Predicted seabird distributions in the North Sea: the consequences of being hungry

Ollason, J. G.; Bryant, Andrew; Davis, Peter; Scott, Beth E.; Tasker, Mark L.

doi:10.1006/jmsc.1997.0252

Cited by 11 publications

(4 citation statements)

References 16 publications

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“…Behavioural modelling has been used to make a wide variety of predictions about population-level processes. For example, for a range of bird species, foraging behaviour has been used to predict patterns of habitat use (Sutherland 1996;Ollason et al . 1997), while territorial behaviour has been used to predict cyclicity in grouse Lagopus lagopus population dynamics (Hendry et al .…”

Section: Introductionmentioning

confidence: 99%

Model complexity and population predictions. The alpine marmot as a case study

Stephens

Frey-Roos²,

Arnold³

et al. 2002

Journal of Animal Ecology

108

114

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Summary1. During the past 15 years, models have been used increasingly in predictive population ecology. Matrix models used for predicting the fates of populations are often extremely basic, ignoring density dependence, spatial scale and behaviour, and often based on one sex only. We tested the importance of some of these omissions for model realism, by comparing the performance of a variety of population models of varying levels of complexity. 2. Detailed data from more than 13 years of behavioural and demographic research on a population of alpine marmots Marmota marmota in Berchtesgaden National Park, southern Germany, were used to parameterize four different population models. The models ranged from a simple population-based matrix model, to a spatially explicit behaviour-based model. 3. The performance of the models was judged by their ability to predict basic population dynamics under equilibrium conditions. Only a spatially explicit individual-based model ignoring optimal behaviour predicted dynamics significantly different to those observed in the field, highlighting the importance of considering realistic patterns of behaviour in spatially explicit models. 4. Using realistic levels of environmental and demographic stochasticity, variance in population growth rates predicted by all models was high, even within the range of population densities experienced in the field. This emphasizes the difficulty of using population-level field data to determine overall patterns of density dependence for use in population models. 5. All models were also used to predict potential density-dependent effects on alpine marmot population growth. In this regard, the models differed greatly. It was concluded that the simplest matrix model was adequate for making predictions regarding population sizes or densities under equilibrium conditions, but that for predictions requiring an understanding of transient dynamics only the behavioural model would be adequate.6. An emergent feature of this study of alpine marmot population dynamics was the prediction of a demographic Allee effect with a profound influence on population dynamics across a very broad range of population sizes. Three mechanisms were identified as underlying this Allee effect: stochastic skews in sex ratio and demographic composition at low population sizes; less efficient social thermoregulation during hibernation in small groups; and difficulties with mate finding during dispersal, even at relatively high population sizes.

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Section: Introductionmentioning

confidence: 99%

Model complexity and population predictions. The alpine marmot as a case study

Stephens

Frey-Roos²,

Arnold³

et al. 2002

Journal of Animal Ecology

108

114

View full text Add to dashboard Cite

show abstract

“…Field data on diet composition under di¡erent conditions of prey abundance are needed to construct empirical functional responses that can be used in models. Ultimately such models will need to predict the spatial pattern of predation by seals in relation to ¢sh distribution and abundance, as has recently been attempted for seabirds (Ollason et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

Interannual variation in the summer diets of harbour seals Phocavitulina at Mousa, Shetland (UK)

Brown¹,

Pierce

Hislop

et al. 2001

J. Mar. Biol. Ass.

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The main prey species in the summer (July–September) diets of harbour seals (Phoca vitulina) on the Island of Mousa (Shetland, UK), 1994–1997, were whiting (Merlangius merlangus), herring (Clupea harengus), sandeel (Ammodytidae) and garfish (Belone belone). Norway pout (Trisopterus esmarkii) was numerically important but comprised no more than 11% of prey weight in any year. There were marked between-year fluctuations in the relative importance of these prey, with whiting comprising 16–34% (by weight) of the diet, herring 12–28%, sandeels 7–18% and garfish 7–22%. Additional data on spring (April–June) diet were available for 1995–1997: sandeels were the most important prey (% weight) in all three years (51–60% of the diet), while herring (8–48%) and gadids (2–22%) varied in importance. The average size of fish eaten was larger than that reported in comparable studies from other areas. Harbour seals appear to have selected larger sandeels, whiting and Norway pout than the average size available in the area, as indicated by survey trawls, although between-year changes in the size of Norway pout in the diet did to some extent reflect availability. Interannual variation in the importance of Norway pout in the diet appeared to track trends in abundance, although the short time series precluded detection of a statistically significant correlation. Thus, some of our results are consistent with harbour seals feeding opportunistically while others point to selectivity, particularly for prey size. Estimated consumption of fish by the 500 harbour seals on Mousa during summer ranged from 152–195 tonnes.

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“…Several models describe time budgets for seabird foraging behaviour (Salamolard & Weimerskirsch 1993; Weimerskirch 1998). However, to our knowledge, only Ollason et al . (1997) have endeavoured to simulate the at‐sea distribution of a seabird, and these authors acknowledge that their model takes no account of constraints associated with nest‐site attendance and chick provisioning.…”

Section: Introductionmentioning

confidence: 87%

“…Our ultimate aim is to reproduce SBA distributions accurately in order to determine the extent of interaction between different classes of bird and fishing vessels. In view of the lack of appropriate data for parameterization, we rejected the mechanistic modelling approach of Ollason et al . (1997) in favour of a phenomenological one.…”

Section: Methodsmentioning

confidence: 99%

Simulating the distribution of southern Buller's albatross using an individual‐based population model

Broekhuizen

Stahl

Sagar

2003

Journal of Applied Ecology

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Summary 1.A spatially explicit, individual-based population model (IBPM) for southern Buller's albatross Thalassarche bulleri bulleri was developed to simulate the species' at-sea distribution and interactions with fishing fleets. 2. Satellite tracking data for birds from colonies on Snares Islands and Solander Island (south of South Island, New Zealand) suggest that the feeding grounds utilized by a bird, and the duration of its foraging trips, are dependent upon colony, sex, pairing status and developmental stage of egg /chick. These dependencies were incorporated into the IBPM. 3. Simulated distributions were compared with independent shipboard observations by using the IBPM to make replicated 'virtual counts' corresponding to each shipboard count. Each shipboard count was assigned a score reflecting the likelihood that a count of this magnitude would have arisen if the true populations behave as described by the IBPM. 4. Randomization tests indicated that, for the months in which we had adequate telemetry data (March-July), predicted and observed distributions were very similar at scales down to 1 degree 2 . There was some evidence that bird densities around the south-west corner of New Zealand's South Island were underpredicted in July, and at the scale of individual shipboard counts the ship data showed greater fine-scale aggregation than the virtual data. 5.Comparison of observed and simulated distributions early in the breeding season (January and February, for which we had no telemetry data) suggested that the foraging behaviour of birds prior to egg laying differs from that exhibited by either breeding or pre-breeding birds later in the season. 6. Synthesis and applications . In combination with reported by-catch rates, our IBPM may enable us to derive fishing gear-specific per -capita capture rates for Buller's albatross. Our results also emphasize that it may be necessary to represent responses of individual birds encountering vessels at a finer spatiotemporal scale before it will be possible to make robust demographic predictions of the consequences of changes in fishing practices. Key-words

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Predicted seabird distributions in the North Sea: the consequences of being hungry

Cited by 11 publications

References 16 publications

Model complexity and population predictions. The alpine marmot as a case study

Model complexity and population predictions. The alpine marmot as a case study

Interannual variation in the summer diets of harbour seals Phocavitulina at Mousa, Shetland (UK)

Simulating the distribution of southern Buller's albatross using an individual‐based population model

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