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Bird-borne video-cameras show that seabird movement patterns relate to previously unrevealed proximate environment, not prey.

Tremblay Y, Thiebault A, Mullers R, Pistorius P - PLoS ONE (2014)

Bottom Line: We found that movement patterns were related to specific stimuli which were mostly other predators such as gannets, dolphins or fishing boats.We demonstrate that movement patterns of foraging seabirds can be heavily driven by processes unobservable with conventional methodology.Except perhaps for large scale processes, local-enhancement seems to be the only ruling mechanism; this has profounds implications for ecosystem-based management of marine areas.

View Article: PubMed Central - PubMed

Affiliation: Centre de Recherche Halieutique Méditerrannéenne et Tropicale, Institut pour la Recherche et le Développement, Unité Mixte de Recherche 212: IRD-IFREMER-UM2 : Expoited Marine Ecosystems, Sète, France.

ABSTRACT
The study of ecological and behavioral processes has been revolutionized in the last two decades with the rapid development of biologging-science. Recently, using image-capturing devices, some pilot studies demonstrated the potential of understanding marine vertebrate movement patterns in relation to their proximate, as opposed to remote sensed environmental contexts. Here, using miniaturized video cameras and GPS tracking recorders simultaneously, we show for the first time that information on the immediate visual surroundings of a foraging seabird, the Cape gannet, is fundamental in understanding the origins of its movement patterns. We found that movement patterns were related to specific stimuli which were mostly other predators such as gannets, dolphins or fishing boats. Contrary to a widely accepted idea, our data suggest that foraging seabirds are not directly looking for prey. Instead, they search for indicators of the presence of prey, the latter being targeted at the very last moment and at a very small scale. We demonstrate that movement patterns of foraging seabirds can be heavily driven by processes unobservable with conventional methodology. Except perhaps for large scale processes, local-enhancement seems to be the only ruling mechanism; this has profounds implications for ecosystem-based management of marine areas.

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Determining the foraging context using GPS data only, in Cape Gannets.Procedure a) and results b) of the classification-tree classifying the foraging context around diving events using some track characteristics.
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pone-0088424-g002: Determining the foraging context using GPS data only, in Cape Gannets.Procedure a) and results b) of the classification-tree classifying the foraging context around diving events using some track characteristics.

Mentions: These descriptions of foraging activity can be inferred from the trajectories' characteristics, using data from all of the 35 birds. Given the numerous pauses on the water surface during boat-foraging periods, the dives performed around boats can be flagged by low flying speeds calculated both at two and six km scales (Figure 2). Foraging in association with dolphins involve different patterns, and are best described by high speed at a 2 km (small) scale, intermediate fractal dimension at 6 km (medium) scale and a relatively low straightness index at 12 km (large) scale (Figure 2). Interestingly the best classifiers involved several scales and the fractal dimension (over 6 km segments) is the second most important factor. The variations (SD) in speed did not appear to be discriminant. Cross-validation for the pruned-tree in figure 2 showed a high percentage of correct classification (95.8%). However, the more robust estimate of correct classification obtained using the bagging procedure indicate a cumulative out-of-bag error of around 0.12, indicative of a lower – but still high – correct classification percentage (88%).


Bird-borne video-cameras show that seabird movement patterns relate to previously unrevealed proximate environment, not prey.

Tremblay Y, Thiebault A, Mullers R, Pistorius P - PLoS ONE (2014)

Determining the foraging context using GPS data only, in Cape Gannets.Procedure a) and results b) of the classification-tree classifying the foraging context around diving events using some track characteristics.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3921161&req=5

pone-0088424-g002: Determining the foraging context using GPS data only, in Cape Gannets.Procedure a) and results b) of the classification-tree classifying the foraging context around diving events using some track characteristics.
Mentions: These descriptions of foraging activity can be inferred from the trajectories' characteristics, using data from all of the 35 birds. Given the numerous pauses on the water surface during boat-foraging periods, the dives performed around boats can be flagged by low flying speeds calculated both at two and six km scales (Figure 2). Foraging in association with dolphins involve different patterns, and are best described by high speed at a 2 km (small) scale, intermediate fractal dimension at 6 km (medium) scale and a relatively low straightness index at 12 km (large) scale (Figure 2). Interestingly the best classifiers involved several scales and the fractal dimension (over 6 km segments) is the second most important factor. The variations (SD) in speed did not appear to be discriminant. Cross-validation for the pruned-tree in figure 2 showed a high percentage of correct classification (95.8%). However, the more robust estimate of correct classification obtained using the bagging procedure indicate a cumulative out-of-bag error of around 0.12, indicative of a lower – but still high – correct classification percentage (88%).

Bottom Line: We found that movement patterns were related to specific stimuli which were mostly other predators such as gannets, dolphins or fishing boats.We demonstrate that movement patterns of foraging seabirds can be heavily driven by processes unobservable with conventional methodology.Except perhaps for large scale processes, local-enhancement seems to be the only ruling mechanism; this has profounds implications for ecosystem-based management of marine areas.

View Article: PubMed Central - PubMed

Affiliation: Centre de Recherche Halieutique Méditerrannéenne et Tropicale, Institut pour la Recherche et le Développement, Unité Mixte de Recherche 212: IRD-IFREMER-UM2 : Expoited Marine Ecosystems, Sète, France.

ABSTRACT
The study of ecological and behavioral processes has been revolutionized in the last two decades with the rapid development of biologging-science. Recently, using image-capturing devices, some pilot studies demonstrated the potential of understanding marine vertebrate movement patterns in relation to their proximate, as opposed to remote sensed environmental contexts. Here, using miniaturized video cameras and GPS tracking recorders simultaneously, we show for the first time that information on the immediate visual surroundings of a foraging seabird, the Cape gannet, is fundamental in understanding the origins of its movement patterns. We found that movement patterns were related to specific stimuli which were mostly other predators such as gannets, dolphins or fishing boats. Contrary to a widely accepted idea, our data suggest that foraging seabirds are not directly looking for prey. Instead, they search for indicators of the presence of prey, the latter being targeted at the very last moment and at a very small scale. We demonstrate that movement patterns of foraging seabirds can be heavily driven by processes unobservable with conventional methodology. Except perhaps for large scale processes, local-enhancement seems to be the only ruling mechanism; this has profounds implications for ecosystem-based management of marine areas.

Show MeSH