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.