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Field Notes: February 7, 2012

Eagles and Ravens and Vultures -- Oh My!

By Dr. Scott Ford

What do bald eagles (Haliaeetus leucocephalus), common ravens (Corvus corax), and turkey vultures (Cathartes aura) have in common? They all feed on dead things!! And on the coast, that often means stuff that washes in from the sea. seals, sea lions, and other marine mammals that die either naturally or, sometimes, from man-made causes. Since marine mammals feed on other smaller marine animals which, in turn, feed upon smaller marine animals, and so on, down to the tinyest creatures (diatoms), then it seems reasonable that we can learn about the health of the marine ecosystem by studying dead marine mammals and the birds that feed on them. Also, because we know that the environment is changing rapidly, it's getting harder to know what is and is not affected by things like climate change, water quality, and loss of habitat. By sampling free-living birds now, we can provide a baseline for future comparisons-- help to create a starting point for measuring environmental changes and its effects.

It was for these reasons that the US Fish and Wildlife Service awarded us a grant to perform this study. Our goal for 2012 is to capture 15-20 birds including bald eagles, ravens, and turkey vultures for sampling. Preferrably, these birds will be captured red-footed-- that is, in the act of feeding on marine mammal remains. Swabs of the trachea and the cloaca (a bird's "rear-end"), a few small feather samples, and a blood sample will be taken. These will be processed to check for the following infectious agents: Avian influenza, adenovirus, paramyxovirus, Chlamydophila psittaci, Mycoplasma spp, Salmonella spp, Coxiella burnetti, Mycobacterium spp, and gastrointestinal and blood parasites. Some of the blood and feather sample will be analyzed for levels of contaminants including heavy metals (including lead and mercury), organochlorines, and PCBs. An isotopic analysis of the feathers will help identify the geographic location of the bird's last molt and the trophic levels (e.g., animal types) upon which the bird has been feeding. Swabs will also be cultured for other bacteria and tested for resistance to various antibiotics. In addition, a serum biochemistry and complete blood count will be performed to assess the organ function and immune system status.

I've been pleased and excited to be a part of this project these past few months as I've helped create the testing protocols for the study. Dr. Dan Varland has been very busy acquiring permits, modifying our capture techniques, and surveying beaches with his volunteers to find suitable marine mammal carcasses where we can set our traps. It takes a lot of time and effort by a lot of people to pull off a project like this!

Do you want to know more? Do you want to DO more? Check out Coastal Raptors for volunteer opportunities or drop me a line:

[Scroll down for answers!]

    1. What do you call an animal that eats dead animals??
    2. What do you call something that is human-caused? (Hint: ANTHRO-pology is the study of people and civilizations)
    3. What is a cloaca and why is it a common sample site in avian medicine?
    4. Isotopes of what element are analyzed when determining geographic location of molt from feathers? 

 Here's a video clip of a blood draw on a peregrine falcon!

ANSWERS: 1) Scavenger. 2) Anthropogenic. 3) The cloaca is the common collection organ for feces, urates/urine (form the kidneys), and contains the openings to the reproductive tracts. Birds expel feces, urates/urine, and gametes (eggs or sperm) through a single orifice called the vent. It's a good place for sampling because it many disease agents and toxins are shed in feces or urates/urine. 4) Hydrogen.

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