Foraging behaviour of sympatric razorbills and puffins

Abstract

Many marine predators coexist at colonies, creating a zone where there could be significant inter-and intraspecific competition. To minimize the potential for direct competition, under the principle of competitive exclusion, sympatric predators may differ in their foraging behaviour at the colony. At Skomer, Wales, razorbills Alca torda and puffins Fratercula arctica both breed at the same time of year, forage on sand eels Ammodytes sp. and their populations are stable or declining, meaning that they may be close to carrying capacity and experiencing competition. To examine how they differ in their foraging behaviour, time-depth-temperature recorders were attached to the legs of chick-rearing individuals of both species. Puffins have lower wingloading and lower total oxygen stores than razorbills and are therefore expected to invest more time in flying and less time in diving than razorbills. Mean (±1 SE) dive depth was 11.8 ± 0.45 m for puffins and 8.2 ± 0.21 m for razorbills, while mean dive duration was 40 ± 0.45 s for puffins and 24 ± 0.21 s for razorbills. Both species spent most of their dive time making shallow, V-shaped dives during daylight hours. In contrast to our prediction, foraging behaviour was very similar between the 2 species, although puffins tended to spend more time both diving and flying. The higher diving and flying rates of puffins may be associated with multiple prey loading, as puffins tend to bring back smaller (and therefore more) prey items than do razorbills.

Evidence of partial deferment of digestion during diving in Steller sea lions (Eumetopias jubatus)

“…The patterns and underlying physiological controls of foraging dives have been investigated in a number of air-breathing vertebrates, including seabirds (Elliott et al, 2013;Heath et al, 2007;Shoji et al, 2015), penguins (Hanuise et al, 2013;Shiomi et al, 2012), sea snakes (Cook and Brischoux, 2014), sea turtles (Bradshaw et al, 2007;Wallace and Jones, 2008), and a host of marine mammals. Current models of the cost of foraging in these diving animals and the resultant theories of optimal foraging strategies treat the acquisition and digestion of prey as physiological processes that are independent of one another (e.g., Burns et al, 2006;Mori, 1998;Sparling et al, 2007b;Thompson and Fedak, 2001).…”

Climate change and functional traits affect population dynamics of a long‐lived seabird

“…Foraging behaviours affect the breeding performance of many seabirds, both directly during the breeding season (Monaghan, 1992;Pinaud & Weimerskirch, 2002) and through carry-over effects during the non-breeding season (Daunt et al, 2014;Shoji et al, 2015). European shags (Phalacrocorax aristotelis) performing late winter foraging trip of short duration were more likely to breed successfully during the following breeding season (Daunt et al, 2014).…”

Assessing the effectiveness of foraging radius models for seabird distributions using biotelemetry and survey data

“…This is likely to reflect the foraging behaviour of these groups, which are restricted to smaller home ranges due to their high flight costs, in contrast with pelagic species. Furthermore, sympatric auk species also rely on niche segregation rather than spatial segregation during the breeding season (Linnebjerg et al 2013, Shoji et al 2015b). Although foraging auks are known to associate with discrete features in the environment, such as tidal currents (Waggitt et al 2016, Bennison et al 2019, auk distribution is generally closely linked to distance to colony (Johnston et al 2015).…”

“…Although foraging auks are known to associate with discrete features in the environment, such as tidal currents (Waggitt et al 2016, Bennison et al 2019, auk distribution is generally closely linked to distance to colony (Johnston et al 2015). Furthermore, sympatric auk species also rely on niche segregation rather than spatial segregation during the breeding season (Linnebjerg et al 2013, Shoji et al 2015b). These factors probably explain why a foraging radius distribution with a uniform decay from the colony appears to be a good representation of their distribution.…”