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Results for “The American Naturalist”

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446 records · Page 25Linked to original sources
USGS1994

Partial migration and wintering localities of American kestrels nesting in the Pacific northwest

Based on banding recoveries, an estimated 89.5% of American kestrels (Falco sparverius) nesting in eastern Oregon, eastern Washington, and Idaho (excluding the Snake River Plain) are migratory and primarily migrate to western Mexico for the winter. Band recoveries from Mexico may be biased; however, we do not know whether the bias is toward more or fewer recoveries. The banding data imply that the remaining kestrels from the region (10.5%) are permanent residents, and we found 2.8% of a northeastern Oregon population on nesting territories in January 1981 (permanent residents). A higher percentage of the nesting population appears to be permanent residents in the valleys along the Snake River Plain than in the remainder of Idaho, eastern Oregon, and eastern Washington (p = 0.02). Limited evidence shows that permanent resident kestrels in eastern Oregon nest earlier than migrants. Information available for the population west of the Cascade Mountains in Oregon and Washington was limited.

Northwestern Naturalist↗
USGS2007

Alligator diet in relation to alligator mortality on Lake Griffin, FL

Alligator mississippiensis (American Alligators) demonstrated low hatch-rate success and increased adult mortality on Lake Griffin, FL, between 1998 and 2003. Dying Lake Griffin alligators with symptoms of poor motor coordination were reported to show specific neurological impairment and brain lesions. Similar lesions were documented in salmonines that consumed clupeids with high thiaminase levels. Therefore, we investigated the diet of Lake Griffin alligators and compared it with alligator diets from two lakes that exhibited relatively low levels of unexplained alligator mortality to see if consumption of Dorosoma cepedianum (gizzard shad) could be correlated with patterns of mortality. Shad in both lakes Griffin and Apopka had high levels of thiaminase and Lake Apopka alligators were consuming greater amounts of shad relative to Lake Griffin without showing mortality rates similar to Lake Griffin alligators. Therefore, a relationship between shad consumption alone and alligator mortality is not supported.

Southeastern Naturalist↗
USGS2011

Identifying nest predators of American avocets (Recurvirostra americana) and black-necked stilts (Himantopus mexicanus) in San Francisco Bay, California

We evaluated predation on nests and methods to detect predators using a combination of infrared cameras and plasticine eggs at nests of American avocets ( Recurvirostra americana ) and black-necked stilts ( Himantopus mexicanus ) in Don Edwards San Francisco Bay National Wildlife Refuge, San Mateo and Santa Clara counties, California. Each technique indicated that predation was prevalent; 59% of monitored nests were depredated. Most identifiable predation ( n = 49) was caused by mammals (71%) and rates of predation were similar on avocets and stilts. Raccoons ( Procyon lotor ) and striped skunks ( Mephitis mephitis ) each accounted for 16% of predations, whereas gray foxes ( U rocyon cinereoargenteus ) and avian predators each accounted for 14%. Mammalian predation was mainly nocturnal (mean time, 0051 h ± 5 h 36 min), whereas most avian predation was in late afternoon (mean time, 1800 h ± 1 h 26 min). Nests with cameras and plasticine eggs were 1.6 times more likely to be predated than nests where only cameras were used in monitoring. Cameras were associated with lower abandonment of nests and provided definitive identification of predators.

California↗
USGS2014

Effects of soil temperature and depth to ground water on first-year growth of a dryland riparian phreatophyte, Glycyrrhiza lepidota (American licorice)

We investigated the effects of soil temperature and depth to ground water on first-year growth of a facultative floodplain phreatophyte, Glycyrrhiza lepidota , in a 2-×-2 factorial greenhouse experiment. We grew plants in mesocosms subirrigated with water low in dissolved oxygen, mimicking natural systems, and set depth of ground water at 63 or 100 cm and soil temperature at cold (ambient) or warm (≤2.7°C above ambient). We hypothesized the moister (63 cm) and warmer soil would be most favorable and predicted faster growth of shoots and roots and greater nitrogen-fixation (thus, less uptake of mineral nitrogen) under those conditions. Growth in height was significantly faster in the moister treatment but was not affected by soil temperature. Final biomass of shoots and of roots, total biomass of plants, and root:shoot ratio indicated a significant effect only from depth of ground water. Final levels of soil mineral-nitrogen were as predicted, with level of nitrate in the moister treatment more than twice that in the drier treatment. No effect from soil temperature on level of soil-mineral nitrogen was detected. Our results suggest that establishment of G. lepidota requires strict conditions of soil moisture, which may explain the patchy distribution of the species along southwestern dryland rivers.

Southwestern Naturalist↗
USGS2013

Use of seeded exotic grasslands by wintering birds

Despite widespread population declines of North American grassland birds, effects of anthropogenic disturbance on wintering habitat of this guild remain poorly understood. We compared avian abundance and habitat structure in fields planted to the exotic grass Old World bluestem ( Bothriochloa ischaemum ; OWB) to that in native mixed-grass prairie. During winters of 2007–2008 and 2008–2009, we conducted bird and vegetation surveys in six native grass and six OWB fields in Garfield, Grant, and Alfalfa counties, Oklahoma. We recorded 24 species of wintering birds in native fields and 14 species in OWB monocultures. While vegetation structure was similar between field types, abundance of short-eared owls ( Asio flammeus ), northern harriers ( Circus cyaneus ) and Smith’s longspurs ( Calcarius pictus ) was higher in OWB fields during at least one year. The use of OWB fields by multiple species occupying different trophic positions suggested that vegetation structure of OWB can meet habitat requirements of some wintering birds, but there is insufficient evidence to determine if it provides superior conditions to native grasses.

Oklahoma↗
USGS2026

Relative activity of three bat species Impacted by white-nose syndrome on the Chesapeake and Ohio Canal National Historical Park

White-nose syndrome, a disease caused by the fungal-pathogen Pseudogymnoascus destructans , has caused drastic reductions in populations of several North American hibernating species of bats including Myotis lucifugus (Little Brown Bat), Myotis septentrionalis (Northern Long-eared Bat), and Perimyotis subflavus (Tricolored Bat). Recent data indicate that populations of Little Brown Bats may be stabilizing and/or increasing in the northeastern region of the US, while others, such as Northern Long-eared Bats, continue to decline. Whether these trends extend to the mid-Atlantic region is currently unknown. To better understand population changes over time, habitat associations, and species dynamics, we developed models of relative activity from bat acoustic data collected on the National Park Service's Chesapeake and Ohio Canal National Historical Park along the Potomac River Corridor in western Maryland between 2016 and 2022. Consistent with pre-disease habitat associations, Little Brown Bats and Tricolored Bats exhibited a positive correlation with proximity to water bodies. Notably, we found Little Brown Bat and Tricolored Bat populations potentially were increasing, whereas Northern Long-eared Bats showed no correlation with examined habitat covariates and had low detection levels, trends consistent with broader declines throughout their range.

Maryland↗
USGS1994

Emperor goose (Chen canagica)

Early naturalists exploring western Alaska were intrigued to find a stocky, blue-gray species of coastal goose unique to that area and nearby Russia. As E. W. Nelson (1887) wrote, "Among the various species of birds more or less peculiar to Alaska this goose is perhaps the most noteworthy." The Emperor Goose nests in the extensive coastal salt marsh habitats of arctic and sub-arctic Alaska and Russia and winters primarily on coastal beaches along ice-free areas of the Aleutian Islands and the Alaska Peninsula. Locally known as the "Beach Goose" from its habit of roosting and feeding near the waters' edge, the diet of this species consists largely of clams, mussels, and algae when wintering and staging in marine and estuarine habitats. When nesting in terrestrial habitats, it eats mostly roots, bulbs, and shoots of vegetation. Although the breeding biology and habitat requirements of this goose have been examined in detail, mostly on the Yukon-Kuskokwim Delta (Y-K Delta) of Alaska, there have been no intensive studies of its wintering or staging biology. Recent studies of migration have confirmed pathways and timing between the Y-K Delta and staging areas on the Alaska Peninsula and wintering areas largely on the Aleutian Islands (Hupp et al. 2007). Observations of substantial molt migrations to the Chukotka Peninsula in eastern Russia (Hupp et al. 2007) suggest a possible change in distribution, or at least a clarification, and raise the possibility of harvest mortality on both continents. Alaska's Emperor Goose population declined precipitously from 139,000 in 1964 to 42,000 in 1986, although its numbers have recovered slightly since then (Fischer et al. 2008). The factors responsible for this quick decline and slow recovery remain poorly known. Hunting, especially subsistence hunting by Native Americans, is probably a factor (Hupp et al. 2008b); coastal oil pollution could also be reducing the survival of overwintering individuals (Byrd et al. 1995); and interspecific competition among brood rearing geese may limit recovery through recruitment (Schmutz and Laing 2002, Lake et al. 2008).

Birds of North America↗
USGS2022

Use of regional breeding bird surveys to estimate bird populations in Big Thicket National Preserve

We used data collected during surveys of seven North American Breeding Bird Survey routes in eastern Texas to estimate avian populations within Big Thicket National Preserve. On only 61 of the 350 count locations located along these routes did observers monitor birds within the boundaries of this preserve. On selected routes, we recorded initial bird detections during the 3-min bird count within 1-min time intervals and within two distance classes (≤50 or >50 m). We used these data, combined with data collected using standard Breeding Bird Survey protocols during 2009–2016, to estimate detection probabilities and effective detection radii for commonly detected species. For species often detected in flocks, we estimated these parameters for group detections. From these parameters, we estimated regional densities for 60 species. Because habitat within Big Thicket National Preserve differed from habitat along surveyed routes, for each species we adjusted the projected population estimate to account for the relationship between density of detected birds and habitat descriptors from the National Land Cover database. On the basis of our estimates of regional density of each species, and accounting for differences in habitat availability, we estimated that commonly detected avian species comprises a population of 192,201 breeding birds (95% confidence interval = 144,269–340,790) within Big Thicket National Preserve.

Texas↗
USGS2018

Monitoring Least Bitterns (Ixobrychis exilis) in Vermont: Detection probability and occupancy modeling

Ixobrychus exillis (Least Bittern) is listed as a species of high concern in the North American Waterbird Conservation Plan and is a US Fish and Wildlife Service migratory bird species of conservation concern in the Northeast. Little is known about the population of Least Bitterns in the Northeast because of their low population density, tendency to nest in dense wetland vegetation, and secretive behavior. Urban and agricultural development is expected to encroach on and degrade suitable wetland habitat; however, we cannot predict the effects on Least Bittern populations without more accurate information on their abundance and distribution. We conducted surveys of wetlands in Vermont to assess the efficacy of a monitoring protocol and to establish baseline Least Bittern abundance and distribution data at a sample of 29 wetland sites. Surveys yielded detections of 31 individuals at 15 of 29 sites across 3 biophysical regions and at 5 sites where occupancy had not been previously reported. Probability of occupancy was positively related to wetland size and number of patches, though the relationships were not strong enough to conclude if these were true determinants of occupancy. Call—response broadcast surveys yielded 30 detections, while passive surveys yielded 13. Call—response broadcasts ( P = 0.897) increased the rate of detection by 55% compared to passive surveys ( P = 0.577). Our results suggest that call—response broadcast surveys are an effective means of assessing Least Bittern occupancy and may reduce bias in long-term monitoring programs.

Vermont↗
USGS2014

Committee on glaciers, 1939–40

The Committee on Glaciers is now composed of the following members: Harry Fielding Reid, Professor Emeritus of Geology, Johns Hopkins University, 608 Cathedral Street, Baltimore, Maryland; William H. Hobbs, Professor Emeritus of Geology, University of Michigan, Ann Arbor, Michigan; Lawrence Martin, Chief of the Division of Maps, Library of Congress, Washington, D.C.; J. E. Church, Professor of Meteorology, Agricultural Experiment Station, University of Nevada, Reno, Nevada; Wm. Osgood Field, Jr., Explorer, 18 West Twelfth Street, New York, N.Y.; Earl A. Trager, Chief of the Naturalist Division, National Park Service, Washington, D.C.; Oliver Kehrlein, Chairman, Committee on Glacier Studies, 1050 Mills Tower, 220 Bush Street, San Francisco, California; Kenneth N. Phillips, Associate Hydraulic Engineer, Water Resources Branch, United States Geological Survey, Chairman, Research Committee of the Mazamas, 606 Post‐Office Building, Portland, Oregon; William S. Cooper, Professor of Botany, University of Minnesota, Minneapolis, Minnesota; Gerald FitzGerald, Senior Topographic Engineer, Alaska Branch, United States Geological Survey, Washington, D.C.; Lawrence M. Gould, Professor of Geology, Carleton College, Northfield, Minnesota; François E. Matthes (Chairman), Senior Geologist, Section of Glacial Geology, United States Geological Survey, Washington, D.C. The international relations of the Committee have changed somewhat during the past year as a result of the consolidation of the International Commission of Glaciers with the International Commission of Snow. That consolidation was effected by the International Association of Scientific Hydrology (to which both commissions belonged) at the triennial meeting in Washington, in September, 1939. Inasmuch as the membership of the new International Commission of Snow and Glaciers comprises the personnel of the two former commissions, our Committee on Glaciers now automatically is represented on the new International Commission by four men—Church, Hobbs, Gould, and Matthes. Moreover, Church is acting President, and it is understood that he will become President as soon as the political situation in Europe permits the holding of a formal election of officers at which all nations interested can exercise their right of voting

Eos, Transactions, American Geophysical Union↗
USGS2019

Adult survival of common eiders in Maine

Although most species of sea ducks are poorly studied, much is known about the population dynamics of the American race of Somateria mollissma dresseri (Common Eider). Although Common Eiders typically have high adult survival and low recruitment rates, their populations in Maine have declined since the early 1990s. Wildlife managers hypothesized this decline was due to reduced adult survival; therefore, they decreased daily bag limits in Maine in 1999 and 2009 to increase local populations. The goals of this project were to assess (a) whether survival rates of adult females captured while nesting varied between historical estimates (1943–1993) and recent estimates (2000–2012), (b) whether survival rates increased from 2000–2009 after the initial harvest restrictions were implemented in 1999, and (c) determine if estimates of survival rates of adult males and females captured while molting differed from estimates of adult females captured while nesting. We used mark–recapture models to estimate survival rates of Common Eiders we banded in Maine (nesting females [ n = 2340] from 2000 to 2012; molting males [ n = 4366] and molting females [ n = 4952] from 2000 to 2009). We found no difference in survival of nesting females based on historical (mean ± SE = 0.9003 ± 0.0841) and recent estimates (0.90 ± 0.015). Although we observed annual fluctuations in survival, survival rates did not increase following the implementation of harvest restrictions. Mean annual survival rates were similarly high for molting females (0.894 ± 0.0205) and nesting females, but lower for molting males (0.855 ± 0.0128). Lower survival rates of adult males may reflect the preference by US hunters to selectively harvest adult males. Overall mean recovery rates of banded birds were low (females: 0.037 ± 0.00043, males: 0.0226 ± 0.0006). We hypothesize that current harvest rates may be influencing decreased survival of adult males to some extent.

Maine↗
USGS2016

A comparison of three macroinvertebrate sampling devices for use in conducting rapid-assessment procedures of Delmarva Peninsula wetlands

Three types of macroinvertebrate collecting devices, Gerking box traps, D-shaped sweep nets, and activity traps, have commonly been used to sample macroinvertebrates when conducting rapid biological assessments of North American wetlands. We compared collections of macroinvertebrates identified to the family level made with these devices in 6 constructed and 2 natural wetlands on the Delmarva Peninsula of Maryland. We also assessed their potential efficacy in comparisons among wetlands using several proportional and richness attributes. Differences in median diversity among samples from the 3 devices were significant; the sweep-net samples had the greatest diversity and the activity-trap samples had the least diversity. Differences in median abundance were not significant between the Gerking box-trap samples and sweep-net samples, but median abundance among activity-trap samples was significantly lower than among samples of the other 2 devices. Within samples, the proportions of median diversity composed of major class and order groupings were similar among the 3 devices. However the proportions of median abundance composed of the major class and order groupings within activity-trap samples were not similar to those of the other 2 devices. There was a slight but significant increase in the total number of families captured when we combined activity-trap samples with Gerking box-trap samples or with sweep-net samples, and the per-sample median numbers of families of the combined activity-trap and sweep-net samples was significantly higher than that of the combined activity-trap and Gerking box-trap samples. We detected significant differences among wetlands for 4 macroinvertebrate attributes with the Gerking box-trap data, 6 attributes with sweep-net data, and 5 attributes with the activity-trap data. A small, but significant increase in the number of attributes showing differences among wetlands occurred when we combined activity-trap samples with those of the Gerking boxtrap or sweep net.

Delaware, Maryland↗
USGS2022

Comparative assessment of laboratory-derived thermal maxima of Gila trout (oncorhynchus Gilae) with current stream temperatures

Gila trout ( Oncorhynchus gilae ) represent an iconic species of the American Southwest. The salmonid has survived extensive logging, livestock grazing, and mining, and is currently threatened by climate change, wildfire, and extended drought. Long-term conservation and recovery of the species and its unique lineages rely on stocking and translocation into historically inhabited streams. Thus, the fish's thermal tolerance is essential in determining suitable habitat and potential vulnerability to a warming climate. We compared a laboratory-derived temperature metric, critical thermal maximum (CTMax), in hatchery-reared Gila trout from three lineages (Main Diamond, South Diamond, and Whiskey Creek) to determine if CTMax differed among the lineages. The average initial (28.9°C, SD = 0.81°C) and final (29.2°C, SD = 0.74°C) temperature at loss of righting responses did not differ across the lineages. We compared the CTMax values with stream temperatures across three drainages representative of extant Gila trout populations from spring 2015 to fall 2018. The East Fork Gila River drainage was represented by more extreme stream temperatures. The maximum daily maximum temperature (i.e., single highest temperature) varied from 24.1 to 33.4°C, exceeding CTMax in four of the five streams. The maximum daily temperature varied from 12.1 to 28.6°C, and the mean weekly maximum temperature varied from 19.9 to 31.1°C. Mean weekly maximum temperature in Lower Diamond Creek exceeded CTMax on 11 occasions. Stream temperatures were cooler within the Middle and the West Fork Gila River drainages and did not exceed CTMax. Intermittency loggers within the East Fork Gila River drainage, which supports Main Diamond and South Diamond lineages of Gila trout, recorded over 300 days of intermittency during a drought. Continued long-term monitoring of stream temperature and comparison with CTMax of Gila trout could assist with decisions of which streams in the Gila Drainage are suitable for Gila trout recovery, stocking, and translocation.

New Mexico↗
USGS2019

Review of Sky dance of the woodcock: The habits and habitats of a strange little bird by Greg Hoch

American Woodcock ( Scolopax minor ) have enthralled conservationists (including Aldo Leopold), bird watchers, wildlife enthusiasts, hunters, and others interested in the natural world for centuries. No doubt, woodcock also have enthralled humans in North America for millennia prior to written descriptions of the woodcock’s courtship displays, habitat preferences, and curious behavior and anatomy. As perhaps the most extensively studied species of shorebird in the world, there is a rich and extensive literature, both scientific and popular, focused on woodcock ecology, behavior, and hunting. To that extensive body of literature, Sky Dance of the Woodcock provides an updated summary of their natural history, habitat relations, and conservation. Sky Dance of the Woodcock takes its title from the courtship display of male woodcock, which consists of an elaborate aerial flight incorporating sound produced both vocally and mechanically via highly modified flight feathers. The aerial displays are accompanied by similarly unusual behavior on the ground, including a distinctive ‘peent’ call. This courtship display happens across much of eastern North America each spring, and Hoch uses this wonder to capture the imagination of the readers of his text. Hoch begins the book with an overview of some of the mystery and fascination surrounding woodcock and builds from that opening to describe woodcock anatomy, natural history, and behavior, before describing their courtship display in greater detail. From there, Hoch describes woodcock-habitat relations, provides a historical overview of woodcock hunting, identifies current threats to woodcock populations, summarizes past and recent woodcock research, and finally, presents an updated overview of woodcock conservation and habitat management. Throughout, there is sometimes surprising information about things as simple as what woodcock eat, to more complex assessment of how woodcock use landscapes and migrate to and from spring and summer breeding areas. This book will undoubtedly appeal to woodcock enthusiasts of a variety to stripes. Woodcock hunters and bird watchers alike will learn something about woodcock-habitat relations, behavior, and conservation. Professional biologists and researchers will benefit from Hoch’s synthesis of a wide range of information about woodcock, and landowners and managers can use some of the concepts in this book to inform their decisions about how to manage lands under their control. Along the way, everyone who reads Sky Dance of the Woodcock is likely to come away with an enhanced appreciation of this captivating bird.

Prairie Naturalist↗