As if this year did not already have enough displacement, entrainment, diversion, and irruption, along comes the Razorbill flight of 2012. Early December saw an unprecedented invasion of this species, which normally winters almost exclusively north of the mid-Atlantic states, into the waters off of Florida, with some individuals rounding Cape Sable and appearing in the Gulf of Mexico! A prophecy to fulfill the Mayan end of days? No. A sign of serious anomalous ocean conditions in the northwest North Atlantic? Probably! An opportunity to predict the first records of Razorbill for Alabama, Mississippi, Louisiana, and maybe Texas? Definitely! Please visit eBird to track and to report this epic influx of Razorbills and other typically colder water species.
Razorbills typically occurs over the Continental Shelf offshore from the Atlantic Provinces in Canada south to the mid-Atlantic states and, sometimes, as far south as Cape Hatteras, NC. Southward invasions of this species are not without precedent. In fact, for this species and many alcids and other seabirds, changes in wintering distribution are often food-driven. If waters are unusually unproductive in their normal haunts, birds may travel extensively in search of suitable conditions and richer food sources. However, the magnitude of this fall’s invasion is unprecedented, and the movement includes other species like Black and White-winged Scoter, Red-throated Loon, Dovekie and Thick-billed Murre, and perhaps others. Furthermore, teams eBird and BirdCast expect that the first records for Razorbill for Gulf Coast states may occur within the coming days given the present location and scale of the movement. Birders in the northern Caribbean should also watch closely for this suite of species, particularly in Cuba, the Bahamas, and Turks and Caicos.
The Sea Surface Temperature Story
Beginning in late fall 2012, alcids and several other species typical of the waters off New England and Atlantic Canada began occurring much further south than usual. Teams eBird and BirdCast suspected ocean temperatures in the western North Atlantic and resultant changes in food availability as the culprits. There seems to be a strong correlation between the extent and direction of the movement and the magnitude of the sea surface temperature (SST) anomalies in the Northwest Atlantic. This fall has seen an unusually large SST anomaly off the Northeast Coast. Along the Continental Shelf from Long Island to George’s Bank (east of Massachusetts), SSTs are approaching 3-4 C above normal (they are presently or have been approximately 10-15 C rather than 6-11 C).
The animation below shows weekly SST anomalies from 1 August through 12 December. Note the extensive areas of the Northwest Atlantic off the North American coast that have +3 C anomalies, colored dark red. These anomalous occurrences presumably result in significant changes in the distribution and types of fish and other food available for foraging. Razorbills are mostly foraging on capelin (a small fish in the smelt family) and krill (small crustaceans) during the winter (see e.g. Gaston and Woo 2008, Lilliendahl 2009). This is exactly the type of environmental change that would fuel long-range dispersal such as that being seen in Florida right now (see Lauria et al. 2012 for example).
This movement of typically colder water species into warmer waters of Florida, perhaps the northern Caribbean, and the Gulf of Mexico, signals what may be an alarming trend related to changing climate. Several research groups have recently highlighted changing circulation in the North Atlantic as a major wild card for climate change effects. Atlantic thermohaline circulation, essentially a process by which warm and less saline Tropical waters flow north, cool, increase in salinity and sinks to the sea floor off of Greenland before flowing along south the sea floor, is closely related to food rich upwelling essential for the life cycles of Arctic seabirds (among other things, to put it mildly!). Recent, fascinating, and alarming discussions of the effects of fresh water on changing salinity in the North Atlantic can be found here and here. To visualize potential effects of these changes in salinity and circulation might have on seabirds, consider this global map of sea surface temperatures and marine chlorophyll distribution and what changes in these distributions might mean for Arctic seabirds.
This 2012 Arctic seabird invasion, with Razorbill as perhaps the poster child, appears to correlate with patterns of sea surface temperature anomalies. How long this anomalous pattern will continue and exactly what pieces of the climate puzzle and over what time scale are responsible remain to be seen. There may be a clear connection between the appearance of Greenland blocks, the distribution of warmer sea surface temperatures in the North Atlantic, and increasingly fresh water infiltrating the typical salty North Atlantic Ocean. Additionally, a potentially ironic twist to present events for Razorbill, in particular: warmer sea surface temperatures off Atlantic Canada during spring and summer likely allow this species’ favored fish and crustacean prey items to expand farther north and east, and Gaston and Woo (2008) suggest that population expansion in Eastern Canada may be tied to these expansions. If this is true, larger numbers of Razorbills seeking food in increasingly poor warm water may be forced to make larger scale movements in search of food. Further examination is clearly necessary to connect SST and food resource changes with recent increases in the occurrences of Razorbills along the East Coast beyond this invasion.
Gaston, A.J. and Woo, K. 2008. Razorbills (Alca torda) follow subarctic prey into the Canadian Arctic: colonization results from climate change? AUK 125: 939-942 DOI:10.1525/auk.2008.07195
Lauria, V., Attrill, M.J., Pinnegar, J.K., Brown, A., Edwards, M. and Votier, S.C. 2012. Influence of Climate Change and Trophic Coupling across Four Trophic Levels in the Celtic Sea. PLoS ONE 7(10): e47408. doi:10.1371/journal.pone.0047408
Lilliendahl, K. 2009. Winter diets of auks in Icelandic coastal waters. Marine Biology Research 5: 143-154.