Black Swift has an estimated world breeding population of 150,000 (BirdLife International 2011), and a distribution of 1,278,000 km2 (BirdLife International 2011). The Breeding Bird Survey reports the area of greatest population concentrations of Black Swift in its North American distribution includes the western slope of the Coast Mountains of British Columbia and southern Alaska (Sauer et al. 2012), but survey effort may be influencing these numbers due to the difficulties in finding remote nesting colonies. The Survey indicates declines are occurring in these aforementioned areas as well as across other areas of their distribution, especially in California. Overall breeding range in California remains largely unchanged from that in the 1940s, but the entire coastal population has been in recent severe decline specifically in San Mateo and Santa Cruz counties (Collins and Robertson 2008). Levad et al. (2008) estimated 1000-1600 breeding birds in the Southern Rocky Mountain area based on surveys of 103 occupied sites, numbers similar to the estimate of 1400-1600 breeding birds in Colorado provided by Boyle (1998). Comparison of observed colony sizes by Levad et al. (2008) with those reported in earlier studies suggests little or no change in population levels over the past 50 years. The Black Swift population is not uniformly distributed across their entire range because of their specialized ecological nesting requirements (Knorr 1961, Levad et al. 2008). Most of the highest quality nesting habitat is already occupied (Levad et al. 2008) by adult swifts with high breeding site fidelity (Collins and Foerster 1995). Thus Black Swift population size may be limited by the availability of suitable nesting habitat (Levad et al. 2008). Black Swifts presumably breed at one year as in the chimney swift (Dexter 1969) and Vaux Swift (Bull and Collins 1996) but this has not been confirmed. They lay one egg per clutch and rear one clutch per season (Lowther and Collins 2002). The maximum reported age is 15 years 1 month (Lowther and Collins 2002). Given that Black Swifts appear to be a long-lived species with a low reproductive rate, food availability is likely playing a significant role in regulating population growth (Wiggins 2004).