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Stephen M. Mullin Mark A. Colwell Sean E. Mcallister Stephen J. Dinsmore 《The Journal of wildlife management》2010,74(8):1792-1798
ABSTRACT An accurate understanding of factors influencing survival and how they affect population growth are required to determine the best conservation strategies for small populations, especially near the limit of a species' range. We estimated adult and juvenile survival for a small population of the threatened western snowy plover (Charadrius alexandrinus nivosus) in coastal northern California over 7 years (2001–2007). We also evaluated population structure and growth to determine the relative importance of immigration and local recruitment. Apparent survival for adult males (φ = 0.61 ± 0.08) was greater than that of adult females (φ = 0.50 ± 0.11), and survival of adults was greater than for juveniles (φ = 0.40 ± 0.06). An algebraic assessment of population growth (Λ) revealed that fecundity and survival were insufficient to maintain the population (Λ = 0.66–0.77), whereas estimates based on consecutive annual counts (Λ = 0.96 ± 0.26) and a Pradel model (Λ = 0.92 ± 0.11) suggested the population was more stable. These results, combined with annual variation in the number of newly marked plovers, indicate that the local population was maintained by immigration and can be classified as a sink. Management actions aimed at increasing fecundity, including predator control and greater restrictions on human activity, may be necessary to maintain this population; actions aimed at increasing adult survival are more challenging. 相似文献
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Kristen S. Ellis Randy T. Larsen Robert N. Knight John F. Cavitt 《Journal of Field Ornithology》2014,85(4):355-363
Occupancy modeling can be used to identify habitat characteristics associated with species occurrence. Additionally, occupancy sampling can provide measures of detection probability, increasing confidence in monitoring efforts. Little is known about the distribution and habitat preferences of a small population of Snowy Plovers (Charadrius nivosus) in western Utah. We conducted a study to estimate occupancy and detection probability of Snowy Plovers in western Utah during 2011 and 2012. We made repeated visits to randomly selected survey plots during the breeding period, sampling 84 64‐ha plots in 2011 and 100 64‐ha plots in 2012 and recording the number of adults and habitat characteristics in each plot. We then modeled the relationship between detection, occupancy, and covariates that included distance to water, distance to roads, land cover types, and characteristics of the vegetation. We also included covariates for observer, Julian date, temperature, cloud cover, and wind speed when modeling detection probability. Detection probability was high (0.74, 95% CI = 0.57–0.86) and positively influenced by temperature. Occupancy of 64‐ha plots was low (0.27, 95% CI = 0.18–0.39) and did not vary by year. Occupancy of Snowy Plovers was negatively associated with distance to water (β = ?0.62 ± 0.31, 95% CI = ?1.23 to ?0.01) and percent shrub cover (β = ?0.28 ± 0.02, 95% CI = ?0.58 to ?0.01). Land cover types also influenced plot occupancy. Management actions that conserve shallow water and adjacent habitats or minimize disturbance in these areas are likely to have conservation benefits for Snowy Plovers where water is scarce. Because our detection probabilities were high, investigators involved in future monitoring efforts can achieve reasonable precision with limited revisits to sample plots. 相似文献
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Sarah T. Saalfeld Warren C. Conway David A. Haukos William P. Johnson 《The Journal of wildlife management》2012,76(8):1703-1711
Snowy plover (Charadrius nivosus) populations have declined throughout their range, in part because of habitat degradation and poor nest success, making information regarding regionally specific nest site selection and spatial patterns important when considering habitat conservation and management guidelines. We determined nest site selection characteristics (n = 180) and examined spatial patterns (n = 215) of snowy plover nests in saline lakes in the Southern High Plains (SHP) of Texas. At 104 nests, we examined the influence of substrate type on nest temperatures and heat mitigation. Snowy plover nests were more likely to be found near an object, on pebble substrate, and with fewer plants than random sites. High use areas were generally located in areas with pebble substrate and on human-made or natural islands, berms, and peninsulas. Overall, nests placed on pebble substrate had lower temperatures during the day than nests placed on sand substrates. Nest placement on pebble substrate may be valuable to nesting snowy plovers, providing thermal advantages to incubating adults and depressing potentially high nest predation rates. Management guidelines for this region should emphasize the importance of addressing key elements of snowy plover nesting habitat including the presence of pebble substrate and reducing vegetation encroachment. © 2012 The Wildlife Society. 相似文献
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Eleanor P. Gaines Stephen J. Dinsmore Michael T. Murphy 《Journal of Field Ornithology》2020,91(2):130-141
Understanding the factors contributing to variation in demographic parameters and their influences on population growth is fundamental to effective conservation of small populations, but this information is often not available. Among shorebirds, population growth is generally most sensitive to changes in adult survival so understanding the factors affecting this vital rate is important. We used a long-term mark–resight dataset and Program MARK to examine the effect of management actions, initiated to improve nesting productivity, on adult survival in a threatened population of Snowy Plovers (Charadrius nivosus) in Oregon, USA. Apparent adult survival averaged 0.71 ± 0.01 (SE), but increased from 1990 to 2014. This increase coincided with a decline in use of protective nest exclosures, but initiation of lethal nest predator management. The unexpected apparent benefit to adult survival of removal of nest predators and the negative effect of protective nest exclosures highlight the importance of understanding how management practices at one life cycle stage may have unintended consequences at other life stages. Our 25-year analysis adds to our knowledge of an intensively managed, threatened species at the northern limit of its range, but, more importantly, knowledge of the negative effect of exclosure use and the positive effect of predator management on adult survival can help inform conservation of less well-studied species with similar life histories. 相似文献
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Abstract: Recent technological innovations allow remote monitoring of avian nest temperature that minimizes disturbance and expense without altering clutch sizes. However, the efficacy of such techniques has not been determined for ground-nesting birds. We compared the efficacy of 2 techniques, iButton® data loggers (Maxim/Dallas Semiconductor Corp., Sunnyvale, CA) and custom-built thermocouples, to measure nest temperature of piping plovers (Charadrius melodus) relative to nest attendance at Cape Cod National Seashore, Massachusetts, USA. Neither technique affected hatching success (U = 389.5, P = 0.874) or rates of predation of nests containing devices (P = 0.894). We estimated nest attendance successfully with thermocouples in nests as long as air and surface temperatures were <29° Cand 43° C, respectively. Although iButtons could not be used to determine duration of on-bouts and off-bouts of incubating piping plovers, they were effective at determining when nests were abandoned or predated. We recommend the use of thermocouples for studying nest attendance of ground-nesting birds, in general, and of threatened and endangered species, in particular, where disturbance should be minimized and altering clutch sizes is not feasible. 相似文献
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LINH P. NGUYEN ERICA NOL KENNETH F. ABRAHAM 《The Journal of wildlife management》2007,71(6):2084-2089
Abstract: The focus of digital photography has moved from documentation to quantitative analysis. To illustrate the potential application of this diagnostic tool to quantify color and shape, we photographed both artificial and natural semipalmated plover (Charadrius semipalmatus) nests to determine what benefits, if any, were derived from egg crypsis (i.e., eggshell color and egg marking shape). This simple and cost-effective method provides precise and repeatable quantification of color and shape that discriminated subtle differences in egg crypsis of artificial and natural nests that were not visible to us. The advantages of digital photography and image-editing software outweigh any shortcomings, as long as standard protocols are followed for capturing and analyzing images. Used with due care, digital photography is useful in studies that need to quickly assign biological traits, such as age and sex, to individuals, and to document temporal change that may occur as a response to management or disturbance. 相似文献
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The common loon (Gavia immer) breeds during the summer on northern lakes and water bodies that are also often desirable areas for aquatic recreation and human habitation. In northern New England, we assessed how the spatial nature of disturbance affects common loon nest site selection and territory success. We found through classification and regression analysis that distance to and density of disturbance factors can be used to classify observed nest site locations versus random points, suggesting that these factors affect loon nest site selection (model 1: Correct classification = 75%, null = 50%, K = 0.507, P < 0.001; model 2: Correct classification = 78%, null = 50%, K = 0.551, P < 0.001). However, in an exploratory analysis, we were unable to show a relation between spatial disturbance variables and breeding success (P = 0.595, R2 = 0.436), possibly because breeding success was so low during the breeding seasons of 2007–2008. We suggest that by selecting nest site locations that avoid disturbance factors, loons thereby limit the effect that disturbance will have on their breeding success. Still, disturbance may force loons to use sub-optimal nesting habitat, limiting the available number of territories, and overall productivity. We advise that management efforts focus on limiting disturbance factors to allow breeding pairs access to the best nesting territories, relieving disturbance pressures that may force sub-optimal nest placement. © 2011 The Wildlife Society 相似文献
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ABSTRACT. Double-observer methodology requires independent collection of data to accurately estimate population parameters. Use of visual nest markers to facilitate matching, relocating, and monitoring nests as part of a double-observer study violates this assumption, but few reliable alternatives exist, especially when working with cryptic nests and high nest densities in homogeneous habitat. We used passive integrated transponder (PIT) tags to nonvisually mark the nests of ground-nesting birds at the Yukon Delta National Wildlife Refuge in western Alaska in a double-observer study of nest density. We marked 70 nests with PIT tags and naïve observers subsequently detected tags at 44 of 50 re-scanned nests (88% correct identification). Failed detections were likely due to either suboptimal tag orientation or tags falling through nest material, and such failures may be an inherent, but uncommon, feature of this nest-marking technique. PIT tags facilitated nest monitoring among independent observers, uniquely and reliably marked nests, provided a minimum of cues to potential nest predators, and allowed us to estimate densities in a double-observer framework while not violating assumptions. These tags should be useful in other studies of nesting birds where nonvisual, reliable nest markers are needed, and they provide a new tool for double-observer studies. 相似文献
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Conservation of rare populations requires managing habitat throughout the year, especially during winter when northern populations may be limited by food and predation. Consequently, we examined distribution of nonbreeding western snowy plovers (Charadrius alexandrinus), including individually marked birds that were year-round residents and others that were migrants, in coastal northern California. Over 2 years, banded plovers exhibited high site faithfulness, occupying small linear stretches of beach (752 ± 626 m). Sites occupied by plovers had more brown algae (e.g., Macrocystis, Nereocystis, Postelsia, and Fucus) and associated invertebrates (e.g., amphipods, and flies), were wider, and had less vegetation than unoccupied sites. Our findings suggest that wintering plovers select habitats with more food and where they could more easily detect predators. Maintaining habitat with attributes that support abundant food (i.e., brown algae) and reduce predation risk (i.e., wide beaches, limited obstructive cover) may be important to individual survival and maintaining the Pacific Coast population of snowy plovers. Protecting occupied sites from human disturbance, which adversely alters nonbreeding habitat (i.e., beach grooming) and directly causes mortality, may be essential for conserving the Pacific coast population of the snowy plover, and it may benefit other shorebirds. © 2011 The Wildlife Society. 相似文献
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Daniel H. Catlin James D. Fraser Joy H. Felio Jonathan B. Cohen 《The Journal of wildlife management》2011,75(2):305-310
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. 相似文献
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Climate change can affect biotic interactions, and the impacts of climate on biotic interactions may vary across climate gradients. Climate affects biotic interactions through multiple drivers, although few studies have investigated multiple climate drivers in experiments. We examined the effects of experimental watering, warming, and predator access on leaf water content and herbivory rates of woolly bear caterpillars (Arctia virginalis) on a native perennial plant, pacific silverweed (Argentina anserina ssp. pacifica), at two sites across a gradient of precipitation in coastal California. Based on theory, we predicted that watering should increase herbivory at the drier end of the gradient, predation should decrease herbivory, and watering and warming should have positive interacting effects on herbivory. Consistent with our predictions, we found that watering only increased herbivory under drier conditions. However, watering increased leaf water content at both wetter and drier sites. Warming increased herbivory irrespective of local climate and did not interact with watering. Predation did not affect herbivory rates. Given predictions that the study locales will become warmer and drier with climate change, our results suggest that the effects of future warming and drying on herbivory may counteract each other in drier regions of the range of Argentina anserina. Our findings suggest a useful role for range‐limit theory and the stress‐gradient hypothesis in predicting climate change effects on herbivory across stress gradients. Specifically, if climate change decreases stress, herbivory may increase, and vice versa for increasing stress. In addition, our work supports previous suggestions that multiple climate drivers are likely to have dampening effects on biotic interactions due to effects in different directions, though this is context‐dependent. 相似文献
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Large-scale industrial activities can have negative effects on wildlife populations. Some of these effects, however, could be reduced with effective planning prior to development. The Coastal Plain of the Arctic National Wildlife Refuge, in northeastern Alaska, USA, is an important maternal denning area for polar bears (Ursus maritimus). Recent legislation has opened the area for potential oil and gas development. As a result, there is interest in conducting winter seismic surveys across the area that could disturb denning female polar bears and lead to decreased cub survival. We sought to demonstrate how different seismic survey designs, with and without aerial den detection surveys, could affect the level of potential effect on denning polar bears during spring (Feb–Apr). We developed 5 hypothetical seismic survey designs for a portion of the Coastal Plain ranging from no spatial or temporal restrictions on activities to explicit consideration of when and where operations can occur. We evaluated how many dens might be disturbed by seismic surveys and the average distance activity came within simulated polar bear dens. Survey design had a large effect on the estimated number of dens that could be disturbed; the scenario with the highest spatial and temporal specificity reduced the number of dens disturbed by >90% compared to the scenario with no restrictions on when and where activity could occur. The use of an aerial den detection survey prior to seismic activity further reduced the number of dens disturbed by 68% across all scenarios. The scenario with the highest spatial and temporal specificity always had the lowest level of disturbance for all scenarios with and without the aerial survey included. Our study suggests that large reductions in the probability of disturbance can occur through careful planning on the timing and distribution of proposed activities even when surveys are planned in areas with a high density of polar bear dens. Published 2019. This article is a U.S. Government work and is in the public domain in the USA. The Journal of Wildlife Management published by Wiley Periodicals, Inc. on behalf of The Wildlife Society. 相似文献
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William E. Grant R. Douglas Slack Hsiao‐Hsuan Wang Masami Fujiwara 《Journal of Field Ornithology》2012,83(1):1-10
ABSTRACT Previous studies of Whooping Crane demography used estimates of fecundity rates based on females in captivity, and breeding success was estimated based on either the number of unbanded pairs nesting or the number arriving in wintering areas with chicks. We analyzed demographic data from 12 cohorts of banded Whooping Cranes (Grus americana) from the Aransas National Wildlife Refuge/Wood Buffalo National Park (ANWR/WBNP) population that had not been compiled previously into a single data base and had not been included in previous population analyses. We estimated age‐specific survival and natality, parameterized an age‐structured density‐dependent model, and projected population sizes assuming two different estimates of wintering ground carrying capacity. Sixty‐seven of 132 birds banded between 1977 and 1988 formed nesting pairs, females first produced hatchlings when 3 to 7 yrs old, and the annual proportion of mature females that reproduced successfully ranged from 0.566 to 0.606. Population projections indicate that the down‐listing criterion of reaching a population size of 1000 individuals might be attained considerably later than the target year (2035) indicated in the Whooping Crane recovery plan. Even assuming that all suitable habitat within a ～100‐km radius of their current winter range could be occupied, projections suggest that population size may be ～700 in 2035, and might not reach 1000 individuals until the mid‐2060s. Based on their territorial behavior on the wintering grounds, long generation time and faithfulness to their migratory route, we suspect that the population growth rate may decrease markedly in the near future and the ANWR/WBNP population may remain below the target down‐listing size of 1000 individuals. 相似文献
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Eben H. Paxton Stephanie G. Yelenik Tracy E. Borneman Eli T. Rose Richard J. Camp Steve J. Kendall 《Restoration Ecology》2018,26(1):165-173
Deforestation of tropical forests has led to widespread loss and extirpation of forest bird species around the world, including the Hawaiian Islands which have experienced a dramatic loss of forests over the last 200–800 years. Given the important role birds play in forest ecosystem functions via seed dispersal and pollination, a bird community's response to forest restoration is an important measure of the success of such conservation actions. We evaluated the bird response to reforestation at an important bird sanctuary, Hakalau Forest National Wildlife Refuge, Hawai′i Island, using 26 years of bird count data. We show that most species from within the diverse avian community increased significantly, but species colonized the restoration forest at different rates. Distance from intact forest and time since restoration were both important predictors of colonization rate, interacting such that for most species it took more time to colonize areas farther from the intact forest. In addition, both forest cover and understory diversity helped to explain bird densities, but the effect varied among species, suggesting that different habitat requirements may help drive variation in colonization rates. This article provides the first detailed evaluation of how a diverse community of birds has responded to one of the largest, ongoing reforestation projects in Hawai′i. 相似文献
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The process of reproduction is a sensitive period for bird offspring, since they are exposed to environmental conditions for several weeks. Within the long reproductive period, adult birds do not only have to maintain their own body condition, they also have to ensure nutritional needs of their nestlings. In the worst case, if weather conditions are very harsh, breeding is not successful and fails. This suggests that weather conditions might be an important driver of breeding success. Here, we studied the effect of weather conditions (temperature and precipitation) on the survival of 350 nests of great tits Parus major during nestling period in six years (2010–2015). We used traditional generalized linear mixed model (binomial response variable) and a dedicated survival-analysis program (MARK) to analyze the data. The two approaches allowed us to highlight and compare the effect of weather conditions on a fine (nestling survival) and coarse (nest fate) scale. Both methods showed that precipitation explained most of the variation in individual nestling and overall nest survival during the 15-day nestling period. Heavy and persistent rainfall did not only lead to brood reduction, it ultimately also led to losses of the entire brood. Likely causes were the negative effects of precipitation on thermoregulation, food availability and predation risk. However, while reduced food availability most likely might have led to brood reduction through selective individual nestling death, predation might have resulted in total nest failures. 相似文献