Prey items of the Black Swift (Cypseloides niger) in Colorado and a review of historical data Author(s): Kim M. Potter, Carolyn Gunn, and Jason P. Beason Source: The Wilson Journal of Ornithology, 127(3):411-420. Published By: The Wilson Ornithological Society https://doi.org/10.1676/14-152.1 URL: http://www.bioone.org/doi/full/10.1676/14-152.1 BioOne (www.bioone.org) is a nonprofit, online aggregation of core research in the biological, ecological, and environmental sciences. BioOne provides a sustainable online platform for over 170 journals and books published by nonprofit societies, associations, museums, institutions, and presses. Your use of this PDF, the BioOne Web site, and all posted and associated content indicates your acceptance of BioOne’s Terms of Use, available at www.bioone.org/page/ terms_of_use. Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder. BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research. The Wilson Journal of Ornithology 127(3):411–420, 2015 PREY ITEMS OF THE BLACK SWIFT (CYPSELOIDES NIGER)IN COLORADO AND A REVIEW OF HISTORICAL DATA KIM M. POTTER,1,4 CAROLYN GUNN,2 AND JASON P. BEASON3 ABSTRACT.—The Black Swift (Cypseloides niger) was first discovered in Colorado in 1880, yet information on prey items taken by this species in Colorado is very rare. We collected and identified prey items of Black Swifts from three breeding locations in Colorado during August over a seven-year period (2006–2012) and identified 5,371 insects representing 10 orders and 54 families. We compare our data with historical Black Swift prey item information from other locations in North America. These data indicate that Black Swifts forage on a wider array of insect taxa and sizes than previously reported in other parts of its range. Received 7 October 2014. Accepted 31 December 2014. Key words: Black Swift, Cypseloides niger, diet, insects, prey. Diet is an important component of a species’ energy and nutritional needs; these insects are life history. Species whose diets are specialized completely swallowed and enter the stomach are potentially more vulnerable to population where they undergo digestion. Black Swifts also declines and extinction than those with generalist collect prey items that are stored in the esophagus diets (Krebs and Davies 1993, McKinney 1997). in the form of one or more boluses which enable Identifying species and populations at higher the birds to forage at long distances from their extinction risk is important for developing con- breeding colonies during the day and carry large servation strategies in relation to current and amounts of prey back to their single nestling expected environmental changes. Given that (Collins 1998, Collins and Peterson 1998). Black Swifts (Cypseloides niger) are a long-lived The only published historical information on species with a low reproductive rate (Wiggins Black Swift prey items for Colorado appears as 2004), food availability may be a significant a note by Drew (1882) who examined 10 birds factor in regulation of their population growth. collected near Howardsville (San Juan County) in Understanding the prey composition in the diet of 1880 and 1881. He reported that the birds had Black Swifts will provide a baseline for un- their crops filled with Ephemeridae, at that time derstanding how they might react to future a recognized broad taxonomic grouping of environmental disturbances including climate mayflies (Ephemeroptera). Over the next 125 change and habitat loss. years, researchers in California, Washington, and Black Swifts, like other swifts, feed exclusively Mexico collected stomach contents or regurgitat- on aerial insects that originate from various ed boluses of Black Swifts. Results of these aquatic and terrestrial habitats. Previous studies previous studies along with unpublished data are reported that Black Swifts are specialized foragers listed in Table 1. Collectively, the historical data concentrating on lipid-rich winged ants, or alates indicates that Black Swifts consumed representa- (Foerster 1987, Marı´n and Stiles 1992, Holroyd tives of more than 83 families of insects 1993, Marı´n 1999, Rudalevige et al. 2003). It has representing 12 orders (Homoptera has been also been suggested that the breeding of Black combined with Hemiptera), supporting Rathbun’s Swifts in southwestern Canada and the western (1925) assertion that “nothing in the nature of US is timed to the swarming period of alate ants aerial insect life is rejected by this bird.” O. A. which represent a concentrated food source found Knorr (pers. comm.) theorized that Black Swifts in dispersed patches (Holroyd and Jalkotzy 1986, will take any airborne insect and that airborne ant Marı´n 1999). Black Swifts ingest prey items for alates constitute only a small portion of an ant two reasons. They consume prey for their own population and their nuptial flights are very brief. Observations of Black Swift diet outside the 1 White River National Forest, Rifle Ranger District, US include those made by Holroyd (1993) who 0094 County Road 244, Rifle, CO 81650, USA. collected droppings of adult and nestling Black 2 P. O. Box 791, Dolores, CO 81323, USA. 3 Rocky Mountain Bird Observatory, 14500 Lark Bunting Swifts in Alberta, Canada that contained digested Lane, Brighton, CO 80603, USA. but identifiable insect parts apparently all 4 Corresponding author; e-mail: [email protected] representing alate ants. Stiles and Negret (1994) 411 412 THE WILSON JOURNAL OF ORNITHOLOGY TABLE 1. Comparison of invertebrate prey items captured by Black Swifts, quantified and listed by Order. Location: Colorado California Washington Mexico Sources: Levada 2004–2005 Drew 1882 Dixon 1935 Foerster 1987 Marı´n 1999 Rudalevige et al. 2003 Archived data 1891–1938b Davis 1931 Collins & Landy 1968 Prey Items: %%%%%% % % % Orders Aranaea ,1 ,1 Blattodea 8 Coleoptera ,151 Diptera 25 1 1 10 Ephemeroptera 25 100 2 Hemiptera 1 2 4 17 Homopterac 5 Hymenoptera 50 100 99 91 95 56 99 100 Isoptera ,1 ,1 N Lepidoptera ,1 ,1 Vol. 127, No. 3, September 2015 Neuroptera ,1 ,1 Psocoptera 1 Tricoptera ,1 Sample Typed/Number: B/2 B/10e S/1 B/2 B/10 B/4 S/22 B & S/1 B/2 Specimens (n) Unknown Unknown ,100 289 1,180 206 2,013 Unknown 276 a Levad, R. G. (unpubl. data). b USGS Patuxent Wildlife Research Center (unpubl. data) from specimens collected in western Washington and California (Jun–Sep). c Homoptera now combined with the Order Hemiptera. d Bolus/esophagus (B), stomach (S). e Difficult to determine exact number of stomachs examined. Potter et al. N BLACK SWIFT PREY ITEMS 413 described Black Swifts in migration near Popa- ruler with 10 mm increments or a calibrated ya´n, Colombia, feeding on large swarms of small ocular micrometer in a 10x eye piece on a Wild beetles represented by two genera of the Scar- M5A stereomicroscope (Leica Microsystems abaeidae (scarab beetles) and one genus in the (Schweiz) AG, Heerbrugg, Switzerland). Coccinellidae (ladybird beetles). There is no In this analysis, we reference unpublished data information about Black Swift diet at recently (R.G. Levad, pers. comm.); published data (Drew discovered wintering areas in South America 1882, Davis 1931, Dixon 1935, Collins and Landy (Beason et al. 2012). 1968, Foerster 1987, Marı´n 1999, Rudalevige et This study describes the taxon, number, and al. 2003); archived data from the USGS Patuxent size of prey items taken by Black Swifts in Wildlife Research Center; collective historical Colorado during the latter half of the breeding data referring to all the above; and data from the season. We summarize the prey items captured by current study. Black Swifts during the breeding season as found A dominance index (Berger and Parker 1970) in previous studies and compare the historical data was used for comparisons among studies because with our current findings. We examine these data of the substantial variation in specimen numbers. collectively to gain a greater understanding of Insect diversity within a bolus is dependent on Black Swifts’ diet. bolus size. The Berger-Parker Index is a simple measure of the numerical importance of the most METHODS abundant taxa and is represented by: d 5 Nmax/N, We collected regurgitated boluses from Black where d represents dominance of one taxon; Nmax Swifts during August 2006–2012 at three loca- is the number of individuals in the most abundant tions in Colorado, USA: Fulton Resurgence Cave taxon, and N is the total number of individuals in in Garfield County at 39u 499 090 N, the bolus. The results are presented as a percent- 107u 389 340 W; Zapata Falls in Alamosa County age. The index can be used at various taxonomic at 37u 379 090 N, 105u 339 110 W; and Box levels. Canyon Falls in Ouray County at 38u 019 060 RESULTS N, 107u 409 440 W. Swifts occasionally regurgi- tate complete or partial boluses from the upper We identified 5,371 insects representing 10 esophagus during handling. Forty fully or partially orders and 54 families from the 40 boluses we regurgitated boluses were retrieved incidentally collected (Appendix). Insects were identified to during mist-netting and banding sessions between the lowest possible taxonomic level; 164 of 1730 and 2140 hrs MDT as adults were returning insects could be identified to species, 2,371 to to their nests in the evening. All boluses were genus, 2,554 to family, 281 to order, and 1 to placed into vials with 70% ethanol and labeled, subclass. In our study, insects from four orders each vial containing only the bolus contents from made up more than 92% of all prey identified a single bird.