We provide a detailed description of a fixed-radius point count method that carries fewer assumptions than most of the currently popular methods of estimating bird density and that can be used during both the nonbreeding and breeding seasons. The method results in three indices of bird abundance, any of which can be used to test for differences in community composition among sites, or for differences in the abundance of a given bird species among sites. These indices are (1) the mean number of detections within 25 m of the observer, (2) the frequency of detections within 25 m of the observer, and (3) the frequency of detections regardless of distance from the observer. The overall ranking of species abundances from a site is similar among the three indices, but discrepancies occur with either rare species that are highly detectable at great distances or common species that are repulsed by, or inconspicuous when near, the observer. We argue that differences in the behavior among species will preclude an accurate ranking of species by abundance through use of this or any other counting method in current use.

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During summer 1997, extant populations of the endemic land snails Discus brunsoni and Oreohelix alpina were rediscovered near the type localities in the Mission Mountains, Montana; last known collections were made 33 and 48 years ago, respectively. D. brunsoni and Oreohelix elrodi (also endemic to the Mission Mountains and nearby Swan Range) were previously reported to be sympatric in subalpine limestone talus. Both species were found in 1997 in diorite talus; the latter species also occupied argillite talus with little, if any, limestone present at any site. Live D. brunsoni (n = 8) were found near the talus surface only on bare rock or foliose lichen on rock during cool, wet conditions. Live O. elrodi were found near the talus surface on rock (n = 9) or organic litter accumulations (n = 55) during all conditions, although in reduced number during warmer and drier weather. Above treeline, live O. alpina were found exclusively in exposed locations under limestone talus, sometimes attached to rock surfaces (n = 7) but more often present in organic detritus (n = 10). Lack of collections of D. brunsoni and O. alpina in recent decades probably resulted from 1) extremely restricted distributions, 2) limited knowledge of habitat requirements, and 3) scarcity of active collectors in the region.

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