When I began my study, very little was actually known about the osprey in Michigan. A check of the literature and the files of the UMMZ revealed less than 30 nest records prior to 1960. During the years 1961 to 1964 I located a number of osprey nests incidental to my investigations of the bald eagle in Michigan. By 1964 I knew of 58 occupied nests in the state. The somewhat incomplete data that I had indicated that nest success was rather low, but no definite population decline could be noticed from the information at hand. In 1965, financial assistance from the National Audubon Society made a more thorough study possible; but despite a greater effort, only 51 occupied osprey nests were found. In summary, low nesting success is leading to a population decrease of ospreys in Michigan. Of 56 nests that I knew to be occupied in 1964, 15 were found in 1965 to be unoccupied. This indicates a decline of some 27%. Observations over several successive years are needed to see if this decline persists. More study is needed in some of the neighboring areas like Wisconsin, Minnesota, and Ontario to see what the osprey populations are doing there.