Adelie penguin area-wide breeding population census, 1991 - 2017.
The fundamental long-term objective of the seabird component of the Palmer LTER (PAL) has been to identify and understand the mechanistic processes that regulate the mean fitness (population growth rate) of regional penguin populations. Two hypotheses have guided this research, with one suggesting t...
| Main Authors: | , |
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| Format: | Dataset |
| Language: | English |
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Environmental Data Initiative
2020
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| Online Access: | https://dx.doi.org/10.6073/pasta/86ef5bd8a8b140074763f0aa1962076c https://portal.edirepository.org/nis/mapbrowse?packageid=knb-lter-pal.87.6 |
| Summary: | The fundamental long-term objective of the seabird component of the Palmer LTER (PAL) has been to identify and understand the mechanistic processes that regulate the mean fitness (population growth rate) of regional penguin populations. Two hypotheses have guided this research, with one suggesting that population mean fitness is best explained by changes in regional krill biomass, and the other proposing that long-term changes in sea ice affects mean fitness by tipping the balance in favor of one species over another in accordance with species-specific evolved life history affinities to sea ice. Although these hypotheses are not mutually exclusive, current evidence in the PAL region tends to favor the latter over the former. Since the inception of PAL, Adélie penguin populations have effectively collapsed, while those of gentoo and chinstrap penguins have increased dramatically, trends that are spatially and temporally coherent with decreasing regional sea ice duration. Adélie penguins are an ice-obligate polar species whose life history is intimately linked to the presence of sea ice, while chinstrap and gentoo penguins are ice-intolerant species whose life histories evolved in the sub-Antarctic, where sea ice is a less permanent feature of the marine ecosystem. In contrast, although krill constitute the most important component of the summer diets by mass of these three penguin species, changes in PAL krill abundances have exhibited no long-term trends, and thus fail to explain the divergent patterns in penguin populations evident in our time series. The PAL study region includes five main islands on which Adélie penguin colonies have historically occurred. These are censused synoptically once a year to determine the overall size of the breeding population. The optimal census date may vary by a few days each season, but ultimately tries to capture the week following peak egg laying when the total number of breeding pairs reaches a maximum. The timing of this census is assisted by the REPRO and HUMPOP data, which provide a daily to weekly rate of change in breeding adult population numbers as new nests are initiated. This census is useful for a number of assessments, one of the most critical being that it directly reflects the effects of environmental variability on adult overwinter survival. |
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