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Nests of American Bitterns (Botaurus lentiginosus), marsh hawks (Circus cyaneus), and short-eared owls (Asio flammeus) are usually found in wetland habitats. Although large marshes containing dense stands of bulrushes (Scirpus), cattails (Typha), or other wetland vegetation are favored nesting cover, these birds have also been reported to nest in stands of tall, dense shrubs and grasses on the upland (Bent 1961, 1963; Palmer 1962; Sealy 1967; Stewart 1975). During 1968-74, we regularly found upland nests of these three species while conducting duck nesting studies in planted fields of undisturbed grass-legume cover in the Dakotas (Duebbert and Lokemoen 1976). Our findings on nest densities, hatching success, site characteristics, clutch sizes, and other ecological factors are presented in this paper.
A bib (1975) indicated that the three species discussed in the present paper, in all or a significant part of their range, currently exhibit potentially dangerous, apparently non-cyclical population declines. Our general observations in North Dakota over the past 20 years also suggest an alarming decrease in populations of these birds during the breeding season. We believe that these population declines may be correlated with the widespread destruction or degradation of essential nesting habitats as agriculture has become increasingly more intensive.