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Post date: Dec 10, 2014 9:08:03 PM
It's been a while since I last updated, but not because I haven't had anything to report! Quite the opposite. Here the most exciting developments from the past few months:
1) In our second season of tracking data collection, we've begun to see some neat fidelity to migration routes. CH24-- our superstar trans-Mexican migrant-- recently crossed Mexico at about the same time, and along approximately the same route, as last year.
CH24's fall migration route-- a little further west than in 2013
He is now wintering in exactly the same grove of trees near the Guatemalan border that he used as his home base last winter. Given that he traveled back and forth to Louisiana in the meantime, this consistency is absolutely incredible.
Locations from CH24 last winter (2013) in Reserva Biosfera La Encrucijada, Chiapas, MX...
... and locations from CH24 over the last 10 days. Same spot!
Some of our other birds have been similarly consistent in their second fall migrations. CH19 crossed the Gulf and is now wintering in the same portion of the Yucatan as last year, and AU40 once again stopped in the Florida Key en route to Cuba. Pelicans who stayed close to their breeding colonies last winter (like may of the Audubon Island, FL breeders) seem to be doing the same this year. I guess pelicans know how to stick with a good thing when the find one.
2) After sorting, measuring, weighing, and identifying 120 pounds of fish, we've finally made it to the fun part: burning them! Well, to be fair, there's a bit more to it than that. We first have to dry all the water out of the fish, which takes about a week-- most of the fish we process are about 75% water!
Ever wonder what a mummified fish looks like?
Once the fish's weight has stabilized, we grind it into fish powder in a mortar and pestle. Next we put it through a lipid extraction, removing all the fat with a chemical solvent.
Using a Soxhlet apparatus to run lipid extractions
Finally, we burn the fat-free remains in a 600° C oven, which removes proteins from the sample.
Each one of these contains one fish, minus water, lipids, and proteins. Cool, no?
Adding together the fat and protein weights and adjusting for their relative values gives us the total energetic content of the fish. Since this value changes over space, time, and a fish's life cycle, we will need to burn lots of different samples to see how much energy pelicans get from different fish, in different places, over different times of the season.
3) In November I visited Baja California Sur, Mexico for the Annual Meeting of the Waterbird Society. I presented a synthesis of some work done by myself and a few colleagues on migration-- we've been seeing several different waterbird species moving across the isthmus that CH24 uses in his migrations. There aren't a lot of documented examples of marine birds migrating across large stretches of land, so it was pretty exciting to be able to present some of the first examples, especially since the work was particularly relevant to Mexico. La Paz is a beautiful city. I had a lot of fun exploring...
... and even saw a few pelicans!
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