The Morro Bay Winter Loon Study About the study
The study of Loons on our bay is being conducted by Darwin Long, head field biologist of the Biodiversity Research Institute (BRI), in conjunction with the Morro Coast Audubon Society (MCAS) . Once trapped the birds are weighed, measured, photographed, feather and blood samples are taken and finally, the birds are banded. Two bands are placed on each leg. The color bands are plastic, approximately ½” wide by 1 “ long. Three of the four bands are colored (orange, green, red, white, yellow, blue). One of the bands, Fish & Wildlife, will always be silver. If you observe a Loon with a band, please record the time, location and color combination. We can often identify the bird with only one color combination.
The study is addressing the following topics:
1) Winter rafting behavior. Again, very little information exists on the social behavior of Loons on their wintering grounds. How do they group, for protection, to facilitate feeding or other social reasons? There seem to be 3 distinct rafts on Morro Bay. Are birds of the same raft related, are they from the same natal area, are they the same age (no), do individuals shift between rafts or are raft “members” stable? We also wish to understand the site fidelity of the wintering Loon. Do the same birds return to Morro Bay each year, are they fluid, moving from one wintering site to another, do they change wintering sites from one year to another based on some variable or combination of variables? By banding (thus identifying each bird) and observing the dynamics of the raft, we are gathering data to answer these questions.
2) Toxicology. As data exists on the contaminant levels of birds on their breeding grounds, we will make a comparison in toxic accumulation and matrix of contaminants and how they differ through the seasons. With this data we will be able to pinpoint where harmful contaminants are present in the food supply or general environment. This data is gathered from the blood and feather samples.
3) Molt sequence. The plumage sequence for subadult common loons between one and four years of age is still largely unknown due to lack of substantial data. As birds are banded and tested, a complete photo documentation is being conducted. Up to 20 photos are quickly taken as we work with the birds, top view, side view, ventral, neck, head and feet. As the photo library grows (and reobservation data comes in) and more information comes in on each bird’s movements, we will be able to piece together the progression of the plumage from the dull gray-brown to the sharper, darker, adult, winter plumage.
4) Genetics. There is no plumage-based sexual dimorphism in Loons, and size differentials are vague due to wide geographic variations. Genetic information derived from the blood samples will yield the sex of the “study” birds. Genetic testing also allows us to identify populations, giving us a broad view of the natal area (coastal, inland, far north). Breeding Loons return to lakes 50 km -70km from their natal grounds. This broad site fidelity creates “clumps” of related individuals. We can track down these “clumps” or large family groupings with the genetics.
5) Radio Isotopes. Radio isotope information allows for a finer focus. With this information, gathered from the facial, secondary and tail feathers, we can pinpoint what lake the birds are migrating to and it will give us a fingerprint of what wintering areas the birds are using. Each body of water yields a distinct signature in the feathers.
MORE TO COME: (wing loading, photo documentation of webbed feet, bill & culmen studies, weights & measures)
