FURTHER EVIDENCE OF BIASES ASSOCIATED WITH HUNTER-KILLED MALLARDS

Assessment of waterfowl management strategies depends upon data that e valuate hypotheses that mallards (Anas platyrhynchos) killed by hunter s are similar to those in the general population. Moreover, data are n eeded to provide further insight into mallard molt progression, the ap parent influence of body mass on survival, and direct and indirect mor tality caused by lead shot ingestion. Thus, we compared body mass, per centage completion of the prealternate molt, and presence of lead shot in gizzards between mallards killed by hunters (hunter-killed) and th ose concurrently collected by researchers (researcher-collected) from the free-living population in the Mingo Basin of southeastern Missouri . Researcher-collected mallards were heavier (P < 0.05) than hunter-ki lled mallards of the same age and sex. Researcher-collected females th roughout the hunting season, adult males in early hunting season, and immature males in middle and late hunting season completed more (P < 0 .05) of the prealternate molt than hunter-killed mallards. The proport ion of hunter-killed mallards with ingested lead shot in their gizzard s was 3.8 times greater than for researcher-collected mallards. Our da ta suggest caution should be used when collecting data from hunter-kil led mallards in field studies; factors causing low body mass and lead ingestion (at least historically) might be associated with the mechani cs of compensatory mortality; and survival probabilities of mallards m ay be heterogeneous relative to body mass and lead ingestion.