Uniparental incubation in a cool climate : behavioural adaptations in the Eurasian dotterel

Abstract

Energetic constraint during reproduction may limit the number or quality of young that a parent can produce per breeding attempt or the parent's longevity or future productivity, ultimately constraining lifetime reproductive success. The Eurasian dotterel Charadrius morinellus experienced energetic constraint during the Incubation period. Dotterel breed in the cold arctic-alpine zone and most breeding attempts are cared for by the male alone. The combination of a cold climate, giving high energetic costs of incubation and thermoregulation, and restricted foraging time due to uniparental Incubation, resulted in non-adaptive mass loss and constrained Investment of time and energy In incubation. If the incubation period is potentially energetically constrained, then behavioural mechanisms that reduce energetic costs could increase the production of young. When more energetically constrained, dotterel reduced the energetic cost of incubation by scheduling trips in conditions when the unattended eggs would have cooled more slowly and by making fewer, but longer trips. When suffering severe energetic constraint, some dotterel neglected their eggs for many hours: dotterel embryos' high chilling tolerance may have been necessary for successful uniparental incubation In a cold and unpredictable environment. Dotterel selected nest sites that allowed them to build larger nests with larger linings. Larger, better insulated nests probably decreased heat loss from the eggs and sitting parents, so reducing energetic costs during incubation. Sitting dotterel oriented into the wind, which probably reduced the disruption of their plumage and minimised their energetic expenditure on thermoregulation. In cooler conditions, dotterel changed their nest defence strategy and used energetically cheaper but probably riskier responses to simulated predators. Behaviours may be shaped under conflicting selective pressures and dotterel's management of their high energetic costs during the incubation period was constrained by egg-predation: dotterel's incubation scheduling appeared to be influenced by diurnal variation in the risk of predation and dotterel's nest defence behaviour traded-off energetic costs and the risk of predation. I declare that this thesis has been composed by myself and that it embodies the results of my own research. Where appropriate, I have acknowledged the nature and extent of work carried out in collaboration with others. This thesis presents data collected by myself over 2,212h spent in the alpine study areas from 288 days during my PhD field seasons in 1996,1997 and 1998. I also analyse some of Scottish Natural Heritage's dataset on dotterel biology collected between 1987 and 1999 by a team of fieldworkers, including myself (in Chapters 2,7 and 8).