Wednesday, May 02, 2007

Return of the Cassin's Auklets

If I asked you to name a sure sign that spring had arrived, egg laying by a krill eating seabird that nests underground likely wouldn't be your first choice. But on the Farallones, Cassin's Auklets mark the beginning of a wave of breeding at the largest seabird colony in the contiguous United States.

These diving birds are Alcids, related to Murres and Puffins, and while they can fly in the air, they are much more graceful "flying underwater" by pumping their wings in pursuit of their favorite prey: krill. The past 2 years were not good ones for Cassin's Auklets, they failed in breeding in both 2005 and 2006 - unprecedented in our over 35 years of continuous research on Farallon seabirds. While these birds normally lay eggs in underground burrows they dig with their feet- we follow their breeding activities in nest boxes which act as artificial burrows. Here we are checking some boxes for nesting auklets.

It seems that major changes in upwelling and ocean currents in the last 2 years meant very little krill available at the right time for breeding auklets. Fewer bred, later in the year, and most abandoned their eggs. But so far for 2007, there is good news! We are seeing auklets breeding in good numbers and incubating their eggs.

This year auklets are breeding in the majority of our study boxes. For the most part, both parents are regularly incubating - which was not the case last year. We have also noticed that birds appear to be heavier, and therefore in better condition, this year than the last 2 years. Here is a picture of an auklet being weighed by intern Caroline Poli. We hope that the return to a "normal spring", with many breeding Cassin's Auklets will signal the beginning of a productive seabird season. As krill feeders lower on the food chain than other seabird species, these birds often act as a "early warning system" for the ocean conditions we are likely to see this summer. So far things look good and once again nights on the Farallones are filled with the mysterious shrill cries of the auklets - think crickets on steroids. Ahh.. spring has sprung....


Anonymous said...

YaY! Thank you for this excellent blog! I love reading about whats going on out there and am SOOOOOO happy to hear the Cassin's are looking good so far! Thank you for this great outreach tool!

Unknown said...

Hey there!

So glad I came across this blog, I've had a casual interest in the Farralones after coming across some material when working at a publishing company. Good to see so much research is still being done!
Best of luck,
Adam - Sydney, Australia.