Distance from riparian edge reduces brood parasitism of southwestern willow flycatchers,whereas parasitism increases nest predation risk

The southwestern willow flycatcher (Empidonax traillii extimus) is a federally endangered subspecies that breeds in increasingly fragmented and threatened habitat. We examined whether temporal and habitat characteristics were associated with risk of predation and probability of brood parasitism by brown-headed cowbirds (Molothrus ater) on flycatcher nests at 6 sites in southern Nevada and northwestern Arizona, USA. For nest predation, we found the most support for a model that included date and an interaction between parasitism status and nesting stage. Daily nest survival decreased from 0.87 (95% CI = 0.81–0.93) to 0.78 (95% CI = 0.72–0.84) through the season for parasitized nests but remained relatively constant for unparasitized nests (0.93, 95% CI = 0.91–0.95 to 0.92, 95% CI = 0.91–93). Parasitized nests had lower survival than non-parasitized nests during the incubation (0.85, 95% CI = 0.84–0.86 vs. 0.92, CI = 0.91–0.93) and nestling (0.79, 95% CI = 0.77–0.81 vs. 0.91, 95% CI = 0.90–0.92) stages. Of the variables included in our parasitism candidate models, model-averaged coefficients and odds ratios supported only distance to habitat edge; odds of parasitism decreased 1% for every 1 m from the habitat edge. Nests greater than 100 m from an edge were 50% less likely to be parasitized as those on an edge, however, only 52 of 233 nests (22%) were found at this distance. Where management and conservation goals include reducing nest losses due to parasitism, we recommend restoration of habitat patches that minimize edge and maximize breeding habitat further from edges. At sites where cowbirds have been documented as important nest predators, controlling cowbirds may be one option, but further study of the link between parasitism and nest predation and the identification of major nest predators at specific sites is warranted. © 2011 The Wildlife Society.     

Avian spatial segregation at edges and interiors of urban parks in Madrid, Spain

Few studies have investigated the effects of urban landscape composition on avian habitat selection at urban-park edges. I assessed how the number of species, density of guilds, and density of individual species varied between edge and interior habitats in six large wooded parks in Madrid (Spain), and analysed such patterns in relation to habitat structure, car traffic, and pedestrian traffic. Few differences in habitat structure were found; whereas car and pedestrian traffic were significantly higher at edges. Species foraging in trees and on the ground, and nesting in trees and in tree cavities had lower numbers and breeding densities at edges, probably as a result of the disturbance from traffic noise and pedestrians. Species highly habituated to human activities (House Sparrows Passer domesticus and Rock Doves Columba livia) displayed opposite patterns, with higher breeding densities at urban-park edges, probably due to their higher foraging opportunities (refuse, people leftovers, deliberate feeding) and nest site availability in adjacent buildings. Urbanisation sprawl may increase the prevalence of edge specialists and diminish the representation of species with specific habitat requirements.     

Lesser Scaup Nest Success and Duckling Survival on the Yukon Flats,Alaska

Abstract: Over the last 20 years scaup numbers have declined, and these declines have been greatest in the northern boreal forests of Canada and Alaska where most lesser scaup (Aythya affinis) nest. We studied nest success and duckling survival of lesser scaup over 3 field seasons, 2001–2003, on the Yukon Flats National Wildlife Refuge in northeastern Alaska, USA. Daily survival rate (DSR) of nests on our study area across all 3 years was 0.943 (n = 177 nests, 95% CI: 0.930–0.954), corresponding to a nest success of only 12.3%, considerably lower than published estimates of an average nest success as high as 57% for lesser scaup in the northern boreal forest. With Mayfield logistic regression, we investigated effects on nest survival of year, clutch initiation date, and nesting habitat type (large wetlands >10 ha, small wetlands <10 ha, and wooded creeks). Neither year nor clutch initiation date influenced nest survival; however, the odds of nest success on large wetlands was 49% lower than on wooded creeks (odds ratio = 0.512, 95% CI = 0.286, 0.918). Based on the model that used only habitat type for estimation, DSR on large wetlands was 0.931 (corresponding nest success = 7.6%), DSR on small wetlands was 0.941 (nest success = 11.1%), and DSR on wooded creeks was 0.963 (nest success = 26.2%). To estimate duckling survival, we monitored 10 broods (n = 75 ducklings) over 3 field seasons by radiotagging hens at nest hatch. Most duckling mortality (94%) occurred in the first 10 days after hatch. Average duckling survival during 1–10 days was 0.321 (95% CI: 0.122–0.772), during 11–20 days was 0.996 (95% CI: 0.891–1.040), and during 21–30 days was 0.923 (95% CI: 0.769–1.041). Three of 10 hens moved all or part of their broods overland between nesting and brood-rearing wetlands for distances of 0.3–1.6 km. Our estimates of lesser scaup nest success and duckling survival on the Yukon Flats were among the lowest ever reported for ducks nesting at northern latitudes, even though the study site was in pristine boreal forest. Estimating and comparing scaup demographic rates from different geographic areas can contribute to improved conservation. Given the scarcity of information on scaup nesting in the boreal forest, basic nesting parameters are important to those trying to model scaup population dynamics.     

Buteo Nesting Ecology: Evaluating Nesting of Swainson’s Hawks in the Northern Great Plains

Swainson’s hawks (Buteo swainsoni) are long-distance migratory raptors that nest primarily in isolated trees located in areas of high grassland density. In recent years, anthropogenic conversion of grassland habitat has raised concerns about the status of the breeding population in the northern Great Plains. In 2013, we initiated a study to investigate the influence of extrinsic factors influencing Swainson’s hawk nesting ecology in north-central South Dakota and south-central North Dakota. Using ground and aerial surveys, we located and monitored nesting Swainson’s hawk pairs: 73 in 2013 and 120 in 2014. We documented 98 successful breeding attempts that fledged 163 chicks; 1.52 and 1.72 fledglings per successful nest in 2013 and 2014, respectively. We used Program MARK to evaluate the influence of land cover on nest survival. The top model, S _{Dist2Farm+%Hay}, indicated that nest survival (fledging at least one chick) decreased as nests were located farther from farm sites and as the percent of hay cover increased within 1200-m of the nest site (34.4%; 95% CI = 27.6%–42.3%). We used logistic regression analysis to evaluate the influence of landscape variables on nest-site selection; Swainson’s hawks selected for nest sites located closer to roads. We suggest that tree belts associated with farm sites, whether occupied or not, provide critical breeding sites for Swainson’s hawks. Additionally, poor breeding success may be related to the late migratory behavior of this species which requires them to occupy marginal habitat due to other raptors occupying the most suitable habitat prior to Swainson’s hawks arriving to the breeding grounds.     

Nest success of northern bobwhite on managed and unmanaged landscapes in southeast Iowa

Range-wide declines in northern bobwhite populations (Colinus virginianus) have been attributed to concomitant loss of breeding habitat. Bobwhite management efforts to restore this habitat resource can be informed by empirical studies of associations between breeding success and multi-scale habitat attributes. We compared bobwhite nest success in 2 southern Iowa landscapes as a function of microhabitat and landscape composition. Lake Sugema Fish and Wildlife Area (LSWA) was managed to promote bobwhite recruitment, and Harrisburg Township (HT) was an adjacent landscape dominated by private agricultural production. Survival rate modeling based on telemetry data provided evidence for age-specific daily nest survival rate. Daily survival rates decreased as nest age increased, but the decline was more severe at HT. Nest survival at LSWA (S = 0.495, SE = 0.103) was nearly twice that on HT (S = 0.277, SE = 0.072). We found no evidence that habitat composition or spatial attributes within 210 m of a nest site significantly influenced nest success. Forb canopy at the nest site had a positive influence on nest success at HT but not at LSWA. We suggest nesting habitat with greater forb canopy cover will increase the opportunity for nesting success in landscapes with limited nesting habitat. © 2010 The Wildlife Society.     

Effects of habitat edges and nest‐site characteristics on Painted Bunting nest success

Declines in populations of Painted Buntings (Passerina ciris) over the past several decades have led to their recent classification as a species of conservation concern. To better assess their status, we investigated factors associated with productivity and abundance of a population in south‐central Louisiana during 2010–2011. We monitored 41 Painted Bunting nests, 14 with video cameras, to identify predators, parasitism events, and improve nest success estimates. Vegetation measurements were also collected at nest sites and non‐nest sites to quantify habitat characteristics. We used an information‐theoretic approach to evaluate support for multiple models evaluating nest success. Highly supported models indicated large negative effects of Brown‐headed Cowbird (Molothrus ater) parasitism, and positive effects of increased canopy cover and distance to habitat edge on daily survival rates. Our estimate of daily survival rate was 0.94 ± 0.03 and the probability of survival was 0.25 ± 0.02. Point‐count data revealed that densities of Painted Buntings were greater in treeline habitats than in open scrub‐shrub and mature forest edge habitats. Furthermore, treelines had higher densities of large trees (>23 cm dbh) and percent canopy cover, variables positively associated with nest success, than open scrub‐shrub and forest edge habitats. In general, survival rates and causes of nest failure in southern Louisiana were similar to those determined for breeding populations of Painted Buntings at other sites. Our results suggest that treelines, despite having a high edge‐to‐area ratio, might be preferred nesting habitat for Painted Buntings in our study area.     

Urban-associated habitat alteration promotes brood parasitism of Acadian Flycatchers

ABSTRACT.   High rates of brood parasitism are generally associated with agricultural landscapes, but recent evidence suggests that urbanization may also increase the likelihood of brood parasitism. I evaluated the extent to which brood parasitism by Brown-headed Cowbirds ( Molothrus ater ) was explained by differences in (1) body size of adult hosts, presumably relating to the ability to defend nest from cowbirds, (2) nest placement in substrate and relative to habitat edges, (3) habitat structure surrounding nests, (4) host density, (5) cowbird abundance, both absolute and relative to host numbers, (6) landscape composition, and (7) Julian date. From 2001 to 2006, I monitored nest fate and measured vegetation characteristics surrounding nests of Acadian Flycatcher ( Empidonax virescens ) breeding in mature riparian forests in central Ohio, USA. The likelihood that a nest would be parasitized was best explained by the number of understory stems surrounding the nest and, to a lesser extent, by the amount of urbanization in the surrounding 1-km-radius landscape. Parasitized nests were surrounded by 1.6 times more stems and nearly twice the amount of urbanization than nonparasitized nests. Numbers of understory stems were positively associated with increasing urbanization, primarily due to invasion of urban forests by Amur honeysuckle ( Lonicera maackii ). Thus, urban-associated changes in habitat characteristics around nests may be important contributors to the greater vulnerability of urban nests to brood parasitism than nests in more rural landscapes. This pattern suggests that ecological restoration, such as removing exotic shrubs, may be an effective strategy to ameliorate certain negative consequences of urbanization near wooded reserves.     

Forest fragmentation relaxes natural nest predation in an Afromontane forest

Nest predation is widely regarded as a major driver underlying the population dynamics of small forest birds. Following forest fragmentation and the subsequent invasion by species from non-forested landscape matrices, shifts in predator communities may increase nest predation near forest edges. However, effects of human-driven habitat change on nest predation have mainly been inferred from studies with artificial nests, despite being regarded as poor surrogates for natural ones. We studied variation in predation rates, and relationships with timing of breeding and characteristics of microhabitats and fragments, on natural white-starred robin Pogonocichla stellata nests during three consecutive breeding seasons (2004–2007) in a Kenyan fragmented cloud forest. More than 70% of all initiated nests were predated during each breeding season. Predation rates nearly quadrupled between the earliest and the latest nests within a single breeding season, increased with distance to the forest edge, and decreased with the edge-to-area ratio of forest fragments. These spatial relationships oppose the traditional perception of edge and fragmentation effects on nest predation, but are in line with results from artificial nest experiments in other East African forests. In case of inverse edge and fragmentation effects on nest predation, such as shown in this study, species that tolerate edges for breeding may be affected positively, rather than negatively, by forest fragmentation, while the opposite can be expected for species restricted to the forest interior. The possibility of inverse edge effects, and its conservation implications, should therefore be taken into account when drafting habitat restoration plans.     

Survival of Wood Duck Ducklings and Broods in Mississippi and Alabama

ABSTRACT Although North American wood ducks (Aix sponsa) are well-studied throughout their range, researchers know little about demographic and environmental factors influencing survival of ducklings and broods, which is necessary information for population management. We studied radiomarked female and duckling wood ducks that used nest boxes and palustrine wetlands at Noxubee National Wildlife Refuge (NNWR) in Mississippi, USA, in 1996–1999, and riverine wetlands of the Tennessee-Tombigbee Rivers and Waterway (TTRW) system in Alabama in 1998–1999. We estimated survival of ducklings and broods and evaluated potentially important predictors of duckling survival, including age and body mass of brood-rearing females, hatch date of ducklings, duckling mass, brood size at nest departure, inter-day travel distance by ducklings, site and habitat use, and daily minimum air temperature and precipitation. At NNWR, survival of 300 radiomarked ducklings ranged from 0.15 (95% CI = 0.04-0.27) to 0.24 (95% CI = 0.13-0.38) and was 0.21 (95% CI = 0.15-0.28) for 1996–1999. Our overall estimate of brood survival was 0.64 (n = 91; 95% CI = 0.54-0.73). At TTRW, survival of 129 radiomarked ducklings was 0.29 in 1998 (95% CI = 0.20-0.41) and 1999 (95% CI = 0.13-0.45) and was 0.29 (95% CI = 0.20-0.40) for 1998–1999. Our overall estimate of brood survival was 0.71 (n = 38; 95% CI = 0.56-0.85). At NNWR, models that included all predictor variables best explained variation in duckling survival. Akaike weight (w_i) for the best model was 0.81, suggesting it was superior to other models (<0.01 < w_i < 0.18). We detected 4 competing models for duckling survival at TTRW. Inter-day distance traveled by ducklings was important as this variable appeared in all 4 models; duckling survival was positively related to this variable. Patterns of habitat-related survival were similar at both study areas. Ducklings in broods that used scrub-shrub habitats disjunct from wetlands containing aggregations of nest boxes had greater survival probabilities than birds remaining in wetlands with such nest structures. Managers may increase local wood duck recruitment by promoting availability of suitable brood habitats (e.g., scrub-shrub wetlands) without aggregations of nest boxes that may attract predators and by dispersing nest boxes amid or adjacent to these habitats. We did not determine an optimal density of nest boxes relative to local or regional population goals, which remains important research and conservation needs.     

Species traits and the response of open‐habitat species to forest edge in landscape mosaics

Human driven changes in land‐use have increased the need to understand how landscape structure affects species distribution. We studied how forest edges affected the distribution of birds in grasslands recently encroached by forest patches. We investigated how species’ biological traits influenced their response to vegetation change near forest edges. We censured birds along 300‐m line transects run into the open habitat perpendicularly to forest edges. We recorded habitat variables and landscape context along each transect and characterized edges and forest patches. We recorded 33 bird species in 153 transects for a total of 654 individuals. We analyzed species response to edges with generalized linear mixed models. Habitat preference was prevalent to explain species response to forest edges. The abundance of open‐habitat birds such as skylark Alauda arvensis decreased significantly in the vicinity of edges. This negative response extended within 150 m from the edge. The effect was disproportionately higher in open‐habitat species with high conservation concern. The abundance of species feeding or/and breeding in both forest and open habitat, such as woodlarks Lullula arborea, sharply increased near edges (positive edge response). Abundance of shrub and non‐shrub dependent species increased with distance to edge. The two species groups did no differ in abundance/distance to edge relationship. Intensity of species response to forest edges varied among transects in relation to transect vegetation characteristics. Edge length or aspect, diet and nest height had no direct effect. We discuss the possible role of variation in resources and nest predation risk to explain observed patterns.     

Density-dependent habitat selection of corridors in a fragmented landscape

This paper assesses the occurrence of density-dependent habitat selection in an urban fragmented landscape, composed of forest fragments (urban parks) connected by corridors (wooded streets), to test the hypothesis that as population density increased in the parks their suitability decreased and individuals entered alternative habitats, such as wooded streets. Density variation of six species was studied during two consecutive breeding seasons. Vegetation structure in wooded streets was significantly less complex than in urban parks, supporting the view that wooded streets were less suitable for breeding birds. Five species (Coal Tit Parus ater , Spotless Starling Sturnus unicolor , Serin Serinus serinus , Black-billed Magpie Pica pica and Woodpigeon Columba palumbus ) showed density- dependent habitat occupation of wooded streets, while the Common Blackbird Turdus merula did not. As park suitability decreased with rising densities, wooded streets became a profitable alternative in terms of foraging, breeding, or for moving between parks. However, the relationships varied both between and within species in different years. Such differences could have been caused by variable rates of human disturbance, renewal of resources and predation risks in wooded streets. More detailed studies are required to determine how birds perceive and regulate their population dynamics in fragments and associated corridors, particularly for species targeted for management.     

Birds nesting survival in disturbed and protected Neotropical savannas

Fragmentation and other habitat disturbances are long known to negatively affect birds, in large part by decreasing nest success due to high nest predation rates. The factors, however, that cause this decrease in nest success are still poorly understood and may vary among regions or species. Here, we show that nest survival is also lower in a disturbed landscape versus a protected cerrado (savanna-like) Neotropical landscape. Also, we tested the importance of garbage in the nest, brood parasitism, microhabitat and bird family in nest survival, controlling for temporal effects. We monitored 144 birds’ nests in a disturbed landscape and 150 nests in a natural reserve of cerrado vegetation in central Brazil, between September and December 2006. We used Program MARK to estimate nest survival probabilities and evaluate the effect of covariates in nest success in the disturbed area. Nest daily survival rate (DSR) was higher in the reserve (survival probability = 29.4%) than in the disturbed landscape (survival probability = 16.6%). Nest daily survival rate (DSR) was smaller in nests with garbage (survival probability = 9.3%) than in nests without garbage (survival probability = 19.5%) in the disturbed landscape. Effects of habitat disturbance on nest survival differed among bird families, with finches and tanagers being more affected mostly due to high nest predation rates. Conservation and management of birds in disturbed landscapes should include actions to decrease nest predation. In poor rural or suburban areas in developing countries, such as Brazil, actions like better garbage treatment may help conserve birds in disturbed landscapes.     

Mid-contract management of Conservation Reserve Program grasslands provides benefits for ring-necked pheasant nest and brood survival

Conservation Reserve Program (CRP) fields may provide good habitat for nesting and brood-rearing ring-necked pheasants (Phasianus colchicus) during early stages of succession. But, the success of hens in early successional CRP, relative to late successional CRP and other grassland habitats, has yet to be evaluated. The reproductive period is especially critical for populations of pheasants, and CRP's benefits to hens and chicks may decrease as fields age because of loss of vegetative diversity, decrease in vegetation density, and accumulation of residual litter. During 2005–2006, we evaluated spatial and temporal variation in nest and brood survival for radio-marked hen pheasants in areas of northeastern Nebraska where portions of CRP fields had been recently disced and interseeded (DICRP) with legumes. Nests in DICRP tended to have a higher daily survival rate (0.984; 95% CI: 0.957–0.994) than nests in grasslands (including CRP) that were unmanaged (0.951; 95% CI: 0.941–0.972). The probability of 23-day nest success was 0.696 (95% CI: 0.631–0.762) for DICRP and 0.314 (95% CI: 0.240–0.389) for unmanaged grasslands. Daily brood survival rates varied by habitat type, brood age, and date of hatch. The probability of a brood surviving to day 21 was 0.710 (95% CI: 0.610–0.856). Brood survival rates increased with time spent in DICRP and as the brood aged. Survival decreased as broods spent more time in cropland and peaked seasonally with broods that hatched on 15 June. Brood survival probability, to 21 days, would be reduced to 0.36 (95% CI: 0.100–0.701) if broods in our sample had not used DICRP. We combined nest and brood survival in a productivity model that suggested 2,000 hens, in a landscape with no DICRP, would produce 1,826 chicks, whereas the same hens in a landscape of 100% DICRP would produce 5,398 chicks. Production of first-year roosters more than doubled when hens nested in DICRP. Without DICRP, population growth rates of pheasant populations usually declined; with DICRP, populations stabilized with at annual survival rates of 0.3 or greater. The positive response of nest and brood survival to discing and interseeding CRP provides further evidence that CRP fields must be managed to optimize wildlife benefits. © 2012 The Wildlife Society.     

Factors that influence vital rates of Seaside and Saltmarsh sparrows in coastal New Jersey,USA

As saltmarsh habitat continues to disappear, understanding the factors that influence the population dynamics of saltmarsh breeding birds is an important step in the conservation of these declining species. Using 5 yrs (2011–2015) of demographic data, we evaluated and compared apparent adult survival and nest survival of Seaside (Ammodramus maritimus) and Saltmarsh (A. caudacutus) sparrows at the Edwin B. Forsythe National Wildlife Refuge in New Jersey, USA. We determined the effect of site management history (unditched vs. ditched marshes) on adult and nest survival to aid in prioritizing future management or restoration actions. Apparent adult survival (61.6%, 95% CI: 52.5–70.0%) of Seaside Sparrows averaged > 1.5 times greater than that of Saltmarsh Sparrows (39.9%, 95% CI: 34.0–46.2%). Nest survival and predation and flooding rates did not differ between species, and predation was the primary cause of nest failure for both species. Apparent adult survival and nest survival did not differ between unditched and ditched marshes for either species, indicating that marsh ditching history may not affect the quality of breeding habitat for these species. Because predation was the primary cause of nest failure for both species in New Jersey, we suggest that future studies should focus on identifying predator communities in salt marshes and the potential for implementing predator‐control programs to limit population declines.     

Nest success of grassland sparrows on reclaimed surface mines

Grasslands resulting from surface mine reclamation support grassland songbird populations in several midwestern and eastern states in the United States, especially where reclaimed mines are large (>1,000 ha). However, most reclaimed surface mines in Pennsylvania are small (<200 ha), and nest success is unknown. We evaluated nest success of grasshopper (Ammodramus savannarum), Henslow's (A. henslowii), and Savannah sparrows (Passerculus sandwichensis) on 4 reclaimed surface mines (50–180 ha) in western Pennsylvania, USA from 2006 to 2007. Overall nest success based on mean covariate values was 0.435 (95% CI = 0.376–0.504) for grasshopper sparrows, 0.396 (95% CI = 0.295–0.533) for Henslow's sparrows, and 0.158 (95% CI = 0.063–0.392) for Savannah sparrows. These estimates of nest success are comparable to those on larger reclaimed mines and other habitats. Grasshopper and Henslow's sparrow nests that were well concealed were less likely to fail than highly visible nests (β_visible = −0.028, CI = −0.051 to −0.005 for grasshopper sparrows; β_visible = −0.063, CI = −0.112 to −0.014 for Henslow's sparrows), and nests in areas with surrounding deep litter were more likely to fail than nests in areas with shallow litter (β_litterD = −0.145, CI = −0.335 to 0.045 for grasshopper sparrows; β_litterD = −0.676, CI = −1.187 to −0.116 for Henslow's sparrows). Savannah sparrow nests in areas with high visual obstruction by vegetation were less likely to fail than nests in areas with sparse and short vegetation (β_VisOb = 0.048, CI = 0.006–0.091). Daily probability of survival for grasshopper sparrow nests was greatest early and late in the breeding season, and Savannah sparrow nest survival followed a decreasing linear trend. Nest survival of Henslow's sparrows was greater on warm days (β_temp = 0.197, CI = 0.014–0.379), whereas for Savannah sparrows nest survival decreased on warm days and on days with rain, but for Savannah sparrows confidence intervals of weather effects included zero (β_temp = −0.098, CI = −0.246 to 0.050; β_rain = 3.13, CI = −14.19 to 20.45). We suggest that small reclaimed surface mine grasslands can provide valuable nesting habitat and could be important to the conservation of grassland bird populations. Because nest success can increase in the latter part of the nesting season, agricultural disturbances or management activities in mid- to late summer could adversely affect reproductive success. © 2011 The Wildlife Society.     

Survival and habitat use in translocated and resident greater prairie-chickens

Translocation, or the purposeful movement of organisms from one location to another for conservation, is currently being used to bolster populations of the endangered greater prairie-chicken (Tympanuchus cupido). We used radiotelemetry to compare survival between 58 resident birds and 54 newly translocated greater prairie-chickens that were sourced from a location more than 325 km away. Model averaged survival estimates were lower in translocated birds (0.42; 95% CI: 0.17–0.66) than in resident prairie-chickens (0.65; 95% CI: 0.46–0.79) through the breeding season. Habitat, sex and year were each included in at least 1 of the top 4 models, but the model averaged confidence intervals for each parameter encompassed zero. Survival of both resident and translocated prairie-chickens increased throughout the breeding season. Both translocated and resident prairie-chickens selected for core prairie habitat over agriculture, and birds tended to avoid surrounding private grasslands and wooded areas. We suggest that future translocation projects account for reduced survival of translocated birds when determining the appropriate release cohort sizes and sex ratios. We also recommend that future management for greater prairie-chicken habitat focus on the expansion of core protected patches of prairie to promote elevated survival and better chances of conservation success.     

Piping plover habitat selection and nest success on natural,managed, and engineered sandbars

Loss of breeding habitat and nest predation have contributed to the decline of many shorebird species. The United States Army Corps of Engineers (USACE) initiated a piping plover (Charadrius melodus) habitat creation and augmentation program on the Missouri River in the summer of 2004. The USACE increased unvegetated sandbar habitat by depositing dredged material (engineered sandbars) and by clearing vegetation from existing sandbars (managed sandbars). We evaluated the effects of this increase in nesting and foraging habitat on habitat selection and nest daily survival rate (DSR) of piping plovers on Lewis and Clark Lake and the Gavins Point Reach of the Missouri River from 2005 to 2007 (n = 623 nests). Piping plovers selected engineered sandbars more often than expected based on area and selected natural and managed habitats less than expected based on area. Daily survival rate on engineered sandbars was significantly higher than on natural or managed sandbars (log odds: 2.50, 95% CI: 1.05–5.94). Thus, plovers' habitat selection may have increased their nesting success. Our results suggest that habitat augmentation may stave off declines in piping plover populations limited by insufficient habitat and low nesting success. © 2011 The Wildlife Society.     

Nest success and hatchling survival of American alligators within inland wetlands of east Texas

Because of liberalization of American alligator (Alligator mississippiensis) harvest management in Texas, estimates of nest success and hatchling survival for inland populations are essential for long-term, sustainable population and harvest management. To date, few studies have examined American alligator nest success and hatchling survival. We initiated a 3-year study from 2006 to 2008 to document alligator nest success and hatchling survival within several wetlands in east Texas. From June 2006 to August 2008, we located 30 nests from 3 wetlands within east Texas, where overall nest success was 44.2% (95% CI = 25.1–63.1%), irrespective of year. Nest circumference and day during the nesting season exerted the greatest influence on nest success. Additionally, from August 2006 to August 2008 we captured, marked, and released 271 hatchling alligators at Little Sandy National Wildlife Refuge, and recaptured an additional 192 hatchling alligators during this time. We estimated yearly apparent survival at 6.0% (95% CI = 2.0–14.6%) for hatchling alligators born in 2006 and 43.0% (95% CI = 28.4–57.8%) for those hatched in 2007. Variation in nest success and hatchling survival was likely attributed to fluctuating water levels and habitat management practices. Alligator harvest regulations need to account for variability in nest success and hatchling survival by including site-specific estimates of these metrics into harvest models. Failing to account for spatial and temporal variation in nest success and hatchling survival may result in unsustainable harvest and/or overharvest. © 2012 The Wildlife Society.     

Black-capped vireo nest predator assemblage and predictors for nest predation

Nest predation is a major limiting factor for songbird productivity, including the federally endangered black-capped vireo (Vireo atricapilla). However, nest predator information is limited across the range of the black-capped vireo in central and southwest Texas. We monitored nests in 3 counties within the breeding range of black-capped vireos in Texas in 2008 and 2009 and used continuous recording digital video cameras to record predation events. We video-monitored 115 nests and documented 39 predation events by at least 9 predator species. Overall, we observed avian species (51%, n = 39), specifically brown-headed cowbirds (Molothrus ater; n = 12), and snakes (26%, n = 39) as the most frequent nest predators. The estimated daily nest survival rate during the laying and incubation stage was 0.985 (95% CI = 0.967–0.993) and 0.944 (95% CI = 0.921–0.961) during the nestling stage. In addition, we analyzed models of predator-specific nest predation using multinomial logistic regression. Effect of nest height on predation rate was significant for snakes; nest stage was significant for nests depredated by avian predators. By identifying and increasing our knowledge of nest predators and vegetation characteristics associated with greater risk of predation in multiple locations within the black-capped vireo's range, we can effectively manage habitat to benefit recovery efforts of the species. © 2012 The Wildlife Society.     

Landscape and Vegetation Effects on Avian Reproduction on Bottomland Forest Restorations

ABSTRACT Forest restoration has been undertaken on >200,000 ha of agricultural land in the Mississippi Alluvial Valley, USA, during the past few decades. Decisions on where and how to restore bottomland forests are complex and dependent upon landowner objectives, but for conservation of silvicolous (forest-dwelling) birds, ecologists have espoused restoration through planting a diverse mix of densely spaced seedlings that includes fast-growing species. Application of this planting strategy on agricultural tracts that are adjacent to extant forest or within landscapes that are predominately forested has been advocated to increase forest area and enhance forested landscapes, thereby benefiting area-sensitive, silvicolous birds. We measured support for these hypothesized benefits through assessments of densities of breeding birds and reproductive success of 9 species on 36 bottomland forest restoration sites. Densities of thamnic (shrub-scrub dwelling) and silvicolous birds, such as yellow-breasted chat (Icteria virens), indigo bunting (Passerina cyanea), and white-eyed vireo (Vireo griseus) were positively associated with 1) taller trees, 2) greater stem densities, and 3) a greater proportion of forest within the landscape, whereas densities of birds associated with grasslands, such as dickcissel (Spiza americana) and red-winged blackbird (Agelaius phoeniceus), were negatively associated with these variables. Vegetation structure, habitat edge, and temporal effects had greater influence on nest success than did landscape effects. Taller trees, increased density of woody stems, greater vegetation density, and more forest within the landscape were often associated with greater nest success. Nest success of grassland birds was positively related to distance from forest edge but, for thamnic birds, success was greater near edges. Moreover, nest success and estimated fecundity of thamnic species suggested their populations are self-sustaining on forest restoration sites, whereas these sites are likely population sinks for grassland and open-woodland species. We recommend restoration strategies that promote rapid development of dense forest stands within largely forested landscapes to recruit breeding populations of thamnic and silvicolous birds that have reproductive success sufficient to sustain their populations.