| Trumpeter Swans (Cygnus buccinator) underwent a severe population decline
during Euro-American settlement of North America but since have recovered from near
extinction by almost a century of active conservation management. Trumpeter Swans
construct unusually large nest mounds in northern marshes characterized by large daily
and seasonal thermal fluctuation. In summer 2020 and 2021, I measured Trumpeter Swan
incubation behavior and nest, egg, and environmental thermal characteristics at active
swan nests within the Red Rock Lakes National Wildlife Refuge in Montana, USA.
Behaviorally, swans were acutely responsive to the thermal environment. During active
incubation, swans maintained an egg temperature of 35.7 ± 0.27 °C. Linear mixed models
of thermal covariates revealed a fine-scale interactive association of nest attendance with
air temperature, solar radiation, and vapor density. Additionally, I observed previously
unreported Trumpeter Swan nesting behaviors, including egg retrieval and simultaneous
co-occupancy of a nest mound by breeding swans and breeding muskrats.
Key words: egg temperature, GLMM, incubation behavior, LMM, swan nesting, thermal
fluctuation, Trumpeter Swan |