Species- and sex-specific differences in foraging behaviour and foraging zones in blue-footed and brown boobies in the Gulf of California

Abstract

When 2 closely related species co-occur, each exhibiting sex-specific differences in size, resource partitioning is expected. We studied sex-specific foraging behaviour of 2 sympatric seabird species in the Gulf of California to disentangle the respective influence of species and sex, but also mass and size of individuals, on observed foraging behaviour. We used highly accurate data loggers to study movements, diving behaviour and activity of brown and blue-footed boobies rearing young chicks. Interspecific differences were limited; brown boobies had longer foraging trips and spent less time on the water than blue-footed boobies. The major differences observed were sex-specific; females of each species tended to have longer foraging trips, foraged farther from the colony, flew greater distances and had larger zones of area-restricted search. These sex-specific differences were more prominent in brown than in blue-footed boobies. Diet and stable isotope analyses showed that, during the study period, both species fed mainly on sardines, at similar trophic levels and in similar zones; outside the breeding season, the carbon and nitrogen signatures from feathers were also similar on average. In these sympatric species that feed on a superabundant prey, sex-specific differences appear to have a greater role than species-specific differences. We suggest that sex-specific differences may be mainly related to breeding involvement, as males are more involved in nest attendance and defence and females are greater provisioners. However, we show that several sex-specific differences in observed foraging behaviour were partly or totally explained by body size (flight speeds, foraging range, flapping frequency) or by body mass (depths attained during diving, duration of dives), which are parameters influenced by biomechanical constraints such as flight and diving.

Chronic lack of breeding by Galápagos Blue-footed Boobies and associated population decline

“…2) differ in presence of their main native predator (Galápagos Hawks Buteo galapagoensis; Anderson 1991, Anderson andHodum 1993) and nesting habitat occupied by Blue-footed Boobies (Townsend et al 2002), yet their respective Blue-footed Booby populations ceased effective breeding simultaneously, suggesting a regional, marinebased cause, such as diet. Along the continental margin, S. n. nebouxii eats primarily schooling, lipid-rich (Schew andRicklefs 1998, Müllers et al 2009) members of two families: Clupeidae (sardines and herrings) and Engraulidae (anchovies; Zavalaga et al 2007, Weimerskirch et al 2009). Before 1997, Galápagos Bluefooted Boobies showed a similar specialization on a clupeid, the South American sardine (Sardinops sagax; Anderson 1989).…”

Environmental Predictors of Seabird Wrecks in a Tropical Coastal Area

“…The probabilities of brown boobies and Cabot’s terns stranding were affected to a lesser extent (β = -0.98 and β = -0.84, respectively). These species forage within 20–25 km from breeding sites [45, 46], and, therefore, their carcasses may be found in relatively distant beaches from their colonies. Quite puzzlingly, the effect size of distance from breeding islands for the magnificent frigatebird was pronounced (β = -1.42), but the species forage within 300 km from colonies [88].…”

“…The brown booby, the magnificent frigatebird, and the kelp gull breed mainly on coastal islands located in the southern limit of the study area, while Cabot’s terns breed on islands in the north (Fig 1). The four species forage and are more abundant within 20 km from the breeding sites [45–48]. At the study site, S .…”

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

“…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).…”