The Mountain Plover (Charadrius montanus) is an endemic species of North America, nesting on the shortgrass prairie mainly east of the Rocky Mountains and wintering from California and Texas to northern Mexico. Information on the of this species on the wintering ground is noticeably lacking. Jurek (1973), however, has found that in California these birds are now absent or rare in many areas where they were previously numerous, although flocks of hundreds still winter in some California valleys. Several researchers have commented on the breeding of this species. Bent (1929) described the main breeding range as extending along the eastern edge of the Rockies, from New Mexico into Canada, and eastward into North Dakota and Texas (fig. 1). Within this area the Mountain Plover was initially described as a common breeding resident (Coues 1874, Knight 1902). In fact, prior to 1900 it was abundant enough to be considered an important game bird by market hunters (Grinnell et al. 1918, Sandoz 1954). Cooke (1915), however, noted that this species seemed to be decreasing in numbers. He acknowledged that market hunting may have been partly to blame for the decrease, but he felt that the major problem was the reduction of the breeding range due to cultivation and dairying activities. Later, Abbot (1939) reported that it was becoming still rarer in the 1930's; he felt that one reason for many fatalities was that they were absurdly dumb. More recently Laun (1957) concluded that the Mountain Plover population had diminished markedly with the majority now breeding in southern Montana, Wyoming, and Colorado. Apparently in response to these reports, this species was included on the status undetermined list of the U.S. Department of the Interior (1973). Aware of the above trend, Webster began a study of the Mountain Plover in 1967 and Graul began work on the species in 1969. We have been hitherto reluctant to estimate the total number of Mountain Plovers because of the limited nature of our data, but it now seems that even a highly tentative estimate is badly needed. We present here our information on the breeding of this plover, and suggestions for preserving the species. Webster studied the Mountain Plover in 1967 and 1968 to determine its current Colorado breeding range. Her study included personal correspondence, organized group field surveys, and much personal travel throughout the bird's known historic Colorado range. Graul (1973a, 1973b, 1974, 1975) conducted field work in 1969-72 and 1974 in Weld County, northeastern Colorado and he corresponded with many people residing in the shortgrass prairie region. In May, 1975, he traveled through 11 eastern Colorado counties in an effort to supplement Webster's work. Our data support Laun's (1957) contention that most Mountain Plovers now breed in Montana, Wyoming, and Colorado. Stewart (1971) listed this species as accidental for North Dakota and, indeed, Graul found no evidence of recent nesting in North Dakota, South Dakota r Kansas. Ross Lock found an adult with one young 6 mi W of Bushnell, Kimball County, Nebraska on 7 June 1975, but this is the only Nebraska record in several years. George M. Sutton (pers. comm.) informed us that in some years they nest in northwestern Oklahoma. Kenneth Seyffert (pers. comm.) in June, 1974, found them nesting in Union County, northeastern New Mexico and saw two birds in Hartley County, northwestern Texas. Hubbard (1970) reported that some nest in central and southwestern New Mexico, but we have not found any recent nesting records for these areas. Duane Tolle