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At least 703 records · Page 39Linked to original sources
USGS1986

Potential impacts of agricultural chemicals on waterfowl and other wildlife inhabiting prairie wetlands: An evaluation of research needs and approaches

The potential for agricultural chemicals to enter prairie-pothole wetlands and impact wildlife dependent on these wetlands for survival and reproduction appears to be great. However, the actual risk to wetland wildlife from the inputs of these chemicals cannot be adequately assessed at this time, because of insufficient data. Available data on the use of pesticides in the prairie-pothole region and the toxicity of these pesticides suggest that insecticides pose the greatest hazard to wetland wildlife, particularly birds. The majority of the most widely used insecticides within the region are very toxic to aquatic invertebrates and birds. Of particular concern are the impacts of agricultural chemicals on the quality of the remaining wetlands in the region and whether or not these impacts have contributed to observed declines in waterfowl populations. Although existing data suggest that adult and juvenile waterfowl may not be more sensitive to these chemicals than are other wetland wildlife, their food habits and feeding behaviors may make them more vulnerable to direct toxic effects or chemical-induced changes in the abundance of aquatic invertebrates. Laboratory and field studies in the United States and Canada are critically needed to assess these potential impacts.

Transactions of the North American Wildlife and Na↗
USGS2021

Breeding waterbird populations have declined in south San Francisco Bay: An assessment over two decades

In south San Francisco Bay, former salt ponds now managed as wildlife habitat support large populations of breeding waterbirds. In 2006, the South Bay Salt Pond Restoration Project began the process of converting 50% to 90% of these managed pond habitats into tidal marsh. We compared American Avocet ( Recurvirostra americana ) and Black-necked Stilt ( Himantopus mexicanus ) abundance in south San Francisco Bay before (2001) and after approximately 1,300 ha of managed ponds were breached to tidal action to begin tidal marsh restoration (2019). Over the 18-year period, American Avocet abundance declined 13.5% (2,765 in 2001 vs. 2,391 in 2019), and Black-necked Stilt abundance declined 30.0% (1,184 in 2001 vs. 828 in 2019). Forster’s Tern ( Sterna forsteri ) abundance was 2,675 birds in 2019. In 2019, managed ponds accounted for only 25.8% of suitable habitats, yet contained 53.9%, 38.6%, and 65.6% American Avocet, Black-necked Stilt, and Forster’s Tern observations, respectively. Conversely, tidal marsh and tidal mudflats accounted for 42.9% of suitable habitats, yet contained only 18.4%, 10.3%, and 19.8% of American Avocet, Black-necked Stilt, and Forster’s Tern observations, respectively. Using a separate nest-monitoring data set, we found that nest abundance in south San Francisco Bay declined for all three species from 2005–2019. Average annual nest abundance during 2017–2019 declined 53%, 71%, and 36%, for American Avocets, Back-necked Stilts, and Forster’s Terns, respectively, compared to 2005–2007. Loss of island nesting habitat as a result of tidal marsh conversion and an increasing population of predatory California Gulls ( Larus californicus ) are two potential causes of these declines. All three species established nesting colonies on newly constructed islands within remaining managed ponds; however, these new colonies did not make up for the steep declines observed at other historical nesting sites. For future wetland restoration, retaining more managed ponds that contain islands suitable for nesting may help to limit further declines in breeding waterbird populations.

California↗
USGS2014

Reviving common standards in point-count surveys for broad inference across studies

We revisit the common standards recommended by Ralph et al. (1993, 1995a) for conducting point-count surveys to assess the relative abundance of landbirds breeding in North America. The standards originated from discussions among ornithologists in 1991 and were developed so that point-count survey data could be broadly compared and jointly analyzed by national data centers with the goals of monitoring populations and managing habitat. Twenty years later, we revisit these standards because (1) they have not been universally followed and (2) new methods allow estimation of absolute abundance from point counts, but these methods generally require data beyond the original standards to account for imperfect detection. Lack of standardization and the complications it introduces for analysis become apparent from aggregated data. For example, only 3% of 196,000 point counts conducted during the period 1992-2011 across Alaska and Canada followed the standards recommended for the count period and count radius. Ten-minute, unlimited-count-radius surveys increased the number of birds detected by >300% over 3-minute, 50-m-radius surveys. This effect size, which could be eliminated by standardized sampling, was ≥10 times the published effect sizes of observers, time of day, and date of the surveys. We suggest that the recommendations by Ralph et al. (1995a) continue to form the common standards when conducting point counts. This protocol is inexpensive and easy to follow but still allows the surveys to be adjusted for detection probabilities. Investigators might optionally collect additional information so that they can analyze their data with more flexible forms of removal and time-of-detection models, distance sampling, multiple-observer methods, repeated counts, or combinations of these methods. Maintaining the common standards as a base protocol, even as these study-specific modifications are added, will maximize the value of point-count data, allowing compilation and analysis by regional and national data centers.

Condor↗
USGS1959

Notes on Bachman's sparrow in Central Louisiana

Notes on the ecology of Bachman’s Sparrow ( Aimophila aestivalis ) were obtained during a study of birds in relation to the direct or artificial seeding of Longleaf Pine ( Pinus palustris ) and Loblolly Pine ( P. taeda ) in central Louisiana from 1955 to 1957. Stoddard (in Burleigh, “Georgia Birds,” pp. 667-668, 1958) has presented an account of the ecology of this species in the pine woods of southern Georgia. Detailed studies in Louisiana have not been reported. Observations were made on experimental lands of the Kisatchie National Forest, about 25 miles southwest of Alexandria, Rapides Parish.

Louisiana↗
USGS2007

Vascular Plant and Vertebrate Inventory of Organ Pipe Cactus National Monument

Executive Summary We summarized inventory and monitoring efforts for plants and vertebrates at Organ Pipe Cactus National Monument (NM) in Arizona. We used data from previous research to compile complete species lists for the monument and to assess inventory completeness. There have been 1,031 species of plants and vertebrates observed at the monument. Most of the species on the list are documented by voucher specimens. There are 59 non-native species established in the monument: one mammal, three birds, and 55 non-native plants. Most non-native plant species were first recorded along roads. In each taxon-specific chapter, we highlight areas that contribute disproportionately to species richness or that have unique species for the monument. Of particular importance are Quitobaquito Springs and Pond, which are responsible for the monument having one of the highest number of bird species in the Sonoran Desert Network of parks. Quitobaquito also contains the only fish in the monument, the endangered Quitobaquito pupfish (Cyprinodon eremus). Other important resources for the plants and vertebrates include the xeroriparian washes (e.g., Alamo Canyon) and the Ajo Mountains. Based on the review of past studies, we believe the inventories of vascular plants and vertebrates are nearly complete and that the monument has one of the most complete inventories of any unit in the Sonoran Desert Network.

Open-File Report↗
USGS2025

An enigmatic wild passerine mortality event in the eastern United States

The ability to rapidly respond to wildlife health events is essential. However, such events are often unpredictable, especially with anthropogenic disturbances and climate-related environmental changes driving unforeseen threats. Many events also are short-lived and go undocumented, making it difficult to draw on lessons learned from past investigations. We report on the response to a mortality event observed predominantly in wild passerines in the eastern United States. The event began in May 2021 when wildlife rehabilitators and private citizens reported large numbers of sick and dead juvenile birds, mostly presenting as single cases with neurologic signs and/or ocular and periocular lesions. Early efforts by rehabilitators, veterinarians, state and federal wildlife agencies, and universities helped gather public reports and fuel rapid responses by government agencies. Collective efforts included live bird and carcass collections; submission to diagnostic laboratories and evaluation; information sharing; and coordinated messaging to stakeholders and interested parties. Extensive diagnostic evaluations failed to identify a causative pathogen or other etiology, although congruent results across laboratories have helped drive further investigation into alternative causes, such as nutritional deficiencies. This report highlights the strengths of a multi-agency, interdisciplinary investigation while exposing the need for an operational framework with approaches and resources dedicated to wildlife health.

eastern United States↗
USGS2006

Avian comparisons between Kingman and Kenilworth Marshes: Final report 2001-2004

In 2001 avi-fauna was added as a parameter to be monitored as an indicator of the status and relative success of the two reconstructed freshwater tidal wetlands residing in the Anacostia River estuary in Washington, D.C. at that time. They were Kenilworth Marsh which was reconstructed in 1993 and Kingman Marsh seven years later in 2000. Other studies were already underway looking at vegetation, seeds, soils and contaminants. Even though these new wetlands were relatively small, together about 70 acres, it was felt this might be sufficient area to sustain and attract birds to the habitat. Birds have been used elsewhere as wetland indicators and we hoped they could prove useful here especially in terms of numbers and species richness. The study was conducted for almost four years (2001-2004) and was designed to ascertain if the recently reconstructed Kingman Marsh evolved similarly with respect to the avi fauna as Kenilworth which had the seven year head start. Twelve observation points were established, six at each marsh, which were to be used weekly so as to alternate the high and low tidal regimes and the observation start times. Additional notations were recorded for species while walking between observation points. The course of the study became interrupted with the incursion of resident Canada geese particularly upon the Kingman Marsh site. Goose herbivory coupled with lowered sediment elevations reduced vegetation cover at Kingman Marsh to less than one-third its intended scope while Kenilworth was barely affected. The result was actually much less impact on the bird populations than on the vegetation. In fact the additional mudflat area at Kingman may have actually helped attract some birds. Together 177 species were identified at the marshes comprising 14 taxonomic orders and 16 families, 137 species at Kingman and 164 at Kenilworth. However, Kingman actually attracted more birds than Kenilworth, whether or not Canada Geese were included. At both wetlands winter usage was significantly greater than at other seasons; however, there were more species in the spring and summer. Three functional guilds were looked at in particular: wetland users, freshwater marsh users and mudflat/shore users. Mudflat users were greatest during the winter while marsh users were greater in the fall. Additional useful data was collected relative to the Canada Goose impacts. The interruption in marsh evolution at Kingman driven by the goose herbivory precluded the opportunity to use the avifauna as an indicator of marsh restoration success.

Book↗
USGS2000

The role of landscape and habitat characteristics in limiting abundance of grassland nesting songbirds in an urban open space

We examine the relationships between abundance of grassland nesting songbirds observed in the Boulder Open Space, CO, USA and parameters that described landscape and habitat characteristics, in order to provide information for Boulder Open Space planners and managers. Data sets included bird abundance and plant species composition, collected during three breeding seasons (1994–1996), and landscape composition and configuration measures from a satellite image-derived land-cover map. We used regression quantiles to estimate the limitations imposed on bird abundance by urban encroachment and decreasing areas of grassland cover-types on the landscape, and habitat characteristics within 200 m diameter sample plots. After accounting for the effect of landscape grassland composition on four species (Western Meadowlark ( Sturnella neglecta ), Vesper Sparrow ( Pooecetes gramineus ), Horned Lark ( Eremophila alpestris ), and Grasshopper Sparrow ( Ammodramus savannarum )), change in abundance with proportion of urban area in the landscape was consistent with the pattern expected for limiting factors that were the active constraint at some times and places. Area of preferred grassland cover-types on the landscape was important for all species, and this remained the case when habitat variables were included in combined landscape–habitat models, with one exception (Western Meadowlark). Analysis of habitat variables enabled identification of important features at the local scale (e.g. shale plant communities in Lark Sparrow ( Chondestes grammacus ) habitat) that were indistinguishable using landscape data alone. Consideration of changes in the landscape due to urbanization and loss of grassland habitat are crucial for open space planning, and habitat features associated with localized and clumped bird species distributions provide important additional information. Widening the management focus to include areas that are not part of the open space system will facilitate a more complete understanding of potential limiting factor processes.

Landscape and Urban Planning↗
USGS2008

Maximizing detection probability of Wetland-dependent birds during point-count surveys in northwestern Florida

We conducted 262 call-broadcast point-count surveys (1-6 replicate surveys on each of 62 points) using standardized North American Marsh Bird Monitoring Protocols between 31 May and 7 July 2006 on St. Vincent National Wildlife Refuge, an island off the northwest coast of Florida. We conducted double-blind multiple-observer surveys, paired morning and evening surveys, and paired morning and night surveys to examine the influence of call-broadcast and time of day on detection probability. Observer detection probability for all species pooled was 75% and was similar between passive (69%) and call-broadcast (65%) periods. Detection probability was higher on morning than evening (t = 3.0, P = 0.030) or night (t = 3.4, P = 0.042) surveys when we pooled all species. Detection probability was higher (but not significant for all species) on morning compared to evening or night surveys for all five focal species detected on surveys: Least Bittern (Ixobrychus exilis), Clapper Rail (Rallus longirostris), Purple Gallinule (Porphyrula martinica), Common Moorhen (Gallinula chloropus), and American Coot (Fulica americana). We detected more Least Bitterns (t = 2.4, P = 0.064) and Common Moorhens (t = 2.8, P = 0.026) on morning than evening surveys, and more Clapper Rails (t = 5.1, P = 0.014) on morning than night surveys.

Wilson Journal of Ornithology↗
USGS2011

Hierarchical modeling of an invasive spread: The eurasian collared-dove streptopelia decaocto in the United States

Invasive species are regularly claimed as the second threat to biodiversity. To apply a relevant response to the potential consequences associated with invasions (e.g., emphasize management efforts to prevent new colonization or to eradicate the species in places where it has already settled), it is essential to understand invasion mechanisms and dynamics. Quantifying and understanding what influences rates of spatial spread is a key research area for invasion theory. In this paper, we develop a model to account for occupancy dynamics of an invasive species. Our model extends existing models to accommodate several elements of invasive processes; we chose the framework of hierarchical modeling to assess site occupancy status during an invasion. First, we explicitly accounted for spatial structure and how distance among sites and position relative to one another affect the invasion spread. In particular, we accounted for the possibility of directional propagation and provided a way of estimating the direction of this possible spread. Second, we considered the influence of local density on site occupancy. Third, we decided to split the colonization process into two subprocesses, initial colonization and recolonization, which may be ground-breaking because these subprocesses may exhibit different relationships with environmental variations (such as density variation) or colonization history (e.g., initial colonization might facilitate further colonization events). Finally, our model incorporates imperfection in detection, which might be a source of substantial bias in estimating population parameters. We focused on the case of the Eurasian Collared-Dove (Streptopelia decaocto) and its invasion of the United States since its introduction in the early 1980s, using data from the North American BBS (Breeding Bird Survey). The Eurasian Collared-Dove is one of the most successful invasive species, at least among terrestrial vertebrates. Our model provided estimation of the spread direction consistent with empirical observations. Site persistence probability exhibits a quadratic response to density. We also succeeded at detecting differences in the relationship between density and initial colonization vs. recolonization probabilities. We provide a map of sites that may be colonized in the future as an example of possible practical application of our work. ?? 2011 by the Ecological Society of America.

Ecological Applications↗
USGS2006

Renesting by dusky Canada geese on the Copper River Delta, Alaska

The population of dusky Canada geese ( Branta canadensis occidentalis ; hereafter duskies) breeding on the Copper River Delta (CRD), Alaska, USA, has been in long-term decline, largely as a result of reduced productivity. Estimates of renesting rates by duskies may be useful for adjusting estimates of the size of the breeding population derived from aerial surveys and for understanding population dynamics. We used a marked population of dusky females to obtain estimates of renesting propensity and renesting interval on the CRD, 1999–2000. Continuation nests, replacement nests initiated without a break in the laying sequence, resulted only after first nests were destroyed in the laying stage with ≤4 eggs laid. Renesting propensity declined with nest age from 72% in mid-laying to 30% in early incubation. Between first nests and renests, mean interval was 11.9 ± 0.6 days, mean distance was 74.5 m (range 0–214 m), and clutch size declined 0.9 ± 0.4 eggs. We incorporated our renesting estimates and available estimates of other nesting parameters into an individual-based model to predict the proportion of first nests, continuation nests, and renests, and to examine female success on the CRD, 1997–2000. Our model predicted that 19–36% of nests each year were continuation nests and renests. Also, through 15 May (the approx. date of breeding ground surveys), 1.1–1.3 nests were initiated per female. Thus, the number of nests per female would have a significant, though relatively consistent, effect on adjusting the relation between numbers of nests found on ground surveys versus numbers of birds seen during aerial surveys. We also suggest a method that managers could use to predict nests per female using nest success of early nests. Our model predicted that relative to observed estimates of nest success, female success was 32–100% greater, due to replacement nests. Thus, although nest success remains low, production for duskies was higher than previously thought. For dusky Canada geese, managers need to consider both continuation nests and renests in designing surveys and in calculating adjustment factors for the expansion of aerial survey data using nest densities.

Alaska↗
USGS2014

Pharmacokinetics of hydromorphone hydrochloride after intravenous and intramuscular administration of a single dose to American kestrels (Falco sparverius)

Objective —To determine the pharmacokinetics of hydromorphone hydrochloride after IV and IM administration in American kestrels ( Falco sparverius ). Animals —12 healthy adult American kestrels. Procedures —A single dose of hydromorphone (0.6 mg/kg) was administered IM (pectoral muscles) and IV (right jugular vein); the time between IM and IV administration experiments was 1 month. Blood samples were collected at 5 minutes, 1 hour, and 3 hours (n = 4 birds); 0.25, 1.5, and 9 hours (4); and 0.5, 2, and 6 hours (4) after drug administration. Plasma hydromorphone concentrations were determined by means of liquid chromatography with mass spectrometry, and pharmacokinetic parameters were calculated with a noncompartmental model. Mean plasma hydromorphone concentration for each time was determined with naïve averaged pharmacokinetic analysis. Results —Plasma hydromorphone concentrations were detectable in 2 and 3 birds at 6 hours after IM and IV administration, respectively, but not at 9 hours after administration. The fraction of the hydromorphone dose absorbed after IM administration was 0.75. The maximum observed plasma concentration was 112.1 ng/mL (5 minutes after administration). The terminal half-life was 1.25 and 1.26 hours after IV and IM administration, respectively. Conclusion and Clinical Relevance —Results indicated hydromorphone hydrochloride had high bioavailability and rapid elimination after IM administration, with a short terminal half-life, rapid plasma clearance, and large volume of distribution in American kestrels. Further studies regarding the effects of other doses, other administration routes, constantrate infusions, and slow release formulations on the pharmacokinetics of hydromorphone hydrochloride and its metabolites in American kestrels may be indicated.

American Journal of Veterinary Research↗
USGS1977

Reproductivity of Japanese quail fed mercuric chloride in the absence of vitamin D

Mercuric chloride (HgCl 2 ) was tested at 16 p.p.m. Hg for vitamin D sparing activity by presenting it dietarily in the presence and absence of 25-hydroxycholecalciferol (25-HCC) to Japanese quail (Coturmx c. japonica) for 25 days. No gross signs characteristic of mercury poisoning were observed, but some predictable effects of vitamin D deficiency on avian reproduction were manifested within 10 days. Rate of lay, egg shell thickness, and hatchability of fertile eggs decreased markedly for birds on vitamin D-deficient diets. Shell-less eggs were laid by these birds after 20 days and laying stopped entirely on the 23rd day. Laying resumed within 5 days after diets were refortified with 25-HCC. There was no detectable interaction between HgCl 2 and vitamin D.

Poultry Science↗
USGS2002

Exposure of free-flying birds to anticholinesterase insecticides in two conventionally managed fruit orchards

Conventionally managed orchards receive extensive applications of anticholinesterase (anti-ChE) insecticides throughout the growing season. Because many avian species make use of these environments for nesting and foraging, they may receive substantial exposure to anti-ChEs. The model used to assess avian risk in these environments is highly simplified, and indicator species used in risk studies may misrepresent the risk of the species in the field. A better understanding of avian risk is needed, and should begin with a closer examination o# their exposure in these environments. Exposure of free-flying birds was examined in two conventional orchards during the nesting seasons of 1999 and 2000. Our goal was to demonstrate the influences of species and chemical differences on the exposure we observed. Plasma ChE activity and ChE reactivation were used to identify exposure in multiple species following anti-ChE applications (applied singly and in mixtures). Chipping sparrows (Spizella passerina), American goldfinches (Carduelis tristis), and American robins (Turdus migratorius) demonstrated significant ChE activity depression in 1999 (p 0.005), and only chipping sparrows demonstrated significant depression in 2000 (p = 0.0002). These three species demonstrated the highest proportion of exposed individuals among all species examined in both years. Because many chemicals were simultaneously present in each orchard, chemical influences on the exposure we observed could not be discerned. This work does demonstrate, however, that avian species differ significantly in their exposure, and that chipping sparrows demonstrated the greatest exposure among the species analyzed. These results underscore the need for multiple species studies and for choosing indicator species on a biologically relevant basis.

Book↗
USGS1985

Breeding chronology, molt, and measurements of accipiter hawks in northeastern Oregon

Most northern goshawks completed laying eggs in April, while most Cooper's hawks completed their clutches in May with essentially no overlap. The sharp-shinned hawks laid in late May and June. Juvenile females represented 4% of the northern goshawk breeding population; 22% of the Cooper's hawk breeding population (highest reported for the species) and 60% of the sharp-shinned hawk breeding population, northern goshawks and Cooper's hawks in juvenal plumage generally nested later in the season, but not sharp-shinned hawks. Females of each species began molting first. Primaries were molted from the innermost outward in all species, but rectrix molt sequence was variable. Usually R1 was molted first. Primary molt of the 2 wings was usually synchronous; however, the rectrix molt was not as orderly. Arrested molt was observed in some individuals of all species; it probably has an energy-saving function. Wing chords of adult northern goshawks from Oregon were not different from Wisconsin fall migrants or birds from Alaska; however, rectrices were significantly shorter in Oregon than Wisconsin. Cooper's hawks nesting in Oregon were much smaller than those trapped in Wisconsin. Wing chords and rectrices were significantly shorter for both sexes, and, although weights were not directly comparable, Oregon Cooper's hawks also weighed much less. The limited number of sharp-shinned hawks measured precluded statistical analyses.

Journal of Field Ornithology↗
USGS2019

The pathogenesis of H7 highly pathogenic avian influenza viruses in Lesser Scaup (Aythya affinis)

Waterfowl are the natural hosts of avian influenza virus (AIV), and through migration spread the virus worldwide. Most AIVs carried by wild waterfowl are low pathogenic strains; however, Goose/Guangdong/1996 lineage clade 2.3.4.4 H5 highly pathogenic (HP) AIV now appears to be endemic in wild birds in much of the Eastern Hemisphere. Most research efforts studying AIV pathogenicity in waterfowl thus far have been directed toward dabbling ducks. In order to better understand the role of diving ducks in AIV ecology, we previously characterized the pathogenesis of clade 2.3.4.4 H5 HPAIV in lesser scaup ( Aythya affinis ). In an effort to further elucidate AIV infection in diving ducks, the relative susceptibility and pathogenesis of two North American lineage H7 HPAIV isolates from the most recent outbreaks in the United States was investigated. Lesser scaup were inoculated with either A/turkey/IN/1403-1/2016 H7N8 or A/chicken/TN/17-007147-2/2017 H7N9 HPAIV by the intranasal route. The approximate 50% bird infectious dose (BID 50 ) of the H7N8 isolate was determined to be 10 3 50% egg infectious doses (EID 50 ), and the BID 50 of the H7N9 isolate was determined to be <10 2 EID 50 , indicating some variation in adaptation between the two isolates. No mortality or clinical disease was observed in either group except for elevated body temperatures at 2 and 4 days postinoculation (DPI). Virus shedding was detected up to 14 DPI from both groups, and there was a trend for shedding to have a longer duration and at higher titer levels from the cloacal route. These results demonstrate that lesser scaup are susceptible to both H7 lineages of HPAIV, and similar to dabbling duck species, they shed virus for long periods relative to gallinaceous birds and don't present with clinical disease.

Avian Diseases↗
USGS1989

Premigrational movements and behavior of young mallards and wood ducks in north-central Minnesota

Movements and behavior of 89 young mallards (Anas platyrhynchos) and 48 young wood ducks (Aix sponsa) were monitored on a 932-km2 study area in north-central Minnesota in late summer and fall, 1972-74, with telemetry, visual observation, and aerial surveys. Initial flights of both species were confined to the natal (brood) marsh; first flights away from the natal marsh occurred in the third week after fledging in both species. First flights of young mallards and wood ducks away from their natal marshes were not significantly different between the sexes (mallard, mean = 4.95 km for females and 5.83 km for males; wood ducks, mean = 2.31 km for females and 2.64 km for males). However, flights away from the brood marshes by wood ducks were significantly shorter than for mallards.As young mallards and wood ducks grew, their daytime use of the natal marshes decreased in an irregular pattern as both species began daily flights between day- and night-use areas. Locally reared mallards made longer daily flights between use areas than did wood ducks, but wood ducks changed use areas with greater frequency before 1 October. Despite often extensive movements, most locally reared mallards and wood ducks remained in the vicinity of their brood marshes throughout fall until migration.Movement of young birds to new habitat was not the result of random searching and thus fortuitous discovery of nearby areas. Instead, birds seemed to learn of new habitat and develop movement patterns by associating with other birds; locally reared young always moved in the company of flocks of conspecifics that included adults and older immatures.Differences in movement patterns between the sexes of young birds and between young and adult birds cause them to be differentially distributed by age and sex on and near the breeding grounds. These differences are ultimately reflected in the distribution of the hunter harvest. We have interpreted generalizations about such phenomena, developed from analysis of continent-wide mallard banding data, using our data obtained from individually marked birds. We document (a) greater distances moved by early than by late-hatched young in the postbreeding period before migration, (b) differential movement of age and sex cohorts that explains greater hunting mortality of young than adults and of females than males near natal marshes, (c) differences in length and timing of postbreeding movements of adult male mallards and the postfledging movements of immature male mallards that help explain the northerly continental recovery distribution of young males, and (d) differential timing and rate of movement by birds through harvest areas (early departure of males and some return of females to natal marshes after the beginning of hunting) that explain differences in the timing of hunting season recoveries. Behavioral differences between the age and sex cohorts in the fall waterfowl population on and near their breeding grounds in north-central Minnesota can explain observed differences in survival and recovery rates of adult and young birds.The behaviors observed suggest to us that restrictive harvest regulations such as small-area closure may have little or no local benefits at the breeding grounds because premigratory assemblages of birds make extensive movements. In particular, protection of postbreeding adult females and locally reared young might only occur by closing large areas or scheduling extreme delays in the season opening, neither of which may be compatible with equitably apportioning waterfowl harvest at higher latitudes. Additional research on the local effects of restrictive regulations, and on age- and sex-specific differences in the timing, rate, and direction of fall movements of postbreeding waterfowl is needed.

Fish and Wildlife Research↗
USGS2024

Identifying conservation introduction sites for endangered birds through the integration of lidar-based habitat suitability models and population viability analyses

Similar to other single-island endemic Hawaiian honeycreepers, the critically endangered ‘ākohekohe ( Palmeria dolei ) is threatened by climate-driven disease spread. To avert the imminent risk of extinction, managers are considering novel measures, including the conservation introduction (CI) of ‘ākohekohe from Maui to higher elevation habitats on the Island of Hawai’i. This study integrated lidar-based habitat suitability models (LHSMs) and population viability analyses (PVAs) to assess five candidate sites currently considered by managers for CI. We first developed an LHSM for the species’ native range on Maui. We then projected habitat suitability across candidate CI sites, using forest structure and topography metrics standardized across sensor types. Given the structural variability observed within the five candidate sites, we identified clusters of contiguous, highly suitable habitat as potential release sites. We then determined how many adult individuals could be supported by each cluster based on adult home range estimates. To determine which clusters could house the minimum number of ‘ākohekohe birds necessary for a stable or increasing future population, we conducted PVAs under multiple scenarios of bird releases. We found that canopy height and relative height 90 had the greatest effects on model performance, possibly reflecting ‘ākohekohe’s preference for taller canopies. We found that a small release of at least nine pairs of equal sex ratios were sufficient for an 80% chance of success and a <1% chance of extirpation in 20 years, resulting in a minimum release area of 4.5 ha in size. We integrated the results of the LHSM and PVA into an interactive web application that allowed managers to consider the caveats and uncertainties associated with both LHSMs and PVAs in their decision-making process. As climate change continues to threaten species worldwide, this research demonstrates the value of lidar remote sensing combined with species-specific models to enable rapid, quantitative assessments that can inform the increasing consideration of time-sensitive conservation introductions.

Hawaii↗