Sexual segregation in timing of foraging by imperial shags (Phalacrocorax atriceps): is it always ladies first?

Harris, Sabrina; Rey, Andrea Raya; Phillips, Richard A.; Quintana, Flavio

doi:10.1007/s00227-013-2177-9

Cited by 26 publications

(29 citation statements)

References 35 publications

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“…Variation in dive depths among sexes may also be related to diet composition in blue-eyed shags, with some studies finding increases in prey size with dive depth [26,28,32,73,74] and others the opposite pattern [40,55]. The diel timing of foraging trips also differs among male and female blue-eyed shags [7,8], which might in turn influence dive depth owing to its correlation with light levels [34]. Further research into these complex interactions is required to attain a complete understanding of niche partitioning by blue-eyed shags.…”

Section: Discussionmentioning

confidence: 99%

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The Roles of Sex, Mass and Individual Specialisation in Partitioning Foraging-Depth Niches of a Pursuit-Diving Predator

et al. 2013

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Intra-specific foraging niche partitioning can arise due to gender differences or individual specialisation in behaviour or prey selection. These may in turn be related to sexual size dimorphism or individual variation in body size through allometry. These variables are often inter-related and challenging to separate statistically. We present a case study in which the effects of sex, body mass and individual specialisation on the dive depths of the South Georgia shag on Bird Island, South Georgia are investigated simultaneously using a linear mixed model. The nested random effects of trip within individual explained a highly significant amount of the variance. The effects of sex and body mass were both significant independently but could not be separated statistically owing to them being strongly interrelated. Variance components analysis revealed that 45.5% of the variation occurred among individuals, 22.6% among trips and 31.8% among Dives, while R2 approximations showed gender explained 31.4% and body mass 55.9% of the variation among individuals. Male dive depths were more variable than those of females at the levels of individual, trip and dive. The effect of body mass on individual dive depths was only marginally significant within sexes. The percentage of individual variation in dive depths explained by mass was trivial in males (0.8%) but substantial in females (24.1%), suggesting that differences in dive depths among males was largely due to them adopting different behavioural strategies whereas in females allometry played an additional role. Niche partitioning in the study population therefore appears to be achieved through the interactive effects of individual specialisation and gender upon vertical foraging patch selection, and has the potential to interact in complex ways with other axes of the niche hypervolume such as foraging locations, timing of foraging and diet.

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Section: Discussionmentioning

confidence: 99%

“…Intra-specific competition occurs among conspecifics and may be reduced via partitioning along several axes of the niche hypervolume, including diet [4-6], timing of foraging [7,8] and foraging location [9-11]. Such partitioning can occur according to sex [12], ontogeny [13-15] or individual specialisation [16].…”

Section: Introductionmentioning

confidence: 99%

The Roles of Sex, Mass and Individual Specialisation in Partitioning Foraging-Depth Niches of a Pursuit-Diving Predator

et al. 2013

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“…It is known that individuals from this population present a certain degree of consistency in behavior while foraging and that males and females differ in some aspects of their behavior (such as timing of foraging, with females foraging in the morning and males in the afternoon, Harris et al 2013). Differences among age groups have also been detected, with young males in particular behaving differently from their older counterparts (Harris et al 2014b).…”

Section: Introductionmentioning

confidence: 98%

Linking foraging behavior and diet in a diving seabird

et al. 2015

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Foraging behavior and diet of breeding seabirds may be analysed simultaneously with the combined use of remote sensing devices and stable isotope analysis. Imperial shag, Phalacrocorax atriceps, breeding at Punta León colony, Argentina, were equipped with global positioning system (GPS) loggers to record foraging trips and blood samples were taken after removal of the devices in order to analyse their nitrogen and carbon stable isotope composition in whole blood and plasma. Whole blood was correlated to plasma isotopic composition for each individual (n = 35), linking diet in the short and medium term. Sexes did not differ in isotopic signatures. The maximum distance reached and the total number of dives that individuals made on two consecutive foraging trips were correlated to their plasma nitrogen isotopic signature. Individuals that went further from the colony and dived fewer times presented more positive signatures, indicative of benthic prey consumption (e.g. Raneya brasiliensis). Diet was predominantly benthic with some individuals incorporating pelagic prey (Engraulis anchoita) and even cephalopods (Octopus tehuelchus). Within breeding pairs (n = 9), different combinations of foraging and prey preferences were observed. Estimated trophic levels of these individuals were similar to those of the same species in other colonies further south along the Patagonian coast.

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“…Blood sampling was performed in the morning, prior to the return of females from their first foraging excursion (see Harris et al 2013), which implied a minimum of about 4-6 hr of fasting. At the time of blood collection, 31% (n = 85) of monitored nests had two chicks (A-and B-chicks), and the remaining nests had only one chick (A-chicks).…”

Section: Data Collectionmentioning

confidence: 99%

Plasma Biochemistries and Morphometric Indices of Body Condition in Imperial Cormorant (Phalacrocorax atriceps) Chicks

et al. 2017

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Sexual segregation in timing of foraging by imperial shags (Phalacrocorax atriceps): is it always ladies first?

Cited by 26 publications

References 35 publications

The Roles of Sex, Mass and Individual Specialisation in Partitioning Foraging-Depth Niches of a Pursuit-Diving Predator

The Roles of Sex, Mass and Individual Specialisation in Partitioning Foraging-Depth Niches of a Pursuit-Diving Predator

Linking foraging behavior and diet in a diving seabird

Plasma Biochemistries and Morphometric Indices of Body Condition in Imperial Cormorant (Phalacrocorax atriceps) Chicks

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