Relocating a historical Black Swift nest and the importance of nest sites to the species.
Beebe (1959) provided the 1st evidence of Black Swift nesting in British Columbia. On 16 August 1958, a flightless Black Swift nestling was delivered to Beebe's home in Victoria. Apparently, the nestling was 1 of 2 Black Swift nestlings that were collected by a teenage boy on 15 August from a single nest located 4.57 m on a vertical rock face adjacent to a waterfall, approximately 2 mi north of Clinton, British Columbia. Beebe cared for the nestling by feeding the bird goat's milk, termites, and crickets; the nestling survived and was successfully released in Victoria, British Columbia on 25 August. There is no indication that Beebe attempted to relocate the nest site, nor that it has ever been relocated (Campbell and others 1990).
There are a number of reasons that would deter readers of Beebe's account from attempting to relocate the Clinton nest site: (1) the site location is a second-hand account from an unnamed teenage boy; (2) the waterfall is unnamed; and (3) the area surrounding Clinton is generally not known for waterfalls. The mention of 2 nestlings being removed from a single nest raises doubt of Beebe's account. It is now well established that Black Swifts lay a single egg per nest (Lowther and Collins 2002; Hirshman and others 2007); therefore, if 2 nestlings were collected in 1958, this would suggest 2 active nests were involved.
In 2014, 56 years after Beebe's nest account, I relocated what is presumed to be the original nesting site described by Beebe (1959). On 29 July 2014, I visited a series of waterfalls located approximately 6.4 km north of Clinton (Fig. 1), and conducted a 2-h search for evidence of nesting Black Swifts. I found 1 active Black Swift nest, but it was immediately clear that a more thorough inventory of the site was needed. I revisited the site on 3 August, and conducted a 7-h inventory over the approximately 500-m length of the Clinton Creek waterfall complex. No additional active Black Swift nests were located; however, I observed 4 empty nest structures that appeared to be Black Swift nests from previous years. The active Black Swift nest was beside the southern edge of Clinton Falls (Fig. 2). I measured the waterfall and nest heights by lowering a white rope marked with black tape at 30-cm intervals, from the top of the waterfall to the plunge pool; the waterfall was 6.75 m high and the nest was 4.35 m above the plunge pool. The substrate underlying the waterfall was limestone, and the exposed rock at the waterfall was eroded with many recessed cavities. The active Black Swift nest was located in a fist-sized cavity, and the nest appeared to be made entirely of moss (Fig. 3). An adult Black Swift remained on the nest during both visits, no egg or nestling was observed, and no additional adults were observed attending the nest. Evening surveys were not conducted at Clinton Falls on the days the site was visited, and Black Swifts were not observed in the area of Clinton during the 3 d of searching the area for waterfalls and Black Swift nests.
The Clinton Creek watershed is approximately 252 [km.sup.2] (Environment Canada 2015) and is the primary source of water for the 650 residents of the Village of Clinton. There are 57 water use permits that draw from Clinton Creek or its tributaries, with a total annual allocation of 2,147,690 [m.sup.3][y.sup.-1] (BC Ministry of Environment 2015). The main water users are the Village of Clinton (566,492 [m.sup.3][y.sup.-1]) and agriculture users (1,581,198 [m.sup.3][y.sup.-1]). The headwaters of Clinton Creek is owned by the Province of British Columbia. The creek then flows through residential and commercial properties in Clinton, followed by approximately 6 km of privately owned agricultural land before reaching Clinton Falls. The Province of British Columbia owns the land immediately surrounding Clinton Falls (Thompson-Nicola Regional District 2015).
It is believed that the nesting site reported here is the same site originally reported by Beebe (1959). There do not appear to be other suitable waterfalls with year-round water flow in the general area surrounding Clinton that fit the description in Beebe (1959) or that would provide suitable nesting habitat for Black Swifts. Black Swift populations may be limited by the availability of suitable nesting sites (Levad and others 2008); if so, relocating the Clinton nest site is significant. This account is also an example of how dependent Black Swifts are on their highly specific nest sites.
Black Swift breeding biology involves a prolonged nesting period and highly specific nestsite requirements. The most detailed account of Black Swift nesting phenology spans 11 y of nest-site monitoring in Colorado: a single egg is laid in late June, incubation lasts an average of 26 d, hatching occurs at the end of July, and is followed by an average 48-d nestling phase that results in fledgling dates into mid-September (Hirshman and others 2007). The prolonged nesting cycle is coupled with the use of cryptic nesting locations, often near or behind waterfalls, narrow canyons, cave entrances, sea cliffs, or sea caves (Lowther and Collins 2002). Black Swifts require nest sites to have 6 specific physical factors: high relief, close proximity to flowing water, inaccessibility to terrestrial predators, darkness, niches for nest placement, and open flight corridors to and from nests (Knorr 1961, 1993; Levad and others 2008). Microhabitat at Black Swift nests is stable, with low air temperatures and high relative humidity compared to ambient conditions, and these conditions remain stable throughout the nesting period. Gun and others (2012) recorded temperature and relative humidity using data loggers placed at Black Swift nests. At the Colorado and New Mexico sites, the median temperature and relative humidity at the nests during the nesting period were 9.4[degrees]C and 89.7%, respectively.
In keeping with the Black Swift's dependency on a potentially limited number of suitable nest sites, this species has relatively high nest-site fidelity. The 1st inland Black Swift nest was located in 1919 by CE Chapman at Johnston Canyon near Banff, Alberta (Bent 1940), and has likely been used continually as a breeding site for over 9 decades (Kondla 1973; Holroyd 1993; J Rogers, pers. comm.). Black Swift nest sites discovered by Knorr (1961) in Colorado between 1949 and 1958 were revisited between 1997 and 2005, occupancy was observed at 23 of 24 sites visited (Levad and others 2008). In California, Collins and Foerster (1995) noted high individual breeding-site fidelity with marked Black Swifts; 1 individual was recaptured at the same breeding colony during 3 breeding seasons over a 10-y period. The longevity record for an individual Black Swift is 16 y, 1 mo of age, based on 4 recaptures of the 89 Black Swifts banded in North America between 1955-2000 (Lowther and Collins 2002). Collins and Foerster (1995) suggested that the high individual nest-site fidelity and long adult life span contributed to long-term breeding at colony sites.
Given the high nest-site fidelity observed at other Black Swift nesting sites in North America, historical accounts of Black Swift nest sites, even vague accounts, should not be dismissed. Locating, monitoring, and protecting Black Swift nesting sites is critical to the conservation of this species.
Key words: Apodidae, Black Swift, British Columbia, Clinton, Cypseloides niger, nest site fidelity
Acknowledgements.--I would like to thank C Rock and R Toochin for their enthusiasm and valuable assistance in searching for Black Swift nests. L Shook of the Clinton Museum provided detailed directions to Clinton Falls. ] Rogers provided an update on the Johnston Canyon site. I thank E Knight for editorial comments on drafts of the manuscript. P Jost created the map used in Figure 1. The following were consulted regarding the known history of the Black Swift nest near Clinton: J Bowling, M McNicholl, I Robertson, M Sheppard, and W Webber.
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|Title Annotation:||GENERAL NOTES|
|Author:||Levesque, Paul G.|
|Publication:||Northwestern Naturalist: A Journal of Vertebrate Biology|
|Date:||Dec 22, 2015|
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