Reproductive success of wading birds using Phragmites marsh and upland nesting habitats

Colonial nesting of long-legged wading birds (Ciconiiformes) in the coastal northeastern U.S. is limited primarily to islands, which provide isolated habitats that are relatively free of ground predators. Estuarine wetlands in this heavily developed region, including foraging wetlands and fringe marshes surrounding nesting islands, are often dominated by Phragmites australis. On Pea Patch Island in Delaware Bay, site of one of the largest and most enduring mixed-species heron colonies on the East Coast, wading birds nest in Phragmites marsh habitat as well as in adjacent upland shrubs and trees. Because Phragmites is aggressively managed in Delaware Bay, we investigated the relative habitat value of marsh and upland nesting sites for the purpose of developing recommendations for marsh and wildlife management. Utilization of marsh habitat by nesting birds ranged from 27-82% during 1993-1998. Two species (great blue heron Ardea herodias and great egret A. alba) never nested in Phragmites, four species (little blue heron Egretta caerulea, snowy egret E. thula, cattle egret Bubulcus ibis, and black-crowned night-heron Nycticorax nycticorax) nested in approximately equal proportions in both habitats, and one species (glossy ibis Plegadis falcinellus) was largely confined to marsh nesting. Productivity (egg and nestling production) varied between habitats for some species. Cattle egrets produced larger clutches and had higher hatching rates in Phragmites compared to upland habitat. Little blue herons were more successful in the uplands. Managers should retain Phragmites marsh at colony sites, such as Pea Patch Island, where it provides critical habitat for nesting wading birds both as substrate for nesting and buffer habitat to control human disturbance.