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Native riparian habitats cover a small percentage of the landscape in most arid lands. Irrigation, however, artificially expands these in some regions. It is important to understand whether human-modified landscapes can support species native to natural ecosystems. We examined butterfly communities in relatively undisturbed (nonagricultural) versus artificially created (agricultural) riparian habitats in the Walker River Basin in the western Great Basin (Nevada and California, USA). Habitat type did not significantly affect species richness. Butterfly abundance was greater, and evenness lower, in agricultural than in nonagricultural sites. Annual variability significantly affected species richness, total abundance, and evenness. The few species largely restricted to agricultural sites were geographically widespread and characteristic of disturbed habitats. Several relatively uncommon species were not present in agricultural sites. Riparian habitats created to support agriculture may help support some native butterfly species, but cannot substitute for undisturbed riparian habitats.

We examined the response of montane butterflies to a 1300-m elevational gradient in the Toiyabe Range, a mountain range in the central Great Basin. We tested whether elevational ranges of montane butterflies conform to Rapoport’s elevational rule (species at higher elevations have greater elevational ranges). We also tested whether the Rapoport-rescue hypothesis (emigrants from higher elevation populations inflate the species richness of lower-elevation sites) could explain the species richness patterns we observed. In addition, we predicted whether global climate change is likely to perturb current elevational gradients in butterfly species richness. Species presence data were collected from 105 100-m vertical elevational bands in 17 canyons. Elevation and species richness were significantly negatively correlated, although species richness peaked at intermediate elevations, and butterflies in species-rich areas had significantly narrower elevational ranges than species in more depauperate areas. Toiyabe ...

The recent occurrence in western North America of wood warblers normally considered to be eastern migrants, especially in the fall, has been well documented by McCaskie and Banks (1964), Tenaza (1967), McCaskie (1970a, b), and others (see especially Audubon Field Notes). In light of the large number of records of these birds on the west coast, it is of interest to examine them from the standpoint of season and timing of occurrence and to contrast these with the usual migratory timing on the east coast. Comments are also made on the status of these species in the West.

Few studies of bird populations have been undertaken in desert communities. Previous studies in North American warm deserts were conducted by Hutchinson and Hutchinson (1941, 1942), Robert (1967), and Sheppard (1968) in California; Hensley (1954) and Tainter (1965) in Arizona; Raitt and Maze (1968) in New Mexico; and Dixon (1959) in Texas. Davis (1963) and Webster (1964) censused desert areas in Mexico. No study has been conducted in the northern Mohave

During ornithological studies in southern Nevada, we obtained noteworthy data on the occurrence and status of several species. Our observations support the suggestion of unstable breeding populations of certain species in the Spring Mountains (Johnson 1965). All records are for Clark County unless specified. Wing and tail measurements are in millimeters. Specimens collected are on deposit in the Biology Museum, University of Nevada, Las Vegas (UNLV) and in the collection of A. M. Rea (AMR), Tucson, Arizona. Additional material from the Museum of Verte

Since 1961 the author has spent considerable time in the field in Clark County, Nevada. The following records derived from this field work extend our knowledge of certain species which are considered uncommon to rare in southern Nevada. I am grateful to Charles G. Hansen, biologist, Desert Game Range, for access to his personal records and to the Desert Game Range Narrative Reports (DGRNR). All specimens are on deposit in the Biology Museum, Nevada Southern University. Porphyrula martinica. Purple Gallinule. Two individuals of this species were observed at Tule Springs Park, 13 miles northwest of downtown Las Vegas, in 1966. Single birds were observed there on 7, 8, and 20 September and a male (B-668, weight 183.2 g, left testis 8 x 2 mm, no fat) was collected on 8 September 1966. This constitutes the first record for Nevada. Charadrius semipalmatus. Semipalmated Plover. Spring records of this species for Henderson Slough, one mile north of Henderson, on 26 April 1967 (5 birds) and Tule Springs on 12 and 15 May 1967 (1 bird) supplement those of Grater (Condor 41:221, 1939) and Hayward et al. (Brigham Young Univ. Sci. Bull., Biol. Series 3:8, 1963). Fall records for Henderson Slough on 16 August (2 birds), 23 August (1 bird), and 2 September 1966 (2 birds), and for 1.5 miles west of Logandale on 13 September 1966 (10 birds) appear to be the first for this season in southern Nevada. Specimens were taken on 16 August (B-626, female, ovary 5 x 3 mm, weight 47.8 g, heavy fat), 23 August (B-655, female, ovary minute, 42.4 g, heavy fat), and 2 September (B-743, female, ovary 7 x 1.5 mm, 39.2 g, moderate fat). Charadrius alexandrinus. Snowy Plover. This species is an uncommon transient in Nevada. I have records of single birds of Henderson Slough on 16 and 23 August 1966. A female (B-627, ovary 5 x 3 mm, 31.2 g, light fat) was collected on 16 August. These appear to be the first fall records for southern Nevada. Arenaria interpres. Ruddy Turnstone. Alcorn (Condor 44:81, 1942) lists the single previous Nevada record of this species. A male (B-665, left testis 3 x 0.5 mm, 74.4 g, light fat) was collected 1.5 miles west of Logandale on 13 September 1966. Erolia bairdi. Baird's Sandpiper. Hayward et al. (op. cit., p. 9) give the only previous report of this species for southern Nevada. There is an unpublished record for Corn Creek on 22 April 1946 (DGRNR, January-April 1946). I have additional records for three birds 1.5 miles west of Logandale on 13 September 1966 (female collected, B-666, ovary 3 x 3 mm, 32.3 g, light fat) and for one at Tule Springs Park on 2 May 1967. Crocethia alba. Sanderling. The Sanderling has not been reported previously for southern Nevada. I saw a single bird at Tule Springs Park, 1-3 May 1966.

Cody (Condor 70:270, 1968) summarized the present knowledge of interspecific territoriality in hummingbirds. Apparently there is no known instance of interaction between Broad-tailed (Selasphorus platycercus) and Calliope (Stellula calliope) Hummingbirds. Reported here are two instances of interspecific territoriality between males of these two species in the Spring Mountains, Clark County, Nevada. The Broad-tailed Hummingbird is a common breeding bird in the montane forests of southern Nevada (Johnson, Condor 67:103, 1965) and territories are established by mid-May (pers. ohserv.). The Calliope Hummingbird is a rare transient in the same region (Austin, Condor 70:391, 1968). Interactions between the two species were first observed in Lee Canyon, 8900 ft, on 23 May 1966 in an open forest of aspen (Populus tremuloides), ponderosa and bristlecone pines (Pinus ponderosa and P. aristata), and white fir (Abies concolor), with an understory of snowberry (Symphoricarpos sp.) and currant (Ribes spp.). The latter were in bloom and are an important nectar source in spring and early summer. Here a calliope was first observed perched at the tip of a small fir. It flew down to feed on the Ribes several times and once hovered at the tip of a fir branch, apparently catching small insects. It always returned to the perch where it was first observed. A broad-tail flew to a currant about 10 ft from the perched calliope. The latter immediately attacked the former, pursued it up the canyon about 30 ft, and returned immediately to its perch. Shortly, another broad-tail approached from the opposite direction and was similarly pursued for about 15 ft. On both occasions both species called continuously. During the next 30 min, no further encounters were observed, although the broad-tails fed just beyond the point to which they had been pursued. An hour later the calliope, still perched in the same spot, was collected. A week later broad-tails were observed feeding in the area from which they had previously been chased. The second encounter was also in Lee Canyon, 8400 ft, on 3 June 1966. This area is dominated by ponderosa pine and white fir. The canopy is not as open as at the above site and there is less understory. Here another calliope was observed on the tip of a larger fir. Several times it hovered near the tips of branches. A broad-tail flew to a currant near the base of the fir and was pursued for about 20 ft, after which the calliope returned to the fir. No other encounter was observed in the succeeding 20 min. Two hours later the calliope was observed again, still in the same place. These appear to be the first records of interspecific aggression between Calliope and Broad-tailed Hummingbirds and add to the paucity of records of a migrant species occupying habitat which would otherwise be used by a related resident species. 1 Present address: Department of Biological Sciences, University of Arizona, Tucson, Arizona 85721. Accepted for publication 31 October 1968.

During the course of field studies in 1970 on the Santa Rita Experimental Range, Pima County, Arizona, we observed eight instances of interspecific aggression by Ash-throated Flycatchers (Myiarchus cinerascens) on Cassin's Sparrows (Aimophila cassinii). The former is a medium-sized tyrannid which nests in abandoned woodpecker holes in much of the southwestern United States and into M6xico. It forages mainly by hawking for insects from the upper limbs of trees. The sparrow is a ground-foraging species, feeding on seeds in winter and ground-inhabiting insects during the summer. Nests are placed near the ground in low vegetation. Its song is delivered in an upward arching flight from upper limbs of trees. The pattern of singing flights closely resembles the hawking maneuvers of the flycatcher. It was during the flight song that the sparrows were attacked by the flycatcher. The latter flew straight at the sparrow and usually knocked it to the ground. Apparently, the flycatcher was responding to a behavioral image which approximates its own foraging maneuvers. Selection against such behavior is probably weak since Cassin's Sparrow is rather restricted in its distribution and then only occurs in grasslands. On the other hand, strong selection pressures may operate to maintain this type of behavior in the flycatcher since it overlaps several potential competitors (Myiarchus spp., Tyrannus spp.). One other observation adds strength to the above suggestion. A Cactus Wren (Campylorhynchus brunneicapillus), flying about 3 m above the ground, suddenly made an upward jog in its straight line flight. This deviation was similar in form to a flycatcher foraging maneuver. Immediately, an Ashthroated Flycatcher, which was perched about 4 m away, flew at the wren and knocked it to the ground. These data were obtained during research supported by the US/IBP Desert Biome program under grant no. GB 15886 from the National Science Foundation.