Incubation strategy in marine birds

Abstract

The incubation shift length of the Ancient Murrelet ( Synthliboramphus antiquus), an exceptionally long and varied for an auk. I studied colonies of this species at East Limestone Island (1993-1995, 2002-2003: data collected by Laskeek Bay Conservation Society) and Reef Island (2007-2008), Haida Gwaii, British Columbia. Incubation shift length was correlated between pair members and my results show that maintaining incubation schedule was an essential component of reproductive success. Incubation shift length varied in response to prevailing local weather and sea conditions (e.g. wind speed, wave height), perhaps as a consequence of reduced foraging efficiency. Incubation shift length was longer in years when sea surface temperature in April was high. In years with longer shift, birds had lower reproductive success and chicks departed the nest with a lower body mass. My results explained if we assume that multi-day incubation shifts in Ancient Murrelets are the adaptively preferred strategy, through reduction in predation risk, but that actual shift lengths are modified by immediate weather and foraging constraints.