Birders along the Pacific Coast of the US, along with The Weather Channel and the Los Angeles Times, have certainly noticed the recent invasion of Blue-footed Boobies in California, whether you’ve read about it on eBird or seen it in person. Similar large-scale movements are occurring for other species along the Pacific Coast (for example, Elegant Tern), with larger numbers appearing farther out of range than “normal.” Presumably, similar mechanisms to those driving influxes of Razorbills South in the western North Atlantic in Fall 2012 are at work in these large-scale influxes and invasions: anomalously warm sea surface temperatures affecting primary food sources. Distribution of pelagic fish are tied to water with specific temperature regimes; and when these regimes change drastically, distributions of fish, and the birds that track them, change drastically. In addition to this brief highlight, Team BirdCast will keep an eye on this story as it continues to unfold during Fall 2013 and probably into Winter 2014. As always, please submit all your bird observations to eBird!
Below is map highlighting Global sea surface temperature anomalies as of 23 September 2013. The scale shows anomalies in degrees of Celsius. Notice the anomalously warm water off the Pacific Coast of Central America and its distribution farther North to Mexico and into the Sea of Cortez. Notice also the pocket of cooler water off the Central and Southern California coast.
Presumably, species like Blue-footed Booby may be departing their core range and moving en masse in search of food. Below is a current map for Blue-footed Booby as of 23 September, with a link to a live eBird map.
Below is a current map for Elegant Tern as of 23 September, with a link to a live eBird map.