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At least 433 records · Page 24Linked to original sources
USGS2020

Frequency of extreme freeze events controls the distribution and structure of black mangroves (Avicennia germinans) near their northern range limit in coastal Louisiana

Aim Climate change is expected to result in the tropicalization of coastal wetlands in the northern Gulf of Mexico, as warming winters allow tropical mangrove forests to expand their distribution poleward at the expense of temperate salt marshes. Data limitations near mangrove range limits have hindered understanding of the effects of winter temperature extremes on mangrove distribution and structure. Here, we investigated the influence of extreme freeze events on the abundance, height and coverage of black mangroves ( Avicennia germinans ) near their northern range limit in Louisiana. Location Coastal Louisiana, USA. Methods We quantified the relationships between the frequency of extreme freeze events and A. germinans abundance, height and coverage using: (a) mangrove observation points recorded via aerial surveys from a fixed‐wing aircraft; (b) 30 years of temperature data; and (c) mangrove mortality and leaf damage temperature thresholds. We used freeze frequency data and mangrove–climate relationships to evaluate and spatially depict the risk of A. germinans freeze damage across Louisiana. Results We identified strong negative relationships between the frequency of extreme freeze events and A. germinans abundance, height and coverage. Avicennia germinans is most abundant, tall and continuous along the south‐eastern outer coast of Louisiana, where the frequency of extreme freeze events is reduced (i.e., lower risk of mangrove freeze damage) by the buffering effects of comparatively warm Gulf of Mexico waters. Conversely, the risk of A. germinans freeze damage has historically been very high across Louisiana's Chenier Plain and within more inland wetlands in the Deltaic Plain. Main conclusions Our analyses advance understanding of how the frequency of extreme freeze events controls the distribution, height and coverage of A. germinans near its northern range limit. In addition to informing climate‐smart coastal restoration efforts, our findings can be used to better anticipate and prepare for the tropicalization of temperate wetlands due to climate change.

Louisiana↗
USGS2013

Variation in body mass dynamics among sites in Black Brant Branta bernicla nigricans supports adaptivity of mass loss during moult

Birds employ varying strategies to accommodate the energetic demands of moult, one important example being changes in body mass. To understand better their physiological and ecological significance, we tested three hypotheses concerning body mass dynamics during moult. We studied Black Brant in 2006 and 2007 moulting at three sites in Alaska which varied in food availability, breeding status and whether geese undertook a moult migration. First we predicted that if mass loss during moult were simply the result of inadequate food resources then mass loss would be highest where food was least available. Secondly, we predicted that if mass loss during moult were adaptive, allowing birds to reduce activity during moult, then birds would gain mass prior to moult where feeding conditions allowed and mass loss would be positively related to mass at moult initiation. Thirdly, we predicted that if mass loss during moult were adaptive, allowing birds to regain flight sooner, then across sites and groups, mass at the end of the flightless period would converge on a theoretical optimum, i.e. the mass that permits the earliest possible return to flight. Mass loss was greatest where food was most available and thus our results did not support the prediction that mass loss resulted from inadequate food availability. Mass at moult initiation was positively related to both food availability and mass loss. In addition, among sites and years, variation in mass was high at moult initiation but greatly reduced at the end of the flightless period, appearing to converge. Thus, our results supported multiple predictions that mass loss during moult was adaptive and that the optimal moulting strategy was to gain mass prior to the flightless period, then through behavioural modifications use these body reserves to reduce activity and in so doing also reduce wing loading. Geese that undertook a moult migration initiated moult at the highest mass, indicating that they were more than able to compensate for the energetic cost of the migration. Because Brant frequently change moult sites between years in relation to breeding success, the site-specific variation in body mass dynamics we observed suggests individual plasticity in moult body mass dynamics.

Alaska↗
USGS2021

Post-fledging spatial dispersion and movement behaviour differs between cavity-nesting and open-cup nesting passerines

Spatial dispersion and movement behaviour vary across animal taxa and can affect fitness. The reasons why species differ in movement behaviour of young and why some species form family groups and other species have dispersed young have been rarely addressed. We tested a hypothesis that spatial dispersion and movement behaviour of dependent young were influenced by their developmental state and mobile capacity. In songbirds, offspring of species that nest in holes leave the nest with well-developed wings and initially are more mobile than species that nest in open cups. We used radio-telemetry to track fledglings of three hole- and three open-nesting songbird species to test if young differ in spatial dispersion and movement behaviour between nest types. We found that mobile young of hole-nesting species moved farther on a daily basis but remained more aggregated as a family than the less mobile young of open-nesting species. Movement distances increased with mobile capacity as young aged, especially in open-nesting species, but families of open-nesting species remained dispersed throughout the first week after fledging. This variation in spatial dispersion and movement behaviour of young can have important implications for parental care strategies and juvenile survival.

Arizona↗
USGS2019

Comparing grasshopper (Orthoptera: Acrididae) communities on tallgrass prairie reconstructions and remnants in Missouri

Tallgrass prairies, which once occupied a large swath of central North America, face the combined challenges of habitat loss and fragmentation. In Missouri, where less than 1% the historical prairie remains, prairies are being reconstructed from agricultural or wooded land. Invertebrates are often assumed to colonise reconstructions if native vegetation returns; however, the limited mobility of many invertebrates, the isolation of many tallgrass remnants, and the difficulty in establishing prairie plants raise serious questions as to whether invertebrate communities on reconstructed prairies are and will be equivalent to those found on remnant prairies. Grasshoppers (Acrididae) display a range of dispersal capabilities and may be valuable for assessing the success of prairie restoration for invertebrates. Our first objective was to compare grasshopper communities on reconstructed and remnant prairies and, if differences existed, identify species or functional groups associated with each habitat type. The second objective was to evaluate the effect of time because prairie reconstruction on grasshopper communities to determine if communities on reconstructions are converging with communities on remnants. Our results suggest that prairie reconstructions in Missouri do not support the same communities of grasshoppers as prairie remnants. Grasshopper diversity was generally greater on remnants. Many species had not colonised nearby reconstructions. Communities on prairie reconstructions were characterised by a few long-winged, generalist species that are typically successful in agroecosystems. Further investigation into the habitat disparities driving low grasshopper diversity on reconstructions could help restore the grasshopper community of reconstructions.

Insect Conservation and Diversity↗
USGS2011

Land use and climate influences on waterbirds in the Prairie Potholes

Aim We examined the influences of regional climate and land‐use variables on mallard ( Anas platyrhynchos ), blue‐winged teal ( Anas discors ), ruddy duck ( Oxyura jamaicensis ) and pied‐billed grebe ( Podilymbus podiceps ) abundances to inform conservation planning in the Prairie Pothole Region of the United States. Location The US portion of Bird Conservation Region 11 (US‐BCR11, the Prairie Potholes), which encompasses six states within the United States: Montana, North Dakota, South Dakota, Nebraska, Minnesota and Iowa. Methods We used data from the North American Breeding Bird Survey (NABBS), the National Land Cover Data Set, and the National Climatic Data Center to model the effects of environmental variables on waterbird abundance. We evaluated land‐use covariates at three logarithmically related spatial scales (1000, 10,000 and 100,000 ha), and constructed hierarchical spatial count models a priori using information from published habitat associations. Model fitting was performed using a hierarchical modelling approach within a Bayesian framework. Results Models with the same variables expressed at different scales were often in the best model subset, indicating that the influence of spatial scale was small. Both land‐use and climate variables contributed strongly to predicting waterbird abundance in US‐BCR11. The strongest positive influences on waterbird abundance were the percentage of wetland area across all three spatial scales, herbaceous vegetation and precipitation variables. Other variables that we included in our models did not appear to influence waterbirds in this study. Main conclusions Understanding the relationships of waterbird abundance to climate and land use may allow us to make predictions of future distribution and abundance as environmental factors change. Additionally, results from this study can suggest locations where conservation and management efforts should be focused.

Iowa, Minnesota, Montana, Nebraska, North Dakota, ↗
USGS2010

Pre‐moult patterns of habitat use and moult site selection by Brent Geese Branta bernicla nigricans: Individuals prospect for moult sites

In environments where habitat quality varies, the mechanism by which individuals assess and select habitats has significant consequences on their spatial distribution and ability to respond to environmental change. Each year, thousands of Black Brent Geese Branta bernicla nigricans migrate to the Teshekpuk Lake Special Area (TLSA), Alaska, to undergo a flightless wing‐moult. Over the last three decades, moulting Brent Geese have changed their distribution within the TLSA, redistributing from inland, freshwater wetlands towards coastal, brackish wetlands. To understand better the mechanism by which Brent Geese select a moult site, as well as reasons behind the long‐term shift of moulting distributions, we examined movements and habitat use of birds marked with GPS‐transmitters during the pre‐moult period. Brent Geese did not generally migrate directly to their moulting site during the pre‐moult period, defined as the time from arrival at the moulting grounds to the onset of flightlessness. Rather, individuals used an average of 3.7 ± 0.6 (se) wetland complexes and travelled a minimum of 95.14 ± 15.84 km during the pre‐moult period. Moreover, 69% of Brent Geese visited their final moult site only to leave and visit other sites before returning for the flightless moult. Brent Geese spent significant time in both inland freshwater and coastal estuarine habitats during the pre‐moult, irrespective of the habitat in which they ultimately moulted. Whereas previous research suggested that Brent Geese choose moult sites based largely upon the experience of previous years, our observations suggest a mechanism of moult site selection whereby Brent Geese ‘prospect’ for moult sites, visiting multiple potential moult sites across varied habitat types, presumably gathering information from each site and correspondingly using this information to choose an appropriate moult site. By allowing individuals to adjust their distributions in response to habitat quality cues that may change annually, such as forage type and availability, prospecting may have influenced the long‐term shift in moulting distributions of Brent Geese in the TLSA .

Alaska↗
USGS2008

Comparative use of riparian corridors and oases by migrating birds in southeast Arizona

The relative importance of cottonwood-willow riparian corridors and isolated oases to land birds migrating across southeastern Arizona was evaluated during four spring migrations, 1989 to 1994, based on patterns of species richness, relative abundance, density, and body condition of birds. We surveyed birds in 13 study sites ranging in size and connectivity from small isolated patches to extensive riparian forest, sampled vegetation and insects, and captured birds in mistnets. The continuous band of riparian vegetation along the San Pedro River does not appear to be functioning as a corridor for many migrating species, although it may for a few, namely Yellow-breasted Chats ( Icteria virens ), Summer Tanagers ( Piranga rubra ), and Northern Rough-winged Swallows ( Steldigopteryx serripennis ), which account for fewer than 10% of the individuals migrating through the area. Small, isolated oases hosted more avian species than the corridor sites, and the relative abundances of most migrating birds did not differ between sites relative to size-connectivity. There were few differences in between-year variability in the relative abundances of migrating birds between corridor and oasis sites. Between-year variability decreased with overall abundance of species and was greater for species with breeding ranges that centered north of 50°N latitude. Body condition of birds did not differ relative to the size-connectivity of the capture site, but individuals of species with more northerly breeding ranges had more body fat than species that breed nearby. Peak migration densities of several bird species far exceeded breeding densities reported for the San Pedro River, suggesting that large components of these species were en route migrants. Peak densities of Yellow Warblers ( Dendroica petechia ) reached 48.0 birds/ha, of Wilson’s Warblers ( Wilsonia pusilla ) 33.7 birds/ha, and of Yellow-rumped Warblers ( D. coronata ) 30.1 birds/ha. Riparian vegetation is limited in extent in the vicinity of our study sites, covering less than 1% of the landscape. We conclude that all riparian patches in southeastern Arizona are important as stopover sites to en route migrants regardless of their size and degree of isolation or connectivity. In light of potential habitat limitation, the protection of both small, disjunct riparian patches and extensive riverine tracts in western landscapes is imperative.

Arizona↗
USGS2011

Investigating and managing the rapid emergence of white-nose syndrome, a novel, fatal, infectious disease of hibernating bats

White-nose syndrome (WNS) is a fatal disease of bats that hibernate. The etiologic agent of WNS is the fungus Geomyces destructans , which infects the skin and wing membranes. Over 1 million bats in six species in eastern North America have died from WNS since 2006, and as a result several species of bats may become endangered or extinct. Information is lacking on the pathogenesis of G. destructans and WNS, WNS transmission and maintenance, individual and site factors that contribute to the probability of an outbreak of WNS, and spatial dynamics of WNS spread in North America. We considered how descriptive and analytical epidemiology could be used to fill these information gaps, including a four-step (modified) outbreak investigation, application of a set of criteria (Hill's) for assessing causation, compartment models of disease dynamics, and spatial modeling. We cataloged and critiqued adaptive-management options that have been either previously proposed for WNS or were helpful in addressing other emerging diseases of wild animals. These include an ongoing program of prospective surveillance of bats and hibernacula for WNS, treatment of individual bats, increasing population resistance to WNS (through vaccines, immunomodulators, or other methods), improving probability of survival from starvation and dehydration associated with WNS, modifying hibernacula environments to eliminate G. destructans , culling individuals or populations, controlling anthropogenic spread of WNS, conserving genetic diversity of bats, and educating the public about bats and bat conservation issues associated with WNS.

Conservation Biology↗
USGS2006

Patterns of foraging and distribution of bluegill sunfish in a Mississippi River backwater: Influence of macrophytes and predation

We studied the trophic interactions and spatial distributions of bluegills Lepomis macrochirus and largemouth bass Micropterus salmoides in a macrophyte bed in Lake Onalaska, a backwater lake in the upper Mississippi River. The diets of adult and age-0 bluegills were similar and changed seasonally probably in response to changes in life stages of macroinvertebrates (i. e. emergence of winged adults). Diets and diel patterns of abundance of bluegill suggest that age-O and adults were feeding in the vegetated, littoral zone. Predation by age-O largemouth bass appears to influence use of vegetated habitat by age-0 bluegills. In summer, when most age-O bluegills were vulnerable to predation by age-O largemouth bass, bluegill abundance was strongly correlated with vegetation biomass. In October and November, piscivory by age-O largemouth bass was limited by gape. Consequently, the relationship between the abundance of age-O bluegills and vegetation biomass was weakened because predation risk by age-O largemouth bass was reduced.

Wisconsin↗
USGS2006

Status of dugongs in waters around Palau

The dugong, Dugong dugon , is widely distributed throughout the Indo-Pacific region in shallow tropical and subtropical waters (Nishiwaki and Marsh 1985).The International Union for Conservation of Nature and Natural Resources lists the species as vulnerable (Thornback and Jenkins 1982), as it is severely depleted or extinct in many parts of its former range (Nishiwaki and Marsh 1985). Many populations at isolated archipelagos have been exterminated through direct human exploitation. Husar (1975) cited evidence of the former existence of dugongs around the Mascarene, Laccadive, Maldive, Barren, Narcondom, Cocos (Keeling), Christmas, and Lesser Sunda islands. An isolated dugong population still occurs around Palau (Republic of Belau), Western Caroline Islands, about 850 km from both Papua New Guinea to the south and the Philippines to the west. The first aerial surveys of this population, in 1977 and 1978, indicated that it was small and other evidence suggested it was subject to persistent poaching (Brownell et al. 1981). We resurveyed this population in 1983 to reassess its status and attempt to detect any changes in distribution or abundance. With the assistance of the Palau Department of Natural Resources, we also interviewed fishermen and knowledgeable residents about dugong abundance, distribution, mortality, and natural history. Surveys were conducted from 19 through 26 August, using a Cessna 206high-wing airplane flown at an altitude of 150 to 300 m and an airspeed of about 170 km/h. An observer sat in each rear seat, and a third observer, who also navigated and recorded the data directly onto maps, sat in the right front seat. Small animals close to another dugong were considered calves. The survey route, based on that of Brownell et al. (19Sl), covered much of the approximately 1,380 sq km of dugong habitat within the archipelago. The islands are surrounded by very deep water, which restricts dugong habitat to lagoon areas within about 3 km of shore. Surveys were flown about 0.5 km offshore and the same distance inside the fringing reefs, with transects about 1 km apart across the larger lagoons. The coast was divided into the same 12 segments used by Brownell et al. (1981) (Fig. 1). However, the area outside the western fringing reef was not surveyed because no dugongs were sighted there in either1977 or 1978. We surveyed the entire archipelago twice and carried out replicated surveys of the lagoon areas and Malakal Harbor, which had been used by relatively large numbers of dugongs in 1977 and 1978 (Table 1). The total survey time was 15 h.265Help Volumes Main Menu

Marine Mammal Science↗
USGS2013

Differentiation of subspecies and sexes of Beringian Dunlins using morphometric measures

Five subspecies of Dunlins (Calidris alpina) that breed in Beringia are potentially sympatric during the non-breeding season. Studying their ecology during this period requires techniques to distinguish individuals by subspecies. Our objectives were to determine (1) if five morphometric measures (body mass, culmen, head, tarsus, and wing chord) differed between sexes and among subspecies (C. a. actites, arcticola, kistchinski, pacifica, and sakhalina), and (2) if these differences were sufficient to allow for correct classification of individuals using equations derived from discriminant function analyses. We conducted analyses using morphometric data from 10 Dunlin populations breeding in northern Russia and Alaska, USA. Univariate tests revealed significant differences between sexes in most morphometric traits of all subspecies, and discriminant function equations predicted the sex of individuals with an accuracy of 83–100% for each subspecies. We provide equations to determine sex and subspecies of individuals in mixed subspecies groups, including the (1) Western Alaska group of arcticola and pacifica (known to stage together in western Alaska) and (2) East Asia group of arcticola, actites, kistchinski, and sakhalina (known to winter together in East Asia). Equations that predict the sex of individuals in mixed groups had classification accuracies between 75% and 87%, yielding reliable classification equations. We also provide equations that predict the subspecies of individuals with an accuracy of 22–96% for different mixed subspecies groups. When the sex of individuals can be predetermined, the accuracy of these equations is increased substantially. Investigators are cautioned to consider limitations due to age and feather wear when using these equations during the non-breeding season. These equations will allow determination of sexual and subspecies segregation in non-breeding areas, allowing implementation of taxonomic-specific conservation actions.

Alaska↗
USGS2009

Bat white-nose syndrome: An emerging fungal pathogen?

White-nose syndrome (WNS) is a condition associated with an unprecedented bat mortality event in the northeastern United States. Since the winter of 2006*2007, bat declines exceeding 75% have been observed at surveyed hibernacula. Affected bats often present with visually striking white fungal growth on their muzzles, ears, and/or wing membranes. Direct microscopy and culture analyses demonstrated that the skin of WNS-affected bats is colonized by a psychro-philic fungus that is phylogenetically related to Geomyces spp. but with a conidial morphology distinct from characterized members of this genus. This report characterizes the cutaneous fungal infection associated with WNS.

Northeast↗
USGS1981

Crustal processes of the Mid-Ocean Ridge

Independent geological and geophysical investigations of the Mid-Ocean Ridge system have begun to focus on the nature of the magma chamber system underlying its central axis. Thermal models predict the existence of a steady-state chamber beneath a thin crustal lid ranging in thickness from 2 to 13 kilometers. The only aspect of the system that these models fail to account for is the extremely slow spreading rates. Seismological studies reveal the existence of a low-velocity zone beneath segments of the East Pacific Rise, which is thought to correspond to a chamber system having a half-width of approximately 5 to 10 kilometers. These estimates compare favorably with those derived separately through petrological investigations of deep-sea drilling results, various sampling programs, and field and laboratory studies of ophiolites. The chamber is thought to be wing-shaped and to remain continuously open; it is thought to be fed from the center while simultaneously solidifying at the sides as spreading carries the two halves apart. Progressive fractionation occurs by crystal settling coupled with repeated replenishment and magma mixing in an open steady-state system. Near-bottom studies reveal that the zone of extrusion above the chamber is narrow, but its eruptive history is cyclic in nature, in conflict with the predictions of a steady-state model. On-bottom gravity data at 21°N on the East Pacific Rise reveal a negative gravity anomaly that may be related to the uppermost part of the chamber. The anomaly is only 2 kilometers wide and 1 kilometer below the sea floor. This feature may be associated with a short-term upper magma reservoir. The cyclic volcanic activity is directly related to the active phase of hydrothermal circulation responsible for the observed negative thermal anomaly. The volume of water associated with this circulation is equal to the entire ocean volume passing through the accretion zone approximately every 8 million years. This is about 0.5 percent of the world's rivers, but the effective transport rates of elements are comparable to those of rivers in that anomalies for individual elements are frequently between 100 and 1000 times the average river composition. The degree of subsurface dilution determines the final exit temperature and composition of the hydrothermal fluids, ranging from manganese domination at extreme dilution to iron at intermediate levels to sulfide deposition when low dilution occurs. The discovery of massive sulfide deposits on the East Pacific Rise is destined to have a profound impact on our understanding of ore-forming processes. Whether it will have any economic significance remains to be seen.

Science↗
USGS2018

Experimental infection of Tadarida brasiliensis with Pseudogymnoascus destructans, the fungus that causes white-nose syndrome

White-nose syndrome (WNS) is causing significant declines in populations of North American hibernating bats, and recent western and southern expansions of the disease have placed additional species at risk. Understanding differences in species susceptibility and identifying management actions to reduce mortality of bats from WNS are top research priorities. However, the use of wild-caught susceptible bats, such as Myotis lucifugus , as model species for WNS research is problematic and places additional pressure on remnant populations. We investigated the feasibility of using Tadarida brasiliensis , a highly abundant species of bat that tolerates captivity, as the basis for an experimental animal model for WNS. Using methods previously established to confirm the etiology of WNS in M. lucifugus , we experimentally infected 11 T. brasiliensis bats with Pseudogymnoascus destructans in the laboratory under conditions that induced hibernation. We detected P. destructans on all 11 experimentally infected bats, 7 of which exhibited localized proliferation of hyphae within the epidermis, dermis, and subcutaneous tissue, similar to invasive cutaneous ascomycosis observed in M. lucifugus bats with WNS. However, the distribution of lesions across wing membranes of T. brasiliensis bats was limited, and only one discrete “cupping erosion,” diagnostic for WNS, was identified. Thus, the rarity of lesions definitive for WNS suggests that T. brasiliensis does not likely represent an appropriate model for studying the pathophysiology of this disease. Nonetheless, the results of this study prompt questions concerning the potential for free-ranging, migratory T. brasiliensis bats to become infected with P. destructans and move the fungal pathogen between roost sites used by species susceptible to WNS.

mSphere↗
USGS2012

Structure of marine predator and prey communities along environmental gradients in a glaciated fjord

Spatial patterns of marine predator communities are influenced to varying degrees by prey distribution and environmental gradients. We examined physical and biological attributes of an estuarine fjord with strong glacier influence to determine the factors that most influence the structure of predator and prey communities. Our results suggest that some species, such as walleye pollock ( Theragra chalcogramma ), black-legged kittiwake ( Rissa tridactyla ), and glaucous-winged gull ( Larus glaucescens ), were widely distributed across environmental gradients, indicating less specialization, whereas species such as capelin ( Mallotus villosus ), harbor seal ( Phoca vitulina ), and Kittlitz's murrelet ( Brachyramphus brevirostris ) appeared to have more specialized habitat requirements related to glacial influence. We found that upper trophic level communities were well correlated with their mid trophic level prey community, but strong physical gradients in photic depth, temperature, and nutrients played an important role in community structure as well. Mid-trophic level forage fish communities were correlated with the physical gradients more closely than upper trophic levels were, and they showed strong affinity to tidewater glaciers. Silica was closely correlated with the distribution of fish communities, the mechanisms of which deserve further study.

Alaska↗
USGS1991

Bear feeding activity at alpine insect aggregation sites in the Yellowstone ecosystem

Bears (Ursidae) were observed from fixed-wing aircraft on or near alpine talus in the Shoshone National Forest between 15 June and 15 September in 1981–1989. Bears fed on insect aggregations at 6 known and 12 suspected alpine talus sites, disproportionately more at elevations > 3350 m, on slopes > 30°, and on south- and west-facing aspects. While at these sites, bears almost exclusively ate invertebrates, typically army cutworm moths (Euxoa auxiliaris). Subadult grizzly bears (Ursus arctos horribilis) appeared to be underrepresented at the sites, and proportionate representation of adult females with young appeared to decrease between 15 June and 15 September. Overall, observations of bears at these sites increased between 1981 and 1989. We suggest that alpine insect aggregations are an important food source for bears in the Shoshone National Forest, especially in the absence of high-quality foraging alternatives in July and August of most years.

Idaho;Montana;Wyoming↗
USGS1995

Nesting success of ducks on the central Yukon Flats, Alaska

Nesting success was studied at Canvasback Lake and Mallard Lake on the Yukon Flats in interior Alaska in 1989–1991. Simple estimates of nesting success were computed using two techniques that assume a constant daily survival rate (DSR). Maximum-likelihood estimates of nesting success for all ducks, assuming constant DSR, ranged among years and sites from near zero to 12%. However, DSRs were not constant but increased with nest age and initiation date ( R 2 = 0.42, P = 0.0001). Nesting success was near zero for nests initiated 1–10 May and increased to 100% for nests initiated after 30 June. Therefore, species nesting in early to mid season, such as Mallard ( Anas platyrhynchos ), Northern Pintail ( A . acuta ), and Northern Shoveler ( A . clypeata ), had lower success than later nesting species such as Green-winged Teal ( A . crecca ) and Lesser Scaup ( Aythya affinis ). In 1990 and 1991, combined nesting success of all species, allowing for variation in DSR with nest initiation date and age of nest, was 12.50%.

Alaska↗
USGS2021

A comparison of methods for the long-term harness-based attachment of radio-transmitters to juvenile Japanese quail (Coturnix japonica)

Background While the period from fledging through first breeding for waterbird species such as terns (e.g., genus Sterna, Sternula) is of great interest to researchers and conservationists, this period remains understudied due in large part to the difficulty of marking growing juveniles with radio transmitters that remain attached for extended periods. Methods In an effort to facilitate such research, we examined the impact of various combinations of harness types (backpack, leg-loop, and 3D-printed harnesses), harness materials (Automotive ribbon, Elastic cord, and PFTE ribbon), and transmitter types (center-weighted and rear-weighted) on a surrogate for juvenile terns, 28-day-old Japanese quail ( Coturnix japonica; selected due to similarities in adult mass and downy feathering of juveniles ), in a 30-day experiment. We monitored for abrasion at points of contact and tag gap issues via daily exams while also recording mass and wing cord as indices of growth. This study was designed to serve as an initial examination of the impacts of marking on the growth and development of young birds and does not account for any impacts of tags on movement or behavior. Results While we found that treatment (the specific combination of the transmitter type, harness type, and harness material) had no impact on bird growth relative to unmarked control birds ( P ≥ 0.05), we did observe differences in abrasion and tag gap between treatments ( P ≤ 0.05). Our results suggest that leg-loop harnesses constructed from elastic cord and backpack harnesses from PFTE ribbon are suitable options for long-term attachment to growing juveniles. Conversely, we found that automotive ribbon led to extensive abrasion with these small-bodied birds, and that elastic cord induced blisters when used to make a backpack harness. Conclusions While these results indicate that long-term tagging of juvenile birds is possible with limited impacts on growth, this work does not preclude the need for small-scale studies with individual species. Instead, we hope this provides an informed starting point for further exploration of this topic.

Animal Biotelemetry↗