These two islands had many name changes throughout the years, and were eventually named Hart Island and Miller Island. Dredged material inflow commenced in 1983 and will continue until approximately 2009. Hart-Miller Island one of the most significant ornithological sites in Maryland. Shorebirds, gulls, terns, and waterfowl are the primary users of this habitat, but the island attracts many other birds as well. Considering the number of rare species that have been seen, as well as the large numbers of more common species, a trip to Hart-Miller can be rewarding in any season.
Conditions vary from week to week due to work at the facility and to the previous week's weather.
During the spring and fall migration, shorebirds can be quite numerous if suitable mudflat conditions are present. Shorebird numbers peak in May and August, with as many as 10,000 shorebirds per day in August, and forty species in all. In the fall, American Golden Plover and Baird's and Buff-breasted Sandpipers occur annually. There have been at least fourteen Ruff and four Curlew Sandpiper records. In November, Dunlin are the most numerous shorebird, seen occasionally in the humdreds.