Bryson Voirin, a doctoral student at the Max Planck Institute for Ornithology in Germany and a fellow at the Smithsonian Tropical Research Institute in Panama, writes from Panama, where he is studying sleep in wild frigate birds.
Wednesday, April 20
The morning after our first successful frigate bird capture, I slowly creep through the thorny brush toward the field tent to check up on the female. It’s been about 12 hours since I put her back on her nest with a sleep logger and GPS unit, and I’m keen to see how she is doing, and if she is still here or if she has switched with her mate and is out foraging. Gazing through my binoculars, I spot her, sitting alert on her nest. I breathe a deep sigh of relief, knowing that her late-night capture did not cause nest abandonment. As in any zoology fieldwork, our first priority is the well-being of our study species. Before starting any project with animals, there is a stringent animal care committee that reviews and approves our protocols and procedures. Even though previous work on frigate birds shows that the birds would not be spooked off their nests, seeing this confirmed the morning after is a welcome sign.
Her sleep logger is still attached and looking fine, held on by the curious skin glue. I watch her head movements as she follows other birds floating overhead; she doesn’t seem affected at all by the device. However, judging by the angry glare she gives me, my presence is making her nervous. I want to avoid stressing the female any more than necessary, so I head back to camp and leave her alone for the rest of the day.
The next morning Sebastian Cruz reports back that a male has switched with her on the nest, meaning that she is out foraging. By the pinkish color of his throat we can tell that this is her nesting mate. Had she abandoned her nest, and another male taken over, that male would have a bright red inflated gular sac.
Relatively little is known about the behavior of magnificent frigate birds, so we can only guess how long the female will be out foraging. Sebastian thinks she will be out for three days, but it’s really only a guess. Magnificent frigate birds are a more coastal species than their strictly pelagic cousins, great frigates, whose foraging trips can last more than five days. Our theory is that our female frigate bird will fly up and down the coast of Panama feeding on small baitfish schooling at the surface.
The following morning, she’s back on her nest. The logger and GPS unit still look to be in pristine condition, and she appears to be quietly napping. Her foraging trip lasted only one night, which is shorter than we expected. Niels Rattenborg, Sebastian and I have a meeting about how to proceed. The sleep logger and GPS unit will record for up to five days, and so far have been recording for only two days. Should we catch her tonight and secure that data, or wait another two days to record a second foraging trip? It’s a difficult decision. Niels chuckles as he says, “A bird in the hand is worth two in the bush.” We decide to recapture the female that evening.
Sebastian Cruz Holding the bird after recapture and examining the logger for any signs of damage.That night, it is absolutely black outside. From the field tent, Sebastian and I crawl through the thorns in the direction of the female frigate bird. Having carefully studied her position during the previous two days, we are confident that we can find her in total darkness. I briefly entertain the idea of trying to locate her with the night vision, but decide that the blinding aftereffect is not worth it. Sebastian, who is a few feet ahead of me and has a keen sense of direction in the dark, motions that he is ready to go. I turn on the spotlight, illuminating both Sebastian and the female frigate bird, which is only five feet from him. Sebastian expertly picks her up and holds her gently under his arm as you would carry a Jack Russell terrier.
Sebastian walks quickly back to the tent, where Niels is ready to remove the loggers. The sleep logger comes off easily. The German skin glue holding the logger in place works as advertised, coming off cleanly and easily. The tape holding on the GPS unit also works as intended, coming right off the feathers and leaving no residue. A few minutes after the bird’s recapture, the sleep and GPS loggers have been cleanly removed, and she is ready to be released. Sebastian swiftly walks her back to her nest, setting her right back in place. She rustles around briefly, flexes her wings once, and quickly settles into her nesting position. From a few feet away, Sebastian watches her close her eyes and fall back asleep.
The three of us return to camp to download the data from the loggers. I feel like a kid waiting to unwrap a series of gigantic presents on my birthday. I fire up the generator and turn on the computer. But as Niels unwraps the sleep logger, his face tells it all. The gauze around the batteries is wet. Saltwater and electronics do not mix well. I connect the logger to the USB downloader, but the device won’t initialize. A sense of despair overcomes us. Somehow, when the frigate bird was feeding, saltwater must have entered the logger. While it’s possible there is data on the sleep logger, we don’t have the tools to dissect the circuit board and rebuild it for downloading in the field. The logger would have recorded until it shorted out, so although it’s not a complete bust, it’s a morale setback.
Bryson VoirinAlthough the logger looks to be in good condition, saltwater entered it at some point during the bird’s foraging trip, and EEG data was unavailable.Our mood improves when we download an exciting data set from the GPS logger. The $30 commercially available unit worked flawlessly, recording a GPS position every five minutes. I upload the data onto MoveBank, a free online database for movement data. The animated visualization of the bird’s flight lets us watch her take off from Isla Iguana, fly southwest around the Azuero peninsula and forage extensively on the western side of the peninsula. Even though we did not get any sleep data from this female, the GPS data alone is very useful to understanding the behavior of these birds. Next, we’ll go after another female frigate bird and hope that improved waterproofing will protect the sleep logger from the elements.
Bryson VoirinThe flight path of the female frigate bird is highlighted in pink. She soars around the coasts, feeds for one night, and then shortcuts across the mainland to the island. Click on the map to view the data at movebank.org. 
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