Diving seabirds share foraging space and time within and among species

Abstract

Ecological theory predicts that animals with similar foraging strategies should not be able to co‐exist without segregating either in space, time or diet. In communities, intra‐specific competition is thought to be more intense than the competition among species, because of the lack of niche partitioning between conspecifics. Hence, while different seabird species can overlap in their foraging distribution, intra‐specific competition can drive the neighboring populations of the same species to spatial segregation of foraging areas. To investigate ecological segregation within and among species of diving seabirds, we used a multi‐species GPS‐tracking approach of seabirds of four species on a small island in the Southwest Atlantic. The present study goes beyond previous work by analyzing simultaneous effects of species and colonies. We observed strikingly strong spatial foraging segregation among birds of the same species, breeding in colonies as close as 2 km from each other. Conspecifics from neighboring colonies used foraging places adjacent to their own colony, and there was little or no overlap with birds from the other colony. A zone with increased predator concentration was completely avoided during foraging trips, likely contributing to the spatial segregation. In addition to spatial segregation, we also observed intra‐specific differences in other components of foraging behavior, such as time of day, dive depth and diet. These were most likely caused by optimal foraging of individuals in relation to habitat differences on a local scale, leading to a complex pattern of interactions with environmental covariates, in particular foraging daytime, foraging water layer temperature and depth, distance to coast and bathymetric depth of foraging areas. As mechanisms leading to the spatial segregation we propose a combination of optimal foraging and avoidance of predation.

Predicting the distribution of a threatened albatross: The importance of competition, fisheries and annual variability

“…This model has received considerable support from some studies (Wanless and Harris, 1993;Grémillet et al, 2004;Masello et al, 2010), but several others documented a broad range of overlaps in foraging areas (Ainley et al, 2004;Wakefield et al, 2011). The very fine-scale data presented here clearly indicate a mixed picture, with a large area of overlap in terms of maximum extent, but obvious avoidance by birds from New Island of the main foraging area used by albatrosses from Steeple Jason, and vice versa.…”

“…data), and also for demersal fish such as red cod Salilota australis (Arkhipkin et al, 2010). It is also an important feeding area for South American fur seals Arctocephalus australis (Thompson et al, 2003) and several seabirds, particularly penguins (Falabella et al, 2009;Masello et al, 2010).…”

Natural and anthropogenic factors affecting the feeding ecology of a top marine predator, the Magellanic penguin

“…As in many other colonial seabirds, intra-specific competition for food resources can be strong for Magellanic penguins due to a lack of dietary segregation (Masello et al 2010). Ecological theory predicts that animals with similar feeding strategies should not coexist without segregating either in space, time or diet.…”

“…Moreover, strong breeding and foraging site fidelity exhibited by these predators indicates that experienced individuals are able to consistently locate adequate food to raise young and the occurrence of predictable food resources or seasonally productive areas are important cues for selecting foraging areas (Weimerskirch 2007, Cama et al 2012, Louzao et al 2012. In addition to these oceanographic features, human fisheries or the abundance and distribution of conspecifics are known to affect the diet and foraging behavior of marine predators in a variety of ways, including facilitation (Henkel 2009, Bartumeus et al 2010, Cama et al 2012 or competition for resources (Crawford 2007, Weimerskirch et al 2009, Masello et al 2010, Bertrand et al 2012. Understanding how top predators respond to variations in such physical, biological and anthropogenic features is a major conservation challenge in marine environments.…”

“…In addition, spatially explicit information derived from monitoring programs of fishing vessels provides a unique opportunity to investigate the interaction between marine predators and fishing activities (Yorio et al 2010, Bertrand et al 2012. Furthermore, the recent development and widespread application of bio-logging techniques have revolutionized our knowledge on the movement ecology and spatial distribution of marine predators (Weimerskirch et al 2009, Masello et al 2010, Louzao et al 2012. Based on this previous information, predictive modeling of species' distribution has provided a popular analytical framework for relating geolocated observations of occurrence to environmental variables that contribute to a species distribution (Monk et al 2012).…”