Seabird diets:

Regurgitations and fatty acid analysis
An important component of our study is knowing what the birds are eating. When environmental changes occur, they are likely to affect the kinds of food that are available to seabirds. In turn, food availability is likely to affect how hard the birds have to work to obtain enough food for themselves and their chicks. We'd like to know how diet differs among species, years, colonies, and even as a single breeding season progresses. We use two different techniques.

1) Collection of diet samples from regurgitations.

Some species (particularly auklets and kittiwakes) are prone to puking up their latest meal in response to startling events like being captured. This becomes even more frequent during chick rearing, when birds are often carrying meals back to feed their chicks. Our dedicated field biologists carefully scrape up every bit of this precious, fishy cargo off the ground and themselves, and package it up for analysis.

Back in the lab, these diet samples are painstakingly examined under microscopes in order to identify the species and age of the prey items. We find everything from squid and lanternfish to small fish like sandlance and tiny shrimp-like crustaceans called Euphausiids.

2) Collection of fat samples for fatty acid analysis.

Seabirds store energy in fat pads on their backs. We are able to make a tiny incision, remove a square millimeter of fat, reglue the incision and release the bird with no ill effects.

The fat sample, once extracted in chloroform, can be analyzed using quantitative fatty acid signature analysis techniques (QFASA). Based on a database of unique fatty acid signatures of prey items, the long-term dietary history of birds can be ascertained from fatty acid signature found in these tiny samples.
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