DOI: 10.5068/d1kt10
title: Lack of synchronized breeding success in a seabird community: extreme events, niche separation, and environmental variability

description: 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.
description: We collected data on five sympatrically breeding seabird species
 (Adélie penguin <i>Pygoscelis adeliae</i>, southern fulmar
 <i>Fulmarus glacialoides</i>, cape petrel <i>Daption
 capense</i>, snow petrel <i>Pagodroma nivea</i>, and
 south polar skua <i>Stercorarius maccormicki</i>) 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.   
 Barbraud, C., K. Delord, and H.
 Weimerskirch. 2015. Extreme ecological response of a seabird community to
 unprecedented sea ice cover. Royal Society Open Science
 2:140456–140456. Chastel, O., H. Weimerskirch, and P.
 Jouventin. 1993. High annual variability in reproductive success and
 survival of an Antarctic seabird, the snow petrel <i>Pagodroma
 nivea</i>. Oecologia 94:278–285. Ridoux, V., and C. Offredo. 1989. The diets
 of five summer breeding seabirds in Adélie Land, Antarctica. Polar Biology
 9:137–145.
description: 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<br> SPECIES -
 species<br> ABUN - number of breeding pairs<br> CHICKS -
 number of chicks<br> BS - chicks per pair
   Other data used in these analyses:
 - Isle of May seabird data were from Lahoz-Monfort et al.
 2013<br> - 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)<br> - Tern
 Island seabird data were from Dearborn et al. 2001<br> - Community
 evenness data (other than those derived from the seabird colonies) were
 from Sugihara et al. 2003<br> - Chl-a data were derived from the
 Globcolour product (http://www.globcolour.info/)
   
 Dearborn, D. C., A. D. Anders, and
 E. N. Flint. 2001. Trends in reproductive success of Hawaiian seabirds: is
 guild membership a good criterion for choosing indicator species?
 Biological Conservation 101:97–103. Lahoz-Monfort, J. J., B. J. Morgan, M. P.
 Harris, F. Daunt, S. Wanless, and S.  N. Freeman. 2013. Breeding together:
 modeling synchrony in productivity in a seabird community. Ecology
 94:3–10. Sugihara, G.,
 L.-F. Bersier, T. R. E. Southwood, S. L. Pimm, and R. M. May. 2003.
 Predicted correspondence between species abundances and dendrograms of
 niche similarities. Proceedings of the National Academy of Sciences
 100:5246–5251.