We used data from an 11-year study of Red-winged Blackbirds (Agelaius phoen
iceus) to test the hypothesis that fledging success is a reliable index of
recruitment at the population and the individual level. Natal philopatry wa
s only 2.37% overall (3.51% for males and 1.49% for females) in our study p
opulation. However, the number of fledglings that returned as breeding adul
ts from an annual fledgling cohort was significantly correlated with the si
ze of the cohort. The correlation was also significant when males and femal
es were analyzed separately despite sex differences in natal philopatry, ag
e of first breeding, and probable differences in mortality factors. Recruit
ment increased disproportionately with the size of the fledgling cohort. Th
us, years of high production produced proportionately more breeding adults.
At the individual level, the number of fledglings sired by a male in his l
ifetime was significantly correlated with the number of his descendants tha
t eventually returned to breed in the study population. These results suppo
rt the widely held assumption in avian field studies that fledging success
is a reliable index of fitness.