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At least 721 records · Page 40Linked to original sources

USGS2007

Hydrologic connectivity and the contribution of stream headwaters to ecological integrity at regional scales

Cumulatively, headwater streams contribute to maintaining hydrologic connectivity and ecosystem integrity at regional scales. Hydrologic connectivity is the water-mediated transport of matter, energy and organisms within or between elements of the hydrologic cycle. Headwater streams compose over two-thirds of total stream length in a typical river drainage and directly connect the upland and riparian landscape to the rest of the stream ecosystem. Altering headwater streams, e.g., by channelization, diversion through pipes, impoundment and burial, modifies fluxes between uplands and downstream river segments and eliminates distinctive habitats. The large-scale ecological effects of altering headwaters are amplified by land uses that alter runoff and nutrient loads to streams, and by widespread dam construction on larger rivers (which frequently leaves free-flowing upstream portions of river systems essential to sustaining aquatic biodiversity). We discuss three examples of large-scale consequences of cumulative headwater alteration. Downstream eutrophication and coastal hypoxia result, in part, from agricultural practices that alter headwaters and wetlands while increasing nutrient runoff. Extensive headwater alteration is also expected to lower secondary productivity of river systems by reducing stream-system length and trophic subsidies to downstream river segments, affecting aquatic communities and terrestrial wildlife that utilize aquatic resources. Reduced viability of freshwater biota may occur with cumulative headwater alteration, including for species that occupy a range of stream sizes but for which headwater streams diversify the network of interconnected populations or enhance survival for particular life stages. Developing a more predictive understanding of ecological patterns that may emerge on regional scales as a result of headwater alterations will require studies focused on components and pathways that connect headwaters to river, coastal and terrestrial ecosystems. Linkages between headwaters and downstream ecosystems cannot be discounted when addressing large-scale issues such as hypoxia in the Gulf of Mexico and global losses of biodiversity.

Journal of the American Water Resources Associatio↗

USGS1977

Band recovery distribution of eastern Maine woodcock

A total of 9,643 American woodcock (Philohela minor) was banded in eastern Maine during the summers of 1962-74. The fall migration of these woodcock, based on 620 recoveries, occurred along a broad front between the Appalachian Mountains and Atlantic Ocean. Most birds wintered in a region extending from southern Virginia to northern Florida; a few woodcock moved as far west as Louisiana and eastern Texas. The band-recovery distribution of Maine woodcock, and band-recovery records from birds wintering in Louisiana published by other investigators, support the idea of Atlantic and Central flyways. However, recoveries from woodcock banded in breeding localities other than eastern Maine must be studied to more precisely relate major breeding and wintering grounds

Wildlife Society Bulletin↗

USGS2000

Determining the size of American alligators using hind-foot track length

Size distribution information is useful for crocodilian management, but can be hard to obtain. Indirect and less costly demographic inferences made from track measurements may be valuable for management decisions. We related hind-foot lengths (HF) with total length (TL) to determine if we could indirectly assess alligator size using track length. Regression showed that HF was an excellent predictor (F1,246= 15722.9, R2=0.98, P<0.01) of TL and track length was an exceptional predictor of HF (F1,14=7520.3, R2= 1.00, P<0.01). The correlation between track length and HF length also was significant (N= 15, r=0.99, P <0.01). Thus, alligator size can be accurately estimated from measures of track length at sites where capture and direct measurement is impractical.

Proceedings of the Annual Conference of the Southe↗

USGS2005

Winter status of White-eyed Vireos in northeastern Louisiana

In December 2004, February 2005, and June 2005, we recaptured a White-eyed Vireo (Vireo griseus) that was banded on 19 May 2004 at the same location on the Tensas River National Wildlife Refuge, Madison Parish, LA. This is the first documented permanent resident White-eyed Vireo outside of resident populations known from Florida and southern Texas. This individual appears to be resident near the northern limit of the winter range for the species. Although White-eyed Vireos are uncommon in northeastern Louisiana during winter, we detected other White-eyed Vireos during line transect surveys and banding during winters 2003-2004 and 2004-2005. The lack of research and observation of winter birds in northern Louisiana and the secretive and inconspicuous behavior of White-eyed Vireos in winter may have led to an underestimation of abundance at the northern limits of their winter range.

North American Bird Bander↗

USGS2013

Influences of riparian vegetation on trout stream temperatures in central Wisconsin

Summer stream temperatures limit the distribution of Brook Trout Salvelinus fontinalis and are affected by riparian vegetation. We used riparian and instream habitat surveys along with stream temperature loggers placed throughout streams to determine the potential for riparian vegetation shading to increase the length of stream that is thermally suitable for Brook Trout. Twelve streams located throughout central Wisconsin were evaluated in the summers of 2007 and 2008. Across all streams, nonparametric ANCOVA modeling was used to identify spatial temperature patterns within a year for individual stream segments. Riparian tree-vegetated segments had a significantly lower mean change in stream temperature per kilometer of stream compared with grass-vegetated segments during the periods of maximum daily and weekly average temperatures, when we accounted for upstream temperature. Riparian grass-vegetated segments increased on average 1.19°C/km (SE, 0.44) during the maximum daily average temperature period and 0.93°C/km (SE, 0.39) during the maximum weekly average temperature period, whereas tree-vegetated segments decreased 0.48°C/km (SE, 0.39) and 0.30°C/km (SE, 0.25) during those respective time periods. Maximum weekly average temperatures were also modeled with different shading levels using a heat budget temperature model, U.S. Fish and Wildlife Service's Stream Segment Temperature Model. Across 11 study streams (one stream model could not be calibrated), modeled stream temperatures in equilibrium with their environmental conditions ranging from 23.2°C to 28.3°C at 0% shading could be reduced to 18.8–23.5°C with 75% shading. Modeled increases in shade up to 75% from the current average of 34% increased the length of surveyed stream thermally suitable to Brook Trout by 4.9 km on Sucker Creek. We conclude that riparian forests are important for maintaining thermal conditions suitable for Brook Trout in central Wisconsin streams and can be managed to increase the amount of stream habitat thermally suitable for Brook Trout.

Wisconsin↗

USGS2000

The northeastern states' waterfowl breeding population survey

Efforts to tailor waterfowl hunting regulations to conditions in the Atlantic Flyway have been hampered by lack of information on local breeding populations. The Atlantic Flyway Council's technical section voted at its 1987 winter meeting (Atlantic Flyway Council Technical Section, Toronto, Canada) to establish a regional waterfowl breeding survey. Consequently, an annual survey was started in 1989 and further refined in 1993 using results from 1989 to 1992. During 1993-1997, annual spring surveys of more than 1,450 randomly selected 1-km2 plots, stratified by physiographic strata, were conducted in the Atlantic Flyway from New Hampshire to Virginia to estimate breeding populations of mallards (Arias platyrhynchos), American black ducks (A. rubripes), wood ducks (Aix sponsa), and Canada geese (Branta canadensis). Ground crews systematically surveyed all potential waterfowl habitat for these species in each plot. The adjusted mean mallard pair estimate over the 5-year period was 375,962 (range 310,299-415,182, mean SE 25,761) for the region surveyed. The estimate for black duck pairs was 31,1 54 (range 27,164'37,521, mean SE 4,978), and for wood duck pairs it was 240,473 (range 218,959-281,916, mean SE 25,408). Total number of Canada geese increased from 526,663 in 1993 to 892,278 in 1997. Population estimates for other species had unacceptably large standard errors.

Wildlife Society Bulletin↗

USGS1995

Shorebirds: East of the 105th meridian

The North American group of shorebirds includes 48 kinds of sandpipers, plovers, and their allies, many of which live for most of the year in coastal marine habitats; other live principally in nonmarine habitats including grasslands, freshwater wetlands, and even second-growth woodlands. Most North American shorebirds are highly migratory, while others are weakly migratory, and even nonmigratory in some parts of their range. Here we discuss shorebirds east of the 105th meridian (roughly east of the Rocky Mountains). Historically, populations of many North American species were dramatically reduces by excessive gunning (Forbush 1912). Most populations recovered after the passage of the Migratory Bird Treaty Act of 1918, although some species never recovered and others have declined again. High proportions of entire populations of shorebirds migrate by visiting one or a small number of "staging sites", areas where the birds accumulate fat to provide fuel before continuing with their long-distance, nonstop flights to the next site (Morrison and Harrington 1979; Senner and Howe 1984; Harrington et al. 1991). Growing evidence (Schneider and Harrington 1981) indicates that staging areas are unusually productive sites with highly predictable but seasonally ephemeral "blooms" of invertebrates, which shorebirds use for fattening. In some cases, especially for "obligate" coastal species, specific sites are traditionally used; even other species sites may shift between years. Because pf this, conservationists believe some species are at risk through loss of strategic migration site (Myers et al. 1987). Other species are threatened by the less of breeding and wintering habitats (Page et al. 1991; Haig and Plissner 1993; B. Leachman and B. Osmundsom, U.S. Fish and Wildlife Service, unpublished data). The predicted consequences of global warming, such as sea-level change, will also strongly affect the intertidal marine habitats, which many species of shorebirds depend upon. Some of the strongest warming effects will be at high latitudes, including those where many shorebirds migrate to breed, as well as south temperate latitudes, where many of them winter.

Book chapter↗

USGS2015

Crocodylus acutus (American Crocodile). Long distance juvenile movement

Crocodylus acutus (American Crocodile) is the most widely distributed New World crocodilian species with its range extending from Peru in the south to the southern tip of peninsular Florida in the north. Crocodylus acutus occupies primarily coastal brackish water habitat, however it also occurs in freshwater to hypersaline habitats (Thorbjarnarson 2010. In Crocodiles. Status Survey and Conservation Action Plan. [Third Edition], American Crocodile Crocodylus acutus, pp. 46–53 S.C. Manolis and C. Stevenson. Crocodile Specialist Group, Darwin). There is limited literature on long distance movements of juvenile crocodilians worldwide and no literature on juvenile crocodiles in Florida. However, adult C. acutus in Florida have been documented to make seasonal movements of 5–15 km from preferred foraging habitat to nesting beaches (Mazzotti 1983. The Ecology of Crocodylus acutus in Florida. PhD Dissertation. The Pennsylvania State University, University Park, Pennsylvania. 161pp), and one adult was documented making a 35 km trip from her nest site to preferred foraging habitat (Cherkiss et. al. 2006. Herpetol. Rev. 38:72–73). Rodda (1984. Herpetologica 40:444–451) reported on juvenile C. acutus movement in Gatun Lake, Panama, and found that juveniles stayed within 1 km of their nest site for the first month. Movements of juvenile Crocodylus porosus (Saltwater Crocodile) in a river system in Northern Australia showed a maximum movement of 38.9 km from a known nest site, with the majority of the crocodiles staying within 15.6 km downstream to 6.8 km upstream (Webb and Messel 1978. Aust. Wildlife Res. 5:263–283). Juvenile movement of Crocodylus niloticus (Nile Crocodile) in Lake Ngezi, Zimbabwe showed crocodiles restricted their movements from 1.0 km up to 4.5 km through the wet and dry seasons (Hutton 1989. Am. Zool. 29:1033–1049). Long distance movements of alligators were recorded for sizes ranging from 28 cm to 361 cm in a coastal refuge in Louisiana, where the distance traveled ranged from 0.3 km to 90.2 km. The data showed that the smaller alligators moved greater distance than larger ones (Lance et al. 2011. Southeast Nat. 10:389–398). An ongoing 30 year mark and recapture study for Crocodylus acutus in Florida allowed us to look at long distance movement (>30 km) of juveniles (30km). Initial and most recent captures as a juvenile were used to analyze distances moved (Fig. 1). These distances were measured linearly between capture locations. Maximum linear distances of 76.3 km and 69.6 km were recorded for animals 4838 and 6662. All crocodiles moved from nesting habitat through potentially optimal nursery habitat prior to reaching their recapture locations. These juvenile long distance movements could be due to larger crocodiles facilitating their dispersal from the nest location (Lance et al. 2011. op. cit.). These data (Table 1.) support that there is exchange of individuals among the nesting colonies and our ongoing efforts to monitor this threatened species allow us to make observations of how juvenile crocodiles are moving throughout the landscape in an ecosystem currently undergoing restoration.

Herpetological Review↗

USGS2015

An empirical evaluation of landscape energetic models: Mallard and American black duck space use during the non-breeding period

Bird conservation Joint Ventures are collaborative partnerships between public agencies and private organizations that facilitate habitat management to support waterfowl and other bird populations. A subset of Joint Ventures has developed energetic carrying capacity models (ECCs) to translate regional waterfowl population goals into habitat objectives during the non-breeding period. Energetic carrying capacity models consider food biomass, metabolism, and available habitat to estimate waterfowl carrying capacity within an area. To evaluate Joint Venture ECCs in the context of waterfowl space use, we monitored 33 female mallards ( Anas platyrhynchos ) and 55 female American black ducks ( A. rubripes ) using global positioning system satellite telemetry in the central and eastern United States. To quantify space use, we measured first-passage time (FPT: time required for an individual to transit across a circle of a given radius) at biologically relevant spatial scales for mallards (3.46 km) and American black ducks (2.30 km) during the non-breeding period, which included autumn migration, winter, and spring migration. We developed a series of models to predict FPT using Joint Venture ECCs and compared them to a biological null model that quantified habitat composition and a statistical null model, which included intercept and random terms. Energetic carrying capacity models predicted mallard space use more efficiently during autumn and spring migrations, but the statistical null was the top model for winter. For American black ducks, ECCs did not improve predictions of space use; the biological null was top ranked for winter and the statistical null was top ranked for spring migration. Thus, ECCs provided limited insight into predicting waterfowl space use during the non-breeding season. Refined estimates of spatial and temporal variation in food abundance, habitat conditions, and anthropogenic disturbance will likely improve ECCs and benefit conservation planners in linking non-breeding waterfowl habitat objectives with distribution and population parameters. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Arkansas, Delaware, Louisiana, Michigan, New Jerse↗

USGS2010

Estimating migratory game-bird productivity by integrating age ratio and banding data

Context: Reproduction is a critical component of fitness, and understanding factors that influence temporal and spatial dynamics in reproductive output is important for effective management and conservation. Although several indices of reproductive output for wide-ranging species, such as migratory birds, exist, there has been no theoretical justification for their estimators or associated measures of variance. Aims: The aims of our research were to develop statistical justification for an estimator of reproduction and associated variances on the basis of an existing national wing-collection survey and banding data, and to demonstrate the applicability of this estimator to a migratory game bird. Methods: We used a Bayesian hierarchical modelling approach to integrate wing-collection data, which provides information on population age ratios, and band-recovery data, which provides information on recovery probabilities of various age classes, for American woodcock ( Scolopax minor ) to estimate productivity and associated measures of variance. We present two models of relative vulnerability between age classes: one model assumed that adult recovery probabilities were higher, but that annual fluctuations were synchronous between the two age classes (i.e. an additive effect of age and year). The second model assumed that adults, on average, had higher recovery probabilities than did juveniles and that annual fluctuations were asynchronous through time (i.e. an interaction between age and year). Key results: Fitting our models within a hierarchical Bayesian framework efficiently incorporates the two data types into a single estimator and derives appropriate variances for the productivity estimator. Further, use of Bayesian methods enabled us to derive credible intervals that avoid the reliance on asymptotic assumptions. When applied to American woodcock data, the additive model resulted in biologically realistic and more precise age-ratio estimates each year and is adequate when the relative vulnerability to sampling only slightly varies or does not vary among components of a population (e.g. age, sex class) among years. Therefore, we recommend using woodcock indices from our analysis based on this model. Conclusions: We provide a flexible modelling framework for estimating productivity and associated variances that can incorporate ecological covariates to explore various factors that could drive annual dynamics in productivity. Applying our model to the American woodcock data indicated that assumptions about the variability in relative recovery probabilities could greatly influence the precision of our productivity estimator. Therefore, researchers should carefully consider the assumption of temporally variable relative recovery probabilities (i.e. ratio of juvenile to adults' recovery probability) for different age classes when applying this estimator. Implications: Several national and international management strategies for migratory game birds in North America rely on measures of productivity from harvest survey parts collections, without a justification of the estimator or providing estimates of precision. We derive an estimator of productivity with realistic measures of uncertainty that can be directly incorporated into management plans or ecological studies across large spatial scales.

Wildlife Research↗

USGS1991

Movements and survival of American black duck and mallard broods on Chesapeake Bay

We attached radio transmitters to day-old American black duck (Anas rubripes) and mallard (A. platyrhynchos) ducklings and monitored duckling habitat use, brood movements, and survival rates for 30 days. Ducklings moved an average of 2.3 km within the first 24 hours and another 1.5 km thereafter. After the initial move, broods usually moved once more. No differences in initial movement distance, subsequent movement distance, or total number of movements were found between black duck and mallard broods. There was some evidence that broods in more human developed areas moved more than broods in less human-developed areas. Black duck duckling survival rates were greater than mallard survival rates in 1 of 2 study years.

Chesapeake Bay↗

USGS2015

Avoidance of unconventional oil wells and roads exacerbates habitat loss for grassland birds in the North American great plains

Oil development in the Bakken shale region has increased rapidly as a result of new technologies and strong demand for fossil fuel. This region also supports a particularly high density and diversity of grassland bird species, which are declining across North America. We examined grassland bird response to unconventional oil extraction sites (i.e. developed with hydraulic fracturing and horizontal drilling techniques) and associated roads in North Dakota. Our goal was to quantify the amount of habitat that was indirectly degraded by oil development, as evidenced by patterns of avoidance by birds. Grassland birds avoided areas within 150 m of roads (95% CI: 87–214 m), 267 m of single-bore well pads (95% CI: 157–378 m), and 150 m of multi-bore well pads (95% CI: 67–233 m). Individual species demonstrated variable tolerance of well pads. Clay-colored sparrows ( Spizella pallida ) were tolerant of oil-related infrastructure, whereas Sprague's pipit ( Anthus spragueii ) avoided areas within 350 m (95% CI: 215–485 m) of single-bore well pads. Given these density patterns around oil wells, the potential footprint of any individual oil well, and oil development across the region, is greatly multiplied for sensitive species. Efforts to reduce new road construction, concentrate wells along developed corridors, combine numerous wells on multi-bore pads rather than build many single-bore wells, and to place well pads near existing roads will serve to minimize loss of suitable habitat for birds. Quantifying environmental degradation caused by oil development is a critical step in understanding how to better mitigate harm to wildlife populations.

Biological Conservation↗

USGS1987

Breeding bird response to cattle grazing of a cottonwood bottomland

We studied avian habitat relationships and the impact of grazing on breeding densities of selected migratory birds in a plains cottonwood ( Populus sargentii ) bottomland in northeastern Colorado. Five 16-ha plots served as controls and 5 were fenced and fall-grazed October-November 1982-84 following a season of pre-treatment study in the spring of 1982. We focused our analysis on bird species directly dependent on the grass-herb-shrub layer of vegetation for foraging, nesting, or both. The guild included house wren ( Troglodytes aedon ), brown thrasher ( Toxostoma rufum ), American robin ( Turdus migratorius ), common yellowthroat ( Geothlypis trichas ), yellow-breasted chat ( Icteria virens ), and rufous-sided towhee ( Pipilo erythropthalmus ). Moderate, late-fall grazing had no detectable impact on calculated densities of any of the 6 species, implying that proper seasonal grazing of a cottonwood floodplain is, at least initially (3 years), compatible with migratory bird use of a site for breeding. Habitat associations suggested that common yellowthroats and yellow-breasted chats were most unique and most likely to respond negatively to higher levels of grazing. We suggest that these latter 2 species are appropriate ecological indicators of the quality of ground-shrub vegetation as breeding bird habitats in lowland floodplains of the Great Plains.

Journal of Wildlife Management↗

USGS2017

Landscape capability predicts upland game bird abundance and occurrence

Landscape capability (LC) models are a spatial tool with potential applications in conservation planning. We used survey data to validate LC models as predictors of occurrence and abundance at broad and fine scales for American woodcock ( Scolopax minor ) and ruffed grouse ( Bonasa umbellus ). Landscape capability models were reliable predictors of occurrence but were less indicative of relative abundance at route (11.5–14.6 km) and point scales (0.5–1 km). As predictors of occurrence, LC models had high sensitivity (0.71–0.93) and were accurate (0.71–0.88) and precise (0.88 and 0.92 for woodcock and grouse, respectively). Models did not predict point-scale abundance independent of the ability to predict occurrence of either species. The LC models are useful predictors of patterns of occurrences in the northeastern United States, but they have limited utility as predictors of fine-scale or route-specific abundances.

Journal of Wildlife Management↗

USGS2012

Harvest and dynamics of duck populations

The role of harvest in the dynamics of waterfowl populations continues to be debated among scientists and managers. Our perception is that interested members of the public and some managers believe that harvest influences North American duck populations based on calls for more conservative harvest regulations. A recent review of harvest and population dynamics of North American mallard (Anas platyrhynchos) populations (Pöysä et al. 2004) reached similar conclusions. Because of the importance of this issue, we reviewed the evidence for an impact of harvest on duck populations. Our understanding of the effects of harvest is limited because harvest effects are typically confounded with those of population density; regulations are typically most liberal when populations are greatest. This problem also exists in the current Adaptive Harvest Management Program (Conn and Kendall 2004). Consequently, even where harvest appears additive to other mortality, this may be an artifact of ignoring effects of population density. Overall, we found no compelling evidence for strong additive effects of harvest on survival in duck populations that could not be explained by other factors.

Journal of Wildlife Management↗

USGS2026

Landscape composition and proximity to water affect American badger occupancy in shortgrass prairies

Land use change in prairie ecosystems is pervasive. Prairie obligate species may be affected by these changes, though many carnivore-specific examples are unknown. We used 3 years (2018–2020) of camera-trap ( n = 381) data from Kansas, USA, to assess multiscale effects of landscape composition on habitat use by American badgers (badger, Taxidea taxus ). We predicted that site occupancy and colonization would be positively associated with the amount of prairie surrounding sites. We also predicted that site occupancy and colonization would be negatively related to amounts of agriculture and the number of wind towers surrounding sites. Badgers were insensitive to amounts of prairie surrounding sites and likely to occupy and colonize sites surrounded by row-crop agriculture. Badgers were also less likely to occupy sites farther from permanent water. Badgers may be exploiting agricultural areas because of increased prey densities or suitable burrowing substrates. Moreover, our study highlights the importance of water resources to badgers in arid regions.

Kansas↗

USGS1975

Summer behavior of adult radio-equipped woodcock in central Maine

The behavior of 26 adult American woodcock ( Philohela minor ) was studied in central Maine during the summers of 1971-73 using radiotelemetry. Adults used diurnal covers and nocturnal sites that were similar to those previously recorded for immature woodcock. The adults, however, were more active during the daylight hours and moved to nocturnal sites later in the evening. Adult woodcock seemed to be less susceptible than immatures to capture by banding crews at night, because adults walked more often between diurnal and nocturnal sites and remained close to the brushy edges at night. Adult birds occupied a smaller composite summer range than the immatures, did not move as far from their capture sites dunng the observation penods, and traveled shorter distances between diurnal and nocturnal sites.

Maine↗

USGS1987

Survival of young American alligators on a Florida lake

A capture-recapture study was conducted on Orange Lake, Florida, from 1979 through 1984 to estimate survival rates of young in an American alligator ( Alligator mississippiensis ) populations. Hatchlings remained together in sibling groups (pods) for at least their 1st year and then began to disperse during their 2nd spring and summer. Mortality through mid-November of their 1st year was negligible. Jolly-Seber (JS) survival estimates of hatchlings for 6 and 12 months were 76 and 41%, respectively. The 2-year JS estimate for the 1980 cohort was 8%. Minimum-Known-Alive (MKA) survival values were 72 and 46% of JS estimates for 6 months and 1 year of age. Survival during the 2nd 6 months of life (spring-summer) tended to be lower than survival during the 1st 6 months (fall-winter).

Florida↗