Conservation and Ecology of Birds IV

Contributed Paper
ROOM: Room 220 – Ruidoso

1:10PM Does Wild Bird Feeding Improve Nest Survival or Clutch Size of Target Species?
Robyn L. Bailey; David N. Bonter
Wild bird feeding is a popular and rapidly growing activity, with an estimated 73% of American households participating in some form. Supplemental feeding can increase survival and reproductive success of bird populations (which is often a goal of supplemental feeding efforts), but there is increasing scientific concern that subsequent changes in predator communities, avian communities, and pathogen prevalence near bird feeders may create ecological traps for avian species. Our objectives were to test whether access to supplemental food during the nesting season influenced (1) nest success or (2) clutch size at a large spatial scale (United States). We examined nest fate data from 12,599 nest attempts submitted to NestWatch (a citizen-science nest monitoring program) from 2014–2016. We modeled the effect of “available supplemental food” on nesting success and clutch size for five cavity-nesting species (bluebirds and chickadees; Sialia sialis, S. mexicana, S. currucoides, Poecile carolinensis, and P. atricapillus). In general, respondents provided supplemental food at a greater proportion of chickadee nests (29–43% of nests had access to “seed and/or suet”) than bluebird nests (3–7% had access to “insects”, i.e., mealworms or waxworms). For all species, the top logistic exposure models predicting nest survival suggested no influence of supplemental feeding (nest survival estimates ranged from 0.60–0.86 across species). Mean clutch sizes were also not different at supplemented nests for any of the examined species. Our results suggest that although supplemental feeding during the nesting season did not substantially increase daily nest survival or clutch size, it also does not appear to create an ecological trap for the species in question.
1:30PM Managed Housing Is A Critical Component to Population Persistence of the Eastern Purple Martin
Blake A. Grisham; Daniel Raleigh; Daniel U. Greene; James D. Ray; Joe Siegrist
The Purple Martin (Progne subis) is entrenched in a consistent, long-term decline, especially east of the Rocky Mountains. Today, Eastern Purple Martins (P. s. subis) nest almost exclusively in provisioned housing provided by citizen scientists. Competition with nonnative European Starlings and House Sparrows for nest sites and subsequently lower productivity due to declining management of available housing may be responsible for their declines. To assess if poor nest survival is contributing to their declines, we analyzed 19 years of nest-check data (1995-2013) collected by citizen scientists. We compared provisioned housing and entrance-hole types from 72,627 nests across 8 regions on nest ecology metrics (clutch sizes, number of fledglings). Nest survival was > 85% in provisioned housing and clutch sizes and number of fledglings were slightly larger in gourd housing with entrances designed to exclude European Starlings, but there was little variation among other parameters. Our findings encourage the use of gourd housing, and while managed artificial housing of any type is beneficial, pressure from European Starlings is common, therefore, starling-resistant entrance holes are recommended. Our results also suggest poor nest survival is not the cause of eastern Purple Martin declines. Use of natural cavities by eastern Purple Martins is almost nonexistent, and their persistence is likely dependent on citizen scientists. Without provisioned and managed housing, there is little doubt that P. s. subis would go extinct due to the impacts of these nonnative species, and highlights the concern for other cavity nesters in the eastern United States and Canada.
1:50PM Effects of Livestock Grazing Management on the Abundance of Grassland Birds in a Northern Mixed-Grass Prairie Ecosystem
Skyler Vold
Grassland bird populations have declined more rapidly than any other guild of birds during the past 50 years as a result of habitat loss. The majority of remaining native grassland in North America is managed for livestock production. Rangeland management and livestock grazing can have significant impacts on the conservation of grassland birds. We evaluated the effects of three common livestock grazing systems on breeding season abundance of native grassland birds in the northern mixed-grass prairie ecosystem of eastern Montana. Our objectives were to: 1) evaluate how species-specific abundances of grassland birds were affected by grazing management, 2) estimate the importance of habitat and vegetation characteristics for grassland birds within pasture treatments, and 3) provide management recommendations to agencies and private landowners for improving habitat quality for grassland birds in northern mixed-grass prairies. During 2016-17, we conducted replicated point-count surveys at 150 survey points located at a 3,008-ha private ranch managed with rest-rotation grazing, and 155 points at adjacent reference properties (4,020-ha) employing either season-long or intensive summer rotational cattle grazing. We evaluated a suite of habitat conditions within a 100-m area around each survey point. We built a set of N-mixture models to evaluate whether abundances of 5 focal grassland bird species were influenced by grazing system while controlling for habitat conditions associated with each survey site. Relative to traditional grazing management, we observed a lower abundance of Baird’s sparrow (Ammodramus bairdii; ß̂ = -0.86 ± 0.25) and grasshopper sparrow (Ammodramus savannarum; ß̂ = -0.31 ± 0.11) and higher abundance of brown-headed cowbird (Molothrus ater; ß̂ = 0.31 ± 0.16) on pastures within rest-rotation grazing systems. Grassland bird community composition was similar among grazing systems. Overall, we found no evidence for improved grassland bird abundance or diversity within pastures managed under rest-rotation grazing when compared to traditional grazing systems.
2:10PM Nonnative Grasses Decouple Density and Nest Success in Grassland Birds
Erik M. Andersen; Robert J. Steidl
Nonnative plants that are structurally similar to native species may provide cues to animals that indicate the availability of resources that are no longer abundant in invaded areas. Migratory birds that breed in arid grasslands may be especially susceptible to this disassociation between evolutionarily-honed cues and future resources because they select breeding sites in spring, but delay nesting until the onset of summer rains when abundance of their insect prey increases markedly. On 140 plots in southeastern Arizona that we established across a gradient of invasion by nonnative grasses, we studied how patterns of territory establishment, density, and nesting success of birds obligate to grasslands changed in response to composition of nonnative grasses. For the two most common bird species, density and nest success were not associated positively. Specifically, as dominance of nonnative grasses increased, density of Botteri’s sparrows (Peucaea botterii) increased and nest success decreased, suggesting that invaded areas might have functioned as ecological traps attracting individuals away from areas of high-quality habitat into areas where reproductive success was markedly lower. Conversely, density of grasshopper sparrows (Ammodramus savannarum) decreased and nest success increased as dominance of nonnative grasses increased, suggesting that individuals avoided invaded areas that did not provide cues that indicated high-quality habitat, even when those sites provided resources that enhanced reproductive success. Settlement patterns confirmed that this decoupling of density and nest success resulted from birds selecting sites perceived as high quality instead of subordinate individuals being relegated to sites of lower habitat quality. By decoupling settlement cues from the resources associated with those cues over evolutionary timescales, nonnative plants can alter substantially the distribution and demography of grassland birds. An understanding of how invasions affect demographic rates can inform conservation and restoration efforts by identifying achievable targets of nonnative grass control that would benefit imperiled species.
2:30PM Understanding Landscape Scale Habitat Associations And Mapping Core and Potential Breeding Habitat for the Tricolored Blackbird
Chad Wilsey; Nicole Michel; Lotem Taylor; Samantha Arthur; Neil Clipperton
The Tricolored Blackbird (Agelaius tricolor) is a colonial nesting species largely endemic to California. The species has experienced dramatic population declines in the last half-century leading to candidacy for listing under the Endangered Species Act. In order to inform habitat conservation and enhancement efforts, we modeled nesting colony occurrence and abundance as a function of landscape composition across four ecoregions of California. We then mapped core and potential breeding habitat across the study area using model predictions for 2014 landcover and simulated habitat enhancements. Finally, we modeled the impact of recent landcover change on colony occurrence and size. Breeding colonies sites were associated with alfalfa, grasslands, and surface water. The largest colonies occurred in proximity to alfalfa, dairies and in areas with denser, greener vegetation (per NDVI). Surface water declined over time in unoccupied colonies but remained stable in occupied colonies. Average percent cover of nearly all foraging habitats, frequency of dairies, and NDVI were all higher in known colony sites over time than unoccupied areas. Over six million acres of core colony foraging habitat was identified. The majority was concentrated in the Central Valley and surrounding foothills (97%) and on private lands (94%). Protection of these lands through acquisition and easements is a key conservation strategy for Tricolored Blackbird. Simulated landcover enhancements suggest a 7-42% increase in core habitat area is possible. Engaging with landowners to inform choices regarding crop selection, land conversion, and surface water management is a necessary strategy for habitat enhancements to slow or reverse Tricolored Blackbird population declines.
2:50PM Refreshment Break
3:20PM Grassland Bird Response to Annual Herbaceous Biomass Harvest on the Leopold Wetland Management District, Wisconsin
BJ Byers; Christine Ribic
The Leopold Wetland Management District (LWMD) manages over 13,300 acres of federally owned Waterfowl Production Areas (WPA) in Wisconsin. Fire is the preferred habitat management tool, however LWMD is unable to apply prescribed fire at the scale and frequency desired. Therefore the Leopold District is exploring other management tools such as haying. Our project evaluated the responses of grassland birds to annual fall haying as a management tool compared with current management practices. Focal bird species were Grasshopper Sparrow (short-grass species), Bobolink (mid-grass), Eastern Meadowlark (mid-grass), and Henslow’s Sparrow (tall-grass). Twelve WPAs were used with 6 randomly chosen for annual fall harvests. Data were collected pre-harvest (2012) and post-harvest (2013-2015). Point count surveys were conducted during the breeding season (mid-May-July). Vegetation structure within fields was measured, specifically vegetation-height density and litter depth. We found that vegetation height density was not affected by the fall harvest, while litter depth was lower on harvested sites. Three of the 4 bird species responded to the treatment with Grasshopper Sparrows densities increasing on harvested sites and Henslow’s Sparrows and Bobolinks densities decreasing. Annual fall haying appears to create conditions more favorable to grassland bird species which prefer short grass and less litter cover for breeding.
3:40PM Estimating the Effect of Perennial Vegetation in an Agricultural Landscape on Grassland Birds
Julia Dale; Matt Stephenson; Lisa Schulte Moore; Robert Klaver
Midwestern grassland birds have faced steep declines due to the expansion of row crop agriculture and the associated loss of habitat. Other concerns associated with Midwestern agriculture include reductions in water quality and soil loss. Integration of strategically placed strips of native prairie vegetation into the larger agricultural landscape has been shown to greatly reduce nutrient and soil export from fields. In addition, integration of small-scale habitat fragments may provide habitat and movement corridors for grassland birds year-round. We investigated bird use of strategically integrated patches of perennial vegetation within the agricultural landscape of Iowa. We conducted bird point counts to estimate bird density in fields with and without integrated perennial vegetation during the summers of 2015 and 2016. Throughout 2015 and 2016 we also investigated bird presence in these fields using autonomous recording units. During point counts, we observed 67 species of birds, with the most common being Red-winged Blackbird (Agelaius phoeniceus), Dickcissel (Spiza americana), Eastern Meadowlark (Sturnella magna), American Robin (Turdus migratorius), Killdeer (Charadrius vociferus), and Common Yellowthroat (Geothlypis trichas). Estimated densities for Red-winged Blackbird and Dickcissel were higher in fields containing strategically integrated perennial vegetation, while overall species diversity was higher in conventionally farmed fields. The results of our research will allow us to make recommendations to researchers, landowners and land managers regarding what factors should be considered in relation to grassland bird conservation when planning integration of native perennial vegetation into a farm.
4:00PM Sandhill Crane Winter Fidelity on the Southern High Plains
Kathryn J. Brautigam; Blake A. Grisham; William P. Johnson; Daniel P. Collins; Shaun L. Oldenburger; Jude R. Smith; Nichole D. Athearn; Warren C. Conway
Approximately 80−90% of the Mid-continent Population (MCP) of Antigone canadensis (sandhill crane) spend part or all of winter on the Southern High Plains (SHP) of Texas and New Mexico. The MCP consists of 4 geographic breeding affiliations: Western Alaska-Siberia (WA-S, 42±4%), Northern Canada-Nunavut (NC-N, 21±4%), West-central Canada-Alaska (WC-A, 23±4%) and East-central Canada-Minnesota (EC-M, 14±3%). The WA-S, NC-N, and WC-A groups spent greater than 60% of their winter on the SHP. Our objectives were to estimate home range sizes and site fidelity rates among MCP cranes wintering on the SHP. Our study area included wetlands in 4 counties across the SHP. We estimated home ranges and winter fidelity of cranes captured during winters 2014−2015 (n=17) and 2015−2016 (n=10) returning 2015−2016 and 2016−2017, respectively, and made comparisons between breeding groups and age classes. We determined age using head plumage and tagged individuals with a leg band-mounted GPS-Argos satellite Platform Transmitter Terminals (PTT) programmed to record 3 diurnal and 2 nocturnal points every day. To delineate home range estimates, we used a Brownian Bridge Movement Model (package bbmm, Program R), truncated to points south of 36°N Latitude to isolate winter locations from the annual range. Size and percent overlap of core area (50%) and home range contours (95%) were compared between individuals of the WA-S (n=16), NC-N (n=10), and WC-A (n=1) breeding groups. We tested for differences in home range size and overlap, and estimated winter fidelity of each breeding affiliation and age class. Home ranges were clustered across 8 main sites, each containing 1 or more wetland suitable for roosting. We then compared home ranges between these sites. We found high variation in fidelity rates among our sample, including some with zero fidelity. High variation in space-use may indicate high variation in habitat quality and quantity among wetland complexes.
4:20PM Effects of Biosolids on Grassland Wildlife in British Columbia
Kirstie J. Lawson; Karen E. Hodges; Frank Doyle
Biosolids, the semi-solid residuals left after municipal wastewater treatments, are applied to grasslands as a fertilizer. This fertilization increases grass growth and improves forage for cattle. However, very little research has looked at the effects of biosolid applications on wildlife. We assessed how insects, songbirds, and grouse used biosolids-applied grasslands at a ranch near Clinton, British Columbia, Canada. Insect collections and songbird point counts were conducted across the ranch to assess richness and density of bird species and insect families in biosolids-treated and untreated grasslands. We captured and radio-collared female dusky grouse (Dendragapus obscurus) to measure individual home range and use of forest, untreated grassland, and biosolids-treated grassland throughout the summer. We sampled vegetation at nest and brood-rearing sites to assess what characteristics hens selected for and whether survival was affected by site selection. Total songbird density in biosolids-treated grasslands was higher than untreated (=9 and 6.11), but we found no difference in insect density (=99.6 and 48.7). The number of species and families was not different between grasslands. For grouse, biosolids did not appear to be a factor in selection of nest sites or brood-rearing sites. Model selection suggested that nest sites are selected based on visual obstruction and grass and shrub cover and brood-rearing sites for presence of moss and visual obstruction. While biosolids appear to affect the densities of both insect and songbird communities, it does not appear to directly affect grassland use by dusky grouse or the number of bird and insect species present. Our study indicates that biosolids may not deter many species, but may instead increase biodiversity on the landscape.
4:40PM Using Stable Isotopes to Estimate Reliance on Agricultural Food Subsidies And Migration Timing for a Migratory Bird
Matthew A. Boggie; Scott A. Carleton; Daniel P. Collins; John Vrandenburg; Christopher J. Sroka
Anthropogenic activities have adversely transformed terrestrial ecosystems consequently encumbering many species to more fragmented and confined areas resulting in increased human-wildlife conflicts. Under some circumstances, this creates a need for active management programs to directly support wildlife populations by subsidizing food resources. Evaluation and improvement of supplementary feeding practices should be implemented to determine dietary importance of supplemental food and identify when to make food resources available, which is an important consideration for migratory species using seasonal environments. To understand resource use, stable isotope analysis can be used to estimate diet composition, tissue-specific rates of isotopic incorporation, and arrival dates of migratory species. Greater sandhill cranes wintering in the Middle Rio Grande Valley of central New Mexico have come into conflict with agricultural practices consequently engendering a mitigation program that subsidizes cranes with cultivated corn to manage foraging behavior and provide nutritive support. To assess dependency of cranes on corn subsidies, we measured stable isotope ratios of liver and muscle tissues of cranes and their food items during the winter. Over 60% of their winter diet came from corn subsidies. Carbon isotope rates of turnover in liver and muscle tissues were 0.03 day-1 ± 0.03 (Mean ± SE) and 0.02 day-1 ± 0.02, respectively, and differed predictably by metabolic activity of different tissues. Estimated arrival date on wintering grounds derived from rates of isotopic incorporation was November 6 ± 3 days (Mean ± SE), similar to the arrival date on the wintering grounds of cranes equipped with satellite transmitters (November 23 ± 2 days). Our approach demonstrates a field-based application of intrinsic biomarkers to inform supplementary feeding practices for wildlife populations by identifying dietary response to supplemental food. Additionally, estimating arrival on wintering grounds supports management decisions by synchronizing availability of supplemental food resources with arrival times.


Contributed Paper
Location: Albuquerque Convention Center Date: September 25, 2017 Time: 1:10 pm - 5:00 pm