Judy Clarke - Academia.edu (original) (raw)
Address: Australian Antarctic Division, Kingston, Tasmania, Australia
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Demographic parameters (age-specifi c survival rates, fecundity levels and population numbers) we... more Demographic parameters (age-specifi c survival rates, fecundity levels and population numbers) were analysed for the Béchervaise Island Adélie penguin colony in eastern Antarctica after 12 years of monitoring under the CCAMLR Ecosystem Monitoring Program (CEMP). A life table was constructed, and predicted rates of population growth and breeding success calculated. The population model predicted an annual population growth rate of 0.3% compared to the 1.2-1.8% increase per annum indicated from fi eld counts. Underestimation of adult survival rates was considered the most likely explanation for the discrepancy. As is the case for most long-lived seabird species, growth/decline rates of the Adélie penguin population at Béchervaise Island were found to be more sensitive to changes in annual survival rates, especially of young breeding adults, than to changes in fecundity parameters. Results are discussed in comparison with data from a declining Adélie penguin population in the Ross Sea studied during the 1960s and 1970s , and in relation to other CEMP parameters, environmental factors and fi shery regulations. The data collection and analysis methods outlined in this paper provide a basis for the development of data reporting formats for CEMP Standard Method A4.
Data on foraging trip durations and meal sizes were collected by means of an automated monitoring... more Data on foraging trip durations and meal sizes were collected by means of an automated monitoring system from breeding Ade lie penguins (Pygoscelis adeliae) at Be chervaise Island over eight breeding seasons, commencing in 1991±92. Signi®cant interannual dierences in duration of foraging trips, meal sizes and diet composition were observed. These parameters were correlated with breeding success and¯edging masses, and provide useful indicators of food availability during the breeding season. Chicks were particularly vulnerable to a decreased availability of food during the ®rst 3 weeks after hatching.
Analyses of the body masses of Ade lie penguins (Pygoscelis adeliae) departing on foraging trips... more Analyses of the body masses of Ade lie penguins (Pygoscelis adeliae) departing on foraging trips of long and short duration (> and<40 h, respectively) during chick rearing showed that the departure weights of birds prior to long trips were signi®cantly lighter than were those prior to short trips. Penguins, particularly males, were signi®cantly heavier at the start of the guard stage than at the end and both sexes gained similar amounts of body mass during the creÁ che period. Results support the hypothesis that the foraging eort of Ade lie penguins at Be chervaise Island is partitioned between the sexes, with males accepting a net rate of negative energy gain to provide regular meals for their ospring during the guard stage. Ade lie penguin foraging behaviour may be driven by a trade-o between the allocation of food to chicks and the storage of parental body reserves, similar to that previously postulated for some species of¯ying seabirds. The relevance of such a foraging strategy to the breeding success of penguins in the Mawson region of eastern Antarctica is discussed in relation to micronekton distribution in the area.
Consistent sex dierences in foraging trip duration, feeding locality and diet of breeding Ade li... more Consistent sex dierences in foraging trip duration, feeding locality and diet of breeding Ade lie penguins (Pygoscelis adeliae) were demonstrated at two widely separated locations over several breeding seasons. Dierences in foraging behaviour were most pronounced during the guard stage of chick rearing. Female penguins made on average longer foraging trips than males, ranged greater distances more frequently and consumed larger quantities of krill. In contrast, males made shorter journeys to closer foraging grounds during the guard period and fed more extensively on ®sh throughout chick rearing. Mean guard stage foraging trip durations over four seasons at Be chervaise Island, Eastern Antarctica and over two seasons at Edmonson Point, Ross Sea ranged between 31 and 73 h for females and 25 and 36 h for males. Ninety percent of males tracked from Be chervaise Island by satellite during the ®rst 3 weeks post-hatch foraged within 20 km of the colony, while the majority (60%) of females travelled to the edge of the continental shelf (80±120 km from the colony) to feed during this period.
The effects of flipper bands, implanted tags, gastric lavage and external instrument attachment o... more The effects of flipper bands, implanted tags, gastric lavage and external instrument attachment on the performance of Adélie penguins were investigated over three seasons at Béchervaise Island, Mac. Robertson Land, Antarctica. The return rates of birds carrying bands and/or implanted electronic transponders were compared to investigate the contribution of bands to bird mortality and to determine rates of band and tag loss. There was a slight reduction in return rates of birds banded for more than one season, but no evidence of band or tag loss over a single winter. The attachment of satellite tracking devices during the incubation period resulted in increased foraging trip durations and reduced breeding success. Attachment for single or multiple foraging trips post-hatching caused no significant increase in foraging trip durations. No reduction in fledging rates of chicks from nests of stomach-lavaged birds was detected over two breeding seasons. The implications of these findings for the CCAMLR Ecosystem Monitoring Program are discussed.
Demographic parameters (age-specifi c survival rates, fecundity levels and population numbers) we... more Demographic parameters (age-specifi c survival rates, fecundity levels and population numbers) were analysed for the Béchervaise Island Adélie penguin colony in eastern Antarctica after 12 years of monitoring under the CCAMLR Ecosystem Monitoring Program (CEMP). A life table was constructed, and predicted rates of population growth and breeding success calculated. The population model predicted an annual population growth rate of 0.3% compared to the 1.2-1.8% increase per annum indicated from fi eld counts. Underestimation of adult survival rates was considered the most likely explanation for the discrepancy. As is the case for most long-lived seabird species, growth/decline rates of the Adélie penguin population at Béchervaise Island were found to be more sensitive to changes in annual survival rates, especially of young breeding adults, than to changes in fecundity parameters. Results are discussed in comparison with data from a declining Adélie penguin population in the Ross Sea studied during the 1960s and 1970s , and in relation to other CEMP parameters, environmental factors and fi shery regulations. The data collection and analysis methods outlined in this paper provide a basis for the development of data reporting formats for CEMP Standard Method A4.
Data on foraging trip durations and meal sizes were collected by means of an automated monitoring... more Data on foraging trip durations and meal sizes were collected by means of an automated monitoring system from breeding Ade lie penguins (Pygoscelis adeliae) at Be chervaise Island over eight breeding seasons, commencing in 1991±92. Signi®cant interannual dierences in duration of foraging trips, meal sizes and diet composition were observed. These parameters were correlated with breeding success and¯edging masses, and provide useful indicators of food availability during the breeding season. Chicks were particularly vulnerable to a decreased availability of food during the ®rst 3 weeks after hatching.
Analyses of the body masses of Ade lie penguins (Pygoscelis adeliae) departing on foraging trips... more Analyses of the body masses of Ade lie penguins (Pygoscelis adeliae) departing on foraging trips of long and short duration (> and<40 h, respectively) during chick rearing showed that the departure weights of birds prior to long trips were signi®cantly lighter than were those prior to short trips. Penguins, particularly males, were signi®cantly heavier at the start of the guard stage than at the end and both sexes gained similar amounts of body mass during the creÁ che period. Results support the hypothesis that the foraging eort of Ade lie penguins at Be chervaise Island is partitioned between the sexes, with males accepting a net rate of negative energy gain to provide regular meals for their ospring during the guard stage. Ade lie penguin foraging behaviour may be driven by a trade-o between the allocation of food to chicks and the storage of parental body reserves, similar to that previously postulated for some species of¯ying seabirds. The relevance of such a foraging strategy to the breeding success of penguins in the Mawson region of eastern Antarctica is discussed in relation to micronekton distribution in the area.
Consistent sex dierences in foraging trip duration, feeding locality and diet of breeding Ade li... more Consistent sex dierences in foraging trip duration, feeding locality and diet of breeding Ade lie penguins (Pygoscelis adeliae) were demonstrated at two widely separated locations over several breeding seasons. Dierences in foraging behaviour were most pronounced during the guard stage of chick rearing. Female penguins made on average longer foraging trips than males, ranged greater distances more frequently and consumed larger quantities of krill. In contrast, males made shorter journeys to closer foraging grounds during the guard period and fed more extensively on ®sh throughout chick rearing. Mean guard stage foraging trip durations over four seasons at Be chervaise Island, Eastern Antarctica and over two seasons at Edmonson Point, Ross Sea ranged between 31 and 73 h for females and 25 and 36 h for males. Ninety percent of males tracked from Be chervaise Island by satellite during the ®rst 3 weeks post-hatch foraged within 20 km of the colony, while the majority (60%) of females travelled to the edge of the continental shelf (80±120 km from the colony) to feed during this period.
The effects of flipper bands, implanted tags, gastric lavage and external instrument attachment o... more The effects of flipper bands, implanted tags, gastric lavage and external instrument attachment on the performance of Adélie penguins were investigated over three seasons at Béchervaise Island, Mac. Robertson Land, Antarctica. The return rates of birds carrying bands and/or implanted electronic transponders were compared to investigate the contribution of bands to bird mortality and to determine rates of band and tag loss. There was a slight reduction in return rates of birds banded for more than one season, but no evidence of band or tag loss over a single winter. The attachment of satellite tracking devices during the incubation period resulted in increased foraging trip durations and reduced breeding success. Attachment for single or multiple foraging trips post-hatching caused no significant increase in foraging trip durations. No reduction in fledging rates of chicks from nests of stomach-lavaged birds was detected over two breeding seasons. The implications of these findings for the CCAMLR Ecosystem Monitoring Program are discussed.