Within-season nest persistence of large wading bird (Ciconiiformes) rookeries in the Atchafalaya Delta, Louisiana was examined during 1994 and 1995. A sample of rookery trees was permanently marked, and the status of 7,864 nests of ten species was followed through time. Nest construction began in early March, and some rookeries were still active into September during both seasons. Uniform nest persistence rates were calculated for each 28-day time period throughout the nesting season. Nest persistence rates per 28 days ranged from 0.00-0.96. During both years the rates tended to be lowest during the early season and increased into the late season. In 1994, nest persistence rates were significantly different, caused by the interaction of season and late nesting of White Ibis. In 1995, nest persistence rates differed significantly by season. The results call into question the value of nest counts obtained by one visit to a rookery complex, as these may greatly underestimate the numbers of breeding birds.