North Atlantic Seabird Success
Seabirds, such as auks, gulls, petrels, terns, and gannets, have spent tens of millions of years adapting to life on the ocean. Some species, such as the Sooty Tern, can spend years at sea before returning to land. The success of these species is dependent on the success of their food sources (such as fish and plankton), and the success of these food sources is dependent on oceanic conditions such as sea-surface temperatures and the behavior of ocean currents. In the North Atlantic, changes in the North Atlantic Oscillation (NAO), or the cyclical change in the pressure difference between the Azores High and Icelandic Low, affect ocean currents. A 30-year study of summertime seabird breeding success indicates that seabird species on both sides of the Atlantic have more offspring in years when the waters are warmer, and in years when the previous year’s winter featured a predominately negative NAO (a negative NOA means that the difference between the aforementioned pressure centers is lower and the westerly winds blowing across the ocean are not as strong). The North Atlantic Basin has experienced an overall warming trend over the last 50 years, although the sub-polar waters, where most of the breeding activity takes place, have actually cooled. Also during this period, the NAO has transitioned from being predominately negative to predominately positive.
Seasons: Spring, Summer, Fall, Winter
Source: Sandvik, H et al. A latitudinal gradient in climate effects on seabird demography: results from interspecific analyses.”" Global Change Biology 14 (2008): 703-713.)