Winter and spring controls on the summer food web of the coastal West Antarctic Peninsula (original) (raw)
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CCAMLR Sci, 1997
This paper presents a summary of the foraging locations of Adelie penguins, determined by satellite tracking, at seven widely-spaced breeding colonies along the coast of eastern Antarctica between 55"E (Enderby Land) and 175"E (Ross Sea). Adelie penguins feeding chicks regularly travelled up to 120 km offshore to the continental shelf and returned with krill, Etlplzausza superba. Locations of penguins on foraging trips
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Chinstrap penguins Pygoscelis antarctica are one of the major consumers of Antarctic krill Euphausia superba in the Southern Ocean. To examine their foraging strategy, we studied foraging trip patterns and diving behaviour of chinstrap penguins breeding at Signy Island, Antarctica, using time-depth recorders. Foraging trips of penguins could be divided into 2 groups, short diurnal (7.8 h) and longer overnight (19.9 h) trips, with diurnal trips (74%) being dominant in number (263 out of 355 trips). The diving depths of our study birds were much deeper (to 179 m) than previous studies on this species, with modal maximum dive depth at around 90 to 100 m. Diving patterns and profiles included typical pelagic dives, but also included series of consecutive square-wave shaped dives reaching similar maximum depth, the typical characteristics of benthic dives. These benthic-type dives were more abundant in diurnal foraging trips than overnight trips. Analysis of stomach contents showed that penguins on both types of trip fed almost exclusively on Antarctic krill. There was a positive relationship between indices of the proportion of benthic feeding and of foraging efficiency (stomach content mass divided by foraging trip duration). These results highlight the potential importance of benthic feeding on Antarctic krill, the first such recorded instance for chinstrap penguins. This previously undescribed foraging strategy by one of the major avian consumers of Antarctic krill provides a new insight into the predator-prey interactions of the Antarctic coastal marine ecosystem.
Deep Sea Research Part II: Topical Studies in Oceanography, 2011
In accord with the hypotheses driving the Southern Ocean Global Ocean Ecosystems Dynamics (SO GLOBEC) program, we tested the hypothesis that the winter foraging ecology of a major top predator in waters off the Western Antarctic Peninsula (WAP), the Adé lie penguin (Pygoscelis adeliae), is constrained by oceanographic features related to the physiography of the region. This hypothesis grew from the supposition that breeding colonies in the WAP during summer are located adjacent to areas of complex bathymetry where circulation and upwelling processes appear to ensure predictable food resources. Therefore, we tested the additional hypothesis that these areas continue to contribute to the foraging strategy of this species throughout the non-breeding winter season. We used satellite telemetry data collected as part of the SO GLOBEC program during the austral winters of 2001 and 2002 to characterize individual penguin foraging locations in relation to bathymetry, sea ice variability within the pack ice, and wind velocity and divergence (as a proxy for potential areas with cracks and leads). We also explored differences between males and females in core foraging area overlap. Ocean depth was the most influential variable in the determination of foraging location, with most birds focusing their effort on shallow (o 200 m) waters near land and on mixed-layer (200-500 m) waters near the edge of deep troughs. Within-ice variability and wind (as a proxy for potential areas with cracks and leads) were not found to be influential variables, which is likely because of the low resolution satellite imagery and model outputs that were available. Throughout the study period, all individuals maintained a core foraging area separated from other individuals with very little overlap. However, from a year with light sea ice to one with heavy ice cover (2001)(2002), we observed an increase in the overlap of individual female foraging areas with those of other birds, likely due to restricted access to the water column, reduced prey abundance, or higher prey concentration. Male birds maintained separate core foraging areas with the same small amount of overlap, showing no difference in overlap between the years. While complex bathymetry was an important physical variable influencing the Adé lie penguin's foraging, the analysis of sea ice data of a higher resolution than was available for this study may help elucidate the role of sea ice in affecting Adé lie penguin winter foraging behavior within the pack ice.
Foraging flexibility of adelie penguins Pygoscelis adeliae: Consequences for an indicator species
Biological Conservation, 1993
Because Adelie penguins Pygoscelis adeliae feed almost exclusively on krill Euphausia spp. the duration of their foraging trips has been suggested as an index of krill abundance. We performed three experiments to test factors that affect foraging trip durations during the incubation stage. In the first two experiments, we increased the time that the adults fasted before the female left on the first foraging trip. In the last experiment we attached real or mock instrument packages to their backs to create additional drag. Time spent fasting before foraging did not affect foraging trip durations. Penguins with instruments attached to their backs did, however, forage significantly longer than control birds. The necessity to relieve their mates on the nest limits foraging adults to a particular schedule during the incubation stage. The penguins can cope with substantial delays and difficulty foraging in order to return to their nests before their mates desert. Consequently, the duration of foraging trips during the incubation phase is not a sensitive index of foraging conditions (i.e. krill abundance) and its potential can only be realized in combination with several other factors.
Clarke et al 1998. Sex differences in Adelie penguin foraging strategies. Polar Biol
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.
Journal of Zoology, 2006
Life-history theory predicts that adults of long-lived species such as seabirds should optimally balance investment in current and future offspring. However, when trying to optimize investment in offspring provisioning, the most energetically costly component of seabird parental care, adults need to contend with large interannual fluctuations in prey availability and hence the cost of chick provisioning. Adults faced with this uncertainty can mechanistically balance parental care by adopting a strategy somewhere along the continuum between maintaining constant investment in foraging effort between years and letting chick provisioning fluctuate or holding chick provisioning constant and varying investment in foraging effort. Using ship-based hydroacoustic assessment of prey, time-depth recorders attached to penguins and land-based observations at the breeding colony, we examined how foraging and reproductive effort in breeding chinstrap penguins Pygoscelis antarctica responded to interannual variation in the abundance of Antarctic krill Euphausia superba in the vicinity of Seal Island, South Shetland Islands, 1990-1992. Regional measures of krill density varied by a factor of 2.5 (47.0, 23.8 and 61.2 g m À2 in 1990, 1991 and 1992, respectively) and was correlated with annual measures of breeding adult body weight and reproductive performance (breeding population size, duration of chick rearing, chick growth, breeding success and fledgling weight). In contrast, measures of penguin foraging effort (dive depth, dive duration, number of trips day À1 , trip duration, number of dives trip À1 and dive rate) did not differ between years. We conclude that chinstrap penguins reduce reproductive success rather than increase foraging effort in response to decreases in prey abundance in a manner consistent with predictions of life-history strategies for long-lived seabirds.
Foraging patterns of polar penguins
Sub-antarctic and polar penguins have revealed important differences in the distances travelled to foraging areas, the physical and biological characteristics of foraging areas, and foraging patterns. Differences are associated with preferred prey and its abundance. Data were acquired using satellite transmitters and time/depth recorders, the former giving location and rates of travel, the latter diving depths and patterns. Distinctions between travel and feeding dives help to assess foraging success. Data were matched to satellite imagery for determination of sea surface conditions. Sub-antarctic penguins travel further than polar penguins, feed near the Antarctic polar front, and are primarily diurnal feeders. Polar species feed at edges of coastal ice, pack ice, and polynyas. Most locations are neritic. Adelies specialise in krill at shallow depth as do sub-polar Macaroni and Royal Penguins. Emperor Penguins target fish in the mesopelagic zone, which is true also of King Penguins feeding at the Antarctic Polar Front. Hunting with 24h of daylight, polar penguins feed continuously with little hourly variation in depth. Subantarctic penguins show considerable diet differences, with reduced feeding at night.
2009
FACTORS AFFECTING ADULT FORAGING AND CHICK GROWTH OF ADÉLIE PENGUINS (PYGOSCELIS ADELIAE ) OFF THE WESTERN ANTARCTIC PENINSULA: A MODELING STUDY Erik W. Chapman Old Dominion University, 2009 Director: Dr. Eileen E. Hofmann Coupled individual-based models that simulate Adélie penguin (Pygoscelis adeliae) adult foraging behavior and chick growth from hatching to fledging were developed and used to explore factors that influence adult foraging energetics and chick fledging mass off the western Antarctic Peninsula (WAP). Adélie penguin colonies in this region are undergoing changes in population size that have been correlated with climate-driven alteration of the marine environment. Simulations were selected to highlight possible linkages between these population changes and climate variability, adult foraging, and chick growth processes. Simulations using the chick-growth model tested the influence on penguin chick fledging mass of variability in 1) timing of Antarctic krill (Euphausia...
Journal of Zoology, 2006
Life-history theory predicts that adults of long-lived species such as seabirds should optimally balance investment in current and future offspring. However, when trying to optimize investment in offspring provisioning, the most energetically costly component of seabird parental care, adults need to contend with large interannual fluctuations in prey availability and hence the cost of chick provisioning. Adults faced with this uncertainty can mechanistically balance parental care by adopting a strategy somewhere along the continuum between maintaining constant investment in foraging effort between years and letting chick provisioning fluctuate or holding chick provisioning constant and varying investment in foraging effort. Using ship-based hydroacoustic assessment of prey, time-depth recorders attached to penguins and land-based observations at the breeding colony, we examined how foraging and reproductive effort in breeding chinstrap penguins Pygoscelis antarctica responded to interannual variation in the abundance of Antarctic krill Euphausia superba in the vicinity of Seal Island, South Shetland Islands, 1990-1992. Regional measures of krill density varied by a factor of 2. 5 (47.0, 23.8 and 61.2 g m À2 in 1990, 1991 and 1992, respectively) and was correlated with annual measures of breeding adult body weight and reproductive performance (breeding population size, duration of chick rearing, chick growth, breeding success and fledgling weight). In contrast, measures of penguin foraging effort (dive depth, dive duration, number of trips day À1 , trip duration, number of dives trip À1 and dive rate) did not differ between years. We conclude that chinstrap penguins reduce reproductive success rather than increase foraging effort in response to decreases in prey abundance in a manner consistent with predictions of life-history strategies for long-lived seabirds.