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A new species of New World flycatcher in the genus Myiopagis (Aves, Tyrannidae, Elaeniinae) is described from Andean submontane forest of eastern Ecuador and eastern Peru. It appears to be most closely related to M. caniceps of lower elevations and more distantly to M. gaimardii, with which it is syntopic.
Few nests of Amazonian antbirds (Thamnophilidae and Formicariidae) have been described. Here we present nesting records for five species of antbirds found in Tinigua National Park, Colombia. A pouch-shaped pensile nest of the Warbling Antbird (Hypocnemis cantator) in a treefall gap within seasonally flooded forest contained two eggs colored like those found in French Guiana but different from those in Amazonian Brazil and Peru. The Black-spotted Bare-eye (Phlegopsis nigromaculata) also nested in seasonally flooded forest; it constructed a cup-shaped nest inside a hollow rotten stump and laid two eggs. Two naked nestlings with bright yellow bills disappeared soon after hatching. Two cup-shaped nests of the Scale-backed Antbird (Hylophylax poecilinota) were in mature terra firme forest. Both contained two eggs similar in color to those of other subspecies; nestlings were naked and had conspicuous yellow bills. Those found in one nest disappeared 11 days after hatching. A nest of the Amazonian Streaked-Antwren (Myrmotherula multostriata) containing one egg was in seasonally flooded forest close to the river bank. This egg differed in coloration from others found in Brazil and from those of other members of the M. surinamensis complex, with which it was formerly considered conspecific. A Striated Antthrush (Chamaeza nobilis) nested in an unlined natural cavity some 3 m above the ground. The nestling closely resembled the adult but was smaller, had yellow bill commissures, and a shorter tail.
The foraging ecology of wintering Harlequin Ducks (Histrionicus histrionicus) is poorly understood and information on basic food habits is lacking for this species in the Aleutian Islands of Alaska where the largest winter concentrations occur. We investigated feeding behavior and food habits of wintering Harlequin Ducks in the western Aleutian Islands of Alaska with respect to sex and temporal and environmental variables to document behavioral responses to winter conditions, resource use, and nutritional requirements. We found that on average, Harlequin Ducks spent most of the diurnal period feeding (70% males, 76% females). However, more time was spent feeding during evenings, midwinter, cold weather, and high tides. Gastropods, crustaceans, and diptera larvae made up 83% of the diet, but diet composition changed throughout winter. Despite change in food habits, diet energy density was stable throughout winter.
Habitat use and home range sizes of female Eastern Wild Turkeys (Meleagris gallopavo silvestris) during preincubation may influence reproductive success. Little information on habitat selection during preincubation at multiple spatial scales is available and the influence of preincubation movement rates on reproductive success is poorly understood. We monitored 35 adult female Eastern Wild Turkeys during preincubation in central Mississippi during 1996–1997. We estimated home range and core area size, macrohabitat selection at multiple spatial scales and movement rates from 1 February until the beginning of incubation. Preincubation home ranges averaged 306.6 (±46.8 SE) ha and core areas 47.3 (±7.4) ha. Females selected 9–15 and 16–29 year-old pine (Pinus spp.) stands over other habitats available when establishing home ranges, but within these home ranges they selected pine stands that were older than 30 years for their core areas and nest sites. However, females used habitats within their established home range in proportion to availability. Movement rates averaged 286.5 (±22.3) m/hr during preincubation and were greater than during other seasons. We detected no correlations between home range or core area size and number of days nests were successfully incubated. However, we detected a positive correlation between movement rates and increased incubation, suggesting females that moved farther during preincubation successfully incubated nests longer. Our findings suggest females selected habitats differentially when establishing pre-incubation home ranges and core areas. Further, our findings suggest movement rates within home ranges may better reflect a female's habitat sampling effort during nest site selection rather than home range or core area size.
We characterized 30 diurnal roost sites of five radio-tagged Northern Saw-whet Owls (Aegolius acadicus) in the winters of 1996–1997 on Assateague Island, Maryland and found they preferred thick cover at roost sites. Roosts occurred most often in loblolly pine forest (Pinus taeda) and shrub swamps dominated by wax myrtle (Myrica cerifera). Vegetation was measured at paired roosts and random sites in similar habitats. Distance to nearest tree and average canopy height were significantly lower at roost sites than random sites. Numbers of stems larger than 2.5 cm diameter at breast height (dbh), stems smaller than 2.5 cm dbh, and roost tree dbh were larger at roost sites. Roost height, canopy cover, canopy height, shrub height, and ground cover differed significantly between pine and shrub swamp roosts, although cover above and below the roost site were similar. Higher densities of stems and shorter distances to the nearest tree at roost sites compared to random sites indicated that owls chose sites with dense cover, probably as protection from predators or weather.
In this study we analyzed geographic variation in the Northern Waterthrush (Seiurus noveboracensis) and reassessed the status of the four subspecies described between 1880 and 1948, three of which were recognized by the AOU Check-list (1957) and Godfrey (1986). We examined 490 specimens that came from throughout the breeding range of the Northern Waterthrush and used four morphometric data sets and three color variables to investigate geographic variation. Males differed from females based on morphometric characters. Males, unlike females, showed a morphometric trend with latitude and longitude. Their wing chord, tail and tarsus lengths showed a gradual decrease in length from north to south, while their tail and tarsus lengths gradually decreased eastward. The body shape showed a longitudinal trend where western specimens tended to have proportionally longer tails than wings compared to specimens from the eastern part of the range. Color was more strongly related to geography than morphometric characters and showed both longitudinal and latitudinal trends. Specimens from the southeastern part of the range were more olive dorsally and yellow ventrally and had fewer underpart markings than most specimens from the northwestern part of the range. Only the wing length permitted us to discriminate between the most distant populations. These trends are clinal and cannot support the recognition of subspecies.
We describe the spatial organization and social behavior of Hermit Thrushes (Catharus guttatus) wintering in pine plantations and an adjacent hardwood forest in Tangipahoa Parish, Louisiana over three winters. We used point counts (n = 403) to collect data on agonistic behaviors and relative abundance within the study area. We used mist-netting to study site fidelity on four 9-ha plots within and among years. We used radio-telemetry to measure Hermit Thrushes' movements and territoriality (n = 50). We found that Hermit Thrushes saturated suitable patches within the study area. Most Hermit Thrushes actively defended small [mean = 0.55 ± 0.03 (SE) ha], minimally overlapping (15.90 ± 3.63%) territories throughout the winter. Hermit Thrushes established and maintained territories using the same agonistic behaviors described for breeding birds. A few non-territorial birds (14%) moved among occupied territories, but most were faithful to a larger neighborhood, apparently awaiting a territory vacancy. Territorial behavior and frequency of non-territorial birds did not differ among age and sex classes, suggesting the absence of a sex- or age-based dominance hierarchy. The behavior of Hermit Thrushes conformed to the emerging view that competition for spatially mediated resources on the wintering grounds, such as food or cover, contribute to limiting populations of many species of migrant passerines.
We compared the effect of nest predation and cowbird parasitism on the breeding success of two simultaneously nesting ecologically similar blackbird species that differ in their breeding strategies. The Scarlet-headed Blackbird (Amblyramphus holosericeus) is a monogamous species that performs territorial defense. In contrast, the Brown-and-yellow Marshbird (Pseudoleistes virescens) is a non-territorial monogamous breeder that performs mate guarding and has helpers at the nest. Both species suffered similar nest predation rates throughout their nesting cycle. However, the Brown-and-yellow Marshbird suffered higher parasitism from Shiny (Molothrus bonariensis) and Screaming cowbirds (M. rufoaxillaris) than the Scarlet-headed Blackbird (62.6% vs 15.4%). Brood parasitism accounted for most of the egg losses and hatching failures in Brown-and-yellow Marshbird. Parasitized nests had lower egg survival and hatching success than non-parasitized ones. Mean clutch size was 1.5 eggs larger in Brown-and-yellow Marshbird than in Scarlet-headed Blackbird. However, Scarlet-headed Blackbird had higher hatching success than Brown-and-yellow Marshbird and similar fledging success. Consequently, both species produced similar numbers of fledglings. We did not detect any relationship between the reproductive success of these species and their breeding strategies. The presence of helpers at Brown-and-yellow Marshbird nests did not affect nest defense or chick survival, but helpers might account for reduced parental effort by supplementing food delivery to chicks/fledglings.
Louisiana Seaside Sparrows (Ammodramus maritimus fisheri) breed and winter exclusively in brackish and saline marshes along the northern Gulf of Mexico. Many Gulf Coast marshes, particularly in the Chenier Plain of southwestern Louisiana and southeastern Texas, are burned intentionally in fall or winter as part of waterfowl management programs. Fire reportedly has negatively affected two Seaside Sparrow subspecies (A. m. nigrescens and A. m. mirabilis) in Florida, but there is no published information regarding effects of fire on A. m. fisheri. We compared abundance of territorial male Louisiana Seaside Sparrows, number of nesting activity indicators, and vegetation structure in paired burned and unburned plots in Chenier Plain marshes in southwestern Louisiana during the 1996 breeding season (April–July) before experimental winter burns (January 1997) and again during two breeding seasons post-burn (1997–1998). We found that abundance of male sparrows decreased in burned plots during the first breeding season post-burn, but was higher than that of unburned plots during the second breeding season post-burn. Indicators of nesting activity showed a similar but non-significant pattern in response to burning. Sparrow abundance and nesting activity seemingly are linked to dead vegetation cover, which was lower in burned plots during the first breeding season post-burn, but did not differ from that in unburned plots during the second breeding season post-burn. We recommend that marsh management plans in the Gulf Coast Chenier Plain integrate waterfowl and Seaside Sparrow management by maintaining a mosaic of burned and unburned marshes and allowing vegetation to recover for at least two growing seasons before re-burning a marsh.
Little is known about the effects of forest fragmentation on bird communities in the boreal forests of western North America. Assessing the impact of forest fragmentation on bird communities has been complicated by the fact that few studies have applied statistical analyses that account for the possibility that individuals are randomly dispersed within landscapes. From 1993–1997, we contrasted bird communities in contiguous forest (54 sites) and nearby forest fragments surrounded by agricultural land (106 sites, 0.2–123 ha). Species were divided into groups based on migratory strategy (resident, short-distance migrant, long-distance migrant, and irruptive) and edge-sensitivity (edge, edge-interior, and interior). For each group, we tested whether richness and abundance were different from what would be expected if birds were distributed randomly across landscapes. Species richness was higher than expected in contiguous forest for interior species, whereas edge and short-distance migratory species were more common in the fragmented landscape. Similarly, the total abundance of interior and long-distance migratory birds was higher in contiguous forest, whereas edge birds were more abundant in the fragmented landscape. Brown Creeper (Certhia americana), Swainson's Thrush (Catharus ustulatus), Tennessee Warbler (Vermivora peregrina), Magnolia Warbler (Dendroica magnolia), Blackburnian Warbler (Dendroica fusca), Black-throated Green Warbler (Dendroica virens), and Bay-breasted Warbler (Dendroica castanea) were virtually absent from the fragmented landscape, yet were common in contiguous forest. Within the fragmented landscape, forest fragment size had little effect on species richness but was significantly correlated with abundance of all migratory and edge-sensitivity groups except edge and short-distance migrants. Probability of occurrence, controlling for random placement, was positively correlated with forest fragment size, percent forest cover within 5 km, or the interaction between size and cover for 19 species, most of which were associated with forest interiors. Predation and brood parasitism were higher on nests of ground and shrub nesting birds in the fragmented landscape than in contiguous forest. Fragmentation of contiguous forest in the southern boreal mixedwood zone of western Canada has a negative impact on the abundance of several resident and long-distance migratory species.
We investigated the distribution of wintering woodland bird species in 47 very small, isolated, woodland fragments (0.54–6.01 ha) within an agricultural landscape in north-central Ohio. Our objectives were to determine correlations between temporal, habitat, and landscape variables and avian presence, density, and species richness within the smallest woodlots occupied by such species. Our results suggest that even common species are sensitive to variation in habitat, landscape, and season. Woodlot area explained the most variation in presence, density, and species richness. Shrub cover was also an important predictor variable for presence of the smallest resident birds. Shrub cover might function as both a refuge from predators and as a windbreak, reducing thermal costs in a flat, open landscape. Landscape factors related to isolation and connectedness were also correlated with species presence and density. The species composition of the community changed through the winter, as did the density of individual species, suggesting that the winter season may play an important role in determining the distributions of bird populations across woodlots. The models presented here for Ohio birds in this specific landscape may have biological inference for other species in similar landscapes.
We surveyed vegetation and bird assemblages in protected and exploited woodlands in the warm temperate, coastal woodlands of Buenos Aires Province, Argentina. Exploited woodland experienced selective logging of Celtis tala until at least 1960; presently it is used for sheltering domestic livestock. Vertical structure and floristic composition were simpler in exploited than in protected woodland. Likewise, avian density and species richness were lower in exploited woodland. Viewing the avifaunas from a guild perspective, we found the insectivore guild and frugivore-insectivore guild differed substantially between protected and exploited woodlands. The bird densities of these guilds were higher in protected woodland, and the species richness of the insectivore guild was lower in the exploited woodland. Apparently the insectivore guild responded primarily to structural differences, whereas the frugivore-insectivore guild may have responded more to differences in floristic composition. The granivore guild also differed between the two woodlands, but primarily because of changes in the density of the Rufous-collared Sparrow (Zonotrichia capensis). This bird species was more abundant in the protected woodland.
Relative abundance and habitat use of 29 forest bird species, including 22 land birds (18 indigenous breeding residents, 3 exotics, 1 migrant) along with a rail, heron, and five seabirds (shearwater, tropicbird, 3 terns) were assessed on Pohnpei [Island] during summer 1994 and compared with the results of the first survey in 1983. The most frequently encountered species in both surveys were the Purple-capped Fruit-Dove (Ptilinopus porphyraceus), Pohnpei Lory (Trichoglossus rubiginosus), Micronesian Starling (Aplonis opaca), and Micronesian Honeyeater (Myzomela rubratra). Among the five species endemic to Pohnpei, the Pohnpei Mountain Starling (Aplonis pelzelni) verges on extinction, with only one confirmed sighting in nearly 50 years; the Long-billed White-eye (Rukia longirostra) is vulnerable to encroaching agriculture in its preferred and limited montane habitat, where nearly 90% of the sightings were on approximately 10% of the land area, and the Pohnpei Lory (Trichoglossus rubiginosus), Pohnpei Flycatcher (Myiagra pluto), and Pohnpei Fantail (Rhipidura kubaryi) are widespread and common, but were less frequently encountered in 1994 than in 1983. The total number of birds encountered per observation station during 8-minute point counts in each of six elevation zones was 67–80% fewer in 1994 than in 1983. Encounter rates (birds/hour) were reduced by at least 50% in both uplands and lowlands in at least 14 of 29 species; none of the 29 showed an overall increase. Artifacts of sampling and sampling bias may have contributed to reduced observation rates, but anecdotal evidence suggests a decline in numbers is real and may be attributed to combined effects of habitat degradation, hunting practices, and possibly predation by introduced species. Protection of the upland forests from further degradation and more frequent monitoring to better assess population trends are recommended.
In grebes of the genus Podilymbus, the upper barbs of the forehead feathers are fused with the shaft into a somewhat flattened, pointed structure. We believe that when raised, these feathers may indicate a low probability of attack.
The number of Hooded Merganser (Lophodytes cucullatus) broods hatching in nest houses on 53 study areas in Massachusetts increased by 289% from 1979–1983 to 1994–1998 and the number of areas used increased from 9 of 53 in 1979 to 26 of 53 by 1998. The number of Hooded Mergansers counted on 21 Massachusetts Christmas Bird Count circles from 1979–1983 to 1994–1998 increased by 225%. The increasing trend lines did not match, suggesting different populations. This appears to support reports of increasing Hooded Merganser populations by other northeastern state waterfowl biologists.
The Northern Harrier (Circus cyaneus) is a widespread raptor that preys mainly upon small mammals and, to a lesser extent, birds. Most published accounts of harrier food habits report the majority of avian prey items are passerines with few large (> 500 g) birds taken. In fall 1999, I observed a Northern Harrier that appeared to have attacked and killed a White-faced Ibis (Plegadis chihi) foraging in a playa wetland in Meade County, Kansas. Field observations of the harrier, in addition to physical evidence, suggest the attack was on an apparently healthy individual that did not have any obvious physical deformities. Northern Harriers appear to attack and kill White-faced Ibis and may prey on large birds more often than reported previously.
Some birds that attempt to nest in habitats such as conifer plantations may experience lower reproductive success and diminished fitness in comparison to conspecifics in other habitats, rendering such habitats sinks or ecological traps. We did not detect significant differences between conifer plantation and non-plantation nests in terms of clutch size, number of bandable young per nest, or nest success for Cooper's Hawks (Accipiter cooperii) in Wisconsin during 1980–1998. Pine plantations contributed recruits to subsequent breeding generations in proportion to their productivity of bandable nestlings. Conifer plantations in Wisconsin also contained nesting densities and productivity indices for Cooper's Hawks that are among the highest reported for the species. Thus, conifer plantations in Wisconsin are neither ecological traps nor population sinks for nesting Cooper's Hawks.
I report some observations of a Chestnut-bellied Euphonia (Euphonia pectoralis) nest in a lowland Atlantic Forest of southeastern Brazil during the early nestling period. During 7.5 hours of observations, the nest was attended 46.3% of the time, 45.6% by the female and 0.7% by the male. Unattended periods lasted 16–38 min. Parents visited the nest most of the time together at 36–59 min intervals. There were 1.06 feeding visits per nestling per hour. The two nestlings in the nest ended up preyed upon by army ants (Labidus praedator, Ecitoninae). The low height of the nest (0.8 m) may have facilitated its detection by the ants.
Generalist birds are thought to be less neophobic than specialists, but the dietary difference is often confounded by differences in experience and food availability. We conducted field tests with an artificial nectar source on a foraging generalist [Lesser-Antillean Bullfinch (Loxigilla noctis)] and a nectarivorous specialist [Bananaquit (Coereba flaveola)] in Barbados. Both species are equally opportunistic and tame on this island. Bullfinches arrived first at the feeding stations and showed a shorter latency to feed in the tests than did Bananaquits, suggesting that differences in specialization lead to the differences in neophobia predicted by ecological plasticity.
On 17 occasions in Chula Vista, California, at least one Belding's Savannah Sparrow (Passerculus sandwichensis beldingi) was observed chasing egg-carrying female fiddler crabs (Uca crenulata) and pecking eggs from ones it caught. Sparrows did not eat any part of the adult crab while eating the eggs. A fledgling learned this novel hunting technique after accompanying its parent for a month.
A Peregrine Falcon (Falco peregrinus) was observed stooping on a Whimbrel (Numenius phaeopus) that was eventually attacked by a nearby Common Raven (Corvus corax). This incident reinforces the idea that ravens are opportunistic and intelligent predators capable of kleptoparasitizing large prey items.
I report avian behavioral responses to a total solar eclipse on the north coast of Venezuela during the afternoon of 26 February 1998. Magnificent Frigate-birds (Fregata magnificens), Brown Pelicans (Pelecanus occidentalis), and Royal Terns (Sterna maxima), which had been foraging over the water before the eclipse, left the bay 39 (terns) or 13 (frigate-birds and pelicans) min before the eclipse became total. The frigate-birds flew inland and the pelicans went to roosts on cliffs bordering the bay. Residents of the local village, who knew the birds' behavior well, remarked that the frigate-birds and pelicans were behaving as they normally did at sunset. Laughing Gulls (Larus atricilla) ceased foraging and flew rapidly back and forth over the water in a tight flock during the 3 min 40 s of totality. Twelve minutes after the solar disc emerged, the frigate-birds and pelicans began to return to the bay, and they and the gulls resumed foraging. The terns still had not reappeared more than 1 hr after totality. Solar eclipses, although of brief duration, apparently reduce light levels sufficiently to temporarily interrupt normal avian diurnal behavior.
The plumage of birds harbors diverse bacteria but their distribution on feathers is unknown. We plucked a single contour feather from the venter of each of 75 passerines captured in mist nets in September, October, and November 1995. Bacteria were significantly more abundant on the distal part of the feather than the proximal part. We suggest that feathers may be a barrier to bacterial infections of the skin and that distal barbs are more likely to be damaged by feather-degrading bacteria than proximal barbs.