The devil is in the detail: small-scale sexual segregation despite large-scale spatial overlap in the wandering albatross

Abstract

Sexual segregation in foraging habitat occurs in many marine predators and is usually attributed to competitive exclusion, different parental roles of each sex or niche specialisation associated with sexual size dimorphism. However, relatively few studies have attempted to understand the patterns and underlying drivers of local-scale sexual segregation in marine predators. We studied habitat use, diet and feeding ecology of female and male wandering albatrosses Diomedea exulans, fitted with GPS and stomach-temperature loggers during the chick-rearing period (austral winter) at South Georgia in 2009. During this period, when oceanographic conditions were anomalous and prey availability was low in waters near the breeding colony, the tracked wandering albatrosses showed high consistency in their foraging areas at a large spatial scale, and both males and females targeted sub-Antarctic and subtropical waters. Despite consistency in large-scale habitat use, males and females showed different foraging behaviours in response to oceanographic conditions at a smaller scale.Males appeared to be more opportunistic, scavenging for offal or non-target fish discarded by fishing vessels in less productive, oceanic waters. They exhibited sinuous movements, feeding mostly on large prey and consuming similar amounts of food during the outbound and return parts of the foraging trip. In contrast, females targeted natural productivity hotspots, and fed on a wide variety of fish and cephalopods. They commuted directly to these areas; most prey were ingested on the outbound part of the trip, and they often started their return after ingesting large prey at the farthest point from the colony. Together, these results indicate that sexual segregation in core foraging areas of wandering albatrosses is driven by sex-specific habitat selection due the low availability of prey in local Antarctic waters. This segregation results in different feeding behaviour at local scales which may be explained by differing breeding roles and degree of parental investment by each sex, with females investing more 3 than males in reproduction. Further investigations are necessary to confirm the existence of this pattern through time under contrasting environmental conditions and to identify the drivers responsible for local-scale sexual segregation in wandering albatrosses.

Mortality cost of sex-specific parasitism in wild bird populations

“…Nematodes are a very diverse group of round worms. Male-biased parasite prevalence in this group could be due to many non-exclusive variables including those previously suggested for overall gastrointestinal parasites (mainly based on differences in body size; see Introduction), in addition to sex-specific foraging behavior as result of niche specialization or competitive exclusion by the dominant sex 85,86 . However, more studies are needed to test these hypotheses.…”

Oxidative status and stress during highly energetic life‐history stages of Chinstrap Penguins: breeding versus molting

“…However, in a previous study of the same penguin rookery, males had higher H/L ratios than females during breeding and molting (Palacios et al 2018). Different environmental conditions (e.g., sea-ice distribution; Clarke et al 2006, Widmann et al 2015 in the same study area in different years could lead to ecophysiological and/or immunological sex differences, e.g., in terms of foraging effort and diet, energy consumption, or body condition (Ismar et al 2017, Pereira et al 2018. Similarly, sex differences in oxidative status have been found in other species of non-breeding birds (Schmidt et al 2007) and other species of Pygoscelis penguins during the breeding cycle (Colominas-Ciur o et al 2017b, but see Beaulieu et al 2010Beaulieu et al , 2011.…”

“…Moreover, antioxidant defenses may play a similar role in both sexes. Also, and as mentioned for the H/L ratio, other ecological factors such as differences in foraging effort, diet, energy consumption, or body condition (Widmann et al 2015, Ismar et al 2017, Pereira et al 2018 could also explain differences between the sexes in oxidative damage.…”

“…, Pereira et al. ). Similarly, sex differences in oxidative status have been found in other species of non‐breeding birds (Schmidt et al.…”

Sexual segregation in a highly pagophilic and sexually dimorphic marine predator

“…This could possibly indicate that male and female snow petrels try to avoid competition and thus diverged in habitat preference in more profitable areas, where intra-specific competition might be more intense. Such a mechanism was also proposed to explain sex-specific differences in broad scale foraging areas in highly sexually size dimorphic species (wandering albatross: Weimerskirch et al 1993, Shaffer et al 2001giant petrels: Gonzáles-Solís et al 2000), but also in foraging habitat at a microhabitat scale (Pereira et al 2018). A major assumption of the intersexual competition hypothesis is that prey capture should be a function of bill size (Selander 1966, Shine 1989).…”