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We monitored two color-marked populations of the Brown-headed Nuthatch (Sitta pusilla) for ≥5 years and collected data on survival, dispersal, territoriality, and cooperative breeding. Adults (n = 284) were sedentary, maintained long-term pair bonds, and had higher apparent annual survival (66–78%) than previously reported. Territories monitored (n = 347) contained up to five adults; the percentage of territories containing >2 adults averaged ∼20% but varied widely. Most groups with >2 adults consisted of a breeding pair and a male helper related to at least one breeding adult (n = 8), but several exceptions were noted. The presence of helpers did not improve nest productivity. Apparent annual survival for females was lower than apparent survival for males in one population and may have influenced cooperative breeding. In the other population, apparent survival was similar between males and females. We suggest food resources and other environmental factors may have influenced cooperative breeding in this setting.
We analyzed capture-mark-recapture (CMR) data from 1,061 Black Brant (Branta bernicla nigricans) using Humboldt Bay, California, during northward migration (Jan–May), 2000–2001. We estimated immigration and emigration rates, and calculated stopover duration (length of stay), volume (total number of birds using the Bay), and chronology (time frame of the migration at this site). Migration of Brant through Humboldt Bay began in late December and ended in mid-May with peak numbers occurring in mid-March (i.e., 13% of the entire flyway population). Median age of newly arrived birds was highest in the first half of February. Immigration probability was nearly constant, but emigration probability increased through time, indicating a seasonally progressive migratory state. Mean (±SE) stopover duration from all birds for January–April at Humboldt Bay was 26 ± 2 days. Stopover duration was inversely related to bird age due to age-specific emigration probabilities; older birds arrived sooner and stayed for less time than younger birds. Estimates of stopover duration from concurrent radiotelemetry of 12 birds were consistent with CMR model selection-derived estimates. Humboldt Bay was visited by approximately 28% of the Pacific Flyway Black Brant population in 2000 and 58% in 2001. Estimates derived from this technique offer statutory authorities improved information upon which to base management action along migratory pathways.
I studied brood-rearing behavior of introduced Swan Geese (Anser cygnoides) in Heidelberg, Germany during 2002 and 2003. Two hypotheses were tested: (1) division of labor between males and females is similar to that of wild Anser species, and (2) parental investment (vigilance behavior) is adjusted for brood size. I used 10-min sessions of focal animal sampling during which I simultaneously recorded the behavior of the male, the female, and a majority of the juveniles every 15 sec. Division of labor was similar to that observed in wild Anser populations: males were more vigilant whereas females spent more time feeding during the first 4 weeks of brood-rearing. As brood-rearing progressed, vigilance and agonistic behavior by both males and females decreased, whereas juveniles decreased feeding and increased vigilance. Adults (males and females combined) adjusted vigilance for brood size. A general linear model showed a significant influence of both brood size and brood age on parental vigilance.
We evaluated and monitored use of 105–133 nest boxes by Common Goldeneye (Bucephala clangula) and Barrow's Goldeneye (Bucephala islandica) during 1999–2004 on 60 lakes of high plateaus of the Laurentian Highlands, in the boreal forest of Québec, Canada. Only three species of birds used nest boxes regularly, American Kestrel (Falco sparverius), Barrow's Goldeneye, and Common Goldeneye. The proportion of nest boxes used by goldeneyes in 2000–2004 ranged from 23 to 43% whereas hatching success ranged from 37 to 67%. Successful Barrow's and Common goldeneye clutches averaged 6.76 ± 0.38 (SE, n = 29) and 7.77 ± 0.44 eggs (n = 31), respectively. Predation in nest boxes was not a major mortality factor. Goldeneyes used all nest boxes independent of their location but reproductive success was lower in nest boxes 25–160 m from shore in clearcuts. The number of Barrow's and Common goldeneye breeding pairs increased between 1999 and 2003, but number of broods remained stable after an increase in 2000.
Red Knots (Calidris canutus) that spend winter in the southeastern United States are known to have been genetically separated from their congeners that migrate to Patagonian wintering grounds for about 12,000 years. We examined and documented differences between the two groups in their use of southward migration stopover locations, flight feather molt, fidelity to wintering zones, and differences in mass at southward migration stopover locations. Red Knots wintering in the southeastern United States do so consistently, and knots wintering in Patagonia have not changed to wintering in the southeastern United States. The two wintering groups have distinct differences in their nonbreeding season biology (e.g., migration strategies, chronology of pre-basic molt), and these differences have been maintained for decades if not millennia.
Winter roosts afford escape from extreme climatic conditions, reduce heat and energy loss, and provide protection from predators for North American woodpeckers. We monitored the use and characteristics of 12 winter roosts used by nine radio-marked Hairy Woodpeckers (Picoides villosus) in ponderosa pine (Pinus ponderosa) forests of northern Arizona that had experienced wildfire in 1996 and 2000. Roost trees were larger in diameter than 95% of non-roost trees and on average 2.5 times larger within burned areas of similar severity. Roost trees were within patches less dense than 95% of measured patches across study sites, which were on average 1.5 times as dense. Two-thirds of roost trees were created by fire and were smaller than those created by other means. Six birds each used one roost and three males each used two roosts. Two-thirds of the roosts were outside or on the edge of estimated home ranges. Maximum straight-line distances traveled, from roost to farthest point of home range, were >1 km for 8 of 9 birds. Woodpeckers have a significant role in providing cavities for secondary cavity nesters. Thus, understanding habitat requirements for winter roosts could provide managers with essential tools to maintain or enhance populations of this species.
The species-group in the genus Percnostola that is sometimes placed in the genus “Schistocichla” is shown to consist of seven, mostly allopatric, species. All seven are distinct morphologically; when their vocalizations were compared, 19 of 21 pairwise comparisons resulted in differences as great as or greater than those of syntopic species-pairs in this family. Differences in the two remaining comparisons were limited to two vocal characters, but one involved a pair whose ranges appear to abut without apparent physical barriers; members of the second pair were separated geographically by ∼2,400 km. Insights into speciation in the complex are relevant to conservation efforts and ultimately will be related to an ongoing genetic study to suggest a phylogeny and contribute to an understanding of avian evolution in Amazonia.
We describe the nest and nest site, and provide the first description of the eggs and nesting behavior of the Black-bellied Wren (Thryothorus fasciatoventris) in central Panama. Nine nests were found near tree-fall gaps, swamps, and roads in moist tropical forests. Nests were dome-shaped with a circular side entrance. They were composed chiefly of strips of dead palm fronds, and were generally built in places where leaf litter and other debris had accumulated at the convergence of several vines near the forest floor. Both males and females participated in building the nest. Clutch size was three, and eggs were laid on consecutive days. Egg color varied from creamy to beige with faint to dark brown speckles that were more concentrated at the blunt end. Females were the sole incubators, but males fed the incubating females. Only the female brooded the nestlings once they hatched, but both parents fed the nestlings.
Bird use of small canopy gaps within mature forests has not been well studied, particularly across multiple seasons. We investigated seasonal differences in bird use of gap and forest habitat within a bottomland hardwood forest in the Upper Coastal Plain of South Carolina. Gaps were 0.13- to 0.5-ha, 7- to 8-year-old group-selection timber harvest openings. Our study occurred during four bird-use periods (spring migration, breeding, postbreeding, and fall migration) in 2001 and 2002. We used plot counts and mist netting to estimate bird abundance in canopy gaps and surrounding mature forest habitats. Using both survey methods, we observed more birds, including forest-interior species, forest-edge species, field-edge species, and several individual species in canopy gap and gap-edge habitats than in surrounding mature forest during all periods. Interactions between period and habitat type often were significant in models, suggesting a seasonal shift in habitat use. Bird activity generally shifted between the interior of canopy gaps and the immediate gap edge, but many species increased their use of forested habitat during the breeding period. This suggests that many species of birds selectively choose gap and gap-edge habitat over surrounding mature forest during the non-breeding period. Creation of small canopy gaps within a mature forest may increase local bird species richness. The reasons for increased bird activity in gaps remain unclear.
We used reobservation of color-banded birds to index annual breeding site fidelity of four species of songbirds that nest in the northern mixed-grass prairie of northcentral Montana (1996–2005). Territorial males of Sprague's Pipits (Anthus spragueii), and Savannah (Passerculus sandwichensis), Grasshopper (Ammodramus savannarum), and Baird's (A. bairdii) sparrows were located on five permanent study sites (1998– 2004) and lured into mist-nets using tape broadcasts of conspecific songs and calls. The proportion reobserved was 5.3% (n = 247) across all banded adult males. Grasshopper Sparrows had the highest proportion of returns (8.9%), followed by Savannah Sparrows (5.4%), Baird's Sparrows (5.1%), and Sprague's Pipits (2.1%). Three nestling Savannah Sparrows were reobserved in subsequent years (n = 193), while no nestlings of the other species were reobserved (n = 401). Our return rates were low for all adults in comparison with typical reports of return rates for songbird species of woodland and shrubland habitats. Migratory nomadism may explain this phenomenon, where grassland migrants are opportunistic in site selection, rather than faithfully returning to potentially uninhabitable former breeding sites.
Most birds consume hard animal fat (suet) through repetitive pecking. Suet hardens considerably as the temperature declines below freezing. The caloric value of suet during the winter months is such that it is worthwhile for many birds to continue simple pecking as temperatures decline, but with diminishing returns. Some Common Ravens (Corvus corax) exhibit a more complex behavior while caching, or feeding young. I report an apparent territorial pair that repeatedly divided suet by carving deep grooves into it. Substantially larger portions of suet and other foods were isolated through this advantageous behavior and carried off, than would be possible through simple pecking.
I report on an incident involving a Steller's Jay (Cyanocitta stelleri) and an American Crow (Corvus brachyrhynchos) at a feeding platform. After repeated failures to drive the crow from the platform by scolding, approaching and diving at it, the jay flew into a bush where it worked vigorously to break off a stick. Having broken off the twig, the jay, with stick in bill, approached the crow and thrust the pointed stick at it. The crow lunged at the jay which then dropped the stick. The crow picked up the stick and flew after the jay. This appears to be the first case of a bird holding an object and using it in a weapon-like way during an aggressive action against another bird.
We describe predictable nocturnal soaring flight in Turkey Vultures (Cathartes aura) feeding at a landfill in eastern Pennsylvania. Birds feeding at the landfill returned to their roosts each evening by gaining altitude while soaring in thermals above flared methane vents at the site. Our results highlight behavioral plasticity in this species, which, in part, may explain why Turkey Vultures are so common throughout much of their extensive range.
Mallards (Anas platyrhynchos) are known to frequent rivers and streams during post-breeding. I describe observations of Mallards feeding on fresh Pacific salmon (Onchorhynchus spp.) carcasses in Alaska on two separate occasions during July– August 2005. These observations represent the first reported use of salmon carcasses by Mallards in Alaska. This strategy may be fairly common for a segment of post-breeding and fall staging Pacific Flyway Mallards in Alaska, particularly those that inhabit streams and rivers used by the five species of Pacific salmon during the spawning season.
The effect of 4.5-g dummy geolocation loggers on the foraging ability of Cook's Petrel (Pterodroma cookii) was assessed over single foraging trips from Little Barrier Island, New Zealand. I compared foraging trip duration and chick provisioning between equipped and unequipped birds and could not detect a detrimental effect of loggers on either parameter. The lack of effect of these loggers may be the result of their small size, the short-term nature of their use, and foraging strategies used by Cook's Petrel. Geolocation studies involving Cook's Petrel and other small gadfly petrel species may be feasible for single foraging trips.
I describe an Eastern Screech-owl (Megascops asio) hatching three Wood Duck (Aix sponsa) eggs in a suburban nest box. Wood Duck(s) removed all five eggs of a completed screech-owl clutch, the earliest of which had already been incubated for at least 19 days, and laid three eggs in their place. The female screech-owl hatched the Wood Duck eggs, preened the ducklings, and attempted to feed them until they exited the nest box within 48 hrs of hatching.
This paper describes an extra-pair copulation (EPC) event between two color-banded Sandhill Cranes (Grus canadensis). This is the first documented occurrence of an EPC during the fertile period of Sandhill Cranes. This event adds to the small list of documented EPCs in long-lived bird species with long-term pair bonds. Participating in an EPC may have allowed the female to potentially gain access to a mate with a breeding territory, something she did not have during the previous two breeding seasons. Benefits to the male may have included increasing his reproductive success without having to raise the offspring or evaluating the female as a potential new mate.
We observed five Snowy Egrets (Egretta thula) on 23 October 2005 swimming and feeding in a small constructed wetland in Boca Raton, Florida. This event occurred 5–10 m from the shoreline in water >1 m in depth over a 2-hr period. We provide the first detailed account of swimming feeding behavior for Snowy Egrets. Elevated numbers of prey fishes at the surface of the pond may have facilitated this previously undocumented feeding behavior of Snowy Egrets.
The literature pertaining to nesting of the Great Hornbill (Buceros bicornis) is ambiguous regarding whether the birds use mud as plaster material to seal their nest cavity entrances. We studied the breeding biology of the species in southern India and detected no evidence of mud delivery or usage in 183 hrs of nest observations. Chemical analysis of plaster material showed that it was composed exclusively of fecal material and not mud.
We provide the first description of the nest, eggs, and breeding behavior of the Mérida Tapaculo (Scytalopus meridanus). Data are from one pair in the moist cloud forest of Yacambu National Park, Venezuela during April–May 2004. Two nests, constructed by the same pair, were globular in structure and consisted of mossy material placed in a rock crevice of a muddy rock wall. The eggs were cream colored with an average mass of 4.19 g. Clutch sizes were one in the first nest and two in the second. The species showed bi-parental care in nest building and incubation. Nest attentiveness (percent time spent on the nest incubating) averaged 83.4 ± 14% (SD). Average on and off bouts were 33.24 and 6.34 min, respectively.
I present the first published record of a foraging association between Nearctic-neotropical migrant bird species during the austral summer in South America. I observed Barn Swallows (Hirundo rustica) and Cliff Swallows (Petrochelidon pyrrhonota) in February 2005 repeatedly foraging on aerial insects flushed by flocks of Bobolinks (Dolichonyx oryzivorous) settling onto soybean plants (Glycine max). Additional observations would be needed to distinguish this behavior between an opportunistic association and a commensal relationship.
We observed a Violet-green Swallow (Tachycineta thalassina) laying an egg in an active Western Bluebird (Sialia mexicana) nest. The Western Bluebird male and not the female, was aggressive to the Violet-green Swallow but the swallow remained to lay the egg. This is the first documented incidence of which we are aware involving altricial interspecific egg-laying during the nestling phase. We suggest the timing of this event was more consistent with incidental egg deposition, or egg-dumping, than brood parasitism or nest usurpation.
I observed a male Western Bluebird (Sialia mexicana) capture a western fence lizard (Sceloporus occidentalis), the first reported incidence of vertebrate-directed raptorial behavior in the Western Bluebird. There are no previously published reports of Western Bluebirds capturing vertebrate prey, although there is one previous report of a Western Bluebird carrying an unidentified lizard in the manner of a prey item, and a few reports of predation on vertebrates by the congeneric Eastern Bluebird (Sialia sialis).
The Yellow Warbler (Dendroica petechia) has a mating system characterized by monogamy and biparental care, and has the broadest breeding distribution of any Dendroica species. When faced with a short breeding season and unpredictable conditions at high latitude, they display physiological responses to help optimize the tradeoff between individual risk and reproductive success. Because these circumstances may also affect behavior, we measured the song rates (songs/hr) of subArctic- and temperate-breeding males during the nestling period. Temperate males sang at higher rates when compared to subArctic males. Maintaining a high song rate while provisioning nestlings may be advantageous if a second brood is attempted. Our results suggest behavioral plasticity as a result of differing constraints on time and reproduction.
A pair of Red-breasted Sapsuckers (Sphyrapicus ruber) was observed nesting in an electric distribution, creosote-treated, wood utility pole in the Willamette Valley, Oregon during spring 2006. To the author's knowledge, this is the first published account of a sapsucker nesting in a utility pole.
A Gray Heron (Ardea cinerea) was found alive on 11 October 1996 in Newfoundland, Canada. It was identified as a Great Blue Heron (A. herodias), and prepared as a study skin for a university teaching collection. We give a description of this first specimen for North America and summarize previous records from the western hemisphere.
We report the occurrence of gang-brooding (i.e., communal brood-rearing) in a population of Northern Bobwhites (Colinus virginianus) in western Texas. Combinations of adult quail (2 mated pairs, 2 males, and 2 females) were observed with broods on several occasions. During the two-year study (2003–2004), communal broods were documented only in summer 2003.