Demography of Ferruginous Hawks Breeding in Western Canada

Abstract: We assessed age-dependent survival, site-fidelity, and, together with data on prey and reproduction, trends in the population of ferruginous hawks (Buteo regalis) breeding in western Canada. Our analysis included 7,129 ferruginous hawks banded near Hanna, Alberta, and Kindersley-Alsask, Saskatchewan, from 1972 to 2003. We estimated annual adult survival rate to be 0.708 (SE = 0.024) and first year survival for nestlings was 0.545 (SE = 0.147). Resighting probability was modeled as a constant for nestlings (0.009, SE = 0.010), but it varied among years for adults consistent with our sampling efforts. Band reporting rate was at 0.022 (SE = 0.007) for both nestlings and adults. Fidelity to the study site was 1.00 (SE = 0.000) for adults and 0.035 (SE = 0.014) for nestlings. Nesting density ranged from 3.1 to 14.0 pairs/100 km² and averaged 9.8 pairs/100 km². We observed an average clutch size of 3.2 (SE=0.06) and brood sizes of 2.71 (SE=0.07) near Hanna and 2.79 (SE = 0.99) at Kindersley-Alsask. Richardson's ground squirrels (Spermophilus richardsonii) made up 95% of ferruginous hawk prey. Prey availability was positively correlated with number of offspring near Hanna and Kindersley-Alsask. We believe the lower than expected adult survival did not result in population decrease; rather, declines in reproduction resulting from declines in the abundance of ground squirrels better explain an observed 4.5-fold decline in nesting densities during the study. The results suggest that ferruginous hawk management should address prey in addition to habitat management, and that management needs are regional in scope with particular emphasis on the breeding range within the northern Great Plains.     

Occupancy Models of Nesting-Season Habitat Associations of Red-Shouldered Hawks in Central Minnesota

ABSTRACT Red-shouldered hawks (Buteo lineatus) are a species of special conservation concern in much of the Great Lakes region, and apparent population declines are thought to be primarily due to habitat loss and alteration. To evaluate red-shouldered hawk-habitat associations during the nesting season and at the landscape scale, we conducted repeated call-broadcast surveys in central Minnesota, USA, across 3 landscapes that represented a range of landscape conditions as a result of differing management practices. In 2004, we conducted repeated call-broadcast surveys at 131 locations in 2 study areas, and in 2005, we surveyed 238 locations in 3 study areas. We developed models relating habitat characteristics at 2 spatial scales to red-shouldered hawk occupancy and assessed support for these models in an information-theoretic framework. Overall, a small proportion of nonforest (grass, clear-cut area, forest <5 yr old), and a large proportion of mature deciduous forest (>40 yr old), had the strongest association with red-shouldered hawk occupancy (proportion of sites occupied) at both spatial scales. The landscape conditions we examined appeared to contain a habitat transition important to red-shouldered hawks. We found, in predominately forest landscapes, the amount of open habitat was most strongly associated with red-shouldered hawk occupancy, but in landscapes that included slightly less mature forest and more extensive open habitats, the extent of mature deciduous forest was most strongly associated with red-shouldered hawk occupancy. Our results suggested that relatively small (<5 ha) patches of open habitat (clear-cuts) in otherwise forested landscapes did not appear to influence red-shouldered hawk occupancy. Whereas, in an otherwise similar landscape, with smaller amounts of mature deciduous forest and larger (>15 ha) patches of open habitat, red-shouldered hawk occupancy decreased, suggesting a threshold in landscape composition, based on both the amount of mature forest and open area, is important in managing forest landscapes for red-shouldered hawks. Our results show that during the nesting season, red-shouldered hawks in central Minnesota occupy at similar rates landscapes with different habitat compositions resulting from different management strategies and that management strategies that create small openings may not negatively affect red-shouldered hawk occupancy.     

Carry-Over Effects of Nonbreeding Habitat on Start-to-Finish Spring Migration Performance of a Songbird

For migratory animals, conditions during the nonbreeding period may carry-over to influence spring migration performance. Animals in low-quality habitats are predicted to be in poorer condition, show later migration timing, and travel at slower speeds. This can result in subsequent negative effects on fitness. We tested the hypothesis that nonbreeding season body condition and habitat quality carry-over to affect spring migration performance of a long-distance migratory songbird, the Wood Thrush (Hylocichla mustelina). We tracked individual birds between multiple breeding sites in North America and nonbreeding sites in Central America. First, we compared body condition of nonbreeding birds migrating to the same general region of the breeding range with spring migration performance (timing, speed, and duration) obtained from light-level geolocators. Second, we assessed the Normalized Difference Vegetation Index (NDVI) as a proxy for nonbreeding habitat quality, and predicted that birds from wetter habitat or in wetter years (higher NDVI) would show improved migration performance relative to birds from drier sites. We found no evidence of individual-level carry-over effects of nonbreeding season body condition on spring migration performance. Lower NDVI of nonbreeding habitat resulted in delayed spring migration departure, but this effect disappeared by arrival at breeding sites. Birds occupying drier nonbreeding sites migrated faster and for fewer days, compensating for their relatively late departure. We also documented a broader pattern in NDVI and migration timing and distance, in that birds that occupied the wettest areas in the southern part of the nonbreeding range departed significantly later and migrated farther. Our results suggest that individual carry-over effects of nonbreeding habitat quality may be compensated for by a faster and shorter migration strategy. At a broad scale, consistently later spring timing and longer migration distances were associated with the wettest areas (the highest quality habitats) of the Wood Thrush non-breeding range. This supports the theory that high-quality habitats offset the costs of farther migration, resulting in a leap-frog migration pattern.     

Sex-Specific Habitat Utilization and Differential Breeding Investments in Christmas Island Frigatebirds throughout the Breeding Cycle

In seabirds, equal bi-parental care is the rule, as it is considered crucial for raising chicks successfully because seabirds forage in an environment with unpredictable and highly variable food supply. Frigatebirds forage in poor tropical waters, yet males reduce and even stop parental care soon after chick brooding, leaving the female to provision the chick alone for an extended fledging period. Using bird-borne tracking devices, male and female Christmas Island Frigatebirds (Fregata andrewsi) were investigated during the brooding, late chick rearing and post-fledging period to examine whether sexes exhibit foraging strategies that may be linked to differential breeding investments. During brooding, males and females showed similar foraging behaviour under average marine productivity of oceanic waters close to the colony, but males shifted to more distant and more productive habitats when conditions deteriorated to continue with reduced chick provisioning. During the late chick rearing period, females progressively increased their foraging range to the more distant but productive marine areas that only males had visited during brooding. Birds spent the non-breeding period roosting in highly productive waters of the Sunda Shelf. The sex-specific utilisation of three different foraging habitats with different primary productivity (oceanic, coastal, and shelf areas) allowed for temporal and spatial segregation in the exploitation of favourable habitats which seems to enable each sex to optimise its foraging profitability. In addition, post-fledging foraging movements of females suggest a biennial breeding cycle, while limited information on males suggests the possibility of an annual breeding cycle.     

石鸡繁殖期栖息地的特征

2005年4~7月,对甘肃西部(东阿尔金山地区和西祁连山地区)和东南部(西秦岭地区)的石鸡(Alectoris chukar)种群栖息地选择进行了调查。主成分分析表明,草本密度、地面异质性和草本盖度是栖息地选择的主要影响因子;方差分析表明,甘肃西部(东阿尔金山和西祁连山)的石鸡种群在海拔、坡度和小石块数目的选择上差异显著。甘肃西部和东南部的石鸡种群在栖息地选择上存在显著的地理变异,西秦岭种群选择海拔低、坡度大、坡位偏上、草本密度低和草本高度高的栖息地。栖息地选择差异可能是在不同的选择压力下,经过长期的隔离进化形成。     

Re-Occupancy of Breeding Territories by Ferruginous Hawks in Wyoming: Relationships to Environmental and Anthropogenic Factors

Grassland and shrubland birds are declining globally due in part to anthropogenic habitat modification. Because population performance of these species is also influenced by non-anthropogenic factors, it is important to incorporate all relevant ecological drivers into demographic models. We used design-based sampling and occupancy models to test relationships of environmental factors that influence raptor demographics with re-occupancy of breeding territories by ferruginous hawks (Buteo regalis) across Wyoming, USA, 2011–2013. We also tested correlations of territory re-occupancy with oil and gas infrastructure—a leading cause of habitat modification throughout the range of this species of conservation concern. Probability of re-occupancy was not related to any covariates we investigated in 2011, had a strong negative relationship with cover of sagebrush (Artemisia spp.) in 2012, was slightly higher for territories with artificial platforms than other nest substrates in 2013, and had a positive relationship with abundance of ground squirrels (Urocitellus spp.) that was strong in 2012 and weak in 2013. Associations with roads were weak and varied by year, road-type, and scale: in 2012, re-occupancy probability had a weak positive correlation with density of roads not associated with oil and gas fields at the territory-scale; however, in 2013 re-occupancy had a very weak negative correlation with density of oil and gas field roads near nest sites (≤500 m). Although our results indicate re-occupancy of breeding territories by ferruginous hawks was compatible with densities of anthropogenic infrastructure in our study area, the lack of relationships between oil and gas well density and territory re-occupancy may have occurred because pre-treatment data were unavailable. We used probabilistic sampling at a broad spatial extent, methods to account for imperfect detection, and conducted extensive prey sampling; nonetheless, future research using before-after-control-impact designs is needed to fully assess impacts of oil and gas development on ferruginous hawks.     

Multiscale Habitat Use and Selection in Cooperatively Breeding Micronesian Kingfishers

Abstract: Information about the interaction between behavior and landscape resources is key to directing conservation management for endangered species. We studied multi-scale occurrence, habitat use, and selection in a cooperatively breeding population of Micronesian kingfishers (Todiramphus cinnamominus) on the island of Pohnpei, Federated States of Micronesia. At the landscape level, point-transect surveys resulted in kingfisher detection frequencies that were higher than those reported in 1994, although they remained 15-40% lower than 1983 indices. Integration of spatially explicit vegetation information with survey results indicated that kingfisher detections were positively associated with the amount of wet forest and grass-urban vegetative cover, and they were negatively associated with agricultural forest, secondary vegetation, and upland forest cover types. We used radiotelemetry and remote sensing to evaluate habitat use by individual kingfishers at the home-range scale. A comparison of habitats in Micronesian kingfisher home ranges with those in randomly placed polygons illustrated that birds used more forested areas than were randomly available in the immediate surrounding area. Further, members of cooperatively breeding groups included more forest in their home ranges than birds in pair-breeding territories, and forested portions of study areas appeared to be saturated with territories. Together, these results suggested that forest habitats were limited for Micronesian kingfishers. Thus, protecting and managing forests is important for the restoration of Micronesian kingfishers to the island of Guam (United States Territory), where they are currently extirpated, as well as to maintaining kingfisher populations on the islands of Pohnpei and Palau. Results further indicated that limited forest resources may restrict dispersal opportunities and, therefore, play a role in delayed dispersal and cooperative behaviors in Micronesian kingfishers.     

Initial Effects of Wildfire on Freshwater Turtle Nesting Habitat

Natural wildfire regimes are important for ecosystem succession but can have negative ecological effects depending on fire characteristics. A portion of a granite rock barrens landscape that extends along the eastern shoreline of Georgian Bay, Lake Huron to eastern Ontario, Canada, burned in 2018 during a wildfire that affected >11,000 ha. This landscape is a biodiversity hotspot providing habitat for many species at risk where freshwater turtles nest in soil deposits in cracks and crevices in the bedrock dominated by moss (Polytrichum spp.) and lichen (Cladonia spp.) cover. To assess the initial effect of wildfire on freshwater turtle nesting habitat, we measured soil depths and estimated moss, lichen, and vascular plant cover at 2 morphology types (crevice, flat) in burned and unburned areas of the landscape. The probability that burned flat plots supported soil was near zero; the burned flat plots had 98% less soil volume compared to unburned flat plots. Although crevices were more resistant to soil loss, burned crevices still had a 15% lower probability of having soil and 35% less soil volume compared to unburned crevice plots. We estimated nest site availability by calculating the number of locations with shallow (5–10 cm), intermediate (10–20 cm), and deep (>20 cm) soils required for a small (5 cm × 5 cm) or medium (10 cm × 10 cm) nest chamber. Overall, the burned open rock barrens had 71–73% fewer sites with suitable soil depth and volume for a nest chamber of either size. Furthermore, burned plots had almost no lichen and moss cover but were dominated by bare soil, forbs, and jack pine (Pinus banksiana) seedlings. Although the loss of tree cover in previously forested areas may increase nest site availability for freshwater turtles in newly open areas, we suggest that organic soil combustion and soil erosion may require restoration activities in the post-fire landscape to support successful nesting of at-risk turtles. © 2020 The Wildlife Society.     

Possible Generational Effects of Habitat Degradation on Alligator Reproduction

ABSTRACT Population decline of the American alligator (Alligator mississippiensis) was observed in Lake Apopka in central Florida, USA, in the early 1980s. This decline was thought to result from adult mortality and nest failure caused by anthropogenic increases in sediment loads, nutrients, and contaminants. Reproductive impairment also was reported. Extensive restoration of marshes associated with Lake Apopka has been conducted, as well as some limited restoration measures on the lake. Monitoring by the Florida Fish and Wildlife Conservation Commission (FFWCC) has indicated that the adult alligator population began increasing in the early 1990s. We expected that the previously reported high proportion of complete nest failure (θ₀) during the 1980s may have decreased. We collected clutches from alligator nests in Lake Apopka from 1983 to 2003 and from 5 reference areas from 1988 to 1991, and we artificially incubated them. We used a Bayesian framework with Gibbs sampler of Markov chain Monte Carlo simulation to analyze θ₀. Estimated θ₀ was consistently higher in Lake Apopka compared with reference areas, and the difference in θ₀ ranged from 0.19 to 0.56. We conducted change point analysis to identify and test the significance of the change point in θ₀ in Lake Apopka between 1983 and 2003, indicating the point of reproductive recovery. The estimated Bayes factor strongly supported the single change point hypothesis against the no change point hypothesis. The major downward shift in θ₀ probably occurred in the mid-1990s, approximately a generation after the major population decline in the 1980s. Furthermore, estimated θ₀ values after the change point (0.21) were comparable with those of reference areas (0.07–0.31). These results combined with the monitoring by FFWCC seem to suggest that anthropogenic habitat degradation caused reproductive impairment of adult females and decreases in θ₀ occurred with the sexual maturity of a new generation of breeding females. Long-term monitoring is essential to understand population changes due to habitat restoration. Such information can be used as an input in planning and evaluating restoration activities.     

Effects of Habitat on Mallard Duckling Survival in the Great Lakes Region

Abstract: Habitat provides food and shelter resources for prefledgling waterfowl and thus plays a critical role in their growth, development, and survival. However, few studies have examined whether and how particular elements of habitat affect duckling survival. We investigated relationships of duckling survival rates with distance of overland travel, wetland vegetation composition, water permanency, and surrounding upland vegetation for 116 mallard (Anas platyrhynchos) broods in the Great Lakes region from 2001 to 2003. We found that the probability, on hatch day, that a mallard duckling will survive to 55 days was positively related to the proportion of wetland area that was vegetated and negatively related to the proportion of forest cover within 500 m of duckling locations. We found little support for relationships between duckling survival rates and the proportions of grasslands or seasonal wetlands or to distances traveled overland by broods. Our results suggest that conservation groups and wildlife managers in the Great Lakes region can improve mallard duckling survival rates by managing for, creating, and protecting vegetated wetlands and focusing efforts within lightly-forested areas.     

Behavioural and Genetic Data Suggest that Bechstein's Bats Predominantly Mate Outside the Breeding Habitat

Investigating mating systems of species with a cryptic lifestyle often requires a combination of behavioural and genetic data. We used such a combined approach to investigate the mating system of the communal breeding Bechstein's bat (Myotis bechsteinii). Although females of this species are philopatric, gene flow among colonies is high. Gene flow occurs if dispersing males mate within the colony to which they moved. Males could gain local matings by defending resources or females in their breeding habitat. Alternatively, mating may take place at swarming sites, apart from the breeding habitat of the females, where males and females of several colonies meet. Whether or not males defend resources or females in the breeding habitat is of importance for understanding the mating system. Detailed observations of individual foraging and roosting behaviour over 4 yr suggest that males do not defend resources or females to gain matings. Moreover, paternity assignment based on microsatellite data of four complete juvenile cohorts showed that local males fathered less than 25% of the juveniles born in the colony where they settled. Even more striking, none of the males that had immigrated into our study area reproduced with the local females.     

四川麻咪泽自然保护区四川山鹧鸪繁殖期对栖息地的利用

四川山鹧鸪Arborophila rufipectus属鸡形目雉科山鹧鸪属,是我国特产珍稀鸟类,国家Ⅰ级重点保护动物,世界自然保护联盟濒危物种。2014年4—5月,在四川麻咪泽自然保护区对四川山鹧鸪及其栖息地进行了野外调查。结果表明,四川山鹧鸪分布在海拔1700~2550 m,主要分布在2100~2300 m;其栖息生境主要为天然阔叶林,尤喜原始林;利用的坡度集中在20°~40°;偏好乔木数量多、高大和郁闭度大的森林生境;其中乔木均高是影响四川山鹧鸪栖息地利用的主要因子。保护四川山鹧鸪偏好的天然阔叶林,减少栖息地的人类干扰,是保护四川山鹧鸪这一濒危物种的首要措施。     

Effects of Tidal and Diel Cycles on Dugong Habitat Use

ABSTRACT Quantifying the factors influencing behaviors of aquatic mammalian grazers may enhance the generic understanding of grazer ecology. We investigated diel and tidal patterns in movements of the dugong (Dugong dugon) by Global Positioning System—tracking 12 animals in 5 inshore—intertidal and 3 offshore—subtidal habitats along the coast of Queensland, Australia. We examined effects of tide height and time of day on the dugong's distance from 1) the nearest coast, 2) water >3 m deep, 3) actual water depth (bathymetry + tide ht) experienced, and 4) distribution of the directions of movements. Both tidal and diel cycles influenced dugong movement. Tracked dugongs tended to be closer to shore at high tide than at low tide and closer to shore at night than during the day. Onshore movement was more prevalent on incoming tides and in the afternoon and evening. Offshore movement was more prevalent on outgoing tides and from midnight through the morning until midday. Tidal and diel variation in water depths used by the inshore—intertidal dugongs was small, but probably underestimated, hidden by a sampling bias in the telemetry equipment. Onshore movement at high tide allowed dugongs to exploit intertidal seagrass beds. Dugongs are closer to shore in afternoons and evenings than in mornings. This behavior may be related to the avoidance of predators or watercraft. Our findings can be used to predict spatial patterns of dugongs within areas of conservation management significance and to assess, avoid, and mitigate adverse effects of anthropogenic disturbance.     

Fire Effects on Cover and Dietary Resources of Sage-Grouse Habitat

Abstract: We evaluated 6 years of vegetation response following prescribed fire in Wyoming big sagebrush (Artemisia tridentata spp. wyomingensis) steppe on vegetation cover, productivity, and nutritional quality of forbs preferred by greater sage-grouse (Centrocercus urophasianus), and abundance of common arthropod orders. Habitat cover (shrubs and tall herbaceous cover [>18 cm ht]) was about 50% lower after burning compared to unburned controls because of the loss of sagebrush. Perennial grasses and an invasive annual forb, pale alyssum (Alyssum alyssoides), increased in cover or yield after fire. There were no increases in yield or nutritional quality of forb species important in diets of sage-grouse. Abundance of ants (Hymenoptera), a significant component in the diet of young sage-grouse, decreased after fire. These results suggest that prescribed fire will not improve habitat characteristics for sage-grouse in Wyoming big sagebrush steppe where the community consists of shrubs, native grasses, and native forbs.     

Effects of Habitat on Competition Between Kit Foxes and Coyotes

Abstract: San Joaquin kit foxes (Vulpes macrotis mutica) are an endangered species with a narrow geographic range whose natural populations are limited by predation by coyotes (Canis latrans). In the warm, arid grassland and shrubland habitats where kit foxes occur, coyotes are more cover dependent than kit foxes, creating the possibility of habitat segregation. Effects of habitat variation on coyote and kit fox competition are unknown. We assessed exploitation and interference competition between coyotes and kit foxes in grassland and shrubland habitats to determine if such competition varies among habitats. With respect to exploitation competition, we evaluated habitat and spatial partitioning, diet, prey abundance, and survival for kit foxes and coyotes at the Lokern Natural Area in central California, USA, from January 2003 through June 2004. Kit foxes partitioned habitat, space, and diet with coyotes. Coyotes primarily used shrubland habitats whereas kit foxes selectively used burned grasslands. Kit foxes and coyotes had high dietary overlap with regards to items used, but proportional use of items differed between the 2 species. Kit foxes selected for Heermann's kangaroo rats (Dipodomys heermanni), which were closely tied to shrub habitats. With respect to interference competition, predation was the primary source of mortality for kit foxes, and survival of individual kit foxes was inversely related to proportion of shrub habitat within their home ranges. Our results suggest that a heterogeneous landscape may benefit kit foxes by providing habitat patches where predation risk may be lower.     

Riparian Conservation Facilitated Expansion of Gray Hawks

Desert riparian ecosystems are among the most threatened biodiversity hotspots in the United States, and efforts to conserve them have been increasing. In 2010–2011 and 2014–2016, we examined shifts in the distribution, habitat characteristics, diet, nest success, and productivity of the gray hawk (Buteo plagiatus), 25 years after a Riparian National Conservation Area was established along the San Pedro River in Arizona, USA, to determine how the removal of grazing and agriculture may have affected the ecosystem. The gray hawk population increased and expanded from mesquite (Prosopis spp.)-dominated areas that they historically occupied into areas that were dominated by grassland. In contrast with the 1990s, percent of mesquite cover in pairs' territories did not correlate with their productivity. Gray hawk diets also included more mammals in our study period, particularly in territories with more grassland. We propose that conservation measures created habitat for gray hawks in areas that were previously unsuitable by allowing grasslands to regenerate and become habitat for their prey, and that management strategies in the San Pedro Riparian National Conservation Area could serve as a model for conservation of other desert riparian ecosystems. © 2020 The Wildlife Society.     

The Effects of Landscape Variables on the Species-Area Relationship during Late-Stage Habitat Fragmentation

Few studies have focused explicitly on the later stages of the fragmentation process, or "late-stage fragmentation", during which habitat area and patch number decrease simultaneously. This lack of attention is despite the fact that many of the anthropogenically fragmented habitats around the world are, or soon will be, in late-stage fragmentation. Understanding the ecological processes and patterns that occur in late-stage fragmentation is critical to protect the species richness in these fragments. We investigated plant species composition on 152 islands in the Thousand Island Lake, China. A random sampling method was used to create simulated fragmented landscapes with different total habitat areas and numbers of patches mimicking the process of late-stage fragmentation. The response of the landscape-scale species-area relationship (LSAR) to fragmentation per se was investigated, and the contribution of inter-specific differences in the responses to late-stage fragmentation was tested. We found that the loss of species at small areas was compensated for by the effects of fragmentation per se, i.e., there were weak area effects on species richness in landscapes due to many patches with irregular shapes and high variation in size. The study also illustrated the importance of inter-specific differences for responses to fragmentation in that the LSARs of rare and common species were differently influenced by the effects of fragmentation per se. In conclusion, our analyses at the landscape scale demonstrate the significant influences of fragmentation per se on area effects and the importance of inter-specific differences for responses to fragmentation in late-stage fragmentation. These findings add to our understanding of the effects of habitat fragmentation on species diversity.