First description of the incubation pattern of an endemic and endangered marine duck species, the Chubut steamerduck ( Tachyeres leucocephalus ), and related environmental characteristics

Information on incubation behaviour and influencing factors is important for species whose incubation is monoparental and of conservation concern. We assessed the incubation pattern of a noteworthy endangered southern South America marine duck species, the Chubut steamerducks ( Tachyeres leucocephalus ), in the Northern San Jorge Gulf, Patagonia, Argentina, in their core breeding area during 2015, 2016, and 2018. We described the laying and incubation period, characterized the nest incubation strategy, and determined the influence of environmental variables on its incubation strategy considering that weather conditions influence the incubation pattern. Our results showed that female Chubut steamerducks laid eggs every two days during sunrise; incubation starts once the female has full clutch size, then she increases nest attentiveness and takes nocturnal recesses ending in the morning. We suggested that nocturnal recesses during the incubation period contribute to minimizing avian predation. Even if weather conditions are one of the most important factors influencing the breeding behaviour of birds, we did not detect an environmental temperature and wind speed effect on the Chubut steamerducks’ breeding behaviour. This is the first description of Chubut steamerducks’ incubation rhythm, and we also present quantified measures of the incubation pattern. Our research provides valuable baseline information and contributes to increase knowledge on previously unknown life history features of this flightless, endemic, and vulnerable waterfowl species in the core of its narrow distribution range.