Abstract Urbanization increasingly exposes birds to multiple sources of direct anthropogenic mortality. Collisions with buildings, and windows in particular, are a top bird mortality source, annually causing 365–988 million fatalities in the United States. Correlates of window collision rates have been studied at the scale of entire buildings and in relation to the surrounding landscape, and most studies have only assessed correlates for all birds combined without considering season- and species-specific risk factors. In Stillwater, Oklahoma, USA, we conducted bird collision surveys at 16 buildings to assess building structural-, vegetation-, and land cover-related collision correlates. Unlike past studies, we focused at the scale of individual building façades, and in addition to considering correlates for total collisions, we assessed correlates for different seasons and separately for 8 collision-prone species. Several façade-related features, including proportional glass coverage, façade length, and façade height, were positively associated with total collisions and collisions for most separate seasons and species. Total collisions were also greater at alcove-shaped façades than flat, curved, and portico-shaped façades. We found that collision correlates varied among seasons (e.g., surrounding lawn cover important in summer and fall, but not spring) and among species (e.g., surrounding impervious cover positively and negatively related to collisions of Painted Bunting [Passerina ciris] and American Robin [Turdus migratorius], respectively). Given the importance of glass proportion, collision reduction efforts should continue to focus on minimizing and/or treating glass surfaces on new and existing buildings. Our species- and season-specific assessments indicate that management of some collision risk factors may not be equally effective for all seasons and species. Future research, policy, and management that integrates information about collision risk for all bird species and seasons, and at multiple scales from building façades to the surrounding landscape, will be most effective at reducing total mortality from bird–window collisions.
Chymotrypsin is a member of the trypsin family of serine proteases and is one of the first proteins successfully studied by X-ray crystallography. It is secreted into the intestine as the inactive precursor chymotrypsinogen; four sequential cleavages of the peptide bonds following residues 13, 15, 146 and 148 occur to generate the active pi, delta, kappa and alpha forms of chymotrypsin. (13)C NMR has shown [O'Connell & Malthouse (1995). Biochem. J. 307, 353-359] that when the delta form of chymotrypsin is inhibited by 2-(13)C-enriched benzyloxycarbonylglycylglycylphenylalanyl chloromethane, a tetrahedral adduct is formed which is thought to be analogous to the tetrahedral intermediate formed during catalysis. This inhibitor complex has been crystallized as a dimer in space group P4(1)2(1)2. The structure has been refined at 2.14 A resolution to an R value of 21.2% (free R = 25.2%). Conformational differences between delta-chymotrypsin and chymotrypsinogen in the region of the flexible autolysis loop (residues 145-150) were observed. This is the first crystal structure of delta-chymotrypsin and includes two residues which are disordered in previous crystal structures of active chymotrypsin. A difference of 11.3 A(2) between the average B values of the monomers within the asymmetric unit is caused by lattice-disordering effects approximating to rotation of the molecules about a crystallographic screw axis. The substrate-binding mode of the inhibitor was similar to other chymotrypsin peptidyl inhibitor complexes, but this is the first published chymotrypsin structure in which the tetrahedral chloromethyl ketone transition-state analogue is observed. This structure is compared with that of a similar tetrahedral transition-state analogue which does not alkylate the active-site histidine residue.
Three species of Buteo hawks nest sympatrically in the southern Great Plains of the United States. Dietary overlap among them is broad and we tested the hypothesis these species partition their breeding habitat spatially. We compared land cover and topography around 224 nests of the three species breeding in shortgrass prairie in 2004 and 2005. Red-tailed Hawks (Buteo jamaicensis) nested almost exclusively in riparian timber surrounded by prairie (95% prairie land cover around nests) and disproportionately used areas with greater topographic relief within prairie landscapes. Swainson's Hawks (B. swainsoni) commonly nested in low-relief areas dominated by small-grain production agriculture but generally used habitats in proportion to availability. Most nest sites of Ferruginous Hawks (B. regalis) were in prairie (78% prairie land cover around nests), but some were in areas that were at least partially agricultural. Ferruginous Hawks had at least two times more sand sagebrush (Artemisia filifolia) around their nests than their two congeners. We conclude that sympatric breeding Buteos on the southern Great Plains spatially partitioned nest sites according to subtle differences in land cover and topography.
We studied seven mixed-species colonies of terns and skimmers on the Virginia barrier islands in 1990 and 1991 to determine the effect of gull predation on nesting success. We compared intensity of gull predation and other agents of egg or chick mortality between tern and skimmer colonies on islands that also contained nesting gulls and colonies on islands that lacked nesting gulls. Terns and skimmers fledged about 3% of all eggs produced, with confirmed gull predation (27%) and tidal flooding (21%) accounting for the majority of nest failures. Gull-present colonies experienced significantly greater rates of disturbance from Herring and Great Black-backed gulls than did gull-absent colonies. Overall levels of gull predation were similar between gull-present and gull-absent colonies, likely due to the added impact of aerially foraging Laughing Gulls. Anecdotal evidence suggests that nest site competition with Herring and Great Black-backed gulls may have led to many terns and skimmers nesting in areas that were prone to frequent tidal flooding. In addition, floods may have indirectly prevented terns and skimmers from adequately protecting their surviving eggs and young, thus rendering flooded colonies more susceptible to gull predation.
Abstract Wind has become one of the fastest growing sources of renewable energy worldwide, but widespread and often extensive fatalities of bats have increased concern regarding the impacts of wind energy development on bats and other wildlife. We synthesized available information on patterns of bat fatalities from a review of 21 postconstruction fatality studies conducted at 19 facilities in 5 United States regions and one Canadian province. Dominance of migratory, foliage‐ and tree‐roosting lasiurine species (e.g., hoary bat [ Lasiurus cinereus ]) killed by turbines was consistent among studies. Bat fatalities, although highly variable and periodic, consistently peaked in late summer and fall, coinciding with migration of lasiurines and other species. A notable exception was documented fatalities of pregnant female Brazilian freetailed bats ( Tadarida brasiliensis ) in May and June at a facility in Oklahoma, USA, and female silver‐haired bats ( Lasionycteris noctivagans ) during spring in Tennessee, USA, and Alberta, Canada. Most studies reported that fatalities were distributed randomly across turbines at a site, although the highest number of fatalities was often found near the end of turbine strings. Two studies conducted simultaneously in the same region documented similar timing of fatalities between sites, which suggests broader patterns of collisions dictated by weather, prey abundance, or other factors. None of the studies found differences in bat fatalities between turbines equipped with lighting required by the Federal Aviation Administration and turbines that were unlit. All studies that addressed relationships between bat fatalities and weather patterns found that most bats were killed on nights with low wind speed (<6 m/sec) and that fatalities increased immediately before and after passage of storm fronts. Weather patterns may be predictors of bat activity and fatality; thus, mitigation efforts that focus on these high‐risk periods could reduce bat fatality substantially. We caution that estimates of bat fatality are conditioned by length of study and search interval and that they are biased in relation to how searcher efficiency, scavenger removal, and habitat differences were or were not accounted for. Our review will assist managers, biologists, and decision‐makers with understanding unifying and unique patterns of bat fatality, biases, and limitations of existing efforts, and it will aid in designing future research needed to develop mitigation strategies for minimizing or eliminating bat fatality at wind facilities.
Abstract Sympatric predators are predicted to partition resources, especially under conditions of food limitation. Spatial heterogeneity that influences prey availability might play an important role in the scales at which potential competitors select habitat. We assessed potential mechanisms for coexistence by examining the role of heterogeneity in resource partitioning between sympatric raptors overwintering in the southern Great Plains. We conducted surveys for wintering Red‐tailed hawk ( Buteo jamaicensis ) and Northern Harrier ( Circus cyanea ) at two state wildlife management areas in Oklahoma, USA . We used information from repeated distance sampling to project use locations in a GIS . We applied resource selection functions to model habitat selection at three scales and analyzed for niche partitioning using the outlying mean index. Habitat selection of the two predators was mediated by spatial heterogeneity. The two predators demonstrated significant fine‐scale discrimination in habitat selection in homogeneous landscapes, but were more sympatric in heterogeneous landscapes. Red‐tailed hawk used a variety of cover types in heterogeneous landscapes but specialized on riparian forest in homogeneous landscapes. Northern Harrier specialized on upland grasslands in homogeneous landscapes but selected more cover types in heterogeneous landscapes. Our study supports the growing body of evidence that landscapes can affect animal behaviors. In the system we studied, larger patches of primary land cover types were associated with greater allopatry in habitat selection between two potentially competing predators. Heterogeneity within the scale of raptor home ranges was associated with greater sympatry in use and less specialization in land cover types selected.
On 6 June 2007, we located a Burrowing Owl (Athene cunicularia) nest southeast of Nash in Grant County, Oklahoma. This is the first record of breeding Burrowing Owls in the county since the 1960s. Additional documentation of breeding activity in Oklahoma will provide valuable information to enhance conservation of Burrowing Owls.
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