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First Records of Least Terns Nesting on Non-Gravel Roofs
T. Natasha Warraich, Ricardo Zambrano, and Elizabeth A. Wright

Southeastern Naturalist, Volume 11, Issue 4 (2012): 775–778

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First Records of Least Terns Nesting on Non-Gravel Roofs T. Natasha Warraich1, Ricardo Zambrano1,*, and Elizabeth A. Wright2 Abstract - Sternula antillarum (Least Tern) and other waterbirds have nested on tar-and-gravel roofs in Florida starting from the early 1950s. Habitat disturbance and loss has been implicated as the primary reason for this shift from the ground to roofs. The Florida Fish and Wildlife Conservation Commission conducted a statewide survey of rooftop-nesting birds between April and July 2010. Two buildings with non-gravel roofs were found to contain Least Tern nests; one was located on Islamorada in the Florida Keys, and the other on Pensacola Beach in the Florida Panhandle. Both of these sites were formerly gravel roofs and were used for nesting by Least Terns for several years; however, they had both been recently reroofed. The Islamorada site has a spray polyurethane foam roof, and the Pensacola Beach site has a mineral built-up roof. Both sites produced chicks, but only the Pensacola site fledged young. These are the first published records of a waterbird species nesting on a non-gravel roof. This discovery may have future implications as gravel roofs, particularly in Florida, are being replaced by newer types of roofs that are safer to humans and surrounding structures during tropical storms and are more energy efficient. Further surveys are needed to determine the extent of Least Tern nesting on non-gravel roofs and the productivity of these rooftop breeding colonies. Sternula antillarum Lesson (Least Tern) traditionally nest on flat beaches, sandbars, and spoil islands, which have coarse sand or shells with little to no vegetation (Thompson et al. 1997). However, because of habitat loss due to coastal development, an increase in human disturbance, and mammalian predation, Least Terns and other beach nesting birds such as Rynchops niger L. (Black Skimmer), Gelochelidon nilotica Gmelin (Gull-billed Tern), Sterna dougallii Montagu (Roseate Tern), and Haematopus palliatus Temminck (American Oystercatcher) have been documented to nest on tarand- gravel roofs (Douglass et al. 2001, Gore et al. 2008, Lott 2006; Thompson et al. 1997, Zambrano and Smith 2003, Zambrano et al. 2000). A tar-and-gravel roof (hereafter a gravel roof) consists of a layer of tar spread over a roof and then covered with a layer of gravel (DeVries and Forys 2004). This rooftop nesting behavior was first reported for Least Terns in Miami Beach, FL in the early 1950s (J.K. Howard in Fisk 1978) and has since been recorded in Maryland, North and South Carolina, Georgia, Mississippi, Louisiana, and Texas (Butcher et al. 2007, Jackson and Jackson 1985, Krogh and Schweitzer 1999). In Florida, Least Terns increasingly have used roofs for nesting, and rooftop nests now outnumber those in ground-nesting colonies. Zambrano et al. (1997) found 93% of Least Terns breeding in southeast Florida nested on roofs and Gore et al. (2007) found 74% of Least Tern colonies on roofs statewide. The Least Tern is listed as a threatened species in Florida, in part, because of the loss and degradation of habitat for ground-nesting colonies (Florida Fish and Wildlife Conservation Commission 2010). The Florida Fish and Wildlife Conservation Commission (FWC) conducted a comprehensive statewide survey from April through June 2010 of historically used and newly reported sites with roof-nesting seabirds and shorebirds. Surveyors visited each site at least once to conduct a peak count of nests and adults where present, and to determine the 1Florida Fish and Wildlife Conservation Commission, 8535 Northlake Boulevard, West Palm Beach, FL, 33412. 2239 8th Street, Apalachicola, FL 32320. *Corresponding author - Ricardo.Zambrano@ Notes of the Southeastern Naturalist, Issue 11/4, 2012 775 776 Southeastern Naturalist Vol. 11, No. 4 site’s current roof type. Follow-up visits were made to active breeding sites to conduct counts of chicks and fledged young. Sites that initially were inactive but still had gravel roofs were surveyed multiple times to determine whether colonies might have been established later in the season. Surveyors typically did not revisit sites that no longer had gravel roofs. To minimize disturbance, surveys were conducted from the periphery of the colony or from a nearby roof using binoculars or spotting scopes, otherwise walk-through nest counts were conducted. Out of 474 sites surveyed in Florida during 2010 statewide, 22% (n = 103) had been reroofed and converted from gravel to newer, non-gravel materials. Least Terns were found nesting on 2 of those non-gravel roofs. These are the first published records of a waterbird species nesting on a non-gravel roof. One site was located in Islamorada in the Florida Keys, and the other site was in Pensacola Beach, in the Florida Panhandle. Both sites were used historically by Least Terns as breeding sites (Gore et al. 2007), both formerly had gravel roofs, and both had been re-roofed with a non-gravel material. Coincidentally, nesting on these non-gravel roofs was first documented at both sites on 28 May 2010. The Islamorada building had a spray polyurethane foam (SPF) roof that consisted of two different components: a light grey elastomeric coating membrane over polyurethane foam (National Roofing Contractors Association 2010b). This site was visited 4 times between May and July 2010. A maximum of 10 nests and 3 chicks was observed at this site. No fledged young were recorded before the site was found abandoned on 27 July 2010. One of the tenants informed us that the roof was converted to an SPF roof in November 2009 and that the Least Terns had nested there for over 25 years (D. Bailey, Islamoradora, FL, pers. comm.). As a follow-up, this site was resurveyed during the 2011 nesting season. Two Least Tern nests were observed on 12 May 2011, and 3 Least Tern nests, 1 flightless chick, and 1 fledged young were recorded on 27 June 20 11. The Pensacola Beach site had a mineral built-up roof, consisting of asphalt-based roll roofing with a sprayed-on surface coating of fine white mineral granules in a polymer base (L. Jackson, Pensacola Beach, FL, pers. comm.; National Roofing Contractors Association 2010a). This site was visited 7 times between May and July 2010 on an approximately weekly basis. A maximum of 2 Least Tern nests and 1 chick was observed. One fledged young was observed flying from this roof and returning to it repeatedly on 12 July 2010. It is unclear how long Least Terns had been nesting on the Pensacola Beach site: FWC records indicate it was identified as active in 1993 and 1998–2000 (Gore et al. 2007, Hovis and Gore 2000). Its gravel roof was replaced with the current roofing material in late 2005, following hurricane damage (L. Jackson, pers. comm.). Due to logistical and personnel constraints, this site was not resurveyed in 2011. Prior to our study, roof-nesting Least Terns had only been recorded on gravel roofs. This decline in the availability of gravel roofs for breeding sites was not unexpected because many buildings owners in Florida are phasing out gravel roofs. Gravel roofs generally have lower solar reflectance and lower heat emittance than new roof materials. New buildings in Florida, must comply with the Florida energy code which sets minimum standards for energy efficiency of roofs (DeVries and Forys 2004). Federal tax incentives also encourage the replacement of gravel roofs with more energy efficient ones (US Environmental Protection Agency 2010). Further, gravel on these roofs may be picked up by strong winds during strong storm events and can cause projectile damage to adjacent structures (US Department of Housing and Urban Development 1993). This has led to at least one state’s building commission to propose legislation prohibiting the use of gravel 2012 Southeastern Naturalist Notes 777 on roofs (Florida Department of Community Affairs 2010). Given that the average life span of a gravel roof is 20–25 years, DeVries and Forys (2004) estimated that most of these roofs would no longer be available in 20 years. Both non-gravel-roof sites discussed in this paper are historically used sites which formerly had gravel roofs. It is unknown whether Least Terns or other beach-nesting birds will nest on non-gravel roofs that have no prior history of use as breeding sites. More information is needed on the reproductive success of beach-nesting birds utilizing non-gravel roofs. If future surveys find certain types of non-gravel roofs more suitable for successful nesting and fledging of young than others, it may be appropriate to recommend these roof materials to developers and building owners or provide financial incentives to encourage their us e. Acknowledgments. We thank Drs. Jeanette Wyneken, Terry Doonan, and Jim Rodgers for reviewing earlier versions of this manuscript. Literature Cited Butcher, J.A., R.L. Neill, and J.T .Boylan. 2007. Survival of Interior Least Tern chicks hatched on gravel-covered roofs in north Texas. Waterbirds 30:595–601. DeVries, E.A., and E.A. Forys. 2004. Loss of tar and gravel rooftops in Pinellas County, Florida and potential effects on Least Tern populations. Florida Field Naturalist 32:1–6. Douglass, N.J., J.A. Gore, and R.T. Paul. 2001. American Oystercatchers nest on gravel-covered roofs in Florida. Florida Field Naturalist 29:75–112. Fisk, E.J. 1978. The growing use of roofs by nesting birds. Bird Banding 49:134– 141. Florida Department of Community Affairs. 2010. Comparison of the 2007 Florida Building Code/2006 ICC with the 2007 Supplement to the 2006 I-Codes. Available online at http://www. Accessed 30 September 2010. Florida Fish and Wildlife Conservation Commission. 2010. Florida’s endangered species, threatened species, and species of special concern. Florida Fish and Wildlife Conservation Commission, Tallahassee, FL. Gore, J.A., J.A. Hovis, G.L. Sprandel, and N.J. Douglass. 2007. Distribution and abundance of breeding seabirds along the coast of Florida, 1998–2000. Final Performance Report. Florida Fish and Wildlife Conservation Commission, Tallahassee, FL. Gore, J.A., H.T. Smith, B.S. Smith, and W.A. Gierhart. 2008. Recent nesting of Gull-billed Terns on gravel roofs in Florida. Florida Field Naturalist 36:83–89. Hovis, J.A., and J.A. Gore. 2000. Nesting shorebird survey. Florida Fish and Wildlife Conservation Commission Final Performance Report, Tallahassee, FL. Jackson, J.A., and B.E.S. Jackson. 1985. Status, dispersion, and population changes of the Least Tern in coastal Mississippi. Colonial Waterbirds 8:54–62. Krogh, M.G., and S.H. Schweitzer. 1999. Least Tern nesting on natural and artificial habitats in Georgia, USA. Waterbirds 22:290–296. Lott, C.A. 2006. Distribution and abundance of the Interior population of the Least Tern (Sternula antillarum), 2005. A review of the first complete range-wide survey in the context of historic and ongoing monitoring efforts. Final Report to the US Army Corps of Engineers. The American Bird Conservancy, The Plains, VA. National Roofing Contractors Association. 2010a. Built-up roof (BUR) membranes. Available online at Accessed 10 October 2010. National Roofing Contractors Association. 2010b. Spray polyurethane foam-based (SPF) roof systems. Available online at Accessed 1 September 2010. Thompson, B.C., J.A. Jackson, J. Burger, L.A. Hill, E.M. Kirsch, and J.L. Atwood. 1997. Least Tern (Sterna antillarum). No. 290, In A. Poole (Ed.). The Birds of North America. Cornell Lab of Ornithology, Ithaca, NY. 778 Southeastern Naturalist Vol. 11, No. 4 US Department of Housing and Urban Development (HUD), Office of Policy Development and Research. 1993. Assessment of damage to single-family homes caused by Hurricanes Andrew and Iniki. Washington, DC. US Environmental Protection Agency. 2010. Federal tax credits for consumer energy efficiency. Accessed 1 September 2010. Zambrano, R., and H.T. Smith. 2003. Southernmost breeding of Black Skimmers along Atlantic Coast of Florida is restricted to rooftops. Florida Field Natur alist 30:1–3. Zambrano, R., H.T. Smith, and M. Robson. 2000. Summary of breeding Roseate Terns in the Florida Keys: 1974–1998. Florida Field Naturalist 28:64–68. Zambrano, R., M.S. Robson, and D.Y. Charnetzky. 1997. Distribution and status of Least Tern nesting colonies in southeast Florida. Florida Field Naturalist 25(3):85–116.