INCIDENCE OF PLASTIC IN SEABIRDS FROM THE TROPICAL PACIFIC, 1984-91 -RELATION WITH DISTRIBUTION OF SPECIES, SEX, AGE, SEASON, YEAR AND BODY-WEIGHT

The incidence of plastic in seabirds was studied (number of individual s of a species containing plastic per number inspected, and number of particles per individual), in 1574 individuals representing 36 species of seabirds collected in the tropical Pacific, mostly between 110 and 150 degrees W longitude, fr om 1984 to 1991. Incidence of plastic was lower in resident species compared to those which bred to the south o r north but wintered in the region, and especially when compared to sp ecies that crossed the tropics in migration between the South and Nort h Pacific. Seasonal and age-related patterns in incidence of plastic, number of particles, and particle type (pellets versus user-plastic) a mong a group of five Procellariiform species (each with > 5% of the in dividuals containing plastic and for which samples were > 20 birds) in dicated that degradation for an individual particle in the gizzard req uired less than one year, and that little plastic was regurgitated by parents to chicks. Two patterns emerged from this data regarding body weight: (i) heavier birds (for a given species, age-class, season and year) were move likely to contain at feast some plastic, from which we hypothesize that birds in better physical condition fed more often in areas where higher densities of plastic and food are found, such as f ronts and convergences; and (ii) among individuals who contained plast ic (grouped by species), there was a significant negative correlation between number of plastic particles and body weight. This is the first solid evidence for a negative relationship between plastic ingestion and physical condition in seabirds. The likelihood that higher quality individuals are more prone to ingestplastic has serious implications regarding health of some seabird populations.