| The Trumpeter Swan (Cygnus buccinator) is North America’s largest waterfowl and a species of conservation concern due to severe population loss during Euro-American settlement of North America. Wildlife agencies are reestablishing Trumpeter Swans by translocating swans into historically occupied habitat, including returning swans to Grays Lake National Wildlife Refuge (GLNWR) in southeastern Idaho. Trumpeter Swans were released from 1989-1991, but the population persistently exhibits high cygnet mortality. I examined two biological factors potentially related to cygnet mortality at GLNWR, (1) incubation behavior of nesting adults and (2) genetic signals of inbreeding. Dysfunctional incubation behavior leads to impaired cygnet development and subsequent post-hatch vulnerability. Inbreeding can express deleterious alleles and can impair cygnet development and subsequent performance. I used continuous videography to measure incubation behavior in detail. To measure inbreeding, I extracted DNA from eggshell embryonic membranes and measured heterozygosity at microsatellite loci. I found no indication of dysfunctional incubation among adults. Cygnets had somewhat low levels of allelic diversity, but allelic diversity was similar to other swan populations. Adult incubation behavior and inbreeding likely are not causes of elevated cygnet mortality. Future research should focus on ecological factors of the marsh environment including food availability, parasitism, and length of breeding season for causes of cygnet mortality.
Keywords: Trumpeter Swan, Grays Lake National Wildlife Refuge, incubation, inbreeding, videography, microsatellite |