Explore the vast range of titles available.

Much attention has been paid to the impacts of plastics and other debris on marine organisms, but the effects of plastic on terrestrial organisms have been largely ignored. Detrimental effects of terrestrial plastic could be most pronounced in intensively human-modified landscapes (e.g., urban and agricultural areas), which are a source of much anthropogenic debris. Here, we examine the occurrence, types, landscape associations, and consequences of anthropogenic nest material in the American crow (Corvus brachyrhynchos), a North American species that breeds in both urban and agricultural landscapes. We monitored 195 nestlings in 106 nests across an urban and agricultural gradient in the Sacramento Valley, California, USA. We found that 85.2% of crow nests contained anthropogenic material, and 11 of 195 nestlings (5.6%) were entangled in their nests. The length of the material was greater in nests in agricultural territories than in urban territories, and the odds of entanglement increased 7.55 times for each meter of anthropogenic material in the nest. Fledging success was significantly lower for entangled than for unentangled nestlings. In all environments, particularly urban, agricultural, and marine, careful disposal of potential hazards (string, packing and hay bale twine, balloon ribbon, wire, fishing line) could reduce the occurrence of entanglement of nestling birds.

Mourning dove (Zenaida macroura) populations are believed to be declining throughout much of the United States since widespread population surveys were implemented in the mid-1960s. However, results from the Mourning Dove Call-Count Survey and North American Breeding Bird Survey indicate no trend for mourning doves in North Dakota. In addition, little is known about how climate and landscape factors may influence trends in mourning dove populations, especially in the northern extent of their breeding range. We used latesummer roadside counts conducted in North Dakota from 1970–2017 (n = 3,368), along with information from National Oceanic and Atmospheric Administration (NOAA) weather stations and the Census of Agriculture (United State Department of Agriculture) to develop generalized linear mixed models to analyze trends and identify weather and landscape variables that may be affecting mourning dove populations in North Dakota. Our results indicated that mourning doves counted along roadside transects have declined over the last 50 years in northcentral, northeast, and southeast regions of North Dakota where agriculture activity is most intensive and total cropland currently makes up at least 65% of the total landscape. Conversely, in northwest, southwest, and southcentral regions of North Dakota, where cropland makes up less than 50% of the landscape, we detected no trends in mourning doves counted during the same period. In our weather and landscape model, area of harvested corn and soybeans had a negative effect on mourning doves counted (β̂ = −0.174, SE = 0.029, 95% CI = −0.232, −0.116), whereas area of woodland had a positive effect on mourning dove abundance (β̂ = 0.137, SE = 0.053, 95% CI = 0.032, 0.241). In addition, we found no evidence that temperature or precipitation were influencing mourning dove populations in North Dakota. Woodland habitat steadily declined in North Dakota during our study period. Additionally, the amount of corn and soybeans planted throughout the state has increased rapidly over the last 20 years, which has decreased cropland diversity, and this pattern of land use change is likely reducing food and cover during the nesting season. To halt declining mourning dove populations in intensively farmed regions, managers should implement conservation programs and private land initiatives that aim to provide a more balanced mix of cropland, grassland, and woodland, with reductions in corn and soybean acres.

Obtaining unbiased survey data for vocal bird species is inherently challenging due to observer biases, habitat coverage biases, and logistical constraints. We propose that combining bioacoustic monitoring with unmanned aerial vehicle (UAV) technology could reduce some of these biases and allow bird surveys to be conducted in less accessible areas. We tested the feasibility of the UAV approach to songbird surveys using a low-cost quadcopter with a simple, lightweight recorder suspended 8 m below the vehicle. In a field experiment using playback of bird recordings, we found that small variations in UAV altitude (it hovered at 28, 48, and 68 m) didn't have a significant effect on detections by the recorder attached to the UAV, and we found that the detection radius of our equipment was comparable with detection radii of standard point counts. We then field tested our equipment, comparing songbird detections from our UAV-mounted recorder with standard point-count data from 51 count stations. We found that the number of birds per point on UAV counts was comparable with standard counts for most species, but there were significant underestimates for some—specifically, issues of song masking for a species with a low-frequency song, the Mourning Dove (Zenaida macroura); and underestimation of the abundance of a species that was found in very high densities, the Gray Catbird (Dumetella carolinensis). Species richness was lower on UAV counts (mean = 5.6 species point−1) than on standard counts (8.3 species point−1), but only slightly lower than on standard counts if nonaudible detections are omitted (6.5 species point−1). Excessive UAV noise is a major hurdle to using UAVs for bioacoustic monitoring, but we are optimistic that technological innovations to reduce motor and rotor noise will significantly reduce this issue. We conclude that UAV-based bioacoustic monitoring holds great promise, and we urge other researchers to consider further experimentation to refine techniques.

The North American Breeding Bird Survey (BBS) was established in 1966 in response to a lack of quantitative data on changes in the populations of many bird species at a continental scale, especially songbirds. The BBS now provides the most reliable regional and continental trends and annual indices of abundance available for >500 bird species. This paper reviews some of the ways in which BBS data have contributed to bird conservation in North America over the past 50 yr, and highlights future program enhancement opportunities. BBS data have contributed to the listing of species under the Canadian Species at Risk Act and, in a few cases, have informed species assessments under the U.S. Endangered Species Act. By raising awareness of population changes, the BBS has helped to motivate bird conservation efforts through the creation of Partners in Flight. BBS data have been used to determine priority species and locations for conservation action at regional and national scales through Bird Conservation Region strategies and Joint Ventures. Data from the BBS have provided the quantitative foundation for North American State of the Birds reports, and have informed the public with regard to environmental health through multiple indicators, such as the Canadian Environmental Sustainability Indicators and the U.S. Environmental Protection Agency's Report on the Environment. BBS data have been analyzed with other data (e.g., environmental, land cover, and demographic) to evaluate potential drivers of population change, which have then informed conservation actions. In a few cases, BBS data have contributed to the evaluation of management actions, including informing the management of Mourning Doves (Zenaida macroura), Wood Ducks (Aix sponsa), and Golden Eagles (Aquila chrysaetos). Improving geographic coverage in northern Canada and in Mexico, improving the analytical approaches required to integrate data from other sources and to address variation in detectability, and completing the database, by adding historical bird data at each point count location and pinpointing the current point count locations would further enhance the survey's value.

AbstractIn regions of intensive agriculture, such as the Yaqui Valley in Sonora, Mexico, unsustainable farming practices such as monoculture, excessive agrochemical use, and removal of native vegetation are prevalent. However, the impact of these practices on biodiversity is not well understood. In this study, we determine the diversity, abundance, and landscape affinities of the bird community in the Yaqui Valley. Between the fall of 2018 and the summer of 2019, we detected 16,775 individuals of 110 species grouped in 37 families along 15 routes. The species with the highest abundance were white-winged dove (Zenaida asiatica), Eurasian collared dove (Streptopelia decaocto), mourning dove (Zenaida macroura), rock pigeon (Columba livia), yellow-headed blackbird (Xanthocephalus xanthocephalus), red-winged blackbird (Agelaius phoeniceus), cliff swallow (Petrochelidon pyrrhonota), and Mexican duck (Anas diazi). The spring season had the highest biodiversity index, with more insectivorous species, followed by fall (carnivore species) and summer (piscivorous species). Of the recorded birds, 51 species were reproductive, 35 terrestrial, and 16 aquatic. They used abandoned fields (Gambel's quail, Callipepla gambelii), farms (Eurasian collared dove), aquatic vegetation (fulvous whistling duck, Dendrocygna bicolor; killdeer Charadrius vociferus), edge herbaceous vegetation (rufous-winged sparrow, Peucaea carpalis; song sparrow, Melospiza melodia; western meadowlark, Sturnella neglecta; common yellowthroat, Geothlypis trichas; yellow-breasted chat, Icteria virens), high arboreal layers (black-bellied whistling duck, Dendrocygna autumnalis), terrestrial vegetation (curve-billed thrasher, Toxostoma curvirostre), irrigation network (black-necked stilt, Himantopus mexicanus; burrowing owls, Athene cunicularia), and aquatic and terrestrial habitats (Mexican duck). Of the 110 species detected, 41 species (37%) are included in at least one conservation instrument, and the vulnerability increases with time. Regarding crop features, harvested_wheat combined with corn and various_crops had the highest bird biodiversity index. In contrast, immature_wheat, one of the most common landscapes in the Yaqui Valley, had the highest abundance of only a few species of birds.

The Conservation Reserve Program (CRP) is a primary tool for restoring grassland in the United States, in part as wildlife habitat, which has benefited declining grassland bird populations. Among potential mid-contract management practices used to maintain early-successional CRP grasslands, cattle grazing had been prohibited and is currently disincentivized during the primary nesting season for birds (much of the growing season), despite the important role that large herbivores historically played in structuring grassland ecosystems. Conservative grazing of CRP grasslands could increase spatial heterogeneity in vegetation structure and plant diversity, potentially supporting higher densities of some grassland bird species and higher bird diversity. Our objective was to determine the effect of experimental cattle grazing on species-specific relative abundance and occupancy, species diversity, and community dissimilarity of grassland birds on CRP grasslands across the longitudinal extent of Kansas, USA (a 63.5-cm precipitation gradient) during the 2017–2019 avian breeding seasons. Fifty-three of 108 fields were grazed by cattle during the growing seasons of 2017 and 2018 and all fields were rested from grazing in 2019. For all analyses, we examined separate model sets for semiarid western versus more mesic eastern Kansas. Using data from line transect surveys, we modeled relative abundances of 5 songbird species: grasshopper sparrow (Ammodramus savannarum), dickcissel (Spiza americana), eastern meadowlark (Sturnella magna), western meadowlark (Sturnella neglecta), and brown-headed cowbird (Molothrus ater). Grazing had delayed yet positive effects on abundances of grasshopper sparrow in western Kansas, and eastern meadowlark in eastern Kansas, but negative effects on dickcissel abundance in western Kansas and especially on burned fields in eastern Kansas. Somewhat counterintuitively, brown-headed cowbirds in western Kansas were more abundant on ungrazed versus grazed fields in the years after grazing began. In addition, we modeled multi-season occupancy of 3 gamebird species (ring-necked pheasant [Phasianus colcicus], northern bobwhite [Colinus virginianus], mourning dove [Zenaida macroura]) and Henslow’s sparrow (Centronyx henslowii); grazing did not affect occupancy of these species. In eastern Kansas, species diversity was highest in grazed, unburned fields. In western Kansas, bird communities in grazed and ungrazed fields were dissimilar, as determined from multivariate analysis. Though regionally variable, conservative stocking of cattle on CRP grasslands during the nesting season as a mid-contract management tool might increase bird species diversity by restructuring habitat that accommodates a greater variety of species and decreasing abundances of species associated with taller, denser stands of vegetation.

Background West Nile virus (WNV) is a mosquito-transmitted disease of birds that has caused bird population declines and can spill over into human populations. Previous research has identified bird species that infect a large fraction of the total pool of infected mosquitoes and correlate with human infection risk; however, these analyses cover small spatial regions and cannot be used to predict transmission in bird communities in which these species are rare or absent. Here we present a mechanistic model for WNV transmission that predicts WNV spread (R 0 ) in any bird community in North America by scaling up from the physiological responses of individual birds to transmission at the level of the community. We predict unmeasured bird species’ responses to infection using phylogenetic imputation, based on these species’ phylogenetic relationships with bird species with measured responses. Results We focused our analysis on Texas, USA, because it is among the states with the highest total incidence of WNV in humans and is well sampled by birders in the eBird database. Spatio-temporal patterns: WNV transmission is primarily driven by temperature variation across time and space, and secondarily by bird community composition. In Texas, we predicted WNV R 0 to be highest in the spring and fall when temperatures maximize the product of mosquito transmission and survival probabilities. In the most favorable months for WNV transmission (April, May, September and October), we predicted R 0 to be highest in the “Piney Woods” and “Oak Woods & Prairies” ecoregions of Texas, and lowest in the “High Plains” and “South Texas Brush County” ecoregions. Dilution effect: More abundant bird species are more competent hosts for WNV, and predicted WNV R 0 decreases with increasing species richness. Keystone species: We predicted that northern cardinals ( Cardinalis cardinalis ) are the most important hosts for amplifying WNV and that mourning doves ( Zenaida macroura ) are the most important sinks of infection across Texas. Conclusions Despite some data limitations, we demonstrate the power of phylogenetic imputation in predicting disease transmission in heterogeneous host communities. Our mechanistic modeling framework shows promise both for assisting future analyses on transmission and spillover in heterogeneous multispecies pathogen systems and for improving model transparency by clarifying assumptions, choices and shortcomings in complex ecological analyses.

Bird populations in grasslands have experienced declines coinciding with loss and fragmentation of prairies. The United States Department of Agriculture (USDA)-administered Conservation Reserve Program (CRP) is the most extensive grassland restoration program in North America and it has especially benefitted grassland birds. Grazing by domestic cattle has been restricted in CRP during avian nesting seasons despite the potential improvements in structuring habitat for a greater diversity of grassland bird species. Potential negative consequences of grazing in CRP grasslands include trampling of nests by cattle, reductions in nest concealment from predators, and attraction of brood-parasitic brown-headed cowbirds (Molothrus ater). We designed an experiment to test for effects of cattle grazing in CRP fields during the nesting season on nest survival and brood parasitism of 5 bird species that commonly nest in CRP grasslands: mourning dove (Zenaida macroura), grasshopper sparrow (Ammodramus savannarum), dickcissel (Spiza americana), and eastern (Sturnella magna) and western (S. neglecta) meadowlarks. Grazing was implemented during summers 2017 and 2018 on 17 of 36 fields followed by a year of rest on all fields in 2019. Of the 879 nests on grazed fields, only 4 were likely trampled by cattle (vs. 54% of all nests estimated as failing because of depredation). Experimental grazing (grazed vs. ungrazed fields) had variable effects on nest survival and cowbird parasitism among the bird species analyzed. Negative effects of grazing on daily nest survival of dickcissel and meadowlarks were apparent, at least in some years. We found no direct effects of grazing on nest survival of mourning dove or grasshopper sparrow. Probability and intensity (cowbird offspring/nest) of cowbird parasitism in dickcissel nests was higher on grazed versus ungrazed sites but only in conservation practice (CP) CP2 (vs. CP25 fields). Parasitism probability of grasshopper sparrow nests by cowbirds was higher on grazed fields in the 2 years after introduction of cattle in 2017. Greater vegetative concealment around nest sites was associated with reduced cowbird parasitism of meadowlark and grasshopper sparrow nests and higher nest survival for grasshopper sparrows. Reductions in vegetative height caused by longer-term or high-intensity grazing might therefore have negative consequences for some grassland birds by increasing nest site visibility and exposure to cowbird parasitism. Our results indicate that cattle grazing in CRP fields during the nesting season might have some negative effects on reproductive success of some grassland bird species, at least in the short term; however, the potential improvements of structuring habitat to accommodate more grassland bird species and increasing landowner participation in the CRP are considerable.

Understanding how free-ranging birds react to approaching aircraft can provide the foundation for predicting and mitigating risk of bird strikes. We characterized responses by avian species to aircraft (propeller-driven, jet, rotorcraft) approach (taxi, takeoffs, landings) at Burke Lakefront Airport, Cleveland, Ohio, USA, from June 2015 through September 2016. Based on opportunistic observations from fixed points on the airfield, we quantified 208 bird-aircraft interactions across 16 species. However, we focused analyses on 5 species with >10 bird-aircraft interactions (n = 176): American kestrel (Falco sparvarious), European starling (Sturnus vulgaris), killdeer (Charadrius vociferous), mourning dove (Zenaida macroura), and red-winged blackbird (Agelaius phoeniceus). We evaluated the common measure of perceived risk, flight-initiation distance (FID), and the likelihood of response (i.e., a measureable FID), each relative to species, flock size, flock altitude, perch height, aircraft approach category, and airframe type. We also assessed effects of light, temperature, and wind speed. None of our predictors contributed to FID. Across the 5 species, birds exposed to direct aircraft approach were ≥2 times more likely to initiate escape as those approached tangentially. The larger mourning dove was, by a factor ≥2, more likely to initiate escape response. As flock size increased, birds were more likely to initiate escape response. Birds were >2 times more likely to initiate escape when approaches involved jets relative to propeller-driven airframes. Because smaller species were less likely to initiate escape response, thereby enhancing the possibility of latent responses close to aircraft, we suggest that airport biologists should not disregard management to reduce strike hazards posed by smaller species. Further, bird habitat on airfields and fixtures that concentrate bird use in a direct line of aircraft approach will inherently increase the frequency of bird-aircraft interactions. Finally, our findings on flock size and airframe type underscore the need for continued efforts to develop methods to enhance avian detection of and response to approaching aircraft.

Understanding how land cover and potential competition with invasive species shape patterns of occupancy, extirpation, and colonization of native species across a landscape can help target management for declining native populations. Mourning dove (Zenaida macroura) populations have declined throughout the United States from 1965–2015. The expansion of the Eurasian collared-dove (Streptopelia decaocto), an introduced species with similar food preferences, may further threaten mourning dove populations. We analyzed data from 2009–2016 from a large-scale monitoring program in the Western Great Plains of the United States in a 2-species occupancy model to assess the effects of collared-doves on mourning dove distributions, while accounting for imperfect detection and variation in land cover across the landscape. Mourning dove occupancy was stable or increasing across our study area, and despite overlap in resource use and co-occurrence between mourning doves and Eurasian collared-doves, we found no evidence that collared-doves are extirpating mourning doves from preferred habitat during the breeding season.