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I compared riparian cottonwood (Populus fremontii) productivity-discharge relationships in a relictual stand along the highly regulated Green River and in a naturally functioning stand along the unregulated Yampa River in semiarid northwest Colorado. I used multiple regression to model flow effects on annual basal area increment (BAI) from 1982 to 2011, after removing any autocorrelation present. Each BAI series was developed from 20 trees whose mean size (67 cm diameter at breast height [DBH]) was equivalent in the two stands. BAI was larger in the Yampa River stand except in 2 y when defoliating leaf beetles were present there. I found no evidence for a Yampa flood-magnitude threshold above which BAI declined....
We collected Salt Creek pupfish (Cyprinodon salinus salinus) from Salt Creek, Death Valley, California, in November 2009 and May 2010. The purpose of our study was to determine whether otoliths displayed interpretable marks that might be used for estimating age and growth. Otoliths exhibited alternating bands of opaque and translucent material. Kendall rank correlation between number of bands on otoliths and length of fish were high for two readers (τ = 0.65 and 0.79) and exact agreement between readers was 51%. Otoliths exhibited 0–5 bands, which provided evidence that longevity of Salt Creek pupfish likely is >1 year. Total length of fish collected in spring and autumn differed for fish with one and three bands...
In 2005, fire ignited by humans swept from Yuma Proving Grounds into Kofa National Wildlife Refuge, Arizona, burning ca. 9,255 ha of Wilderness Area. Fuels were predominantly the native forb Plantago ovata. Large fires at low elevations were rare in the 19th and 20th centuries, and fires fueled by native vegetation are undocumented in the southwestern deserts. We estimated the area damaged by fire using Moderate Resolution Imaging Spectroradiometer and Normalized Difference Vegetation Index, which are more accurate and reduce subjectivity of aerial surveys of perimeters of fires. Assemblages of upland and xeroriparian plants lost 91 and 81% of live cover, respectively, in fires. The trees Olneya tesota and Cercidium...
The white-ankled mouse (Peromyscus pectoralis) was previously known only from Carlsbad Caverns National Park and nearby areas in extreme southeastern New Mexico. I discovered 15 new localities for P. pectoralis, which extend its distribution 225 km north-northwest. This new distribution does not represent a recent northward expansion of P. pectoralis in New Mexico but reflects the lack of mammalian surveys in the region and misidentification of museum specimens from past surveys. At present, the distribution of P. pectoralis in New Mexico includes the Guadalupe Mountains and lowland habitats between the Sacramento Mountains and Pecos River.
Whiskered screech-owls (Otus trichopsis) and northern pygmy-owls (Glaucidium gnoma) delivered freshly caught Yarrow's spiny lizards (Sceloporus jarrovi) and striped plateau lizards (S. virgatus) to nestlings from dusk to dark in southeastern Arizona. This observation stimulated studies of the prey deliveries by the owls and lizard activity patterns, because the lizards are not known to be nocturnal. Lizards were more frequent prey of both owls than endothermic vertebrates but infrequent compared to arthropods, a pattern in the pygmy-owl that differs from its northern populations. Yarrow's spiny lizard, the most abundant and frequently captured lizard, was most active in the morning but also active in the evening....
Six male paddlefish, Polyodon spathula, were implanted with ultrasonic temperature-sensing transmitters and tracked during June through August 1997 to quantify effects of physicochemical conditions on their distribution and movement in Keystone Reservoir, Oklahoma. Paddlefish moved about twice as much during night than day. Movement rate of paddlefish was related to reservoir water level, inflow, and discharge from the reservoir at night; however, none of these variables was significant during the day. Location in the reservoir (distance from the dam) was negatively related to water level and positively related to inflow during day and night periods. Location in the reservoir was negatively related to discharge...
The northern pygmy mouse (Baiomys taylori), fulvous harvest mouse (Reithrodontomys fulvescens), and Merriam's pocket mouse (Pemgnathus merriami) are new to the diet of the western burrowing owl (Athene cuniculana hypugaed). All three species were identified from remains in regurgitated pellets collected from roost sites of burrowing owls in southern Texas over a period of 4 winters. Together, northern pygmy mice and fulvous harvest mice represented 58% of mammals identified in 182 pellets regurgitated by western burrowing owls. Merriam's pocket mouse accounted for only 4% of identified mammalian prey. Frequency of occurrence in pellets was 16% for northern pygmv mice, 11% for fulvous harvest mice, and 3% for Merriam's...
A survey was taken of bird losses in crude oil pits near the central Texas Gulf Coast and in northwestern Texas. At one pit near the Texas Coast, 297 bird carcasses (largely ducks) were counted. Duck losses from oil pollution in northwestern Texas occurred largely in playa basins of the Permian Basin south of the Panhandle. To determine the fate of birds that die in oil pits, 40 carcasses of nine bird species were placed in two crude oil pits near the central Texas Coast in October (19) 1981 and December (15) 1981 and April (6) 1982 and studied for 5 months. Rate of sinking and disappearance of carcasses were positively related to carcass size. In a comparison of three seasons, the time required for a carcass to...
[No abstract available]
This study was conducted to characterize fishery resources inhabiting salt-evaporation ponds and sloughs in South San Francisco Bay, and to identify key environmental variables that influence distribution of fishes. The ponds, which were originally constructed and operated for commercial production of salt, have undergone preliminary modifications (installation of culverts, gates, and other water-control structures) in preparation for full restoration to mostly tidal wetlands over the next 2 decades. We sampled fish from two salt-pond complexes (Alviso complex and Eden Landing complex), each consisting of several pond systems and their associated sloughs. Cluster analysis of species of fish indicated that at least...
Several aquatic vertebrates have been introduced into freshwater systems in California over the past 100 years. Some populations of the two-striped garter snake (Thamnophis hammondii) have lived in sympatry with these species since their introduction; other populations have never encountered them. To assess the possible adaptation to a novel prey, we tested the predatory responses of T. hammondii from different populations to different chemosensory cues from native and introduced prey species. We presented chemical extracts from potential prey types and 2 control odors to individual snakes on cotton swabs and recorded the number of tongue flicks and attacks directed at each swab. Subject response was higher for...
The western burrowing owl (Athene cunicularia hypugaea) is threatened in Mexico, endangered in Canada, and declining in most of the western United States. Most previous research has focused on burrowing owl breeding biology, and little is known about its winter ecology. We determined characteristics of roost sites used by western burrowing owls in southern Texas during winter. Data on 46 winter roost sites were collected from 15 November 2001 to 15 February 2002. Of these roost sites, 87% were located on agricultural land, 80% were along roads, and 74% were concrete, steel, or cast-iron culverts. Mean diameter (??SE) of roost site openings was 22 ?? 1.5 cm. Most roost sites (70%) were located on inaccessible private...
We used bioenergetics models for humpback chub, Gila cypha, and rainbow trout, Oncorhynchus mykiss, to examine how warmer water temperatures in the Colorado River, Grand Canyon, Arizona, through a proposed selective withdrawal system (SWS) at Glen Canyon Dam, would affect growth, consumption, and predation rates. Consumption by the rainbow trout population was at least 10 times higher than by the smaller humpback chub population. Water temperature increases of 6??C during autumn increased growth of humpback chub and likely increased their survival by reducing the time vulnerable to predation. Water temperature increases caused by drought in 2005 did not alter humpback chub growth as much as the SWS. Increased temperatures...
We collected a Dirhinus texanus (Hymenoptera: Chalcididae) in Salt Creek Canyon, Canyonlands National Park, San Juan County, Utah. This is the first record for D. texanus in Utah.
The boreal toad (Bufo boreas) is an endangered species in Colorado and is considered a candidate species for federal listing by the United States Fish and Wildlife Service. Boreal toads are absent from many areas of suitable habitat in the Southern Rocky Mountains of Colorado presumably due to a combination of causes. We moved boreal toads from existing populations and from captive rearing facilities to habitat which was historically, but is not currently, occupied by toads to experimentally examine methods of repatriation for this species. Repatriation is defined as the release of individuals into areas currently of historically occupied by that species (Dodd and Seigel, 1991). This effort was in response to one...
Fewer mammalian species occurred on summits of sheer-walled buttes than occurred in similar "mainland" control sites, but density of small mammals on buttes equaled or exceeded mainland density. Peromyscus crinitus, the only terrestrial mammal on Jug Butte, occupied a larger habitat niche there than in control areas. No such niche expansion was noted for P. crinitus on Junction Butte, where four other species of small mammals (Eutamias quadrivittatus, Neotoma lepida, Neotoma cinerea, Peromyscus truei) and at least one large mammal (Canis latrans) also occurred. At least 18 species of terrestrial mammals inhabit the control sites. It is hypothesized that the species number remains static on each butte and is a function...
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