Environmental heterogeneity and the evolution of foraging behaviour in long ranging greater albatrosses

Abstract

Habitat selection in heterogeneous environments is assumed to allow diversification. Wide‐ranging species like pelagic seabirds present a paradox, in that their diversity appears difficult to reconcile with a frequent lack of geographical isolation between populations. We studied the foraging strategies of three closely related species of greater albatrosses, wandering albatross, Diomedea exulans, Amsterdam albatrosses D. amsterdamensis and royal albatross, D. epomophora, in relation to environmental heterogeneity at coarse‐grained and fine‐grained scales. During the incubation period the three species foraged at long distances from their colonies. We observed significant differences between the species in the duration of foraging trips and the distance travelled per day. There were significant differences in preference for habitat types in relation to bathymetric features, and in chlorophyll a concentrations in the waters traversed. Royal albatross preferred shallower waters (<1500 m depth), which were rich in chlorophyll (>0.5 mg/m3), while the other species spent on average 80% of their time in waters deeper than this, where chlorophyll levels were lower. Wandering albatrosses foraged in colder waters than Amsterdam albatrosses. Patterns of activity divided the species into two groups: those exploiting oceanic habitats (wandering and Amsterdam albatrosses) spent high proportions of time on the water (49%), and had on average 1.35 takeoffs and landings per hour, while royal albatross, which foraged mainly over neritic waters spent only 35% of their time sitting on the water, and made on average 2.6 takeoff per hour. Further, royal albatross showed a similar pattern of activity during all periods of the day, while wandering and Amsterdam albatrosses were mostly inactive during the night. We link these differences in activity to prey patch availability in two contrasting habitats – continental shelf areas compared to open ocean habitats. The divergent styles of foraging observed in this study suggest that these closely‐related and wide‐ranging species could effectively co‐exist by dividing the resources available to them by different modes of exploitation.

Seasonal sexual segregation in twoThalassarchealbatross species: competitive exclusion, reproductive role specialization or foraging niche divergence?

“…Similarly, in a recent interspecific comparison of variation in habitat preferences of great albatrosses (Diomedea spp. ), Waugh & Weimerskirch (2003) suggested that the longer wings relative to body mass of Amsterdam albatrosses facilitated their foraging in tropical waters.…”

Stage-dependent distribution of the Critically Endangered Amsterdam albatross in relation to Economic Exclusive Zones

“…At-sea distribution and movements of the Amsterdam albatross were previously largely unknown (see fragmented information on adults in Inchausti & Weimerskirch 2001, Waugh & Weimerskirch 2003, Rivalan et al 2010. Notably, both the apparent similarity of these birds with juvenile or immature birds of the more abundant wandering albatrosses and the extremely reduced population numbers precluded reliable ship-based surveys of their distribution (Roux et al 1983, Weimerskirch et al 1997).…”

“…Our survey aims to identify which countries share responsibility for the species' conservation at sea, where it is legally feasible to engage efforts. Little information was previously available on this species' distribution during breeding (Waugh & Weimerskirch 2003), and thanks to the tremendous development of telemetric approaches (Wilson & Vandenabeele 2012), we have been able to compile a unique data set of individual tracking records on all age-(juvenile, immature, adult) and breeding-related (incubation, brooding, chick-rearing, sabbatical, failed breeder) classes of the population, including prolonged phases the birds spend exclusively at sea (Weimerskirch & Wilson 2000, Weimerskirch et al 2006. Our study provides (1) one of the first tracking surveys of an albatross species covering its entire life cycle (see also Weimerskirch et al 2014), and (2) the scientific basis for the implementation of conservation measures within EEZs.…”

Movements, winter distribution and activity patterns of Falkland and brown skuas: insights from loggers and isotopes

“…During the breeding season, adults are amenable to the short-term deployment and retrieval of devices such as satellite transmitters and Global Positioning System (GPS) loggers, and the burgeoning of studies since the early 1990s has provided unprecedented opportunities to investigate the complex variation within and between species in at-sea distributions (Hyrenbach et al 2002, Waugh & Weimerskirch 2003, Phillips et al 2005a). These suggest a number of mechanisms that may reduce the level of inter-specific competition for resources, including spatial, dietary and behavioural segregation at sea, and to a lesser extent differences in timing of breeding and hence peak demand for prey.…”