Sex and age characteristics of Northern Fulmars Fulmarus glacialis used in programs to monitor plastic ingestion.

Carcasses of beached or accidentally killed Northern Fulmars Fulmarus glacialis, collected for monitoring plastic ingestion, have shown that the incidence of litter may vary over time and by region. Age, sex, and season of fulmar collection appear to affect the quantity of plastics ingested. More detailed analyses of monitoring data thus require reliable and consistent methods for assessing age and sex. Methods were first described in a monitoring manual in 2004 and later in international guidelines, but age and sex definition required further clarification. A large dataset of 3,790 dissected birds now allows for detailed descriptions of sex and age characteristics for different seasons. Such results may assist in further improvement and calibration of age and sex determination among the international research teams participating in this type of monitoring.