high conservation need locally and throughout their range. Also, a high proportion (17.6%) of this species' total population occurs within this physiographic area, indicating that this area has high responsibility for the conservation of this species. Williamson's Sapsuckers are not adequately monitored by the BBS within Physiographic Area 62, and data collected between 1969 and 1996 are too sparse to allow analysis of trends (n = 13 routes). Williamson's Sapsuckers were present on an average of 23.22% (SE = 4.39) of the BBS routes run in Physiographic Area 62 in Colorado during 1988-1997, at an average abundance of 0.46 (SE = 0.13) individuals per route. The mean number of routes run each year was 21.1 (SE = 3.06). This species is monitored by MCB with point transects.

Biological Objective: Maintain or increase the species' distribution and abundance, with progress toward meeting this objective based upon results of the BBS, MCB, or other monitoring programs.

Selected References: Andrews and Righter 1992, Crockett and Hadow 1975, Dobbs et al. 1997, Kingery 1998, Sousa 1983.