Intersexual differences in the diving behaviour of Imperial Cormorants

Gómez‐Laich, Agustina; Quintana, Flavio; Shepard, Emily L. C.; Wilson, RP

doi:10.1007/s10336-011-0714-1

Cited by 26 publications

(33 citation statements)

References 58 publications

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“…Shepard et al 2009, Cook et al 2012 should have increasing bottom durations (e.g. Wilson et al 2011, Gómez-Laich et al 2012. However (second process), as total dive durations in crease, animals have to spend disproportionately longer periods at the surface recovering from dives (e.g.…”

Section: Effect Of Attached Devices On the Foraging Of Birdsmentioning

confidence: 99%

Are bio-telemetric devices a drag? Effects of external tags on the diving behaviour of great cormorants

Vandenabeele¹,

Shepard²,

Grémillet³

et al. 2015

Mar. Ecol. Prog. Ser.

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Externally attached remote-sensing devices used to study animals in their environment are a possible source of disturbance, notably in terms of drag, for diving species. The aim of the present study was to assess the possible effect of device-induced drag on the diving performance of great cormorants Phalacrocorax carbo. Based on wind-tunnel measurements, we assessed the effect of device size on drag and derived a formula to predict how drag changes as a function of both swim speed and device cross-sectional area. Tests on captive cormorants indicated that drag had an effect on the energy expenditure (using dynamic body acceleration as a proxy) during the dive. Wind tunnel-derived drag metrics were combined with data from the literature to construct a model predicting the power consumption of diving cormorants according to device size. Applying the model to dive data from 6 free-living great cormorants (recorded using implanted time-depth recorders) indicated that a device constituting only ca. 3% of the bird's cross-sectional area could cause a 1.7% increase in power consumption when swimming. However, if a bird maintains constant power underwater, e.g. by decreasing foraging speed with increasing drag, this would result in a 7.1% reduction in the distance travelled during the bottom (active hunting) phase of the dive. Device-related increases in drag are also likely to reduce the maximum speeds achievable by these pursuit predators. The present study highlights the interaction between both drag coefficient and swim speed for diving animals with externally attached devices.

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Section: Effect Of Attached Devices On the Foraging Of Birdsmentioning

confidence: 99%

Are bio-telemetric devices a drag? Effects of external tags on the diving behaviour of great cormorants

Vandenabeele¹,

Shepard²,

Grémillet³

et al. 2015

Mar. Ecol. Prog. Ser.

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show abstract

“…It seems plausible that males hunting in the late afternoon when whitefish already commence their ascent are likely to catch this species at Chiemsee. Furthermore, males diving deeper than females have been reported for other cormorant species (e.g., Gomez Laich et al., ; Watanuki et al., ); this could make whitefish in the Alpine foreland even better accessible for males.…”

Section: Discussionmentioning

confidence: 86%

Sex‐specific prey partitioning in breeding piscivorous birds examined via a novel, noninvasive approach

Thalinger

Oehm

Zeisler

et al. 2018

Ecology and Evolution

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Piscivorous birds frequently display sex‐specific differences in their hunting and feeding behavior, which lead to diverging impacts on prey populations. Cormorants (Phalacrocoracidae), for example, were previously studied to examine dietary differences between the sexes and males were found to consume larger fish in coastal areas during autumn and winter. However, information on prey partitioning during breeding and generally on sex‐specific foraging in inland waters is missing. Here, we assess sex‐specific prey choice of Great Cormorants (Phalacrocorax carbo) during two subsequent breeding seasons in the Central European Alpine foreland, an area characterized by numerous stagnant and flowing waters in close proximity to each other. We developed a unique, noninvasive approach and applied it to regurgitated pellets: molecular cormorant sexing combined with molecular fish identification and fish‐length regression analysis performed on prey hard parts. Altogether, 364 pellets delivered information on both, bird sex, and consumed prey. The sexes differed significantly in their overall prey composition, even though Perca fluviatilis, Rutilus rutilus, and Coregonus spp. represented the main food source for both. Albeit prey composition did not indicate the use of different water bodies by the sexes, male diet was characterized by higher prey diversity within a pellet and the consumption of larger fish. The current findings show that female and male cormorants to some extent target the available prey spectrum at different levels. Finally, the comprehensive and noninvasive approach has great potential for application in studies of other piscivorous bird species.

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“…In many studies, this might mean that just the coarse‐scale behaviors need to be identified; for example, when comparing time‐activity budgets between individuals or groups (Gómez Laich et al. ; Le Vaillant et al. ) or for isolating certain behaviors to calculate associated energetic costs (Wilson et al.…”

Section: Introductionmentioning

confidence: 99%

Interpreting behaviors from accelerometry: a method combining simplicity and objectivity

Collins

Green

Warwick-Evans

et al. 2015

Ecology and Evolution

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Quantifying the behavior of motile, free‐ranging animals is difficult. The accelerometry technique offers a method for recording behaviors but interpretation of the data is not straightforward. To date, analysis of such data has either involved subjective, study‐specific assignments of behavior to acceleration data or the use of complex analyses based on machine learning. Here, we present a method for automatically classifying acceleration data to represent discrete, coarse‐scale behaviors. The method centers on examining the shape of histograms of basic metrics readily derived from acceleration data to objectively determine threshold values by which to separate behaviors. Through application of this method to data collected on two distinct species with greatly differing behavioral repertoires, kittiwakes, and humans, the accuracy of this approach is demonstrated to be very high, comparable to that reported for other automated approaches already published. The method presented offers an alternative to existing methods as it uses biologically grounded arguments to distinguish behaviors, it is objective in determining values by which to separate these behaviors, and it is simple to implement, thus making it potentially widely applicable. The R script coding the method is provided.

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Intersexual differences in the diving behaviour of Imperial Cormorants

Cited by 26 publications

References 58 publications

Are bio-telemetric devices a drag? Effects of external tags on the diving behaviour of great cormorants

Are bio-telemetric devices a drag? Effects of external tags on the diving behaviour of great cormorants

Sex‐specific prey partitioning in breeding piscivorous birds examined via a novel, noninvasive approach

Interpreting behaviors from accelerometry: a method combining simplicity and objectivity

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