Testing for sub-colony variation in seabird foraging behaviour: ecological and methodological consequences for understanding colonial living

Understanding the determinants of species' distributions is a fundamental aim in ecology and a prerequisite for conservation but is particularly challenging in the marine environment. Advances in bio-logging technology have resulted in a rapid increase in studies of seabird movement and distribution in recent years. Multi-colony studies examining the effects of intra-and inter-colony competition on distribution have found that several species exhibit inter-colony segregation of foraging areas, rather than overlapping distributions. These findings are timely given the increasing rate of human exploitation of marine resources and the need to make robust assessments of likely impacts of proposed marine developments on biodiversity. Here we review the occurrence of foraging area segregation reported by published tracking studies in relation to the density-dependent hinterland (DDH) model, which predicts that segregation occurs in response to inter-colony competition, itself a function of colony size, distance from the colony and prey distribution. We found that inter-colony foraging area segregation occurred in 79% of 39 studies. The frequency of occurrence was similar across the four seabird orders for which data were available, and included species with both smaller (10-100 km) and larger (100-1000 km) foraging ranges. Many predictions of the DDH model were confirmed, with examples of segregation in response to high levels of inter-colony competition related to colony size and proximity, and enclosed landform restricting the extent of available habitat. Moreover, as predicted by the DDH model, inter-colony overlap tended to occur where birds aggregated in highly productive areas, often remote from all colonies. The apparent prevalence of inter-colony foraging segregation has important implications for assessment of impacts of marine development on protected seabird colonies. If a development area is accessible from multiple colonies, it may impact those colonies much more asymmetrically than previously supposed. Current impact assessment approaches that do not consider spatial inter-colony segregation will therefore be subject to error. We recommend the collection of tracking data from multiple colonies and modelling of inter-colony interactions to predict colony-specific distributions.

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“…We did not consider studies that examined foraging areas at sub‐colony level only, such as Waggitt et al . () and Bogdanova et al . ().…”

Section: Occurrence Of Intraspecific Inter‐colony Segregation Of Seabmentioning

confidence: 85%

A review of the occurrence of inter‐colony segregation of seabird foraging areas and the implications for marine environmental impact assessment

Bolton

Conolly

Carroll

et al. 2018

Ibis

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“…Therefore, we report only results for KD h=9.1, as this is similar to values commonly used in the analysis of gannet spatial data (Stauss et al 2012, Waggitt et al 2014) and directly comparable with the time-in-area approach. Results for KD ad hoc are included in Table S2 The mean bootstrapped proportion of all for aging events occurring in the core foraging area at 25, 50 and 75% probability of use was larger when designated using KD analysis than with the time-in-area approach (Table 2).…”

Section: Proportion Of Foraging Events In Core Foraging Areamentioning

confidence: 96%

Time-in-area represents foraging activity in a wide-ranging pelagic forager

Warwick-Evans¹,

Atkinson²,

Gauvain³

et al. 2015

Mar. Ecol. Prog. Ser.

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Successful Marine Spatial Planning depends upon the identification of areas with high importance for particular species, ecosystems or processes. For seabirds, advancements in biologging devices have enabled us to identify these areas through the detailed study of at-sea behaviour. However, in many cases, only positional data are available and the presence of local biological productivity and hence seabird foraging behaviour is inferred from these data alone, under the untested assumption that foraging activity is more likely to occur in areas where seabirds spend more time. We fitted GPS devices and accelerometers to northern gannets Morus bassanus and categorised the behaviour of individuals outside the breeding colony as plunge diving, surface foraging, floating and flying. We then used the locations of foraging events to test the efficiency of 2 approaches: time-in-area and kernel density (KD) analyses, which are widely employed to detect highly-used areas and interpret foraging behaviour from positional data. For KD analyses, the smoothing parameter (h) was calculated using the ad hoc method (KD ad hoc ), and KD h=9.1 , where h = 9.1 km, to designate core foraging areas from location data. A high proportion of foraging events occurred in core foraging areas designated using KD ad hoc , KD h=9.1 , and time-inarea. Our findings demonstrate that foraging activity occurs in areas where seabirds spend more time, and that both KD analysis and the time-in-area approach are equally efficient methods for this type of analysis. However, the time-in-area approach is advantageous in its simplicity, and in its ability to provide the shapes commonly used in planning. Therefore, the time-in-area approach can be used as a simple way of using seabirds to identify ecologically important locations from both tracking and survey data.

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“…Australasian gannets ( Morus serrator ) also appear to utilise similar rafts to gain information about potential foraging areas (Machovsky‐Capuska et al ., ). As many seabirds form such assemblages just outside colonies, the potential for inadvertent information transfer on the edges of colonies should be taken into account in future studies (Racine et al ., ; Waggitt et al ., ).…”

Section: Foraging Informationmentioning

confidence: 97%

Information use in colonial living

2015

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Despite the fact that many animals live in groups, there is still no clear consensus about the ecological or evolutionary mechanisms underlying colonial living. Recently, research has suggested that colonies may be important as sources of social information. The ready availability of information from conspecifics allows animals to make better decisions about avoiding predators, reducing brood parasitism, migratory phenology, mate choice, habitat choice and foraging. These choices can play a large part in the development and maintenance of colonies. Here we review the types of information provided by colonial animals and examine the different ways in which decision-making in colonies can be enhanced by social information. We discuss what roles information might take in the evolution, formation and maintenance of colonies. In the process, we illustrate that information use permeates all aspects of colonial living.

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Testing for sub-colony variation in seabird foraging behaviour: ecological and methodological consequences for understanding colonial living

Cited by 13 publications

References 37 publications

A review of the occurrence of inter‐colony segregation of seabird foraging areas and the implications for marine environmental impact assessment

A review of the occurrence of inter‐colony segregation of seabird foraging areas and the implications for marine environmental impact assessment

Time-in-area represents foraging activity in a wide-ranging pelagic forager

Information use in colonial living

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