Trends in the Breeding Population of Adélie Penguins in the Ross Sea, 1981–2012: A Coincidence of Climate and Resource Extraction Effects

Abstract

Measurements of the size of Adélie penguin (Pygoscelis adeliae) colonies of the southern Ross Sea are among the longest biologic time series in the Antarctic. We present an assessment of recent annual variation and trends in abundance and growth rates of these colonies, adding to the published record not updated for more than two decades. High angle oblique aerial photographic surveys of colonies were acquired and penguins counted for the breeding seasons 1981–2012. In the last four years the numbers of Adélie penguins in the Ross and Beaufort Island colonies (southern Ross Sea metapopulation) reached their highest levels since aerial counts began in 1981. Results indicated that 855,625 pairs of Adélie penguins established breeding territories in the western Ross Sea, with just over a quarter (28%) of those in the southern portion, constituting a semi-isolated metapopulation (three colonies on Ross Island, one on nearby Beaufort Island). The southern population had a negative per capita growth rate of −0.019 during 1981–2000, followed by a positive per capita growth rate of 0.067 for 2001–2012. Colony growth rates for this metapopulation showed striking synchrony through time, indicating that large-scale factors influenced their annual growth. In contrast to the increased colony sizes in the southern population, the patterns of change among colonies of the northern Ross Sea were difficult to characterize. Trends were similar to southern colonies until the mid-1990s, after which the signal was lost owing to significantly reduced frequency of surveys. Both climate factors and recovery of whale populations likely played roles in the trends among southern colonies until 2000, after which depletion of another trophic competitor, the Antarctic toothfish (Dissostichus mawsoni), may explain the sharp increasing trend evident since then.

High Summertime Aerosol Organic Functional Group Concentrations from Marine and Seabird Sources at Ross Island, Antarctica, during AWARE

“…The three penguin habitats on Ross Island are all less than 50 miles from McMurdo Station ( Figure S2) 30 (Lyver et al, 2014) . Penguin activities have been linked previously to particle formation (Weber et al, 1998) , enriching aerosols with oxalate (Legrand et al, 2012) and containing CNHO fragments (Schmale et al, 2013) .…”

“…Penguin activities have been linked previously to particle formation (Weber et al, 1998) , enriching aerosols with oxalate (Legrand et al, 2012) and containing CNHO fragments (Schmale et al, 2013) . Since McMurdo Station is most frequently downwind from Cape Crozier, its estimated ~300,000 penguins are a likely source of this organic and ammonium contribution to particles (Lyver et al, 2014) .…”

Two Recent Massive Breeding Failures in an Adélie Penguin Colony Call for the Creation of a Marine Protected Area in D'Urville Sea/Mertz

“…Recently, satellite measurements have led to a new estimate that suggests an increase in the total number of Adélie penguins, as well as in the number of colonies across the continent (Lynch and LaRue, 2014). Using this technique and ground-based surveys, Adélie populations have been shown to be generally in decline in the Antarctic Peninsula, while other populations are stable or slightly increasing (Cimino et al, 2013;Lyver et al, 2014;Southwell et al, 2015). The use of satellite counts has contributed to the downgrading of the species on the IUCN scale from "Near Threatened" to "Least Concerned" in 2017.…”

The ecological value of long-term studies of birds and mammals in Central America, South America and Antarctica

“…Adélie penguin populations in the southern Ross Sea have been increasing (0.067 annual growth rate, 2001-2012), though numbers remain lower than they were in early 1980s [81]. In contrast, emperor penguins have been in decline, with a 50% drop in numbers since the 1970s [71,82].…”

“…One explanation for the decline in emperor penguins is a warming event that occurred in the southern Indian Ocean during the 1970s and that reduced sea ice extent [71,82]. A comparison of the Terre Adélie colony with another declining colony at Haswell Island (66°32′S, 93°0 7′E), revealed that numbers of breeding male emperor penguins correlated similarly to sea ice extent in both colonies, suggesting climate fluctuations as a main cause of population changes in the species ( [83]; but see [73,81]). Decreasing sea ice cover seems to be correlated with population declines in both species.…”