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David Grémillet - One of the best experts on this subject based on the ideXlab platform.
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Evidence of age-related improvement in the Foraging Efficiency of Adélie penguins.
Scientific reports, 2019Co-Authors: Amélie Lescroël, Grant Ballard, Melanie Massaro, Katie M. Dugger, Scott Jennings, Annie Pollard, Elizabeth L. Porzig, Annie E. Schmidt, Arvind Varsani, David GrémilletAbstract:Age variation in reproductive performance is well-documented but the mechanisms underlying this variation remain unclear. Foraging Efficiency is likely to be a key source of demographic variation as it determines the amount of energy that can be invested in fitness-related activities. Evidence of age-related changes in the Foraging Efficiency of adult seabirds is scarce and inconsistent. We investigated the effects of age on the Foraging Efficiency of breeding Adelie penguins, a relatively short-lived seabird species, in order to gain a broader perspective on the processes driving variation in ageing rates. We found support for a positive effect of age, either linear or levelling off at old ages, on both our proxies for daily catch rate and catch per unit effort. Across all age classes, males were more performant foragers than females. We found no strong evidence for differing ageing patterns between sexes or individual quality levels, and no evidence for senescence. We infer that continuous individual improvement could be responsible for a larger amount of the variation in Foraging Efficiency with age at our study site, compared with selective disappearance of underperforming phenotypes. The different results reported by other studies highlight the need to conduct longitudinal studies across a range of species in different environments.
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Sex‐specific food provisioning in a monomorphic seabird, the common guillemot Uria aalge: nest defence, Foraging Efficiency or parental effort?
Journal of Avian Biology, 2009Co-Authors: Chris B. Thaxter, David Grémillet, Francis Daunt, Keith C. Hamer, Yutaka Watanuki, Michael P. Harris, G. Peters, Sarah WanlessAbstract:Sexual differences in food provisioning rates of monomorphic seabirds are well known but poorly understood. Here, we address three hypotheses that attempt to explain female-biased food provisioning in common guillemots Uria aalge: (1) males spend more time in nest defence, (2) females have greater Foraging Efficiency, and (3) males allocate a greater proportion of Foraging effort to self-maintenance. We found that males spent no more time with chicks than females but made longer trips and travelled further from the colony. There was extensive overlap between sexes in core Foraging areas, indicating that females were not excluding males from feeding opportunities close to the colony. However, as a result of their longer trips, the total Foraging areas of males were much greater than those of females. There was no difference between sexes in overall dive rate per hour at sea, in behaviour during individual dives or in a number of other measures of Foraging Efficiency including the frequency, depth and duration of dives and the dive: pause ratio during the final dive bout of each trip, which was presumably used by both sexes to obtain prey for the chick. These data strongly suggest that sexes did not differ in their ability to locate and capture prey. Yet males made almost twice as many dives per trip as females, suggesting that males made more dives than females for their own benefit. These results support the hypothesis that female-biased food provisioning arose from a difference between sexes in the allocation of Foraging effort between parents and offspring, in anticipation of a prolonged period of male-only post-fledging care of the chick, and not from differences in Foraging Efficiency or time spent in nest defence
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sex specific food provisioning in a monomorphic seabird the common guillemot uria aalge nest defence Foraging Efficiency or parental effort
Journal of Avian Biology, 2009Co-Authors: Chris B. Thaxter, David Grémillet, Francis Daunt, Keith C. Hamer, Yutaka Watanuki, Michael P. Harris, G. Peters, Sarah WanlessAbstract:Sexual differences in food provisioning rates of monomorphic seabirds are well known but poorly understood. Here, we address three hypotheses that attempt to explain female-biased food provisioning in common guillemots Uria aalge: (1) males spend more time in nest defence, (2) females have greater Foraging Efficiency, and (3) males allocate a greater proportion of Foraging effort to self-maintenance. We found that males spent no more time with chicks than females but made longer trips and travelled further from the colony. There was extensive overlap between sexes in core Foraging areas, indicating that females were not excluding males from feeding opportunities close to the colony. However, as a result of their longer trips, the total Foraging areas of males were much greater than those of females. There was no difference between sexes in overall dive rate per hour at sea, in behaviour during individual dives or in a number of other measures of Foraging Efficiency including the frequency, depth and duration of dives and the dive: pause ratio during the final dive bout of each trip, which was presumably used by both sexes to obtain prey for the chick. These data strongly suggest that sexes did not differ in their ability to locate and capture prey. Yet males made almost twice as many dives per trip as females, suggesting that males made more dives than females for their own benefit. These results support the hypothesis that female-biased food provisioning arose from a difference between sexes in the allocation of Foraging effort between parents and offspring, in anticipation of a prolonged period of male-only post-fledging care of the chick, and not from differences in Foraging Efficiency or time spent in nest defence.
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at sea activity and Foraging Efficiency in chick rearing northern gannets sula bassana a case study in shetland
Marine Ecology Progress Series, 1999Co-Authors: Stefan Garthe, David Grémillet, Robert W FurnessAbstract:Chick-rearing northern gannets Sula bassana from Hermaness, Shetland (UK), were equipped with both stomach temperature loggers and external temperature loggers (attached to the leg). Detrimental device effects on the birds could not be detected. Three complete data sets covering several Foraging trips by 3 birds showed that the logger-equipped birds spent 39 to 49% of their time in the colony, 22 to 30 % flying and 22 to 34 % swimming. Foraging trips lasted between 2 h 45 min and 27 h 08 min, with a mean length of 13 h. Maximum Foraging range was estimated to be 128 km. Dives lasted between 1 s and 7.5 s, with a mean of 4.4 s. Median food quantity swallowed per feeding event was 101 g (n = 32), with 745 g being the maximum. No Foraging activity occurred at night. Catch per unit effort was assessed to range between 0.9 and 2.8 g fish min -1 flying and between 0.5 and 1.3 g fish min -1 at sea. Foraging Efficiency varied between 0.6 (negative energy budget) and 1.5 (positive energy budget). More data on Foraging Efficiency, preferably from different colonies and different years, could show how efficiently this top predator utilises food resources.
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catch per unit effort Foraging Efficiency and parental investment in breeding great cormorants phalacrocorax carbo carbo
Journal of Materials Science, 1997Co-Authors: David GrémilletAbstract:The feeding ecology of breeding great cormorants (Phalacrocorax carbo carbo) was studied in 8 males and 6 females using automatic nest-balances and a radio-tracking system. Birds were shown to be extremely efficient predators with median catch per unit effort of 15.2 g of fish taken per minute spent underwater (n=89; gross Foraging Efficiency 3.25) in males and 9.0 g min −1 in females (n=91; gross Foraging Efficiency 3.46). Mean daily food intake was also high (828±166 g, n=7 in males and 829±271 g, n=6 in females) and was positively related to brood biomass. Catch per unit effort was not related to Foraging range, showing that birds do not tend to visit distant Foraging areas to compensate for prey stock depletion around the breeding site. Furthermore, breeding adults responded to increasing food requirements of the brood by increasing the number of Foraging trips per day, but maintained constant Foraging effort, load size and catch per unit effort. Parents thus increased their overall Foraging effort and food intake but kept their body mass constant.
Christer Brönmark - One of the best experts on this subject based on the ideXlab platform.
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Foraging Efficiency and prey selectivity in a visual predator differential effects of turbid and humic water
Canadian Journal of Fisheries and Aquatic Sciences, 2013Co-Authors: Mikael Jönsson, Lynn Ranåker, Anders P Nilsson, Christer BrönmarkAbstract:Predators exert strong regulating forces on lower trophic levels through predation. As most fish are visual foragers, visual conditions in the water may alter the strength of this regulation. We evaluated effects of turbidity and humic water on Foraging Efficiency and prey-size selectivity in Northern pike (Esox lucius) feeding on roach (Rutilus rutilus). Encounter rates decreased in both turbid and humic water but were not counteracted by increased searching activity. Capture success was unaffected by turbidity but was nonlinearly affected by humic water by being high in clear and highly humic water but low in less humic water. In highly humic water, the visual range approached pike's strike distance and, together with its cryptic colours, pike may have initiated its attack before the prey detected it, limiting the possibility for prey evasive manoeuvres. Prey-size selectivity towards small prey in clear water disappeared in turbid water but was maintained in humic water. Owing to its optical properties, turbidity degrades the quality of the visual information more through scattering than humic water does through absorption. We show that the effect of visual degradation on Foraging depends on the cause of visual degradation, which has not previously been acknowledged in the visual Foraging literature. (Less)
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Foraging Efficiency and prey selectivity in a visual predator: differential effects of turbid and humic water
Canadian Journal of Fisheries and Aquatic Sciences, 2013Co-Authors: Mikael Jönsson, Lynn Ranåker, P. Anders Nilsson, Christer BrönmarkAbstract:Predators exert strong regulating forces on lower trophic levels through predation. As most fish are visual foragers, visual conditions in the water may alter the strength of this regulation. We evaluated effects of turbidity and humic water on Foraging Efficiency and prey-size selectivity in Northern pike (Esox lucius) feeding on roach (Rutilus rutilus). Encounter rates decreased in both turbid and humic water but were not counteracted by increased searching activity. Capture success was unaffected by turbidity but was nonlinearly affected by humic water by being high in clear and highly humic water but low in less humic water. In highly humic water, the visual range approached pike’s strike distance and, together with its cryptic colours, pike may have initiated its attack before the prey detected it, limiting the possibility for prey evasive manoeuvres. Prey-size selectivity towards small prey in clear water disappeared in turbid water but was maintained in humic water. Owing to its optical properties, turbidity degrades the quality of the visual information more through scattering than humic water does through absorption. We show that the effect of visual degradation on Foraging depends on the cause of visual degradation, which has not previously been acknowledged in the visual Foraging literature.
Mikael Jönsson - One of the best experts on this subject based on the ideXlab platform.
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Foraging Efficiency and prey selectivity in a visual predator differential effects of turbid and humic water
Canadian Journal of Fisheries and Aquatic Sciences, 2013Co-Authors: Mikael Jönsson, Lynn Ranåker, Anders P Nilsson, Christer BrönmarkAbstract:Predators exert strong regulating forces on lower trophic levels through predation. As most fish are visual foragers, visual conditions in the water may alter the strength of this regulation. We evaluated effects of turbidity and humic water on Foraging Efficiency and prey-size selectivity in Northern pike (Esox lucius) feeding on roach (Rutilus rutilus). Encounter rates decreased in both turbid and humic water but were not counteracted by increased searching activity. Capture success was unaffected by turbidity but was nonlinearly affected by humic water by being high in clear and highly humic water but low in less humic water. In highly humic water, the visual range approached pike's strike distance and, together with its cryptic colours, pike may have initiated its attack before the prey detected it, limiting the possibility for prey evasive manoeuvres. Prey-size selectivity towards small prey in clear water disappeared in turbid water but was maintained in humic water. Owing to its optical properties, turbidity degrades the quality of the visual information more through scattering than humic water does through absorption. We show that the effect of visual degradation on Foraging depends on the cause of visual degradation, which has not previously been acknowledged in the visual Foraging literature. (Less)
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Foraging Efficiency and prey selectivity in a visual predator: differential effects of turbid and humic water
Canadian Journal of Fisheries and Aquatic Sciences, 2013Co-Authors: Mikael Jönsson, Lynn Ranåker, P. Anders Nilsson, Christer BrönmarkAbstract:Predators exert strong regulating forces on lower trophic levels through predation. As most fish are visual foragers, visual conditions in the water may alter the strength of this regulation. We evaluated effects of turbidity and humic water on Foraging Efficiency and prey-size selectivity in Northern pike (Esox lucius) feeding on roach (Rutilus rutilus). Encounter rates decreased in both turbid and humic water but were not counteracted by increased searching activity. Capture success was unaffected by turbidity but was nonlinearly affected by humic water by being high in clear and highly humic water but low in less humic water. In highly humic water, the visual range approached pike’s strike distance and, together with its cryptic colours, pike may have initiated its attack before the prey detected it, limiting the possibility for prey evasive manoeuvres. Prey-size selectivity towards small prey in clear water disappeared in turbid water but was maintained in humic water. Owing to its optical properties, turbidity degrades the quality of the visual information more through scattering than humic water does through absorption. We show that the effect of visual degradation on Foraging depends on the cause of visual degradation, which has not previously been acknowledged in the visual Foraging literature.
Piotr Tryjanowski - One of the best experts on this subject based on the ideXlab platform.
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Foraging Efficiency of white stork ciconia ciconia significantly increases in pastures containing cows
Acta Oecologica-international Journal of Ecology, 2020Co-Authors: A Zbyryt, Tim H Sparks, Piotr TryjanowskiAbstract:Abstract Recent changes in agriculture have had a very strong impact on avian populations, but detailed mechanistic explanations are scarce. Some proposed solutions to avian declines can be complicated because responses are not linear. For example, abandoning pasture management can be detrimental to many open-nesting birds, but also to some others, because livestock perform ecosystem engineering, changing sward height and creating microhabitats for invertebrates, as well as for insectivorous mammals. Both these features affect the Foraging Efficiency of birds, for example white stork Ciconia ciconia. We studied the Foraging activities of storks in the presence and absence of grazing cows, and we show that in extensive farmland in NE Poland, the presence of cows has a highly significant effect on stork Foraging Efficiency (in our study area mainly catching insects), which may be crucial to improving breeding success. Our results may also be important from a practical point of view. In white stork recovery projects where supplementary food is offered to storks (e.g. chicken and fish provided on feeding platforms) we believe that establishing extensive cattle pastoralism would be better from an ecological as well as from an aesthetical viewpoint.
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Foraging Efficiency of white stork ciconia ciconia significantly increases in pastures containing cows
Acta Oecologica-international Journal of Ecology, 2020Co-Authors: A Zbyryt, Tim H Sparks, Piotr TryjanowskiAbstract:Abstract Recent changes in agriculture have had a very strong impact on avian populations, but detailed mechanistic explanations are scarce. Some proposed solutions to avian declines can be complicated because responses are not linear. For example, abandoning pasture management can be detrimental to many open-nesting birds, but also to some others, because livestock perform ecosystem engineering, changing sward height and creating microhabitats for invertebrates, as well as for insectivorous mammals. Both these features affect the Foraging Efficiency of birds, for example white stork Ciconia ciconia. We studied the Foraging activities of storks in the presence and absence of grazing cows, and we show that in extensive farmland in NE Poland, the presence of cows has a highly significant effect on stork Foraging Efficiency (in our study area mainly catching insects), which may be crucial to improving breeding success. Our results may also be important from a practical point of view. In white stork recovery projects where supplementary food is offered to storks (e.g. chicken and fish provided on feeding platforms) we believe that establishing extensive cattle pastoralism would be better from an ecological as well as from an aesthetical viewpoint.
Lisa Nagaoka - One of the best experts on this subject based on the ideXlab platform.
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Differential Carnivore Damage as a Potential Indicator of Resource Availability and Foraging Efficiency
Journal of Archaeological Method and Theory, 2014Co-Authors: Lisa NagaokaAbstract:Carnivore damage is typically documented in faunal assemblages to understand if attrition of elements or element portions has occurred. Thus, the amount of carnivore damage often is used to simply reflect how “complete” the assemblage is. However, gnawing is a means for carnivores to extract within bone nutrients. Thus, according to the marginal value theorem, the amount of time a carnivore gnaws on an element should be related to the availability of higher-ranked resources or Foraging Efficiency. In resource-rich environments, less damage is expected than in less productive ones. This expectation was tested by examining the degree of carnivore damage on fur seal remains from three archaeological sites in New Zealand that vary in availability of high-ranked resources. The analysis indicates that the extent and intensity of carnivore damage can relate to resource availability and thus may be a useful measure in prey choice studies. This research also has implications for the hominid scavenging-hunting debate where the degree of carnivore damage has been used to determine primary (hunting) versus secondary (scavenging) access to carcasses.
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declining Foraging Efficiency and moa carcass exploitation in southern new zealand
Journal of Archaeological Science, 2005Co-Authors: Lisa NagaokaAbstract:The application of Foraging theory to understanding carcass exploitation is a relatively recent development. The methodology developed by archaeological and ethnoarchaeological research on butchery/transport studies has been integrated into a behavioral ecological framework to create models that can be used to understand archaeological carcass exploitation. In this paper, I use such a model to examine how New Zealand foragers altered their use of moa carcasses as the availability of these large birds declined. Moa data from the Shag River Mouth site in southern New Zealand are analyzed to test changes in butchery/transport and skeletal element breakage patterns expected with resource depression and declining Foraging Efficiency. This research shows that at Shag Mouth, field processing of moas increased and marrow, and possibly grease extraction intensified over time.
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The effects of resource depression on Foraging Efficiency, diet breadth, and patch use in southern New Zealand
Journal of Anthropological Archaeology, 2002Co-Authors: Lisa NagaokaAbstract:While many studies have examined human impacts on prehistoric environments, few have explicitly examined how foragers adapt to the changing environmental situations that they have created. The goal of this analysis is to study the relationship between human Foraging economies and human-related environmental change in southern New Zealand. Foraging theory is used to generate predictions about subsistence change resulting from the declining abundance of important resources such as moas and seals. In particular, these predictions examine changes in (1) the kind of resources exploited (Foraging Efficiency), (2) the number of resources utilized (diet breadth), and (3) the habitats exploited (patch choice). The predictions are tested using the large assemblage of vertebrate faunal remains from the well-stratified and well-dated Shag River Mouth site. This study shows that using Foraging theory models to structure analysis provides a more fine-grained spatial and temporal resolution of subsistence change in southern New Zealand than has been previously achieved.