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At least 55 records · Page 3Linked to original sources
USGS2001

Newly emergent and future threats of alien species to Pacific birds and ecosystems

Although the devastating effects of established alien species to Pacific birds and ecosystems are generally well recognized by the avian conservation community, we raise the under appreciated issue of effects of incipient and future invasions. Although special attention to Pacific bird species “on the brink” is to a certain extent appropriate and necessary, a comparable focus on stopping new invasions appears desperately needed. All indications suggest that introductions will escalate with the trend toward ever increasing commerce and unrestricted trade unless stronger preventative measures are implemented very soon. The threat to Pacific island avifaunas from the brown tree snake ( Bniga irregularis ) is well-known, but as many as several hundred of the world’s snake species, some of which are repeatedly smuggled illegally as pets, might have similar impacts on native birds if transported to Pacific islands. We touch upon a sampling of obviously severe potential future threats, with the hope of raising awareness and resolve to fix the current woefully inadequate system for prevention of and rapid response to new invasions.

Studies in Avian Biology↗
USGS2001

Breeding productivity and survival of the endangered Hawai'i Creeper in a wet forest refuge on Mauna Kea, Hawai'i

We studied the demography of the endangered Hawai‘i Creeper ( Oreomystis muna ) from 1994-1999 at three sites in Hakalau Forest National Wildlife Refuge (NWR). Hawai‘i Creepers bred from January to June, with peak breeding in February through May (about 120-l 80 days), and molted from May to August. A small proportion (4.9%) of individuals overlapped breeding and molting activities. We located and monitored the fates of 60 nests. Mean clutch size was 2.1 eggs, nest building required 19 days, incubation was 16 to 17 days, and nestling period lasted 18 days. Of all nest attempts, 25% were abandoned before egg laying, 6.7% were removed for captive propagation, 13.3% had undetermined fates, 38.3% failed during incubation or nestling periods, and 16.7% were successful. Thus, of 33 nests that were active through egg laying and outcome was confirmed, only 30% were successful. The daily survival rate of active nests was 0.960 t 0.009 SE. An average of 1.7 chicks fledged from successful nests. Thirty-two percent of hatch-year birds were alive and in the study area at least one year later. Annual adult survival was high (0.88 t 0.03). The primary factors limiting productivity of Hawai‘i Creeper in Hakalau Forest NWR appear to be low reproductive potential in combination with high rates of nesting failure. Further research into the causes of nest failure, the length of the breeding season, and renesting behavior of females is needed, and protection of the forest from the degrading impacts of introduced mammals is paramount.

Hawai'i↗
USGS2001

What caused the population decline of the Bridled White-eye on Rota, Mariana Islands?

The Bridled White-eye ( Zosterops conspicillatus rotensis ) was Once thought to be common and widespread on Rota, Commonwealth of the Northern Mariana Islands, but is now restricted to several patches of native limestone forest in and adjacent to the Sabana region. Surveys conducted in 1990 indicated that the population had declined by 87% between 1982 and 1990 for unknown reasons. The low density and restricted habitat association of the Bridled White-eye on Rota contrasts with the situation on Saipan, Tinian, Agiguan, and formerly on Guam, where the Bridled White-eye is the most common forest bird and occurs at all elevations and in all habitat types. We surveyed the entire range of the Rota Bridled White-eye in 1996 to estimate its current numbers and distribution. We also reviewed existing information on the white-eye and evaluated potential causes of its decline, including predation by Black Drongos ( Dicrurus macrocercus ), rats ( Rattus spp.), and the brown tree snake Boiga irregularis ); pesticides; avian disease; and habitat loss and alteration. We found that 94% of the extant population of 1,165 white-eyes on Rota was restricted to four patches of old-growth, native limestone forest covering only 259 ha. We believe that the population decline and current localized distribution is primarily a result of habitat changes due to agricultural development and typhoons, but the absence of white-eyes from several stands of native forest above 200 m remains unexplained. The Rota white-eye may be a different species from white-eyes found on Saipan, Tinian, Agiguan, and Guam, with different habitat preferences.

Rota↗
USGS2001

Drepanidine movements in relation to food availability in subalpine woodland on Mauna Kea, Hawai'i

Flowers of the mamane tree ( Sophoru chrysophylla ) are the primary nectar source for Hawaiian honeycreepers in subalpine woodland on Mauna Kea Volcano on the island of Hawai‘i. Mamane seeds are the primary food resource of the endangered Palila ( Loxioides bailleui ), which is now restricted to subalpine woodland on Mauna Kea. The objectives of this study were to determine the patterns and relative scales of movements of the drepanidine community in relationship to food availability and tree density on leeward Mauna Kea. ‘I‘iwi ( Vestiaria coccinea ) and ‘Apapane ( Himatione sanguinea ) densities were related to mamane flower abundance. Palila densities were related to mamane pod abundance. These species also had higher densities in mamane woodland than in naiomamane woodland, unlike the more insectivorous Hawai‘i ‘Amakihi ( Hemignathus virens ) whose densities did not differ between woodland types. Palila and Hawai’i ‘Amakihi do not make movements on the same scale as ‘I‘iwi and ‘Apapane, whose densities changed by more than an order of magnitude. Ungulate eradication, grass reduction, tire management, and restored corridors of mamane woodland would benefit all drepanidines on Mauna Kea, particularly the Palila.

Hawai'i↗
USGS2001

The Hawai'i rare bird search 1994-1996

We compiled the recent history of sightings and searched for 13 rare and missing Hawaiian forest birds to update status and distribution information. We made 23 expeditions between August 1994 and April 1996 on the islands of Hawai‘i, Maui, Moloka‘i, and Kaua‘i totaling 1,685 search hours, 146 field days, and 553 person days. During our surveys we found four critically endangered birds: the Po‘ouli ( Melamprusops phaeosoma , five to six individuals), Maui Nukupu‘u ( Hemignathus lucidus affinis , one individual), ‘I‘iwi ( Vestiaria coccinea ) on Moloka‘i (one individual), and the Puaiohi ( Myadestes palmeri , 55-70 individuals). Detection rates for each species were 0.013, 0.002, 0.012, and 0.318 detections/hr, respectively. Although not visually confirmed during our surveys, auditory detections, unconfirmed sightings, and other reports suggest the possible existence of ‘O‘u ( Psittirostra psittacea ) on Hawai‘i, Kaua‘i Nukupu‘u ( Hemignathus lucidus hanapepe ), and Maui ‘Akepa ( Loxops coccineus ochraceus ) in perilously low numbers. Six undetected forest bird populations, Kama‘o ( Myadestes myudestinus ), Kaua‘i ‘O‘o ( Moho braccatus ), Bishop’s ‘O‘o ( Moho bishopi ), ‘O‘o on Kaua‘i, Greater ‘Akialoa ( Hemignafhus ellisianus ), and Kakawahie ( Paroveomyza flammea ) have high probabilities of being extinct. Oloma‘o ( Myadestes lanaiensis ) from Moloka‘i are probably extirpated from the areas searched on that island but may persist on the unsurveyed Oloku‘i Plateau.

Hawai'i↗
USGS2001

Immunogenetics and resistance to avian malaria in Hawaiian honeycreepers (Drepanidinae)

Although a number of factors have contributed to the decline and extinction of Hawai‘i’s endemic terrestrial avifauna, introduced avian malaria ( Plasmodium relicturn ) is probably the single most important factor preventing recovery of these birds in low-elevation habitats. Continued decline in numbers, fragmentation of populations, and extinction of species that are still relatively common will likely continue without new, aggressive approaches to managing avian disease. Methods of intervention in the disease cycle such as chemotherapy and vaccine development are not feasible because of efficient immune-evasion strategies evolved by the parasite, technical difficulties associated with treating wild avian populations, and increased risk of selection for more virulent strains of the parasite. We are investigating the natural evolution of disease resistance in some low-elevation native bird populations, particularly Hawai‘i ‘Amakihi ( Hemignathus virens ), to perfect genetic methods for identifying individuals with a greater immunological capacity to survive malarial infection. We are focusing on genetic analyses of the major histocompatibility complex, due to its critical role in both humoral and cell-mediated immune responses. In the parasite, we are evaluating conserved ribosomal genes as well as variable genes encoding cell-surface molecules as a first step in developing a better understanding of the complex interactions between malarial parasites and the avian immune system. A goal is to provide population managers with new criteria for maintaining long-term population stability for threatened species through the development of methods for evaluating and maintaining genetic diversity in small populations at loci important in immunological responsiveness to pathogens.

Hawai'i↗
USGS2004

Coping with mist-net capture-rate bias: Canopy height and several extrinsic factors

Many factors other than a species' actual abundance can affect mist-net capture rates. We used ANCOVA models to quantify some potential biases and control their effects, producing adjusted estimates of capture rates that are more directly comparable among mist-net stations. Data came from 46 two-day mist-net sessions from September 1990 to May 1992 at six subtropical forest stations in the Rio Bravo Conservation and Management Area, northwest Belize. Factors evaluated included canopy height at net sites, long-term net shyness (days elapsed between first and last netting day of the entire study period), season (wet vs. dry), total rainfall during a netting session, and temperature. Number of individuals and species captured/10 net-h declined at each net with increasing canopy height above the net. Capture rates differed significantly among some of the stations. Elapsed days and rainfall caused significant bias in capture rates, which were statistically controlled within the ANCOVA, whereas season and temperature did not. Capture rates varied among sessions, but there was a slight and significant decline over the entire study period for all stations combined. Rainfall significantly depressed capture rates somewhat on a daily basis, but capture rates did not differ between wet and dry seasons. When we replaced the station variable in the ANCOVA with mean canopy height, the model was still highly significant, but did not explain as much of the variation in capture rates. Statistical analysis provides an objective means of interpreting data and estimating reliability, but only if statistical assumptions of the analyses are met. We discuss the need for including randomization in the experimental design, standardizing netting protocol, and quantifying sources of bias in the field, before ANCOVA or other parametric statistical techniques can be used to partition effects of biases.

Studies in Avian Biology↗
USGS2004

Recommendations for the use of mist nets for inventory and monitoring of bird populations

We provide recommendations on the best practices for mist netting for the purposes of monitoring population parameters such as abundance and demography. Studies should be carefully thought out before nets are set up, to ensure that sampling design and estimated sample size will allow study objectives to be met. Station location, number of nets, type of nets, net placement, and schedule of operation should be determined by the goals of the particular project, and we provide guidelines for typical mist-net studies. In the absence of study-specific requirements for novel protocols, commonly used protocols should be used to enable comparison of results among studies. Regardless of the equipment, net layout, or netting schedule selected, it is important for all studies that operations be strictly standardized, and a well-written operation protocol will help in attaining this goal. We provide recommendations for data to be collected on captured birds, and emphasize the need for good training of project personnel

Studies in Avian Biology↗
USGS1994

Shorebirds in western North America: Late 1800s to late 1900s

Only anecdotal information is available to assess whether populations of the 47 shorebird species that breed or winter west of the Rocky Mountains changed in size or distribution during the past century. Unregulated hunting from 1870 to 1927 reduced populations of several species, at least temporarily, and was a factor in bringing the Eskimo Curlew ( Numenius borealis ) close to extinction. Large scale transformation of native grasslands and wetlands for agriculture and other purposes resulted in population declines and nesting range contractions of several temperate-zone breeders. In general, upland species were affected more than wetland species, breeding ranges contracted westward, and alteration of breeding habitat was the factor most responsible for range contractions and population declines. A ranking system assessing shorebird susceptibility to habitat alteration also predicted temperate breeders to be among the most vulnerable species to environmental change. The few estimates for current population sizes of western North American shorebirds range from fewer than 50 Eskimo Curlews to a few million Western Sandpipers ( Calidris mauri ), the most abundant species. Concentrations of at least 1000 shorebirds occur on migration at over 120 western North American sites and of 100,000 to 1,000,000 shorebirds at 18 sites. Whether populations are limited by conditions on breeding, wintering or migration ranges is unknown for most species. Expansion of ongoing programs coupled with economical new census efforts could be useful for monitoring the majority of western North American shorebirds during the next century.

Studies in Avian Biology↗
USGS1990

The aggregative response of common murres and Atlantic puffins to schools of capelin

I studied the aggregative responses of Common Murres and Atlantic Puffins to schools of capelin during three summers (1982-1984) at Witless Bay, Newfoundland, by conducting hydroacoustic surveys for capelin in synchrony with seabird censuses. Murres and puffins foraged offshore prior to the arrival inshore of spawning schools of capelin. Both species were abundant during peak periods of capelin abundance from late June to late July, but only puffins continued to forage inshore after capelin schools dispersed in August. On individual surveys, murre and puffin flocks were significantly correlated with capelin schools at fine and coarse spatial scales. Aggregation intensity and spatial correlations peaked at measurement intervals of 2-6 km. At that scale, murres and puffins exhibited sigmoidal (Type III) aggregative responses to capelin schools. Inflection points (thresholds) in sigmoidal aggregative response curves occurred at higher densities of capelin for murres than for puffins and foraging thresholds for both species varied daily with overall capelin abundance in Witless Bay. Murres probably foraged on denser schools of capelin than puffins because of their larger body size and associated higher food demands. The implications of differing foraging thresholds for population ecology of alcids are discussed.

Newfoundland↗
USGS2016

Survival and habitat use of fledgling Golden-winged Warblers in the western Great Lakes region

Postfledging habitat use and fledgling survival remain unstudied for most songbirds, but this period is critical for understanding breeding habitat associations and full-season productivity. We used radiotelemetry to study movements, cover-type selection, and survival of fledgling Golden-winged Warblers ( Vermivora chrysoptera ) during the dependent postfledging period in managed forest landscapes of the western Great Lakes region. We used logistic exposure models to determine the relative importance of various habitat characteristics for explaining fledgling survival. In addition, we used compositional analysis, corrected for age-specific fledgling movement capabilities, to test for resource selection, as use versus availability, among cover types. We estimated that 48% of fledglings were depredated before independence from adult care at 25 days after fledging. Fledgling survival was lowest immediately after fledging, and 86% of predation occurred in the first 8 days following fledging. Distance from the nest to forest-shrubland edge was the strongest predictor of young fledgling survival, as survival decreased with nest distance into shrubland cover types and increased with nest distance into forest cover types. Fledglings from nests in shrubland cover types moved toward the nearest forest-shrubland edge, whereas fledglings from nests in forest cover types did not move toward edge. Fledglings selected mature forest and sapling-dominated clear-cuts over all other cover types during the early postfledging period, and fledgling survival in mature forest and sapling-dominated clearcuts was greater than in shrub-dominated clearcuts or wetland shrublands. Fledglings that were 9–25 days postfledging experienced high survival (daily survival >0.99) that was independent of any habitat variables we measured, and birds selected mature forest and shrub-dominated clear-cuts over all other cover types during that period. We conclude that sapling-dominated clear-cuts or mature forest with dense understory and shrub layers, cover types traditionally not associated with breeding, are important for fledgling survival, and therefore full-seasonal productivity in Golden-winged Warblers

Studies in Avian Biology↗
USGS2016

Spatially explicit models of full-season productivity and implications for landscape management of Golden-winged Warblers in the western Great Lakes Region

The relationship between landscape structure and composition and full-season productivity (FSP) is poorly understood for most birds. For species of high conservation concern, insight into how productivity is related to landscape structure and composition can be used to develop more effective conservation strategies that increase recruitment. We monitored nest productivity and fledgling survival of Golden-winged Warblers ( Vermivora chrysoptera ), a species of high conservation concern, in managed forest landscapes at two sites in northern Minnesota, and one site in southeastern Manitoba, Canada from 2010 to 2012. We used logistic exposure models to identify the influence of landscape structure and composition on nest productivity and fledgling survival. We used the models to predict spatially explicit, FSP across our study sites to identify areas of low relative productivity that could be targeted for management. We then used our models of spatially explicit, FSP to simulate the impact of potential management actions on our study sites with the goal of increasing total population productivity. Unlike previous studies that suggested wetland cover types provide higher quality breeding habitat for Golden-winged Warblers, our models predicted 14% greater productivity in upland cover types. Simulated succession of a 9-ha grassland patch to a shrubby upland suitable for nesting increased the total number of fledglings produced by that patch and adjacent upland shrublands by 30%, despite decreasing individual productivity by 13%. Further simulated succession of the same patch described above into deciduous forest reduced the total number of fledglings produced to independence on a landscape by 18% because of a decrease in the area available for nesting. Simulated reduction in the cumulative length of shrubby edge within a 50-m radius of any location in our landscapes from 0.6 to 0.3 km increased FSP by 5%. Our models demonstrated that the effects of any single management action depended on the context of the surrounding landscape. We conclude that spatially explicit, FSP models that incorporate data from both the nesting and postfledging periods are useful for informing breeding habitat management plans for Golden-winged Warblers and that similar models can benefit management planning for many other species of conservation concern.

Studies in Avian Biology↗
USGS2016

Golden-winged Warbler nest-site habitat selection: Chapter 7

Avian habitat selection occurs at multiple spatial scales to incorporate life history requirements. Breeding habitat of Golden-winged Warblers ( Vermivora chrysoptera ) is characterized by largely forested landscapes containing natural or anthropogenic disturbance elements that maintain forest patches in early stages of succession. Breeding habitat occurs in a variety of settings, including shrub and forest swamps, regenerating forests following timber harvest, grazed pastures, and reclaimed mined lands. We identified structural components of nest sites for Golden-winged Warblers by measuring habitat characteristics across five states (North Carolina, New York, Pennsylvania, Tennessee, and West Virginia) in the Appalachian breeding-distribution segment and two states (Minnesota and Wisconsin) in the Great Lakes breeding-distribution segment. We measured habitat characteristics at the nest-site scale with a series of nested plots characterizing herbaceous vegetation (grasses and forbs), woody shrubs and saplings, and overstory trees. We measured similar variables at paired random plots located 25–50 m from the nest within the same territory to evaluate selection. We used conditional logistical regression to identify which parameters were important in habitat selection and Simple Saddlepoint Approximation (SSA) to aid in management interpretation of identified parameters for each study site. Study site was an important determinant for which parameters were significant in nest-site selection, although selection for some parameters was consistent across sites. The amount of woody cover at the nest-site scale was consistently present in the top nest-site selection models across sites, although the direction of the relationship was not the same across all sites. We also identified grass, forb, woody cover, and vegetation density as important components of Golden-winged Warbler nest-site selection. Based on SSA, we identified vegetation thresholds to aid in designing habitat management prescriptions to promote creation or restoration of Golden-winged Warbler nesting habitat across the eastern portion of their breeding distribution.

Studies in Avian Biology↗
USGS2016

Space and habitat use by breeding Golden-winged Warblers in the central Appalachian Mountains

Spot-mapping, or recording locations of observed use by territorial songbirds, is often used to delineate core breeding territories. However, a recent radiotelemetry study in Minnesota found that male Golden-winged Warblers ( Vermivora chrysoptera ) occurring in high-density populations used resources outside their spot-mapped territories. We compared differences in space use and quantified vegetation characteristics in territories and home ranges of individual male Golden-winged Warblers that we monitored using both spot-mapping and radiotelemetry. Our study sites in Pennsylvania and West Virginia had lower population density than in Minnesota. We recorded 524 telemetry locations among 12 male Golden-winged Warblers in Pennsylvania and 488 telemetry locations among seven males in West Virginia. Telemetry-delineated home ranges (100% and 50% minimum convex polygons [MCPs]) were two to four times larger than spot-mapped territories. Spot-mapped territories had minimal overlap among individual males, but home ranges had extensive space-use overlap in both the number and amount of MCP overlap among several males. Forty percent of telemetry locations were outside of spot-mapped territories. Sapling abundance was greater in home ranges (mean 22.5 saplings ± 2.1 SE) than spot-mapped territories in Pennsylvania (11.8 ± 1.9). In managed pastures of West Virginia, tree abundance was greater in home ranges (7.3 trees ± 0.8) than spot-mapped territories (1.9 ± 0.6). More telemetry locations than spot-mapped locations occurred in forest in both states, and telemetry locations were closer to intact forested edges of shrublands than spot-mapped locations in West Virginia. On several occasions, we observed radiomarked individuals >200 m (maximum of 1.5 km) from their MCP spot-mapped territory boundaries. Why Golden-winged Warblers leave their spot-mapped territories is unknown, but our observations suggest foraging, forays for extra-pair mating, and reconnaissance for postbreeding movements as possible motives. Our results from areas with low Golden-winged Warbler territory densities are similar to patterns reported for a high-density population in Minnesota. Ultimately, spot-mapping alone does not accurately reflect space use of Golden-winged Warblers during the breeding season, nor does it characterize all cover types used even in areas with relatively low territory densities. Current conservation plans for Golden-winged Warblers that are based on habitat characteristics measured within spot-mapped territories or at the landscape scale may not adequately incorporate space use at intermediate spatial scales of clusters of territories or home ranges.

Studies in Avian Biology↗
USGS2016

Research on Golden-winged Warblers: Recent progress and current needs

Considerable advances have been made in knowledge about Golden-winged Warblers ( Vermivora chrysoptera ) in the past decade. Recent employment of molecular analysis, stable-isotope analysis, telemetry-based monitoring of survival and behavior, and spatially explicit modeling techniques have added to, and revised, an already broad base of published knowledge. Here, we synthesize findings primarily from recent peer-reviewed literature on Golden-winged Warblers, from this volume and elsewhere, and we identify some of the substantial remaining research needs. We have organized this synthesis by stages of the Golden-winged Warbler annual cycle. First, we discuss the relatively well-studied breeding-grounds ecology including nesting and post-fledging ecology and hybridization with closely related Blue-winged Warblers ( Vermivora cyanoptera ). Second, we discuss the much-less-studied, non-breeding-grounds ecology, including the first empirical studies of non-breeding-grounds cover-type associations and spatial and social behavioral ecology. Third, we address migratory connectivity and migration ecology, for which little is known and research has only just begun. Last, we close with cautious optimism that current knowledge is adequate to inform initial conservation and management plans for Golden-winged Warblers, and with a sobering acknowledgement of the quantity of research still needed.

Studies in Avian Biology↗
USGS2016

Management implications of brood division in Golden-winged Warblers

Brood division in the postfledging period is a common avian behavior that is not well understood. Brood division has been reported in Golden-winged Warblers ( Vermivora chrysoptera) , but it is not known how common this behavior is, whether males and females exhibit different strategies related to parental care and habitat use, or how brood division might influence management strategies. We radiomarked fledglings and monitored divided broods of Golden-winged Warblers from fledging until independence from parental care at three sites in the western Great Lakes region from 2010 to 2012 to assess differences in strategies between male and female parents and to consider possible management implications. Male - and female-reared sub-broods exhibited different space use during the dependent post-fledging period despite similar fledgling survivial, cover-type use, and microhabitat use. By independence, female-reared sub-broods traveled over twice as far from the nest (mean = 461 ± 81) SE m) as male-reared sub-broods (164 ± 41 m). Additionally, female-reared sub-broods traveled over three times as far from the natal patch edge (35 ± 72 m) as male-reared sub-broods (108 ± 36 m). Without accounting for differential space use by male- and female-reared sub-broods, we would have reported broods traveling 292 (± 46 m) from the nest and 214 (± 40m) from the natal patch edge - distances that do not reflect how far females move sub-broods. Parental strategies differ between sexes with regard to movement patterns, and we recommend incorporating the differences in space use between sexes in future management plans for Golden-winged Warblers and other species that employ brood division. Specifically, management actions might be most effective when they are applied at spatial scales large enough to incorporate the habitat requirements of both sexes throughout the entire reproductive season.

Studies in Avian Biology↗
USGS2012

Conservation implications when the nest predators are known

Conservation and management of passerines has largely focused on habitat manipulation or restoration because the natural communities on which these birds depend have been destroyed and fragmented. However, productivity is another important aspect of avian conservation, and nest predation can be a large source of nesting mortality for passerines. Recent studies using video surveillance to identify nest predators allow researchers to start evaluating what methods could be used to mitigate nest predation to help passerines of conservation concern. From recent studies, we identified latitudinal and habitat-related patterns in the importance of predator groups that depredate passerine nests. We then reviewed how knowledge of specific nest predators can benefit conservation of bird species of concern. Mammals were the dominant predator group in northern grasslands. Snakes were the dominant predator group in southern habitats. Fire ants were only a nest predator in southern latitudes. Differences in the importance of predator species or groups were likely the result of both their geographic patterns of distribution and habitat preferences. Some direct and indirect predator control measures developed for waterfowl management potentially could be used to benefit passerine productivity. We reviewed three examples-cowbirds, snakes in shrublands, and ground squirrels in grasslands-to illustrate how different predator control strategies may be needed in different situations. Mitigation of passerine nest predation will need to be based on knowledge of predator communities to be effective. This requires large samples of predation events with identified predators; video technology is essential for this task.

Studies in Avian Biology↗
USGS2001

Linking habitat selection to brood success in greater sage-grouse

Examining links between the fitness of individual organisms and their habitat-based decisions is useful to identify key resources for conservation and management of a species, especially at multiple spatial scales because selection of habitat attributes may vary with spatial scale. Decisions of habitat use by brood-rearing Greater Sage-Grouse (Centrocercus urophasianus) may influence the survival of chicks. We conducted radiotelemetry on 38 sage grouse broods within Mono County, California, during 2003–2005. At relocation and random sites, we measured habitat characteristics at three spatial scales using field procedures (scale, 0.03 ha) and Geographical Information System tools (scales, 7.9 ha and 226.8 ha). We then conducted three data analyses using an information-theoretic modeling approach. The purpose of these analyses was to: (1) identify habitat factors that were selected (defined as use disproportionate to availability) by sage grouse broods; (2) identify habitat factors associated with brood success (defined as 1 live chick at 50 days post-hatch; 24 were successful, 14 unsuccessful); and (3) evaluate brood success as a function of habitat selection indices for brood-rearing sage grouse. At the smallest spatial scale (0.03 ha), grouse with broods selected areas with greater perennial forbs and higher richness of plant species. At larger scales (7.9 ha and 226.8 ha), areas with Utah juniper (Juniperus osteosperma) and singleleaf pinyon pine (Pinus monophylla) encroachment were avoided by grouse. Most importantly, the probability of fledging a brood increased as sage grouse females selected habitats with greater densities of perennial forbs (0.03 ha) and higher meadow edge (perimeter to edge ratio; 7.9 ha), perhaps because these areas provided a balance of food and protective cover for chicks. These results suggest that managers should discourage tree encroachment and preserve and enhance sagebrush stands interspersed with perennial forbs and a mixture of small upland meadows.

Studies in Avian Biology↗