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Great Cormorants on Greenland
Reference
White, C.R., Boertmann, D., Gremillet, D., Butler, P.J., Green, J.A. and Martin, G.R. 2011. The relationship between sea surface temperature and population change of Great Cormorants Phalacrocorax carbo breeding near Disko Bay, Greenland. Ibis: The International Journal of Avian Science 153: 170-174.

What was done
Using data for sea surface temperature (SST) in the vicinity of Greenland's Disko Bay that they obtained from the U.S. National Climate Data Center, plus data for the number of breeding pairs of Great Cormorants in Disko Bay and adjacent areas that they obtained from aerial and boat-based surveys described by Boertmann et al. (1996) and Boertmann (2006) for the period 1946-2005, White et al. analyzed how Great Cormorant numbers varied over the years in response to concomitant changes in SST.

What was learned
The six scientists determined that population change rates of Great Cormorant colonies in the vicinity of Disko Bay "were significantly positively correlated with mean winter SST," adding that "populations increased during relatively warm years and decreased during relatively cold years," while also noting that "the highest rates of population change correspond with periods of relatively high SST in recent years and during the 1960s."

What it means
White et al. conclude that, "taken together, the positive relationship between rates of population change in Cormorants and SST, the likely positive impact of Arctic warming on the preferred prey species of Cormorants, and the flexible food preferences and foraging strategies of Cormorants suggest that Cormorants are likely to benefit from a warming Arctic." However, they also note that "the foraging of Cormorants is visually guided (Martin et al., 2008)" and that "their visual acuity is strongly dependent on ambient illumination (White et al., 2007)," which suggests, in their words, that "sensory constraints on foraging behavior may therefore restrict expansion of the winter range of Cormorants in Greenland, even if SSTs rise and populations increase." This problem, however, has always been a problem; and, therefore, the several benefits the researchers foresee should still prove a boon (albeit possibly somewhat attenuated) to the region's Great Cormorants.

References
Boertmann, D. 2006. Survey of Kittiwake colonies in Disko Bay and adjacent waters. Research Note, National Environmental Research Institute, Aarhus, Denmark.

Boertmann, D., Mosbech, A., Falk, K. and Kampp, K. 1996. Seabird colonies in western Greenland (60°-79°30'N. lat.). Research Note, National Environmental Research Institute, Aarhus, Denmark.

Martin, G.R., White, C.R. and Butler, P.J. 2008. Vision and the foraging technique of Great Cormorants Phalacrocorax carbo: pursuit or close-quarter foraging? Ibis 150: 485-494.

White, C.R., Day, N., Butler, P.J. and Martin, G.R. 2007. Vision and foraging in cormorants: more like herons than hawks. PLoS ONE 2: 10.1371/journal.pone.0000639.

Reviewed 16 February 2011