The breeding ecology of Piping Plovers (Charadrius me/odus) was examined on the central barrier islands of Long Island, N.Y. during the 1992 and 1993 breeding seasons. The estimated breeding populations were 79 pairs in 1992 and 82 pairs in 1993. Productivity was 1.08 chicks fledged per pair. The population appeared stable, but below carrying capacity. Predation was the leading cause of nest loss (300/0), and crows (Corvus brachyrhynchos and/or C. ossifragus) accounted for 71% of nests lost to predation. Probability of survival was greater for nests with predator exclosures than for nests without (64% vs. 20%). Evidence supported the hypothesis that ephemeral pools were of greater quality for brood-rearing than other ocean beach habitats (intertidal zone, intertidal zone wrack, berm, berm wrack, and open vegetation). Broods with access to ephemeral pools spent more time in them, and when in them had greater foraging rates and were exposed to greater arthropod abundances than in other ocean beach habitats. In 1992 (though not 1993), survival was greater for broods with access to ephemeral pools than for those without. On beaches without ephemeral pools and bay habitats, intertidal zone wrack and open vegetation were important brood foraging habitats. A non-nesting beach in 1992 was breached in winter 1993; a recurved sandspit and mudflats formed on the bay side west of the new inlet. Five pairs nested near the mudflats. Brood-rearing quality of bay mudflats appeared greater than that of ocean intertidalal zone wrack (and other ocean beach habitats) based on colonization by adults and on use by broods, but similar to ocean intertidal zone wrack based on foraging rates, arthropod abundance, and survival. Pedestrian disturbance probably contributed to low brood survival in 2 locations, and off-road vehicles killed 2 chicks. Effects of predation on brood survival could not be quantified and may have confounded effects of foraging habitat quality and disturbance. A logistic regression model for Jones Beach indicated that the probability of plover nesting diminished with increasing pedestrian disturbance. A model of Fire Island and Westhampton Beach indicated that the probability of plover nesting increased with increasing open vegetation width. Beaches with suitable brood-rearing habitat (the storm-maintained habitats of open vegetation, ephemeral pools, breaches, and overwash fans) were scarce on Fire Island National Seashore. Frequency of overwashes and breaches on Fire Island has decreased since 1939, apparently due to anthropogenic barrier island stabilization. / Master of Science