Williamson's Sapsucker (Sphyrapicus thyroideus)
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
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
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
Selected References: Andrews and Righter 1992, Crockett and Hadow 1975, Dobbs et al. 1997,
Kingery 1998, Sousa 1983.