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Rose-breasted Grosbeaks (Pheucticus ludovicianus) commonly breed in the deciduous woodlands of southern Ontario, but have become a species of conservation concern due to recent population declines (2% per year in Ontario from 1966 to 2004). We investigated whether habitat alterations may be contributing to these declines through decreases in nest survival at nest and randomly selected sites in 23 woodlots varying in the intensity of partial harvest. Rose-breasted Grosbeaks consistently selected nest sites with more sapling cover, less canopy cover, and a lower surrounding basal area than available. The best supported model of daily nest survival included a measure of nest concealment, with the top 15 models containing nest concealment indicating higher nest survival rates at less concealed nests. Model-averaged estimates produced positive slopes for canopy cover, sapling cover, and nest height indicating higher survival at higher canopy cover, sapling cover, and nest height. Heavy-cutting practices appear to create woodlots that act as ecological traps. These woodlots provide “preferred” nest sites that result in low nest survival probabilities for the Rose-breasted Grosbeak.
The Florida Scrub-jay (Aphelocoma coerulescens) is listed as a threatened species primarily because of habitat loss throughout much of its range. The Ocala National Forest in Florida contains one of three main subpopulations that must be stable or increasing before the species can be considered for removal from federal listing. However, little information is available on Florida Scrub-jay reproductive success or predation pressure on this forest. I used video cameras during 2002 and 2003 to identify nest predators and timing of predation events. The presence of the video system did not significantly affect the rate of nest abandonment. Thirteen nests were video-monitored of which one was abandoned, five experienced no predation, three were partially depredated, and four had total loss of nest contents. Snakes were responsible for more losses from predation than either mammals or birds. I monitored 195 other scrub-jay nests (no video-monitoring) and measured the mean number of eggs, nestlings, and fledglings produced per breeding pair. No significant difference in reproductive success was detected between years or between year and helper status. Groups with helpers produced significantly more fledglings (0.5 per breeding pair) and had higher daily survival rates of nests in the egg stage, nestling stage, and the entire breeding season than groups lacking helpers.
We studied Red-cockaded Woodpeckers (Picoides borealis) to examine the effect of status and gender on foraging behavior. Foraging behavior of breeding pairs extended beyond separation by foraging height to include zones (bole, trunk in crown, primary limb, secondary limb) of the tree used and foraging methods (scaling, probing, excavating). Helper males and juvenile females maintained partial spatial separation from breeding adults. Helper males maintained spatial separation from breeding adults by exploiting limbs within tree crowns in both longleaf (Pinus palustris) and loblolly-shortleaf (P. taeda, P. echinata) pine forests, but also increased use of boles in loblolly-shortleaf pine in concert with reduced use of boles by adult females. Breeding males tended to forage less by scaling, probably due to the reduced proportion of foraging on boles of trees where scaling tends to predominate.
We investigated several reproductive attributes among three spatially and morphometrically separable northern populations of breeding Cooper's Hawks (Accipiter cooperii) in differing ecological settings in British Columbia, North Dakota, and Wisconsin during 1995–2001. We did not detect significant inter-year variation in reproduction within any of our study areas. Cumulative clutch and brood sizes were significantly higher in British Columbia (mean = 4.41 and 3.60, respectively) and Wisconsin (4.26 and 3.73) than in North Dakota (3.5 and 3.0), but not significantly different between British Columbia and Wisconsin. Total nest success rates (91 and 82% in British Columbia and Wisconsin, respectively) varied significantly among all three study sites, but were lowest in North Dakota (68%). We hypothesize that smaller clutch and consequentially lower brood sizes in North Dakota may be the result of the comparatively later nesting phenology in this highly migratory population. Our results underscore the significance of clutch size data, and the need for further research on regional and other large-scale variation in avian demographic parameters to help decide if, when, and where population demographics may warrant a management response.
Grassland birds are considered to be rapidly declining in North America. Management approaches for grassland birds frequently rely on prescribed burning to maintain habitat in suitable condition. We evaluated the relationships among years since burn, vegetation structure, and overwintering grassland bird abundance in coastal prairie. Le Conte's Sparrows (Ammodramus leconteii) were most common in areas that had: (1) been burned within the previous 2 years, (2) medium density herbaceous vegetation, and (3) sparse shrub densities. Savannah Sparrows (Passerculus sandwichensis) were associated with areas: (1) burned within 1 year, (2) with sparse herbaceous vegetation, and (3) with sparse shrub densities. Sedge Wrens (Cistothorus platensis) were most common in areas that had: (1) burned greater than 2 years prior and (2) dense herbaceous vegetation. Swamp Sparrows (Melospiza georgiana): (1) were most common in areas of dense shrubs, (2) not related to time since burnings, and (3) demonstrated no relationship to herbaceous vegetation densities. The relationships to fire histories for all four bird species could be explained by the associated vegetation characteristics indicating the need for a mosaic of burn rotations and modest levels of woody vegetation.
We used radio telemetry to study post-breeding movements of adult female and juvenile Eastern Meadowlarks (Sturnella magna) in southwestern Wisconsin in 2002–2004. Twenty-one adult females were found 58% of the time in their nest field regardless of nest fate. Three adult females were not found outside of the field where their nests were located. Fifteen of 18 females that moved from the nest field at least once moved to Conservation Reserve Program fields or pasture. The average maximum distance females moved was 662 m. Once females left the nest field, 61% did not return. Twelve juveniles from different broods survived to the end of the post-breeding season. Two juveniles did not move from their nest fields during the monitoring period. Eight of 10 juveniles that moved at least once moved into Conservation Reserve Program fields, remnant prairie or pasture. The average maximum distance moved by juveniles was 526 m. Once juveniles started to leave the nest field, 67% did not return. Grassy habitats appear to be important in the post-breeding period for Eastern Meadowlarks. Management should be directed toward maintaining or enhancing the amount and quality of those habitats.
Tropical birds may differ from temperate birds in their sensitivity to forest edges. We provide predictions about the proportions of tropical and temperate species that should avoid or exploit edges, and relationships between natural-history characters and edge responses. We conducted exploratory meta-analyses from 11 studies using 287 records of 220 neotropical and temperate species' responses to edges to address our predictions. A higher proportion of neotropical species were edge-avoiders compared with temperate species and a higher proportion of temperate species were edge-exploiters compared with neotropical species. Edge-avoiding responses were positively associated with being an insectivore for neotropical birds, and with being of small body mass and a latitudinal migrant for temperate birds. Temperate edge-exploiters were less likely to be insectivores and migrants than temperate birds that were not edge-exploiters. A greater proportion of neotropical birds than temperate birds may be at risk from forest fragmentation if edge-avoidance is a reasonable indicator of an inability to adapt to land-cover change. Future progress in our understanding of forest bird responses to edges is dependent upon greater standardization of methods and designing studies in the context of recent theoretical developments.
The Banded Ground-cuckoo (Neomorphus radiolosus) is a rare and endangered bird species whose basic biology is poorly known. We provide the first information on nesting biology for the species. We documented two nesting attempts in the Mache-Chindul Ecological Reserve, Esmeraldas Province, northwest Ecuador. Both the first nest, active in March and April 2005, and the second nest, active in May 2005, were in primary rain forest. Both nests were ∼5 m above ground in small understory trees (Melastomataceae). A pair of adult Banded Ground-cuckoos attended the first nest and contributed equally to incubation, brooding, and provisioning of a single nestling. The nestling spent 20 days in the nest from hatching to fledging and was fed a wide range of both invertebrates (primarily grasshoppers) and vertebrates (mainly small frogs). The chick fledged successfully. The second nest, also attended by a pair of adults, failed during incubation. We relate our findings to what is known of other ground-cuckoo species and discuss the conservation implications of our results.
The basic ecology of most of the Andean guans is poorly known. However, knowledge of the natural history of members of Cracidae has increased in the last decade, but most studies involve lowland species. We present basic natural history data for the Sickle-winged Guan (Chamaepetes goudotii) on the western slope of the Central Range of the Andes, Colombia. The density estimate for the Sickle-winged Guan in the study area was 13.7 individuals/km2 and the mean (± SD) group size was 1.5 ± 0.76 individuals. These groups used all forest strata but usually foraged in the middle stratum (8.6 ± 6.1 m). The diet consisted of fruits (84.5%), flowers (3.9%), leaves (5.8%), and invertebrates (5.8%). We observed wing-drumming displays, nests, and fledglings from January through June. We discuss the ability of the Sickle-winged Guan to colonize and establish populations in restored habitats.
We studied the effect of sunlight (280–750 nm) on Bacillus licheniformis, a feather-degrading bacterium that commonly occurs in the plumage of birds. Colony-forming units (a measure of bacterial abundance) of B. licheniformis were numerous on feathers inoculated with B. licheniformis and shielded from all sunlight, whereas colony-forming units were significantly less common on inoculated feathers exposed to full spectrum sunlight and sunlight from which the shorter ultra-violet wavelengths were blocked. Sunlight appears to inhibit the growth of feather-degrading bacilli. Given that many avian species sun themselves and that feather-degrading bacilli occur commonly in avian plumage, we suggest that regulation of potentially harmful plumage microorganisms through exposure to sunlight could be one reason that birds sunbathe.
The global population of the Black-faced Spoonbill (Platalea minor) has increased steadily. We estimated global population growth rates of the Black-faced Spoonbill based on annual counts of wintering populations in East Asia between 1991/1992 and 2003/2004. The mean (±SD) annual growth rate was 1.13 ± 0.08. The estimated survival rate was 86.6 ± 9.3% based on the annual return rates of color-banded birds in Taiwan between 1998 and 2005. We predicted global Black-faced Spoonbill populations in 2003/2004–2013/ 2014 using a stochastic exponential model and showed the mean global population in 2013/2014 would exceed 4,000 ± 950. The probability of a global population decline to less than the 2003/2004 level is low (P = 0.06). If the 1991–2004 growth rate is sustained, the probability for the global population to increase to twice that of the 2003/2004 level is 0.98 and the predicted mean wintering population in Taiwan could exceed 2,000 in 2013/ 2014. Establishment of new protective areas and increasing food availability at existing reserves and adjacent fish ponds in southwestern Taiwan will be necessary to ensure continued growth.
All historical records of White-browed Crake (Porzana cinerea) in mainland Southeast Asia were south of the Isthmus of Kra, suggesting a Sundaic distribution. The first records from continental Thailand, Cambodia, Vietnam, and Laos revise the known resident distribution north almost to China. Information is inadequate to assess whether the species was historically overlooked across this huge area, or has genuinely expanded its range. Several factors suggest the latter, a pattern shown by no other bird species, and surprising given the pressing threats faced by wetlands and rallids in Southeast Asia.
The search for the Ivory-billed Woodpecker (Campephilus principalis) in eastern Arkansas and northwestern Florida has yielded double raps recorded by autonomous recording units (ARUs) in White River National Wildlife Refuge and along the Choctawhatchee River, respectively. These double raps have been presented as suggestive evidence for the presence of the species in those regions. We present data comparing double raps produced by wing collisions from an aerial Gadwall (Anas strepera) flock to double raps documented by ARUs. Close similarities in amplitude ratios, peak-to-peak times between raps, and auditory quality between ARU recordings and wing collisions from a Gadwall flock illustrate the ability of flying ducks to produce sounds easily mistaken for the double raps of Campephilus woodpeckers. All ARU double raps suggesting the presence of an Ivory-billed Woodpecker should be reconsidered in light of the phenomenon of duck wingtip collisions, especially those recorded during winter months when duck flocks are common across flooded bottomlands of the southeastern United States.
The Chihuahuan Raven (Corvus cryptoleucus) is abundant and conspicuous throughout its range, but much remains unknown about its breeding biology and social system. We studied the breeding biology of this species in southern New Mexico in 2000 and 2001, and hypothesized that environmental variability of desert habitats represents a major selective force. We predicted that variable food supplies and limited nest sites might select for cooperative provisioning of young similar to behavior in several other members of the genus Corvus. We examined nesting behavior and social relationships of nesting groups. Nest observations revealed that both males and females incubate eggs, brood nestlings, and feed young. Nesting pairs were primarily territorial in the immediate vicinity of the nest, but occasionally tolerated intruders, and at other times were joined by the intruders in communal mobbing of potential predators. Average group size near the nest was 1.7 birds and we did not detect auxiliary birds at or near the nest. We found no sign of cooperative breeding in the population of Chihuahuan Ravens we studied. However, we did find cooperation in predator defense within groups of nesting ravens.
Black (Coragyps atratus) and Turkey (Cathartes aura) vultures feed heavily on carrion from domestic animals in agricultural landscapes. A recent study indicates vultures at a forested site in South Carolina had much larger home ranges than those residing in agricultural landscapes. Vulture home ranges at the forested site contained few residential or agricultural lands, and we hypothesized that vultures at that site fed extensively on wild carrion. We collected 65 regurgitated pellets from a communal night roost between 16 October 2000 and 9 April 2002 to test this hypothesis. The pellets contained undigested parts of consumed carrion including hair, bone, scales, and claws. Wild mammals, particularly white-tailed deer (Odocoileus virginianus), common raccoons (Procyon lotor), Virginia opossums (Didelphis virginiana), and striped skunks (Mephitis mephitis), were common food items. The only domestic animal recovered (in two pellets) was the house cat (Felis catus). This study supports the observations that carrion resources affect distributions and movement patterns of Black and Turkey vultures.
We document 21 observations of interspecific stealing of nesting material involving Cerulean Warblers (Dendroica cerulea), Red-eyed Vireos (Vireo olivaceus), Blue-gray Gnatcatchers (Polioptila caerulea), Northern Parulas (Parula americana), Black-throated Green Warblers (D. virens), American Redstarts (Setophaga ruticilla), and Orchard Orioles (Icterus spurius) that occurred during studies of Cerulean Warbler breeding biology. These incidents involved a variety of combinations of nest owner and nest material thief suggesting that each of these species is both a perpetrator and recipient of this behavior in our study areas. Kleptoparasitic incidents occurred at all stages of the nesting cycle from nest-building through post-fledging. Two possible motivations for this behavior are related to saving time in finding nest materials and collecting this material for nest construction.
We present the first use of necklace radio transmitters to document the home range and dispersal of juvenile Burrowing Owls (Athene cunicularia floridana) during the breeding and post-breeding period in rural Florida. Juvenile Burrowing Owls (n = 4) were detected close to main and satellite burrows during 65 day-time relocations. Home range estimates (95% kernel) for juvenile owls varied from 98 to 177 m2. Juvenile Burrowing Owls were not detected near main and satellite burrows during three evening relocations. Dispersal of juvenile owls coincided with flooding of burrows during the rainy season. Juvenile owls upon fledging used an extensive patch of saw palmetto (Serenoa repens) before dispersing beyond the range of ground telemetry capabilities. Aerial telemetry assisted in locating one juvenile Burrowing Owl using scrub oak (Quercus spp.) habitat approximately 10.1 km southeast of its main and satellite burrows.
We observed 56 forced copulation (FC) events in a breeding colony of American White Pelicans (Pelecanus erythrorhynchos) in Saskatchewan, Canada during the 2005 nesting season. All FCs were directed at nestlings >21 days of age that were not continuously attended by an adult. The onset of FCs occurred in close synchrony with an unexpected late-season increase in adult copulation attempts. We suggest that FC directed at nestlings is not simply an aberrant and non-adaptive behavior. Rather, copulations with nestlings result from adult male pelicans being inappropriately stimulated to copulate with nestlings when actually seeking copulations with adult females.
Penguins, Southern Hemisphere birds, were introduced to the Northern Hemisphere several times in the 1930s. None of the four species introduced became established but some individuals survived for at least a decade. Humboldt Penguins (Spheniscus humboldti) were observed in waters off the west coast of North America several times in the 1970s and 1980s and one was caught in a fishing net in Alaska in 2002. Penguins theoretically might be able to swim to suitable habitat in the Northern Hemisphere, but we argue the most likely explanation for their arrival in the Pacific Northwest was by fishing boat.
We report bilateral gynandromorphy in a White-ruffed Manakin (Corapipo altera) collected near Santa Fé, Panamá in 2004. The specimen had an oviduct and ovary on the left side and a single testis on the right. The plumage was phenotypically female on the right side and male on the left. The weight and genetic affinity of the specimen were characteristically female. Both Z and W chromosomes were detected in genetic samples from multiple tissue types and toe pads from both feet. This report is a novel record of gynandromorphy in a suboscine passerine.
A female White-tipped Sicklebill (Eutoxeres aquila aquila) was caught on 3 February 2006 at 1,050 m elevation in Agua Blanca, Municipio Andrés Bello, Mérida, Venezuela, 2 km southeast of La Azulita. This account represents the first record of this hummingbird species in Venezuela, extending the taxon's known distribution at least 500 km northeastward.
It may be reasonable to assume that raptors would likely perish as the result of an injury that potentially impaired their ability to capture prey. We present results from 98 wild-caught raptors that support the converse claim: raptors can and do survive with many types of injuries. We report a conservative injury estimate of 14% for wintering populations of Red-tailed Hawks (Buteo jamaicensis), American Kestrels (Falco sparverius), and Cooper's Hawks (Accipiter cooperii) in northeastern Arkansas. Injuries in these species included broken or missing talons, ulcerative pododermatitis (bumblefoot), missing toes, healed wing fractures, and iris damage.
This study was based on spring temperatures, laying dates, and clutch size of the first nesting attempt of the Blue Tit (Parus caeruleus) from 1982 to 2004 in Hrvatsko Zagorje rural area (46° 00′ N, 15° 55′ E), Croatia. The results suggest that timing of breeding of the Blue Tit is influenced by spring air temperatures. There was a significant correlation between spring temperature and years, consistent with a global warming trend. The date of clutch initiation in the Blue Tit population studied did not decrease over a 23-year period. Correlations between spring temperatures and clutch size, and year and clutch size were not significant.
We report the first known observation of mother-son parental care and potential inbreeding in Horned Larks (Eremophila alpestris) near Smithers, British Columbia, Canada. The nest was found with four nestlings and was attended by a female and her son from the previous year. The nestlings appeared healthy, were above average mass, and fledged successfully. The high return rates of adult and juvenile Horned Larks at our study site may have facilitated this social pairing by close relatives. The possibility the son was a helper at the nest is discussed.
The social behaviors of Le Conte's (Ammodramus leconteii) and Nelson's Sharp-tailed (A. nelsoni) sparrows are poorly documented, as are their interactions with one another, even in the prairie marshes they share during the breeding season. We report the regular coincident presence and similar habitat associations of these species at a fall migration stopover, the Baker University Wetlands, near Lawrence, Kansas, over an 11-year period, and describe social behaviors (several previously unrecorded) at the site, including an aggressive interspecific encounter.
Barn Swallows (Hirundo rustica) historically nested along cliffs, in caves, and in other natural situations. Currently, nearly all reported nests of this species are on walls and beams of bridges, buildings, and other human-derived structures. Both natural and man-made nest sites typically share one thing in common: a horizontal surface for nest attachment. We describe a Barn Swallow nest that was constructed on a branch overhanging a river in southeastern Oregon. This is the first documented occurrence of this behavior by Barn Swallows and we believe it to be the result of high competition for a limited number of suitable nest sites in the study area.
We report on mortality caused by an evening hailstorm to a night-time roost of Great-tailed Grackles (Quiscalus mexicanus) and European Starlings (Sturnus vulgaris) in Austin, Texas. The hailstorm was of short duration (6 min), and hail stones were not too large (most <20 mm in diameter). Approximately 7% of female grackles, 12% of male grackles, and 26% of starlings died. Greater mortality in male grackles suggests that preferred roost locations were more exposed to hail.
I report the first record of Bronzed Cowbird (Molothrus aeneus) parasitism of the Common Bush-tanager (Chlorospingus ophthalmicus). This represents the 97th known host for this cowbird species and the 10th known host from the Family Thraupidae. This record is based on feeding behavior observations and vocalizations recorded in Xalapa, Veracruz, Mexico.