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At least 91 records · Page 5Linked to original sources
USGS2014

Selection of forest canopy gaps by male Cerulean Warblers in West Virginia

Forest openings, or canopy gaps, are an important resource for many forest songbirds, such as Cerulean Warblers ( Setophaga cerulea ). We examined canopy gap selection by this declining species to determine if male Cerulean Warblers selected particular sizes, vegetative heights, or types of gaps. We tested whether these parameters differed among territories, territory core areas, and randomly-placed sample plots. We used enhanced territory mapping techniques (burst sampling) to define habitat use within the territory. Canopy gap densities were higher within core areas of territories than within territories or random plots, indicating that Cerulean Warblers selected habitat within their territories with the highest gap densities. Selection of regenerating gaps with woody vegetation >12 m within the gap, and canopy heights >24 m surrounding the gap, occurred within territory core areas. These findings differed between two sites indicating that gap selection may vary based on forest structure. Differences were also found regarding the placement of territories with respect to gaps. Larger gaps, such as wildlife food plots, were located on the periphery of territories more often than other types and sizes of gaps, while smaller gaps, such as treefalls, were located within territory boundaries more often than expected. The creations of smaller canopy gaps, <100 m 2 , within dense stands are likely compatible with forest management for this species.

Wilson Journal of Ornithology↗
USGS2014

Age-Ratios and Condition of En Route Migrant Blackpoll Warblers in the British Virgin Islands

The en route migration ecology of Blackpoll Warblers ( Setophaga striata ) is poorly understood, yet intriguing. Blackpoll Warblers undertake the longest open water migration of any wood warbler species, traveling from northeastern North America to South America, with the first potential landfall being the West Indies. This migration requires substantial energy reserves and subjects Blackpoll Warblers to unpredictable weather events, which may influence survival. Few studies have examined age ratios or condition of Blackpoll Warblers while the warblers are en route through the Caribbean region. I captured and banded Blackpoll Warblers in the British Virgin Islands over 10 consecutive autumn migrations. Ratios of hatch-year to adult Blackpoll Warblers were variable but averaged lower than the ratios reported at continental departure locations. Average mass of Blackpoll Warblers was less than that reported at continental departure locations, with 26% of adults and 40% of hatch-year birds below the estimated fat free mass; hatch-year birds were consistently in poorer condition than adults. Blackpoll Warblers captured in the British Virgin Islands were also in poorer condition than those reported from the Dominican Republic and Barbados; this may be because of the British Virgin Islands being the first landfall after the transatlantic crossing, whereas Blackpoll Warblers arriving at the other Caribbean study locations may have had opportunities for stopover prior to arrival or have departed from farther south on the continent. However, this suggests that the British Virgin Islands likely provide important stopover habitat as a first landfall location for Blackpoll Warblers arriving from the transatlantic migration route.

Guana Island↗
USGS2016

Reproductive success and habitat characteristics of Golden-winged Warblers in high-elevation pasturelands

The Golden-winged Warbler ( Vermivora chrysoptera ) is one of the most rapidly declining vertebrate species in the Appalachian Mountains. It is the subject of extensive range-wide research and conservation action. However, little is known about this species' breeding ecology in high-elevation pasturelands, a breeding habitat with conservation potential considering the U.S. Natural Resource Conservation Service's Working Lands for Wildlife program targeting private lands in the Appalachian Mountains. We located 100 nests of Golden-winged Warblers in pastures in and around the Monongahela National Forest in West Virginia during 2008&ndash;2012. Daily nest survival rate (mean &plusmn; SE = 0.962 &plusmn; 0.006), clutch size (4.5 &plusmn; 0.1), and number of young fledged per nest attempt (2.0 &plusmn; 0.2) and successful nest (4.0 &plusmn; 0.1) fell within the range of values reported in other parts of the species' range and were not significantly affected by year or the presence/absence of cattle grazing. Classification tree analysis revealed that nests were in denser vegetation (&ge;52%) and closer to forest edges (<36.0 m) and shrubs (<7.0 cm) than random locations within the male's territory. Successful nests had significantly more woody cover (&ge;9%) within 1 m than failed nests. Our results suggest that cattle grazing at 1.2&ndash;2.4 ha of forage/animal unit with periodic mowing can create and maintain these characteristics without interfering with the nesting of Golden-winged Warblers. High-elevation pasturelands may provide a refuge for remaining populations of Golden-winged Warblers in this region.

Wilson Journal of Ornithology↗
USGS2014

Daily survival rates for nests of Black Skimmers from a core breeding area of the Southeastern USA

Little is known about the reproductive success of Black Skimmers ( Rynchops niger ) throughout the southeastern USA where availability of undisturbed beaches for nesting is limited. Daily survival rates (DSR) of nests were examined at three nesting sites in Cape Romain National Wildlife Refuge (CRNWR), South Carolina, USA, 2009&ndash;2010. The percent of successful nests ( n = 346 nests) ranged from 42&ndash;69% among colony sites when data were pooled across both years. The DSR of nests was primarily related to colony site, predation risk, height of high tide, and clutch size. Predation and overwash were the principal causes of identifiable nest loss, each accounting for &sim;33% of nest failures during the two study years. Because of the challenges of resighting skimmer chicks, we were not able to measure chick survival effectively and therefore accurate measures of productivity remain elusive. High variability in nest success among sites within close proximity to each other (<20 km) suggests factors at local scales such as disturbance, predation, and overwash events strongly influenced nest success of Black Skimmers during these 2 years as opposed to more region-wide stressors such as tropical storms or food availability. Although time-intensive techniques to control predators do exist, management options to limit flooding and overwash are far more limited. Conservation of Black Skimmers in the southeastern USA would benefit from coordinated, multi-state efforts to measure nest and chick survival.

South Carolina↗
USGS2014

The historical distribution of Gunnison Sage-Grouse in Colorado

The historical distribution of Gunnison Sage-Grouse ( Centrocercus minimus ) in Colorado is described based on published literature, observations, museum specimens, and the known distribution of sagebrush ( Artemisia spp.). Historically, Gunnison Sage-Grouse were widely but patchily distributed in up to 22 counties in south-central and southwestern Colorado. The historical distribution of this species was south of the Colorado-Eagle river drainages primarily west of the Continental Divide. Potential contact areas with Greater Sage-Grouse ( C. urophasianus ) were along the Colorado-Eagle river system in Mesa, Garfield, and Eagle counties, west of the Continental Divide. Gunnison Sage-Grouse historically occupied habitats that were naturally highly fragmented by forested mountains and plateaus/mesas, intermountain basins without robust species of sagebrush, and river systems. This species adapted to use areas with more deciduous shrubs (i.e., Quercus spp., Amelanchier spp., Prunus spp.) in conjunction with sagebrush. Most areas historically occupied were small, linear, and patchily distributed within the overall landscape matrix. The exception was the large intermountain basin in Gunnison, Hinsdale, and Saguache counties. The documented distribution east of the Continental Divide within the large expanse of the San Luis Valley (Alamosa, Conejos, Costilla, and Rio Grande counties) was minimal and mostly on the eastern, northern, and southern fringes. Many formerly occupied habitat patches were vacant by the mid 1940s with extirpations continuing to the late 1990s. Counties from which populations were recently extirpated include Archuleta and Pitkin (1960s), and Eagle, Garfield, Montezuma, and Ouray (1990s).

Colorado↗
USGS2014

Habitat and food preferences of the endangered Palila (Loxioides bailleui) on Mauna Kea, Hawai'i

Seeds and flowers of the leguminous māmane ( Sophora chrysophylla ) tree are the primary food resource of the federally endangered Palila ( Loxioides bailleui ; Fringillidae: Drepanidinae), which is now restricted to dry subalpine woodland on Mauna Kea Volcano on the island of Hawai'i because of centuries of habitat degradation by non-native ungulates. Palila are morphologically and behaviorally adapted to consume m&Auml;mane seeds by grasping seed pods with their feet and opening pods with stout bills and demonstrate limited ability to exploit alternative food resources. This degree of single species dependency is rare among birds and illustrates unique adaptations that also occurred in other Hawaiian species that are now extinct. In mixed-woodland with co-dominant naio ( Myoporum sandwicense ), Palila spent 1.7-3.9 times longer in māmane than in naio during foraging observations where naio was 1.3-4.6 times as dense as māmane. Naio fruit was readily available, but it comprised proportionally <11% of food items taken by Palila. Although māmane flowers were more abundant than māmane pods throughout this study except at one lower-elevation mixed-woodland site, Palila spent more time foraging on pods than flowers in both māmane woodland and mixed-woodland, but consumed more flowers than pods in mixed-woodland. Insects, which have been reported as an important component of the diet of Palila, were apparently taken rarely in this study. Protecting and restoring māmane in woodlands adjacent to the current range of Palila will benefit their recovery, allowing them to exploit increased food availability in areas of their former range.

Hawai'i↗
USGS2015

Daily nest survival rates of Gunnison Sage-Grouse ( Centrocercus minimus ): assessing local- and landscape-scale drivers

The Gunnison Sage-Grouse ( Centrocercus minimus ) is a species of conservation concern and is a candidate for listing under the U.S. Endangered Species Act because of substantial declines in populations from historic levels. It is thought that loss, fragmentation, and deterioration of sagebrush ( Artemisia spp.) habitat have contributed to the decline and isolation of this species into seven geographically distinct subpopulations. Nest survival is known to be a primary driver of demography of Greater Sage-Grouse ( C. urophasianus ), but no unbiased estimates of daily nest survival rates (hereafter nest survival) exist for Gunnison Sage-Grouse or published studies identifying factors that influence nest survival. We estimated nest survival of Gunnison Sage-Grouse for the western portion of Colorado's Gunnison Basin subpopulation, and assessed the effects and relative importance of local- and landscape-scale habitat characteristics on nest survival. Our top performing model was one that allowed variation in nest survival among areas, suggesting a larger landscape-area effect. Overall nest success during a 38-day nesting period (egg-laying plus incubation) was 50% (daily survival rate; SE = 0.982 [0.003]), which is higher than previous estimates for Gunnison Sage-Grouse and generally higher than published for the closely related Greater Sage-Grouse. We did not find strong evidence that local-scale habitat variables were better predictors of nest survival than landscape-scale predictors, nor did we find strong evidence that any of the habitat variables we measured were good predictors of nest survival. Nest success of Gunnison Sage-Grouse in the western portion of the Gunnison Basin was higher than previously believed.

Wilson Journal of Ornithology↗
USGS2014

Breeding biology of the Spotted Barbtail ( Premnoplex brunnescens )

The Spotted Barbtail (Furnariidae) is poorly studied but shows some extreme traits for a tropical passerine. We located and monitored 155 nests to study this species for 7 years in an Andean cloud forest in Venezuela. Spotted Barbtails have an unusually long incubation period of 27.2 &plusmn; 0.16 days, as a result of very long (3&ndash;6 hr) off-bouts even though both adults incubate. The long off-bouts yield low incubation temperatures for embryos and are associated with proportionally large eggs (21% of adult mass). They also have a long nestling period of 21.67 &plusmn; 0.33 days, and a typical tropical brood size of two. The slow growth rate of the typical broods of two is even slower in broods artificially reduced to one young. Nonetheless, the young stay in the nest long enough to achieve wing lengths that approach adult size.

Wilson Journal of Ornithology↗
USGS2015

Roost habitat of Mexican Spotted Owls (Strix occidentalis lucida) in the canyonlands of Utah

In large portions of their geographic range, Mexican Spotted Owls (Strix occidentalis lucida) roost in forest-dominated environments, but in some areas the owls use relatively arid rocky canyonlands. We measured habitat characteristics at 133 male roosts (n = 20 males) during 1992-95, and 56 female roosts (n = 13 females) during 1994-95. Across all years and study areas, 44% of Mexican Spotted Owl roosts occurred in mixed-conifer forest patches, 30% in desert scrub habitat, 16% in pinyon-juniper woodlands, and 10% of roosts occurred in riparian vegetation. Two basic substrates were used as perches by owls, including rock ledges or various trees, where roost height averaged 9 m (0.54 SD), and average height of cliffs above perched owls was 50 m (58 SD). For both males and females, trees types used most frequently included various firs (51%), followed by pinyon pine (18%), Utah juniper (15%), and big-tooth maple or box elder combined (15%). Roost sites were located in canyons composed of cliff-forming geologic formations, primarily oriented north-west to south-east. The width of canyons measured at roosts averaged 68 m (105 SD), but ranged from 1-500 m. Canopy cover at roosts used by owls ranged from 44% to 71%, mean tree height of all trees present was 9.5 m and mean diameter of trees was 25.4 cm. Non-roost habitat was warmer, not as steep, and possessed fewer caves and ledges than roost habitat. Trees present in roost plots were taller, and thus showed greater average diameter than trees present in non-roost habitat.

Utah↗
USGS2015

Unusual behavior in the parental care of a house wren ( Troglodytes aedon ): Post fledging use of an old nest during cold nights

I report on the unusual behavior of an adult House Wren ( Troglodytes aedon ) leading recently fledged young back to the nest for two consecutive nights. The ambient temperature reached below 0&deg;C during both nights. Despite disadvantages associated with remaining in the nest, this observation suggests that adult birds may assess trade-offs between perceived risks versus the benefits of engaging in other activities, in this case roosting communally for thermoregulation.

Oregon↗
USGS2015

Flight feather molt in Yellow-headed Blackbirds ( Xanthocephalus xanthocephalus ) in North Dakota

Yellow-headed Blackbirds ( Xanthocephalus xanthocephalus ) in central North Dakota undergo prebasic molt or prejuvenile molt during late summer. Nestling Yellow-headed Blackbirds initiate a complete prejuvenile molt, grow their primary and secondary regimes in about 40 days, completing molt after they leave the nest by the first week in August. Remiges are not replaced during the subsequent preformative molt, being retained until the second prebasic molt. Nonlinear (logistic) regression of primary remex growth during definitive prebasic molts of Yellow-headed Blackbirds indicated 38 days were required to complete the linear phase of growth (between 10% and 90% of total primary length). Males added 19.5 mm/d and females added 15.7 mm/d to the total length of all primaries during this linear growth phase; an average of 4&ndash;5 mm per primary remex per day. Definitive prebasic molting of primary remiges in males and females was initiated in late June, after nesting and brood rearing were completed. Molts of Yellow-headed Blackbirds were completed by early September, before birds emigrated from North Dakota during mid-September. Because of their comparatively early completion of molt and emigration from the state, as well as their more diverse diet, agricultural depredation caused by Yellow-headed Blackbirds in North Dakota is likely less than that of Red-winged Blackbirds and Common Grackles.

North Dakota↗
USGS2015

The nest-concealment hypothesis: New insights from a comparative analysis

Selection of a breeding site is critical for many animals, especially for birds whose offspring are stationary during development. Thus, birds are often assumed to prefer concealed nest sites. However, 74% of studies ( n = 106) that have evaluated this relationship for open-cup nesting songbirds in North America failed to support the nest-concealment hypothesis. We conducted a comparative analysis to identify factors that contribute to variation in the ability of researchers to find support for the nest-concealment hypothesis. We found that some of the discrepancy among studies can be explained by interspecific differences in morphological and extrinsic factors that affect nest predation. Moreover, methods that investigators used to estimate concealment affected whether studies found support for the nest-concealment hypothesis; 33% of the studies that used quantitative estimates found support for the nest-concealment hypothesis whereas only 10% of the studies that used qualitative estimates found support. The timing of measurements also explained some of the ambiguity; studies that provided little information regarding the timing of their foliage density estimates were less likely to support the nest-concealment hypothesis. Species with more conspicuous male plumage were less likely to support the nest-concealment hypothesis when we analyzed studies that used visual estimates. Whereas species with more conspicuous female plumage were more likely to support the nest-concealment hypothesis when we analyzed studies that used quantitative measures. Our results demonstrate that support for the nest-concealment hypothesis has been equivocal, but that some of the ambiguity can be explained by morphological traits and methods used to measure concealment.

Wilson Journal of Ornithology↗
USGS2016

Eastern Whip-poor-wills (Antrostomus vociferus) are positively associated with low elevation forest In the central Appalachians

Populations of the Eastern Whip-poor-will ( Antrostomus vociferus ) are thought to be declining because of a range of potential factors including habitat loss, pesticide use, and predation. However, this species is nocturnal and, as a consequence, it is poorly studied, and its population status is not well assessed by traditional diurnal bird surveys. We used nocturnal road surveys to study habitat associations and distribution of Eastern Whip-poor-wills to better understand and contextualize their population status and to provide a framework for subsequent research and management. We used occupancy models to associate presence of Eastern Whip-poor-wills with habitat characteristics. Global models with habitat associations at a radius of 1600 m (1.0-ha area) were the best supported by the data, suggesting that this was the scale at which the species responded to the habitat parameters we measured. At this scale, Eastern Whip-poor-wills most frequently occupied areas lower in elevation and characterized by forested, herbaceous, and wetland cover types. In contrast, high elevation conifer forest communities had substantially fewer Eastern Whip-poor-wills. Detection rates were positively correlated with moon visibility and negatively correlated with noise. We used the results of our surveys to generate a regional model to predict distributions of Eastern Whip-poor-wills and that can be used as a framework for future management. Our results suggest that succession of agricultural fields and other clearings into forested habitats with dense understory may be a contributing factor to ongoing declines of Eastern Whip-poor-wills.

West Virginia↗
USGS2016

Hanging out at the airport: Unusual upside-down perching behavior by Eurasian Jackdaws (Corvus monedula) in a human-dominated environment

Animals occupying human-dominated environments show the capacity for behavioral flexibility. Corvids are among the most intelligent synanthropic bird species. During a layover at Schipol Airport in Amsterdam, Netherlands, I photographically documented Eurasian Jackdaws ( Corvus monedula ) perching upside down from a building cornice. In contrast to other reports of hanging birds, these jackdaws did not forage or play while upside down and appeared to use the perching spot to observe their surroundings. Although Corvids and Psittacines are known to hang upside down, especially in captive situations, such behaviors are rarely documented in the wild, and never before in association with human-built structures.

Wilson Journal of Ornithology↗
USGS2012

Reoccurrence of 'Ōma'o in leeward woodland habitat and their distribution in alpine habitat on Hawai'i island

The endemic solitaire, 'Oma'o (Myadestes obscurus), is common in windward forests of Hawai'i Island, but has been historically extirpated from leeward forests. The last detections of 'Oma'o on the leeward side of the island were in woodland habitat on the western flank of Mauna Loa in 1978. 'Oma'o were detected in woodland habitat in relatively low densities during a 2010 forest bird survey of Hawai'i Volcanoes National Park. The source of the population is unknown. It is probable they originated from a documented but unsurveyed population of 'Oma'o in scrub alpine lava. Alternatively, the birds may have persisted undetected for nearly 35 years, or expanded from windward mesic forests on southeast Mauna Loa. There is no evidence 'Oma'o recolonized the wet mesic forests of leeward Mauna Loa. The 'Oma'o can occupy diverse native habitats compared to other species in the Hawai'i Myadestes genus, of which most species are now extinct. The connectivity of each population is not understood but we assume there are significant geographic, physiological, and behavioral barriers for scrub alpine and wet mesic forest populations. The expansion of 'Oma'o to leeward woodlands is encouraging as the species is Hawai'i Island's last native frugivore capable of dispersing small and medium sized seeds of rare angiosperms, and could have an important role in re-establishing ecosystem function.

Hawaii↗
USGS2012

Red-tailed Hawk movements and use of habitat in the Luquillo Mountains of Puerto Rico

The Red-tailed Hawk ( Buteo jamaicensis ) is a top predator of upland ecosystems in the Greater Antilles. Little information exists on the ecology of the insular forms of this widely distributed species. We studied movements and resource use of the Red-tailed Hawk from 2000 to 2002 in the montane forests of northeastern Puerto Rico. We captured 32 and used 21 radio-marked Red-tailed Hawks to delineate home range, core area shifts, and macrohabitat use in the Luquillo Mountains. Red-tailed Hawks in the Luquillo Mountains frequently perched near the top of canopy emergent trees and were characterized by wide-ranging capabilities and extensive spatial overlap. Home range size averaged 5,022.6 ± 832.1 ha (305–11,288 ha) and core areas averaged 564.8 ± 90.7 ha (150–1,230 ha). This species had large mean weekly movements (3,286.2 ± 348.5 m) and a preference for roadside habitats. Our findings suggest fragmentation of contiguous forest outside protected areas in Puerto Rico may benefit the Red-tailed Hawk.

Puerto Rico↗
USGS2012

Growth Rate and Relocation Movements of Common Nighthawk (Chordeiles minor) Nestlings in Relation to Age

Relocation by dependent young is a survival strategy that occurs among a wide range of taxa. The Common Nighthawk (Chordeiles minor) lays its eggs on bare substrate and, once hatched, nestlings may relocate to new sites daily. We located and monitored eight Common Nighthawk nests in Grand Teton National Park, Wyoming, quantified inter-use-site distances in relation to nestling age, and calculated a nestling growth rate curve. Common Nighthawk nestlings grow in a nearly linear fashion. Nestlings moved up to 48 m in a single day and larger, older nestlings tended to move greater distances between daily use-sites.

Wilson Journal of Ornithology↗