Translocation and early post-release demography of endangered Laysan teal |
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Authors: | M H Reynolds N E Seavy MS Vekasy J L Klavitter & L P Laniawe |
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Institution: | US Geological Survey, Pacific Islands Ecosystem Research Center, Hawaii National Park, Hawaii, HI, USA; Hawaii Cooperative Studies Unit (PACRC, UH Hilo), US Geological Survey, Pacific Island Ecosystems Research Center, Hawaii National Park, Hawaii, HI, USA; US Fish and Wildlife Service, Midway Atoll National Wildlife Refuge, Honolulu, HI, USA |
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Abstract: | In an attempt to reduce the high extinction risk inherent to small island populations, we translocated wild Laysan teal Anas laysanensis to a portion of its presumed prehistoric range. Most avian translocations lack the strategic post-release monitoring needed to assess early population establishment or failure. Therefore, we monitored the survival and reproduction of all founders, and their first-generation offspring using radio telemetry for 2 years after the first release. Forty-two Laysan teal were sourced directly from the only extant population on Laysan Island and transported 2 days by ship to Midway Atoll. All birds survived the translocation with nutritional and veterinary support, and spent between 4 and 14 days in captivity. Post-release survival of 42 founders was 0.857 (95% CI 0.86–0.99) during 2004–2006 or annualized 0.92 (95% CI 0.83–0.98). Seventeen of 18 founding hens attempted nesting in the first two breeding seasons. Fledgling success was 0.57 (95% CI 0.55–0.60) in 2005 and 0.63 (95% CI 0.62–0.64) in 2006. The effective founding female population ( N e) was 13. We applied these initial demographic rates to model population growth. The nascent population size increased to >100 after only 2 years post-release ( λ =1.73). If this growth rate continues, the size of the Midway population could surpass the source population before 2010. |
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Keywords: | Laysan duck Anas laysanensis matrix model asymptotic growth rate wild reintroduction effective breeding population |
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