This data package presents legacy loon and waterfowl breeding biology data collected at study sites near the Old Chevak Field Station on the Yukon Delta National Wildlife Refuge (formerly the Clarence Rhode National Wildlife Range), Alaska during the summers of 1973 through 1975. These data were collected to provide a basis for the evaluation of long-term changes in loon (Pacific and Red-throated Loon) biology on the Yukon-Kuskokwim Delta in western Alaska. Additional data corresponding to waterfowl breeding biology, habitat classification and fish sampling are also provided in this data release.