A COMPARISON OF 2 METHODS FOR SURVEYING MORTALITY OF BEACHED BIRDS INBRITISH-COLUMBIA

Systematic surveys of beached birds are often limited in their ability to classify the causes of death of the carcasses recovered. Two metho ds of determining the cause of death of seabirds encountered during su rveys of beaches of southwestern Vancouver Island, British Columbia, a re compared. Birds were either subjected to external visual examinatio ns by volunteer beach surveyors or submitted for gross postmortem exam ination by a verterinarian. The reliance on external examination of bi rds on beaches often prevented the accurate classification of the repr oductive status and cause of death of the birds collected, but was val uable for describing the species, locations, and numbers of birds affe cted. The use of gross postmortem examinations of carcasses allowed fo r a more refined classification of the cause of death, as well as prov iding reliable descriptions of the bodily condition and sex of the bir ds examined. However, almost one half of the carcasses encountered wer e unsuitable for necropsy because of scavenging and decomposition. It is concluded that a combination of field and necropsy observations pro vides a useful method with which to monitor the pattern of mortality o f beached seabirds.