Synchrony in ecological systems, the degree to which elements respond similarly over time or space, can inform our understanding of how ecosystems function and how they are responding to global change. While studies of ecological synchrony are often focused on within-species dynamics, synchrony among species may provide important insights into how dynamics of one species are indicative of conditions relevant to the larger community, with both basic and applied implications. Ecological theory suggests there may be conditions under which communities might exhibit increased synchrony, however the degree to which these patterns are borne out in natural systems is currently unknown. We used long-term breeding success data from a community of Antarctic seabirds to assess the degree of interspecific, community synchrony and the role that extreme events play in driving these dynamics. We assessed theoretical links between community synchrony, niche separation, and environmental variability using data from this and three other seabird communities as well as a simulation study. Results show that reproductive success for individual species in the Antarctic seabird community fluctuated relatively independently from one another, resulting in little synchrony across this community, outside of extreme years. While an exceptionally poor year for a given species was not necessarily associated with an exceptionally poor year for any other species, one community-wide extreme year existed. When compared to other seabird communities, this group of Antarctic seabirds exhibited lower overall synchrony and higher estimated niche separation, supporting theoretical predictions. Empirical and simulation-derived results suggest that communities where temporal variation is small for conditions in which species respond substantially differently, and large for conditions in which species respond similarly, may exhibit more synchronous dynamics. Identifying where and why synchronous dynamics might be more apparent has the potential to inform how ecological communities might respond to future global change.

We collected data on five sympatrically breeding seabird species (Adélie penguin Pygoscelis adeliae, southern fulmar Fulmarus glacialoides, cape petrel Daption capense, snow petrel Pagodroma nivea, and south polar skua Stercorarius maccormicki) at breeding sites at Pointe Géologie, Antarctica (66.67°S, 140.00°E) during the Antarctic summer (December – March). These five seabird species are highly site faithful and feed on prey items found in the marine environment (e.g., krill, fish, and squid), with the exception of south polar skua, which preys primarily upon Adélie penguin eggs and young during the breeding season at Pointe Géologie (Ridoux and Offredo 1989). The number of breeding pairs and number of chicks fledged were recorded from 1980-2016, although data were not available for every species in all years (Appendix A). Breeding success data were collected from the entire colony for southern fulmar, cape petrel, south polar skua, and Adélie penguin, while a subset of nests were monitored for snow petrel (approximately 180 – 300 nests; [Chastel et al. 1993, Barbraud et al. 2015]). Given the well-defined nature of nests and survey methods, a high level of data accuracy was presumed. See Barbraud et al. (2015) for detailed data collection protocols.

We provide here the raw data from counts of breeding pairs and number of chicks for 5 species seabirds at Pointe Géologie. Before using the data please contact Christophe Barbraud (barbraud@cebc.cnrs.fr) or Karine Delord (delord@cebc.cnrs.fr).

Data fields:

YEAR - year
SPECIES - species
ABUN - number of breeding pairs
CHICKS - number of chicks
BS - chicks per pair

Other data used in these analyses:

- Isle of May seabird data were from Lahoz-Monfort et al. 2013
- Southeast Farallon Island seabird data were collected by PRBO Conservation Science in collaboration with the United States Fish and Wildlife Service (available here: https://data.prbo.org/cadc2/index.php?page=colony-data)
- Tern Island seabird data were from Dearborn et al. 2001
- Community evenness data (other than those derived from the seabird colonies) were from Sugihara et al. 2003
- Chl-a data were derived from the Globcolour product (http://www.globcolour.info/)