Peregrine Tissues Cleaner
Every Year

by Gordon Court
Conservation Magazine - 2011 Spring/Summer | Return to contents

The Spring/Summer 2011 issue of Conservation Magazine featured a story on the remarkable comeback of Alberta's peregrine falcons. Since then, DDT analysis of egg residue has revealed some encouraging results that could help delist the species.

Peregrines were extirpated in southern Canada and many other parts of the world following post-World War II use of the pesticide DDT. DDE, the primary metabolite of DDT, was eventually linked to shell thinning in peregrines (and many other birds as well). The compound was banned from agricultural use in Canada in 1969.

The Alberta Fish and Wildlife Division has been monitoring levels of organochlorine pesticide residues, like DDE, in dead falcon eggs since the mid-1960s. It has one of the best data sets chronicling the decline of DDT pollution in peregrines anywhere in Canada. Any population of peregrines with DDE levels averaging over 15 parts per million in their eggshells is likely to experience significant eggshell thinning (i.e., more than 17% thinner than normal). Such populations show low productivity and decline. In the Alberta Peregrine Falcon Recovery Plan 2002-2010, a primary goal for the population (before any delisting action can be considered) is having DDE residues in dead peregrine eggs average no more than five parts per million in the preceding five years.

Unfortunately, measuring organochlorine residues in animal tissue is expensive, often costing over $400 per sample, which makes annual monitoring of residues in peregrine eggs difficult. Fortunately, an opportunity recently arose to clear a backlog of samples. Grant money from Alberta Sport, Recreation, Parks and Wildlife; in-kind support from the environmental division of ALS Laboratories in Edmonton; and a financial contribution from Capital Power, allowed Fish and Wildlife to measure residues in 31 peregrine eggs from 18 clutches. The results were extremely encouraging.

Figure 1. Residue results show peregrines in Alberta averaged about 1.6 parts per million DDE in their eggs over the last five years, almost one tenth of what they were 40 years ago.