when the air above the snow is colder than -50°F. But neither a large bird nor a small one can survive 10m; in an arctic or subarctic winter without an ample supply of food."

My daughter in Kentville, N.S., had a flock of about 50 redpolls frequenting her feeders. She saw what she first thought was an albino Common Redpoll, before she realized it must be a Hoary. r

Incidentally, I had about 6 Pine Siskins enjoying my niger, black oil sunflower, and Finch Delight seeds. I gather they are not too plentiful this winter in other areas of the Island. I would be interested to hear any comments. The largest number of redpolls frequenting my backyard diner at any one time is only six.

(Replies can be sent to David at 90 Prince Charles Drive, Charlottetown, PE ClA 3C2)

MONITORING THE HEALTH OF LOONS, GANNETS, HERONS, AND EAGLES by Pierre—Yves Daoust, AVC

The complexity of most ecosystems often precludes the selection of a single indicator species for monitoring their quality. However, the health of animal species at higher levels of the food chain represents a reasonably good parameter of such quality. The health of these species at the population level may be assessed through demographic studies (analysis of population statistics), such as determination of the number of young produced each year, but also, to some extent, by examining what goes on at the other end of the life history of these animals, i.e. what diseases, infectious, toxic, or other, are most often associated with mortality. This type of investigation represents an unobtrusive way of studying populations of wild ~animals, but it depends to a very large extent on the willingness of people in the field to collect and submit carcasses of wild animals to the proper agencies or laboratories for examination. The Canadian Cooperative Wildlife Health Centre (Atlantic Region), based at the Atlantic Veterinary College (AVC), University of Prince Edward Island, specializes in the necropsy (examination after death) of ‘wild animals, including gross, microscopic, microbiological, and toxicological examination. As a result of submission of carcasses of Common Loons during the past year, some coming from the Canadian Wildlife Service, others from the Nova Scotia Department of Natural Resources (via the Provincial Veterinary Diagnostic Laboratory in Truro), it has become apparent that a substantial proportion of

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