Associated Species: Black Swift habitat is very specialized and there are no associated species.

Distribution: Black Swifts breed in scattered colonies in North America, from southeast Alaska to central Mexico (Kingery 1998). They tend to be more common along the west coast states from Mexico north into Canada. Their range extends into Arizona and Colorado. In Colorado the species is an uncommon summer resident in the San Juan Mountains and is very local in most other mountain ranges in the state. Breeding was first confirmed in the state in 1949 (Knorr and Baily 1950).

Habitat Requirements: Due to their exacting nesting requirements, Black Swifts probably never have been numerous in Colorado (Knorr 1961). They nest on precipitous cliffs near or behind high waterfalls. They tend to congregate in nesting colonies, usually fewer than ten pairs (Knorr 1961). Knorr outlined six specific habitat requirements for breeding Black Swifts in Colorado:

• Black Swifts nest within close proximity to falling water on a cliff. They place nests in small cavities within the spray zone or directly behind sheets of falling water.
• Nest sites have a commanding view from the nest colony over the surrounding terrain, enabling swifts to fly straight out from the nest colony and very quickly be hundreds of feet above the valley floor.
• The cliff face should be free of obstructions such as dense forest that would inhibit access to nests.
• Black Swift nest ledges are in deep shade the majority of the day, sunlit only late in the day as ambient air temperatures decline.
• The nest niche often has water flowing around or in front of the opening, but the nest cup itself is usually dry. Nest niches are often covered with moss and other hydrophilic plants.
• Occupied nest niches are always inaccessible to ground predators.

Ecology: Black Swifts arrive in Colorado in late May and begin nesting in June. They have extremely long incubation (24-27 days) and nestling (45-49 days) periods, and young do not fledge until September. All reports of Black Swift clutch sizes are of one egg only. Foraging birds range widely at high elevations over most montane and adjacent lowland habitats, seeking widely scattered "blooms" of aerial insects, particularly flying ants. Nestlings spend the day alone without food: typically adults return only in the evening with a meal of partly digested insects. Faced with day-long fasts, young grow extremely slowly, and may even exhibit torpor, a slowing of metabolism that could explain why Black Swifts choose cold, damp nest sites even when dry ledges exist nearby (Holroyd 1993). Another theory postulates that two other factors dictate the choice of nest sites: constant temperatures to ameliorate outside changes and high humidity to aid in attaching the nest to the cliff.

Management Issues and Conservation Recommendations: Conflicts related to nesting Black Swifts could include rock climbing, spelunking, mining, road construction, hiking, bicycling, horseback trails, water diversions, and housing developments. Probably the greatest disturbance to Black Swift nesting habitat is hiking trails to the base or top of waterfalls and any rock or ice climbing. The effect that ice climbing may have on nesting habitat needs research. Rock climbing can remove lichens, mosses and other hydrophilic plants needed in the building of nests, and climbing at waterfalls could disturb incubation, brooding, and foraging of swifts. Protect known nest sites and potential nest sites from disturbance, rerouting hiking trails or enforcing seasonal closures around the base or top of some cliffs during the breeding season. Establish buffer zones to minimize conflicts around important Black Swift nesting sites. Identify and designate sites as special areas (Research Natural Areas, Areas of Critical Environmental Concern, Special Management areas, Important Bird Areas, or sanctuaries). Determine whether winter ice climbing has any negative effects on nesting habitat (e.g., removal of hydrophilic plants). Determine whether roads, housing developments, or other human related activities have a negative impact on nesting or foraging habitat. Research Black Swift food sources particularly flying ants for threats such as herbicides or pesticides that would have a direct or indirect impact on those aerial insects.

Status and Reasons for Concern: This species has a high conservation need locally and throughout its range. Although the statewide total probably does not exceed a few hundred pair breeding at fewer than 50 known sites, at least 20% of all Black Swifts breed in Colorado (Kingery 1998). The 1998 Partners in Flight Watch List ranked Black Swifts nationally as a High Priority species (Carter et al. 1999). The Colorado Natural Heritage Program for rare and imperiled species ranks the Black Swift as vulnerable in the state. The Black Swift is classified as a Sensitive Species in U.S. Forest Service Region 2. BBS data are not adequate for meaningful analysis. CBO initiated a statewide monitoring program in 1998, and previously unknown breeding sites have been documented in 1998 and 1999. This species is monitored by MCB with a statewide census.

Biological Objective: Maintain current breeding densities at all known nest sites. Continue to monitor known breeding sites and survey other potential nest sites within the state. There is a high probability that there are unknown nest sites in Colorado.

Selected References: Andrews and Righter 1992, Bent 1940, Carter et al. 1999, Holroyd 1993, Kingery 1998, Knorr 1961, Knorr and Baily 1950.