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We encountered white-eyes (Zosterops) that did not match any known species during ornithological field observations in the Togian Islands, Gulf of Tomini, Sulawesi, Indonesia. Subsequently, we collected a specimen and made tape recordings. We consider the Zosterops of the Togian Islands to be a new species that differs most strikingly from the Black-crowned White-eye (Z. atrifrons) in lacking a white eye ring and in soft-part colors. The new species has a somewhat higher-pitched, less modulated song than Z. atrifrons. It seems uncommon and has been encountered only near sea level on three small islands, and it may be best considered Endangered. This brings the number of endemic species in the Togian Islands to two and, under BirdLife International criteria, this island group (which has recently been declared a National Park) now qualifies as an Endemic Bird Area.
New information on vocalizations of populations of the White-eyed Foliage-gleaner (Automolus leucophthalmus), and analysis of biometric and plumage characters, reveal that it consists of two biological species. One form is restricted to the Pernambuco Center of Endemism in coastal northeastern Brazil and the second occupies much of the remainder of humid Atlantic Forest from Bahia, Brazil south to northeastern Argentina and eastern Paraguay. The northeastern form, although cryptically similar morphologically to other subspecies of Automolus leucophthalmus, is highly differentiated in several vocal characters. The vocal difference between the two groups exceeds that between other accepted species pairs within the genus. Reciprocal tape-playback experiments offer supporting evidence that vocal differences within the White-eyed Foliage-gleaner complex are sufficient to act as isolating mechanisms in the event of secondary contact between the two groups. The northeastern form is shown to have vocal and morphological similarities to the Para Foliage-gleaner (Automolus paraensis) of southeastern Amazonian Brazil, supporting hypothesized Amazonian origins of the leucophthalmus complex, as well as a sister relationship with the Automolus infuscatus/paraensis complex.
Tropical birds offer unique opportunities to test ecological and evolutionary theory because their life history traits are so diverse and different from temperate zone models upon which most empirical studies are based. We review recent studies on the behavioral ecology of tropical birds, studies that explore new advances in this field. Life histories and their evolution remain the focus of research on tropical birds. Clutch size manipulations in two species showed that food limitation does not explain small clutch size. In antbirds, enlarged clutches decreased post-fledging survival whereas in thrushes, enlarged broods were costly due to high nest predation. Small clutches may be favored via different ultimate selective forces and shared underlying tradeoffs between the immune, metabolic, and endocrine systems in the body may account for the commonly observed ‘slow pace of life’ in tropical birds. The physiological tradeoff between testosterone and immunocompetence may explain the evolution of low testosterone levels in tropical passerines where adult survival is paramount. In contrast to life history theory, few studies have explored temperate-tropical differences in territoriality, mating systems, and song function. The idea that low breeding synchrony in tropical birds is associated with low levels of extra-pair fertilizations was supported by several new paternity studies conducted on tropical passerines. Seasonally breeding tropical birds have higher testosterone levels than tropical birds with prolonged breeding seasons, although it is unclear if this pattern is driven by mating systems per se or selection from pathogens. Recent work on relations between pair members in permanently paired tropical passerines focuses on the question of mate defense versus territorial defense and the extent of cooperation versus selfish interests in inter-sexual relations.
The Rufous Twistwing (Cnipodectes superrufus), a newly described Amazonian tyrant-flycatcher, is known from five specimens and five localities in Cuzco and western Madre de Dios departments, Peru. We report three additional specimens and eight new localities extending the known range of the species east across Dpto. Madre de Dios, Peru, into Dpto. Pando, Bolivia, and Acre State, Brazil. The new localities increase the distribution from ∼3,400 to ∼89,000 km2. We collected biometric data from five individuals, made behavioral observations in the field, and recorded three separate types of vocalizations, two of which (including the song) were previously unknown. We provide quantitative description of these vocalizations, consider their function, and compare them with vocalizations of the only known congener, the Brownish Twistwing (Cnipodectes subbrunneus). Unique vocal repertoires support the classification of these two forms as sister species. The Rufous Twistwing resembles the Brownish Twistwing in producing loud vocalizations from regular song posts and both species appear to have a polygamous mating system. We provide further evidence consistent with the hypothesis the Rufous Twistwing is a Guadua bamboo specialist and recommend that it be listed as Vulnerable on the IUCN Red List.
The Aldabra Rail (Dryolimnas [cuvieri] aldabranus) is endemic to Aldabra Atoll, Seychelles and is the last remaining flightless bird in the tropical western Indian Ocean. We studied it over two breeding seasons from 1999 to 2001. Pairs formed strong bonds, defended territories year-round, and were mate and territory faithful across seasons. Reproductive duties are shared by males and females. Breeding was closely tied to the rainy season and pairs responded to favorable conditions by increasing clutch size and clutch frequency. Clutches contained 1–4 eggs and replacement clutches were laid if nests failed early in the season. The incubation period was 19–24 days and hatching was usually synchronous. Mayfield estimates of daily survival of eggs and nesting success were 98.8% and 77.0%, respectively. Hatching success was 60.9% and 57% of chicks that hatched were successfully reared to independence. Chicks are sub-precocial and fledged chicks were cared for in the natal territory for at least 2 months, after which they were forcibly evicted. A large repertoire of behaviors and ritualized displays are described including pseudo-copulation and reverse mounting.
We used radio telemetry to study post-fledging dispersal patterns of juvenile Swainson's Thrushes (Catharus ustulatus) in central coastal California from 2000 to 2002. We followed 30 different broods during the dependent period and 35 juveniles after independence. Adults with dependent juveniles had two types of movements, drifting and stationary, similar to those described for Wood Thrush (Hylocichla mustelina). All juveniles established at least one post-fledging dispersal area (n = 29) after independence and most (62%) established a second; therefore, most home ranges were comprised of disjunct dispersal areas. Median home range (95% fixed-kernel) and core (50% fixed-kernel) areas were 2.0 ha (range = 0.2–9.0) and 0.41 ha (range = 0.05–1.6), respectively. Juveniles spent from 3 to 39 days in different post-fledging dispersal areas; they generally had a primary dispersal area where they spent the majority of their time. Juveniles spent an average of 22.7 ± 1.5 days in primary and 9.6 ± 0.9 days in secondary dispersal areas. The median post-fledging dispersal distance was 147 m (range = 28–1,040 m) for initial dispersal from a brood-rearing area and 418 m (range = 154–2,624 m) for subsequent dispersal movements. Initial dispersal was not directed; however, final dispersal (brood-rearing area to final location) was directed to the northwest for all plots combined and west for one plot. We suggest that post-fledging movements and spatial habitat-use patterns are affected by adult breeding strategies, and by spatially and temporally clumped resources.
Stopover behavior and migratory pathways of neotropical migrant birds in Central and South America have received little study. We examined stopover ecology of Swainson's Thrush (Catharus ustulatus) on the Osa Peninsula, Costa Rica, during spring migration, 2002–2005. Capture rates per net hour were high (;amx = 21.8 individuals/100 net hrs) suggesting large numbers pass through lowland coastal areas in spring. Mean passage date of males was ∼6 days earlier than females. Timing of passage by age class was variable; after-second year (ASY) birds preceded second-year (SY) birds in 2 years, SYs preceded ASYs in 1 year, and both had the same mean passage date in 1 year. We also observed annual variation in relative abundance of the two age groups. Only 1.7% of marked Swainson's Thrushes were recaptured on subsequent days suggesting most individuals left the immediate area soon after initial capture. Stopover lengths ranged from 1 to 9 days, although most were <4 days. Many individuals had some energy stores on arrival (fat score ≥ 1) but reserves varied between years and tended to be lower in SYs compared to ASYs. Regression of body mass against time of day indicated that individuals tended to gain mass throughout the morning (0.67% of lean body mass/hr on average). Our findings for stopover lengths, rates of mass gain, and recapture rates are within the range observed at North American stopover sites in spring. However, our capture rates were relatively higher, perhaps because the small land mass of southern Central America concentrates individuals at stopover sites in these regions.
We quantified demographic parameters of Eastern Yellow Wagtails (Motacilla tschutschensis) breeding at Cape Romanzof, Yukon Delta National Wildlife Refuge, Alaska. We monitored 79 nests in an 837-ha area during 1997–1999 and banded 160 individuals. Mayfield nest success differed among years and ranged from 0.14 to 0.63/year. Most nest failures were attributed to predation. Annual fecundity (mean number of fledglings/female) ranged from 0.7 to 3.7. At least 8.8% of nests had polygynous males; females paired with polygynous males had the same fecundity as monogamous females. Forty-two to 100% of the breeding males returned the following year, usually to the same territory while no adult females returned. Four nestlings banded in the study area returned to nest the following year. The best model for annual survival accounted for differences between both age groups and years. The demography of Eastern Yellow Wagtails at Cape Romanzof varied and was characterized by relatively high adult male survival and site fidelity, female-biased dispersal, and weak natal philopatry. The absence of returning females is significant and possible differences in migration stopovers and wintering locations should be investigated. Moderate levels of male immigration may be necessary in periodic pulses to maintain a local population, but female immigration would need to be massive and sustained.
We studied the breeding ecology of the Narcissus Flycatcher (Ficedula narcissina elisae) in subalpine secondary broad-leaf forest near Beijing, China during 2003–2006. The Narcissus Flycatcher arrived in the breeding area at the beginning of May with first-spring males arriving later than older males. Nests of first-spring male Narcissus Flycatchers were at lower altitudes (1,271.0 ± 20.7 m) than those of older males (1,363.8 ± 22.5 m). Narcissus Flycatchers nested in diverse sites on different plant species with Betula dahurica being most commonly used. Nests of Narcissus Flycatchers were exposed and 2.5 ± 0.3 m above the ground with mean clutch size of 4.3 ± 0.2. Mean egg length was 17.2 ± 0.1 mm, mean egg width was 13.2 ± 0.1 mm. and mean egg mass was 1.5 ± 0.0 g. The mean incubation period was 13.4 ± 0.2 days and mean nestling period was 13.2 ± 0.2 days. Fledging success was 4.0 ± 0.3 fledglings per successful nest. The Narcissus Flycatcher had low breeding success (51.2%), mainly because of predation.
We investigated the impacts of urbanization on reproductive success of House Wrens (Troglodytes aedon). We compared reproductive effort and success for 33 nesting attempts in suburban sites (2.5–10 buildings/ha) and 43 nesting attempts in rural sites (<2.5 buildings/ha) in and around the Washington, D.C.– Baltimore, Maryland, metropolitan area. There were no differences in clutch initiation dates or clutch sizes between suburban and rural nests. However, nestlings at suburban nests weighed less and had smaller body size prior to fledging compared to nestlings at rural nests. Parental feeding rates differed between suburban and rural nests during the “early nestling stage” (day 3 to day 6), but not in the “late nestling stage” (day 8 to day 12) suggesting average quality of prey for nestlings may be lower at suburban sites. Overall, suburban nests fledged more young than rural nests largely because of higher rates of nest predation on rural nests. Further research on how food availability and predation affects nesting success of House Wrens and other birds along urbanization gradients may provide important insights into impacts of urbanization on birds.
We studied the breeding habitat of Cerulean Warblers (Dendroica cerulea) in southern Indiana in the Ohio River Valley in 2002–2003 to identify similarities and differences in habitat characteristics compared to breeding habitats reported for this species in other geographical regions. Ten 259-ha study plots were surveyed for Cerulean Warblers and territories were mapped using locations of perched, singing males. We measured slope and vegetation characteristics including canopy height and cover, ground cover, number of shrubs and shrub species, number of trees, DBH, and number of snags at Cerulean Warbler territories and non-use sites. Habitat characteristics associated with Cerulean Warbler territories compared to non-use sites were higher canopy height (28 m) and cover (84%), larger trees (>38 cm DBH), higher slope (11°), fewer number of trees (30), and fewer trees between 3 and 23 cm DBH. Calculated Mayfield estimate of nest productivity (0.165) was lower compared to Mississippi Alluvial Valley sites (0.242).
Grassland birds have experienced greater population declines than any other group of birds monitored by the North American Breeding Bird Survey. Our goal was to compare demographic rates among years within species and among species of grassland birds. Eight-hundred and eleven nests of Henslow's Sparrows (Ammodramus henslowii), Grasshopper Sparrows (A. savannarum), Field Sparrows (Spizella pusilla), Dickcissels (Spiza americana), and Eastern Meadowlarks (Sturnella magna) were monitored between 1999 and 2003. Mayfield nest success including the egg-laying stage, as well as the incubation and nestling periods, was 20, 34, 15, 20, and 18%, respectively. Most nest failures were attributed to predation. Nest parasitism by Brown-headed Cowbirds (Molothrus ater) was infrequent (<2% of all nests parasitized). Clutch size decreased during the nesting season for Dickcissels, Grasshopper Sparrows, and Field Sparrows. Nesting phenology suggests the possibility of multiple-brooding for all five species in this study.
We describe post-fledging movements and evaluate the effects of local vegetation, temporal, and biological factors on home range size for two species of declining grassland birds in southwestern Missouri from 2002 to 2004. We obtained ≥30 detections for 74 individual juvenile Dickcissels (Spiza americana) and 64 juvenile Eastern Meadowlarks (Sturnella magna) during the post-fledging period. Juvenile Eastern Meadowlarks had a greater total number of days (6.7 ± 0.6) with large (>300 m) movements than juvenile Dickcissels (5.0 ± 0.5 days). Average Dickcissel home range size was larger and three times as variable in 2002 (77.0 ± 22 ha) compared to 2003 (31.4 ± 7.5 ha) and 2004 (34.9 ± 7.5 ha). There were year-specific effects of the variability in vegetation height on home range size of juvenile Dickcissels. Home range size was similar among years for juvenile Eastern Meadowlarks (2002, 109.4 ± 39.2 ha; 2003, 82.7 ± 29.4 ha; 2004, 70.7 ± 11.6 ha), but there was a year-specific effect of variability in grass cover on home range size of juvenile Eastern Meadowlarks. Local vegetation conditions are important factors affecting home range size and movements during the post-fledging period.
We compared abundance, daily survival rate, nest site characteristics, food availability, nest activity, and nestling size of Dark-eyed Juncos (Junco hymenalis) between burned and unburned mechanically-thinned ponderosa pine (Pinus ponderosa) forest units. Dark-eyed Junco territory density, number of detections in point counts, and daily nest survival were similar between treatments. Average bare ground was 4.8 times higher and litter cover was 2.6 times lower at nest sites in burned units compared to unburned nest sites. However, there was 28% less burned area around nests compared to random points in burned units, indicating that juncos placed nests in unburned portions of burned units. They also selected non-traditional nesting sites in burned units such as root holes and in trees. Arthropod abundance was higher in burned units 1-year post burn although numbers were similar in the second-year post burn. Nest attentiveness and feeding rates were three times higher in burned units, possibly in response to increased food availability. The potentially negative effect of prescribed burning through reduction of litter and increase in bare ground was offset by novel nesting strategies and increased food availability.
There are increasing conservation concerns associated with boreal regions, but little is known about winter habitat requirements of bird species inhabiting them. We examined flock size, winter habitat preference, and home range size of Boreal Chickadees (Poecile hudsonica) in a boreal forest harvested for timber near Quebec City, Quebec, Canada. We investigated whether and to what extent home range size was affected by clearcuts and regeneration forest stands. Flocks included an average of four individuals and occupied a mean winter home range of 14.7 ha. Flock membership and size were stable during the winter. Boreal Chickadees strongly preferred mature stands of commercial value (>7 m in height) and used regenerating stands (4–7 m in height) to a lesser extent. Younger stands (<4 m in height) and open areas were avoided. Home range size was not associated with landscape composition, but flocks with larger home ranges used them less evenly than those with smaller home ranges. This resident species prefers stands of commercial value and logging may contribute to apparent population declines of Boreal Chickadees.
We studied the possible long-term (1987 vs. 2003–2004) effects of wastewater irrigation of forests to habitat and a songbird community in central Pennsylvania. The study site, Toftrees, is a wastewater-irrigated deciduous forest interspersed with agriculture grasslands and crop fields that receives ∼260 cm of wastewater annually. Habitat variables were quantified within 15 random 0.04-ha circular plots in 2003 and 20 random plots in 1987. We conducted bird surveys twice weekly during 2003 and mist-netted birds for 1,250 hrs during 2004. Surveys and mist-netting efforts paralleled those conducted in 1987. A major decline in density of understory trees and short shrubs was noted between 1987 and 2003; in contrast, cover of herbaceous vegetation and density of tall shrubs dramatically increased. Ground-shrub foraging bird species and two mid-canopy foragers, Red-eyed Vireo (Vireo olivaceus) and Eastern Wood-Pewee (Contopus virens), declined from 1987 to 2003–2004. Conversely, Gray Catbirds (Dumetella carolinensis) increased dramatically over this time period.
Breeding bird populations were sampled between 1954 and 1963, and 1990 and 2000 in an old-growth forest, the Natural Area of Huntington Wildlife Forest (HWF), in the Adirondack Mountains of New York. Trends were compared with data from regional North American Breeding Bird Surveys (BBS) and from a forest plot at Hubbard Brook Experimental Forest, New Hampshire. Trends for 22 species in the HWF Natural Area were negative, eight were positive, and one was zero; 20 were significant. Fifteen of 17 long-distance migrants declined, whereas 7 of 14 short-distance migrants and permanent residents declined. Most (74%) HWF Natural Area species, despite differences in sampling periods and local habitat features, matched in sign of trend when compared to Adirondack BBS routes, 61% matched northeastern BBS routes, and 71% matched eastern United States BBS routes, while 66% matched Hubbard Brook species. The agreement in population trends suggests that forest interior birds, especially long-distance migrants, are affected more by regional than local factors. The analysis indicated that bird trends generated from BBS routes may not be as biased toward roads as previously suggested.
We investigated patterns of mortality during post-breeding migrations of California Gulls (Larus californicus) nesting near Laramie, Wyoming, USA. We used 151 recoveries and 647 sightings of banded and patagially-marked gulls to compare ratios of mortalities to observations of live birds (1) during four time periods (early and late fall migration, winter, and spring migration), (2) at two locations (Pacific coast and inland), and (3) among three age-classes of gulls (fledglings, 1- and 2-year-olds, and breeding-age adults). Mortality rates were higher in inland areas (35%) than in coastal areas (15%) and were dependent on season within inland areas, but not in coastal areas. Mortality in inland areas during early fall (21%) was comparable with that in coastal areas (13%) but was higher during late fall (68 vs. 13%) and spring migration (46 vs. 17%). Both fledgling (71%) and adult (64%) gulls experienced high mortality rates during late fall migration, possibly because some gulls were too weak to make their way to the Pacific coast and became trapped by poor weather conditions. Adult gulls also experienced high mortality inland during spring migration; few subadults made the costly migration to and from the breeding area. Some adults also skipped breeding and remained in coastal areas during the breeding season.
We placed predator exclosures around 31 Black Tern (Chlidonias niger) nests in Maine in 2001–2002 to measure growth and survival of chicks. Fifty-four percent of exclosed nests that hatched young were depredated in 2001 and four exclosed nests were abandoned prior to hatch. We modified our exclosure design in 2002 and only one nest (7%) was depredated and no nests were abandoned prior to hatch. Kaplan-Meier estimates of chick survival in the absence of predation were 0.87 to 18 days in 2001 and 0.90 to 15 days in 2002. Mass ratios among first, second, and third-hatched chicks indicated that size hierarchies were present in broods near time of brood completion, but linear growth rates and asymptotic mass were not affected by hatch order in 2- or 3-chick broods. Predation was the primary determinant of chick survival in Black Tern colonies studied and food availability was not limiting chick growth. Predator exclosures did not prevent all depredation, but our exclosure design was effective at protecting and retaining chicks until fledgling age at 70% of nests; the majority of adults readily accepted predator exclosures.
Geophagy has been documented in many species of birds, including many parrots, and its proposed functions include detoxification of dietary poisons, mineral supplementation, and acid buffering. Most geophagy reports involve tropical South American species; we present the first published report of clay-lick use by the Maroon-fronted Parrot (Rhynchopsitta terrisi), a species inhabiting high elevation temperate pine-oak (Pinus spp.–Quercus spp.) forest of the Sierra Madre Oriental. Thirty-six observation sessions were made at the four dispersed licks known from the restricted breeding range of this species. All known licks were near valley bottoms far below most nesting cliffs. Parrot visitations to ingest clay were characteristically in groups and the average number of parrots per group was nine individuals. Group visits averaged 18.3 min in duration and peaked between 0900 and 1100 hrs. The total number of parrots visiting licks during any day represented only a fraction of the known population of the species, suggesting that unless additional licks have yet to be discovered, visits of individuals to licks are relatively infrequent.
I examined cavity number and use by other species as correlates of Red-cockaded Woodpecker (Picoides borealis) group size at Camp Blanding Training Site (CBTS) and Goethe State Forest (GSF), Florida. Group size was positively correlated with cavity number at CBTS but not at GSF. Other species occupied 1.75 (34%) and 1.19 (27%) cavities/territory at CBTS and GSF, respectively. Statistically controlling for use by other species yielded significant positive correlations between group size and cavity number in 4 of 5 years at CBTS and 2 of 4 years at GSF. Correlations between group size and total use by other species, controlling cavity number, were significantly negative at both sites. Separating total use by species, group size was negatively correlated only with southern flying squirrels (Glaucomys volans) at CBTS and only with Red-bellied Woodpeckers (Melanerpes carolinus) at GSF, as flying squirrels occupied >3 times more cavities/territory at CBTS than at GSF (0.87 vs. 0.28) while Red-bellied Woodpeckers occupied ∼0.75 cavities/territory at both sites. Flying squirrels may obscure the relationship between the two woodpecker species by limiting their cavity use.
We present the first nest descriptions for two Hispaniolan endemic songbirds, the Western Chat-tanager (Calyptophilus tertius) and Hispaniolan Highland-tanager (Xenoligea montana) from a montane broadleaf forest site in the Sierra de Bahoruco of the Dominican Republic. Single Western Chat-tanager nests were found on 17 May 2002 and 9 June 2004. Both were coarsely-built, partially-domed, bulky structures 1.0–1.5 m above ground. One nest was freshly-depredated when found, whereas the second contained two eggs which hatched on 19 and 20 June. The nestlings were depredated on 25 June. A Hispaniolan Highland-tanager nest found on 27 June 2004 fledged a single chick the following day. This nest, in a vine tangle 2.5 m above ground, was an open cup structure composed of moss, small herbaceous stems, leaf fragments, lichens, and other plant fibers. We describe the eggs of both species, the nestlings of Western Chat-tanager, and the juvenal plumage of Hispaniolan Highland-tanager. We believe that depredation by introduced feral cats (Felis domesticus) and rats (Rattus spp.) is a serious problem in these montane forests.
The ‘Akikiki or Kaua‘i Creeper (Oreomystis bairdi) is a rare, little-known Hawaiian honeycreeper endemic to the island of Kaua‘i. Its range is contracting, the population is declining, and it is a candidate for listing under the U.S. Endangered Species Act. We report an instance of foraging by excavation observed on 22 May 2006, a behavior previously unknown in this species, and on parental behavior at two nests observed on 24 May 2006 and 27 May 2007, about which there is little previous information. Both parents brought food to the nest, the male provided food for the female, and the female also foraged independently. The nesting pair in 2007 had a juvenile from a previous nest, indicating the ‘Akikiki will attempt to raise two broods. These observations are of limited extent, but even small facts can contribute to our understanding of the biology of the ‘Akikiki and causes of its decline.
I observed a pair of Olive-backed Euphonias (Euphonia gouldi) in the Caribbean lowlands of Costa Rica singing a prolonged antiphonal duet on 28 February 2006. The male and female were perched near one another within a larger conspecific flock, and exchanged closely-coordinated notes in phrases lasting ∼5 sec. This appears to be the first report of duetting behavior for this species or for any member of family Fringillidae.
The Reddish Hermit (Phaethornis ruber) is a commonly encountered hummingbird within the understory of tropical forests from Venezuela to south-east Brazil. Reddish Hermits, like many hummingbirds, perform elaborate displays associated with mate and territory acquisition. We provide the first detailed description with supporting illustrations of intricate displays between two male P. ruber to which we refer as “Rotation” and “Arc” displays.
The Banded Ground-cuckoo (Neomorphus radiolosus) is a rare, endangered, and poorly known species endemic to the Chocó Biogeographic Zone. We summarize 7 months of data from radio tracking an adult in northwestern Ecuador. Home range estimates were 42.2 ha (minimum convex polygon) and 49.9 ha (95% kernel analysis); the core area was 3.4 ha (50% kernel analysis). The bird favored undisturbed habitat and avoided secondary forest. It was primarily insectivorous and rarely associated with army ants (Eciton sp.) and not with mammals. Breeding occurred from March through June and the marked bird was seen with an unmarked individual throughout the study. The Banded Ground-cuckoo has a large home range, limited dispersal ability, and apparently depends on undisturbed forest. Deforestation and habitat fragmentation appear to be the gravest threats facing the species.
American Robins (Turdus migratorius) depend on fruit in fall and winter and, accordingly, juvenile robins must quickly learn to acquire this resource. We compared the foraging abilities of juveniles and adults foraging for mulberries (Morus spp.), the first fruit that ripens after juveniles have become independent. Juveniles were significantly less successful than adults at obtaining mulberries; 23% of juveniles' attempts to remove fruit were successful compared to 69% of attempts by adults to remove fruit. As a result, juveniles consumed 0.4 mulberries/min whereas adults consumed 2.8 mulberries/min. Further investigations of juveniles' ability to forage for fruit are needed to understand the mechanisms involved in the development of skills to forage for this vital resource.
We report new food items for six species of Costa Rican birds. This report includes the first egg predation observed for Hoffman's Woodpecker (Melanerpes hoffmannii), the first vertebrate recorded in the diet of Sooty Thrush (Turdus nigrescens), and records for Groove-billed Ani (Crotophaga sulcirostris), Black-and-white Owl (Strix nigrolineata), Blue-crowned Motmot (Momotus momota), and Clay-colored Thrush (Turdus grayi).
We observed Red-cockaded Woodpeckers (Picoides borealis) wedging longleaf pine (Pinus palustris) seeds into crevices in tree bark in Polk County, Florida from October to December 2004. Five individuals, four uniquely color-banded and one unidentified individual, wedged ∼14 seeds. Initially, we thought the birds were caching the seeds. Additional observations indicated the seeds were being wedged under the ends of the flaking bark of longleaf pines so seeds could be held firm and opened for consumption. Anvil use, where items are wedged for subsequent manipulation, is known to occur in several avian taxa, but most notably in Piciformes, Corvidae, Passerida, and Sittidae. At least 16 woodpeckers worldwide have been reported using anvils. This is the first report of Red-cockaded Woodpeckers using longleaf pine bark as an anvil to facilitate extracting the seed.
Correct gender identification in monomorphic species is often difficult especially if males and females do not display obvious behavioral and breeding differences. We compared gender specific morphology and behavior with recently developed DNA techniques for gender identification in the monomorphic Grasshopper Sparrow (Ammodramus savannarum). Gender was ascertained with DNA in 213 individuals using the 2550F/2718R primer set and 3% agarose gel electrophoresis. Field observations using behavior and breeding characteristics to identify gender matched DNA analyses with 100% accuracy for adult males and females. Gender was identified with DNA for all captured juveniles that did not display gender specific traits or behaviors in the field. The molecular techniques used offered a high level of accuracy and may be useful in studies of dispersal mechanisms and winter assemblage composition in monomorphic species.
We studied the reproductive ecology of Rio Grande Wild Turkeys (Meleagris gallopavo intermedia) in the Edwards Plateau region, Texas during 2005 and 2006. Runt eggs from a single adult female were observed through three nesting events over 2 years. Mean mass and volume for the runt eggs were 44% of normal Wild Turkey eggs. Production of runt eggs is common in domesticated gallinaceous birds, yet little information is available on runt egg production in wild gallinaceous birds. To our knowledge, our observations are the first which indicate runt egg production occurs in Wild Turkeys.
We describe three successful predation events by the Barred Forest Falcon (Micrastur ruficollis) in the Atlantic Forest of coastal southeast Brazil. The prey items were a Plumbeous Pigeon (Patagioenas plumbea), a Brown Tinamou (Crypturellus obsoletus), and a large toad (Chaunus ictericus). This is the first report of successful attacks on prey heavier than the forest falcon, of which none was successfully carried away. These large prey items represent a trade-off between high nutrient value and safety of carrying prey to a secure perch.