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The geographic range of the Scale-backed Antbird (Willisornis poecilinotus) encompasses Amazonia. Seven currently defined subspecies are distinguished from one another by diagnostic plumage characters except for one pair. Six pairs of subspecies are apparently parapatric and lack a known barrier to intergradation in at least a portion of their contact zone; yet confirmed hybrids are known only for one pair in one location. An analysis of >350 recordings, however, found vocal differences among them insufficient to recommend elevating subspecies to the species level with one exception. Populations in southeastern Amazonia should be considered a distinct species, Willisornis vidua (Hellmayr), Xingu Scale-backed Antbird, on the basis of their distinct loudsongs, raspy call series, and contact calls. Within the widespread Willisornis poecilinotus, Common Scale-backed Antbird, the remaining instances of parapatry without extensive intergradation provide a focus for future fieldwork to define interrelationships in contact zones and mechanisms of species recognition that may be sustaining them on independent evolutionary paths.
Antbirds (Thamnophilidae) are a diverse component of neotropical forest avifaunas, and are particularly vulnerable to population declines and extirpations in fragmented landscapes. We lack estimates of apparent survival and dispersal for the majority of species, despite their value in effectively managing populations of understory birds. We studied a population of Chestnut-backed Antbird (Myrmeciza exsul) from 2004 to 2009 in a large rain forest preserve in northern Costa Rica to generate estimates of apparent annual survival (ϕ), and breeding dispersal (i.e., movement from one breeding territory to another) in continuous forest. Estimates of ϕ (± SE) of adults based on weighted model averages were high (males: 0.794 ± 0.037; females: 0.798 ± 0.050) compared to independent juveniles (males: 0.629 ± 0.159; females: 0.629 ± 0.168). Detection (recapture/reobservation) probabilities (p) were higher for males (adults: 0.916 ± 0.034; juveniles: 0.915 ± 0.049) than for females (adults: 0.544 ± 0.104; juveniles: 0.540 ± 0.115). Overall annual turnover (disappearing from the study area territory switching) was comparable to other antbirds (∼32%). Territory switching was rare, and generally limited to short movements to adjacent or nearby territories (mean distance moved = 372 m, range = 145–840 m, n = 9). Our results suggest Chestnut-backed Antbirds: (1) have relatively high adult annual survival, and (2) have limited breeding dispersal, even in a large, forested study area.
We inventoried the bird fauna of an isolated enclave of white-sand vegetation, known locally as a campina/campinarana, in the western extreme of the Brazilian State of Acre between 22 and 31 January 2007 (wet season). A total of 114 bird species was registered in 1,425 net-hrs of mist-netting and 8 hrs of recordings of vocalizations. This included six species known to be associated with campinas and campinaranas in western Amazonia. A number of important records were made of species endemic to the southwestern Amazon Basin, but poorly-known in Brazil. Despite the relatively small size of the campina/campinarana enclave, these records indicate the area is extremely important for conservation of local biodiversity, and reinforces the need for further studies of both the avifauna and other groups of animals.
We examined δ15N and δ13C values of feathers from nine species, belonging to three feeding guilds (herbivores, omnivores, and insectivores), of wild passerines at eight sites along an altitudinal gradient (339–2,876 m asl) within Taroko National Park, Taiwan. We examined: (1) if altitudinal patterns in feather δ15N and δ13C are consistent with previously published values for plants and soils, (2) if feather δ15N and δ13C differ among sites, and (3) if there are year-to-year and/or month-to-month fluctuations in feather δ15N and δ13C of the same birds. We found no simple relationship between feather isotope values and altitude. Feather δ15N values decreased significantly with increasing altitude for insectivores, but not for herbivores and omnivores. Feather δ13C values increased significantly with increasing altitude for herbivores and omnivores, but not for insectivores. Altitudinal trends in feather δ15N and δ13C values exhibit even more inconsistent patterns when data were analyzed by species; feather δ15N and δ13C values for some species increased significantly with increasing altitude, others decreased significantly with increasing altitude, and still others exhibited no significant relationship between isotopic values and altitude. The R2 for the relationship between feather δ15N, δ13C values and altitude was generally low regardless of whether the analysis was by feeding guilds or species. This indicates much of the variation cannot be explained by altitude. There were either no significant differences between sites, or significant differences between some but not all sites when investigating δ15N or δ13C, whether by feeding guilds or by species. Our study suggests that carbon and nitrogen isotopes may be not useful markers to track altitudinal migration of montane passerines.
Saltcedar (Tamarix spp.) has increasingly dominated riparian floodplains relative to native forests in the southwestern U.S., but little is known about its impacts on avian productivity or population status. We monitored 86 Arizona Bell's Vireo (Vireo bellii arizonae), 147 Abert's Towhee (Melozone aberti), and 154 Yellow-breasted Chat (Icteria virens) nests to assess reproductive parameters in cottonwood-willow (Populus-Salix), saltcedar, and mesquite (Prosopis spp.) stands along the San Pedro River, Arizona during 1999–2001. We also assessed source-sink status for each species in each vegetation type using field data combined with data from the literature. There were no significant differences in reproductive parameters between vegetation types for Abert's Towhee or Yellow-breasted Chat, although seasonal fecundity was quite low across vegetation types for the latter (0.75 ± 0.14; mean ± SE). Bell's Vireo had extremely low seasonal fecundity in saltcedar (0.10 ± 0.09) and significantly fewer fledglings per nest in saltcedar (0.09 ± 0.09) compared with cottonwood (1.07 ± 0.32). Point estimates of λ were substantially <1 for all three focal species in all habitats indicating the entire study area may be performing as a sink; 90% CI of included 1 only for Abert's Towhee across vegetation types and Bell's Vireo in cottonwood vegetation. These results are surprising given the San Pedro is considered to be one of the best remaining occurrences of lowland native riparian vegetation in the southwestern United States.
Herbaceous buffers are strips of herbaceous vegetation planted between working agricultural land and streams or wetlands. Mowing is a common maintenance practice to control woody plants and noxious weeds in herbaceous buffers. Buffers enrolled in Maryland's Conservation Reserve Enhancement Program (CREP) cannot be mowed during the primary bird nesting season between 15 April and 15 August. Most mowing of buffers in Maryland occurs in late summer or fall, leaving the vegetation short until the following spring. We studied the response of wintering birds to fall mowing of buffers. We mowed one section to 10–15 cm in 13 buffers and kept another section unmowed. Ninety-two percent of birds detected in buffers were grassland or scrub-shrub species, and 98% of all birds detected were in unmowed buffers. Total bird abundance, species richness, and total avian conservation value were significantly greater in unmowed buffers, and Savannah Sparrows (Passerculus sandwichensis), Song Sparrows (Melospiza melodia), and White-throated Sparrows (Zonotrichia albicollis) were significantly more abundant in unmowed buffers. Wintering bird use of mowed buffers was less than in unmowed buffers. Leaving herbaceous buffers unmowed through winter will likely provide better habitat for wintering birds.
We studied wintering grassland bird communities in De Soto National Forest in southern Mississippi, USA to assess differences in bird communities and vegetation structure among different stand types. We also examined which vegetation structure and plant species predicted occurrence of Bachman's Sparrow (Peucaea aestivalis), Henslow's Sparrow (Ammodramus henslowii), and Sedge Wren (Cistothorus platensis). Bachman's Sparrows occurred only in uplands ( = 0.5 birds/ha) and stands managed for Red-cockaded Woodpeckers (Picoides borealis; = 0.9 birds/ha), Henslow's Sparrows occurred only in bogs ( = 3.8 birds/ha) and stands managed for Red-cockaded Woodpeckers ( = 2.1 birds/ha), while Sedge Wrens occurred in all stand types ( = 0.1–0.3 birds/ha). There were no significant differences among stand types in total bird densities for all three species combined. Dense, spatially uniform herbaceous cover and cover of Scleria muhlenbergii, a preferred food item in bogs, best predicted Henslow's Sparrow occurrence (39% s2 explained). Increased woody understory vegetation and decreased tree density best predicted Sedge Wren occurrence (17% s2 explained). Management for Henslow's Sparrows should focus on small-scale herbaceous ground-layer restoration in bogs. Bachman's Sparrows will respond more to thinning dense upland stands. Sedge Wrens and Bachman's Sparrows benefit from Red-cockaded Woodpecker management, whereas Henslow's Sparrow use of woodpecker stands is ephemeral.
We studied sound emission in the non-oscine Cuban Tody (Todus multicolor) to quantify its acoustic repertoire and to document geographic variation in its songs across the Cuban archipelago. Cuban Todies emitted three types of sounds. The characteristic song of the species was recorded from 98% of 116 individuals. The characteristic song of the species and a variant form recorded from two individuals consisted of trains of multi-harmonic short, downward frequency modulated notes emitted at peak frequencies below 4 kHz. A third type of sound in the limited repertoire of the species recorded from two birds is presumably produced with the wings and appears in the spectrograms as a train of short clicks with frequencies also below 4 kHz. Evidence of geographic variation was found in the characteristic song. Birds from Isla de la Juventud and Pinar del Río emitted more notes per train spaced at longer intervals than birds from the rest of the provinces. The peak frequency of the notes had lower values in birds from Isla de la Juventud. A discriminant function analysis grouped todies from different provinces into two main clusters corresponding to western Cuba and eastern Cuba. This geographic song variation may indicate genetic differences in this sedentary forest bird, and the existence of two “incipient species” of todies in Cuba. Isolation may have been caused by discontinuities in the mainland of Cuba that occurred between the Pleistocene and Holocene or by deforestation occurring in Cuba for the last five centuries.
The Royal Sunangel (Heliangelus regalis) is endemic to sandstone ridges in southeast Ecuador and northeast Peru. This hummingbird is currently considered endangered, although little has been published on its natural history, distribution, and conservation. We found H. regalis in three habitat types, but abundance was higher in stunted shrubland, at ridgetops. It was observed to feed on seven plant species, mostly following regular feeding routes, between 0 and 2.5 m above ground. We describe six different vocalizations, as well as two flight displays, and observations on social interactions. We also discuss its current conservation status in Ecuador, where we estimate that ∼2,500 individuals might persist.
We report nesting behavior of Szechenyi's Monal-Partridge (Tetraophasis szechenyii) in treeline habitats of the Pamuling Mountains, Sichuan Province, China. Szechenyi's Monal-Partridge used both ground and tree nests. Ground nests were scrapes in the soil, positioned at the base of a tree or scrub, and occurred in all habitats except Sichuan kobresia (Kobresia setchwanensis) meadow. Tree nests were cup shaped and placed 1.9–12.0 m above ground level, distributed proportionally in all habitats except scrub hollyleaf-like oak (Quercus aquifolioides) and Sichuan kobresia meadow habitats. The proportion of nest types between first and re-nesting attempts did not vary significantly. Only 54% of ground nests and 33% of tree nests survived until hatching with predation being the principal cause of ground nest failure. Hatching success was 97%. We recorded six re-nesting attempts, four of which were tree nests, but all were unsuccessful. Preserving a mosaic of treeline habitats that include ground vegetation, and fir/oak woodland habitat will be essential for maintaining suitable nesting habitats for Szechenyi's Monal-Partridge in the Pamuling Mountains.
The Swallow-tailed Kite (Elanoides forficatus) formerly bred in Arkansas, but no nesting attempts were observed in the state for over a century. We initiated a study in 2001 to investigate the species' reproductive status in east-central Arkansas, USA. We located five nests between 2001 and 2009, all of which failed. Two nests were abandoned (one due to researcher caused disturbance), one failure was likely caused by a Red-shouldered Hawk (Buteo lineatus) or Barred Owl (Strix varia), one was suspected to be caused by a rat snake (Elaphe obsoleta), and one failed from unknown causes. Nests were built in overcup (Quercus lyrata) and Nuttall oaks (Q. texana) with a mean (± SD) diameter at breast height of 83.92 ± 7.20 cm, mean tree height of 31.28 ± 4.78 m, and mean projection of 7.15 ± 5.66 m above surrounding trees. Nests were at a mean height of 25.09 ± 4.85 m and positioned 0.30 ± 2.36 m above the surrounding trees. All nests were within a circular area 4 km in diameter. Our discovery of a nest in 2002 represented the first documented case of nesting Swallow-tailed Kites in Arkansas in >100 years and is a considerable (370 km) distance from the closest known nesting site in Louisiana.
We recorded and quantified the nocturnal activity and parental care of a brooding Common Potoo (Nyctibius griseus) using an infrared camera in southeastern Brazil. Parents alternated care of the nestling and decreased their presence as the nestling grew. Nestling feeding on passing insects while sitting on the nest, movements on the nest, wing exercising, preening, and defecating were recorded primarily while it was alone. The frequency of begging calls per hour was higher when the nestling was accompanied by one of the parents. Nocturnal recordings of this species on the nest revealed behaviors that were not cited in past studies, including: feedings bouts on passing flies performed by the nestling and adults, nestling defecation, and nestling plumage maintenance. The well-known plus newly quantified behaviors of the Common Potoo reinforce their value to survival during the long nestling period.
We collected observational data in three consecutive breeding seasons to study interactions between the botfly Philornis seguyi and Red-crested Cardinals (Paroaria coronata) in a temperate zone near the southern limit of Philornis distribution. We analyzed: (1) seasonal trends in prevalence of parasitism, (2) influence of botfly parasitism on nestling growth rate and survival, and (3) the association between nest site vegetation at different scales (i.e., nest tree, vegetation surrounding the nest tree, and landscape) and probability of botfly parasitism. Prevalence of parasitism was 28% and was higher later in the breeding season. Botfly parasitism produced sub-lethal (lower growth rate of nestlings that survive) and lethal (lower nestling survival) effects. The lethal effect was negatively associated with age at the time nestlings were parasitized. Botfly parasitism was not associated with vegetation characteristics at the level of nesting tree or vegetation surrounding the nesting tree, but was associated with landscape features. Parasite prevalence was higher in large continuous woodland patches than in small isolated patches. However, we did not observe increased use of isolated patches of forest by Red-crested Cardinals, suggesting that use of nest sites with high botfly parasite intensity could be the consequence of high host density.
We document seasonal changes in the ratio of phosphatidylcholine (PC) to phosphatidylethanolamine (PE) in pectoralis muscles of captive and wild White-throated Sparrows (Zonotrichia albicollis). We manipulated day length in captive sparrows to induce ‘winter’ or ‘migratory’ condition. The PC/PE ratio in these sparrows was 1.87 ± 0.11 (mean ± SE), and did not vary significantly between treatments. However, the PC/PE ratio was higher in wild adult sparrows in winter (1.90 ± 0.19) than those caught in migration (1.20 ± 0.13 in spring; 1.37 ± 0.14 in fall). No effect of migratory state on PC/PE ratio was found among wild juveniles (1.32 ± 0.09 in fall, 1.18 ± 0.14 in winter). Seasonal changes to PC/PE ratios may be a result of migratory exercise, rather than migratory condition per se.
The long breeding period and high reproductive investment of seabirds make use of resource-rich foraging areas pivotal both during and between breeding seasons. We tracked adult Australasian Gannets (Morus serrator) from their New Zealand breeding colony at Cape Kidnappers to Australia during the non-breeding period to assess wintering behavior and migratory routes for this species. Data from three recovered geolocation sensor (GLS) tags showed that both a male and a female M. serrator, and a hybrid M. capensis × M. serrator migrated across the Tasman Sea to winter in Australian and Tasmanian coastal waters. Tracked birds covered distances of up to 13,000 km on their migration. These movements were consistent with historical records of band recoveries.
We identified 25 species of birds representing nine avian Orders from remains in digestive tracts of 85 Burmese pythons (Python molurus bivittatus) collected in Everglades National Park, Florida, USA, from 2003 to 2008. Four species of birds identified in this study are of special concern in Florida and a fifth, the Wood Stork (Mycteria americana), is listed as federally endangered. This represents the first detailed analysis of the avian component of the diet of the introduced Burmese python, now established in Everglades National Park, Florida and highlights the potential for considerable negative impact of this invasive species on native bird populations.
I analyzed the occurrence of intermediates between Western (Aechmophorus occidentalis) and Clark's (A. clarkii) grebes, of mixed pairings, and of species composition in populations of Aechmophorus grebes in California and Oregon, USA. Western Grebes comprised 69% of the aggregated total of grebes identified while intermediates represented ~3.5% (41–46 individuals) in the populations investigated. I conclude that numbers of intermediates between purebred parental individuals have increased. Higher percentages of mixed pairings were observed at Lake Almanor; an aggregated 7.9% of nesting pairs were not composed of two purebred grebes of the same species. Statistically, mating remained strongly assortative.
The Brown Wood Rail (Aramides wolfi) is a globally threatened, poorly known species endemic to the Chocó rain forests of South America. We provide a first report on the species' nesting biology, home range, and habitat use. Nests (n = 16) were open cups ∼2 m above ground and were more common in secondary forest than expected by chance. Median clutch size was four eggs, incubation lasted >19 days, the precocial young departed the nest within 24 hrs of hatching, and 66% of nests successfully produced young. At least two adults participated in parental care and pair bonds appear to be maintained year-round. The home range of an adult radio-tracked for 7 months was 13.5 ha in secondary and selectively-logged forest contiguous to primary forest. This easily overlooked species may be more resilient to moderate levels of habitat degradation than previously suspected, but extensive deforestation throughout its range justifies its current status as ‘Vulnerable to Extinction’.
We describe the nest and eggs of the Chestnut-headed Crake (Anurolimnas castaneiceps) based on observations of two nests found in the border of the Lliquino River, Pastaza Province, Ecuador. Nests were found in June and December with birds incubating eggs. Both nests were on fallen logs covered by vines and epiphytes in natural small gaps. They were open cups and built principally with dead leaves. The coloration of the eggs was pinkish white with scattered brown spots, similar to other Amazonian rails and crakes. The nests were similar in structure to those of wood rails (Aramides spp.) suggesting a close relationship between Anurolimnas and Aramides.
Breeding of the poorly known Snowy-cheeked Laughingthrush (Garrulax sukatschewi) was studied in a conifer-dominated forest at Lianhuashan (southern Gansu), China. Snowy-cheeked Laughingthrushes nested at sites with fewer conifers and denser shrubs compared with the available vegetation. Bowl-shaped nests were 2.4 ± 0.1 m (x¯ ± SE, n = 31) above ground in six plant species. Spruce (Picea spp.) was used (74%) more often than expected based on availability at nest sites. The breeding season (early May to mid Jul) was shorter than for other timaliids. Twelve of 20 (60%) nests with known outcomes were successful. The average clutch size was 3.5 ± 0.2 eggs (2–5, n = 21) with 2.7 ± 0.2 hatchlings (2–4, n = 15) and 2.2 ± 0.2 fledglings (1–3, n = 12) per nest. Incubation was by both males and females and lasted 14 days (n = 1); both parents cared for the nestlings for 16–18 days (n = 3).
We collected 17 (13 females, 4 males) Shiny Cowbirds (Molothrus bonariensis) during the passerine nesting season in July 1999 and 2003 in Jasper County, southwestern South Carolina. Five females (38%) were laying eggs, as ascertained from the condition of their reproductive organs. Two females collected on 1 July 1999 and 19 July 2003 had eggs in their oviducts, and would have deposited eggs within 1 day. Shiny Cowbirds have been in North America for at least 24 years, but only males had been collected before this study. Most of those collected had enlarged testes, as did the four collected in the present study, but these data are not proof that breeding actually occurred. The reproductive condition of the females we collected provides material evidence that the species breeds in North America. It is not known which species are being parasitized by Shiny Cowbirds, but several species widespread in the southeastern United States are highly suitable hosts.
Increasing proportions of Sharp-shinned Hawks (Accipiter striatus) migrated later in autumn at the Hawk Ridge Bird Observatory, Duluth, Minnesota during 1974–2009. Migration averaged about 4 days later over 35 years since 1974, and about 8 days later during late September through October in the last 16 years of the study. Our results augment previous findings demonstrating recent shifts in phenological events for birds. The proximate causes and potential consequences of this later timing of migration should be investigated.
Seasonal migration is an important component in the life cycle of Northern Saw-whet Owls (Aegolius acadicus). We evaluated the influence of the four lunar events (new moon, first quarter moon, full moon, and last quarter moon) on nocturnal activity of Northern Saw-whet Owls based on captures during fall migration, 2000–2008. We found differences between the lunar events with decreased capture rates during the full moon and the new moon. These results suggest lunar phase influences migratory movements and behaviors in this species. This may be attributed to predator avoidance during periods of relative brightness or darkness at night.
Nocturnal migration is a common strategy among North American passerines. Birds of the Fringillidae have typically been labeled as predominately diurnal migrants. We used pressure-zone microphones and automated sound detection software to record flight calls of nocturnally migrating birds from 2 to 16 October 2008 from 2000 to 0600 hrs EST at three locations near Gardiner, Maine. We detected and recorded 190 Pine Siskin (Spinus pinus) flight calls from throughout the night at three separate locations. This is the first published documentation of apparent nocturnal migration in this species. Nocturnal migration may be a facultative migration strategy in the Fringillidae that occurs only in years in which large irruptive movements occur as for Pine Siskins in fall 2008.
Ambient temperature may influence selection of foraging sites by organisms that use sap as a primary food source. I examined the spatial orientation of sap wells excavated by Yellow-bellied Sapsuckers (Sphyrapicus varius) on pine trees (Pinus spp.; n = 43) in eastern Kansas. Sap wells were oriented toward the southwest (ā = 246.04°, s = 65.46°, P = 0.004), unlike in previous studies. Benefits of southwesterly sap well orientation may include avoidance of high winds while foraging and increased flow of sap on the sides of trees warmed by afternoon light.
We report observations of the Austral Parakeet (Enicognathus ferrugineus) feeding on larvae in the northern part of its distribution in the austral temperate forests of Argentine Patagonia during the pre- and post-reproductive seasons. Larvae consumed were Aditrochus fagicolus (Chalcidoidea: Pteromalidae) in leaf galls of Nothofagus pumilio (79 observations), larvae from Homoptera, Lepidoptera, and Diptera in seed galls of N. pumilio (12 observations), and larval Nemonychidae (Coleoptera) in male cones of Araucaria araucana (69 observations). Our observations suggest Enicognathus ferrugineus could be more insectivorous than previously thought, perhaps to help meet their demand for high-quality food during the pre- and post-reproductive seasons.
Foraging associations between birds and other groups of animals have been widely reported in the literature. I report the first observation of a foraging tactic involving a flock of Greater Ani (Crotophaga major), which deliberately followed fish along an artificial ditch in the Pantanal wetlands, feeding on animals flushed by the movement of the vegetation on the ditch banks. Further observations of the feeding behavior and foraging tactics of Greater Anis are necessary to ascertain if this type of behavior is a frequent event or merely sporadic.
Documentation of interspecific adoption of young is rare in the published literature among birds. We survey six cases of young Common Buzzards (Buteo buteo) adopted in nests of White-tailed Sea Eagle (Haliaeetus albicilla) in central Europe (Czech Republic and Hungary). Common Buzzard nestlings adopted were in good condition and adult White-tailed Sea Eagles fed and cared for them properly. Young Common Buzzards successfully fledged and left the White-tailed Sea Eagle nests. The most probable explanation of this phenomenon is a non-lethal predation of Common Buzzards followed by White-tailed Sea Eagle parental care as a result of parental recognition error. Similar cases of adoption of Red-tailed Hawk (Buteo jamaicensis) nestlings in nests of Bald Eagle (Haliaeetus leucocephalus) have been documented in North America.
Avian mortality during fall migration has been studied at many anthropogenic structures, most of which share the common feature of bright lighting. An additional, unstudied source of avian mortality during fall migration is recreational cruise ships that are brightly lit throughout the night. I documented a single mortality event of eight Common Yellowthroats (Geothlypis trichas) on one ship during part of one night in fall 2003, but suggest this is a more wide-spread phenomenon. The advertised number of ship-nights for 50 cruise ships in the Caribbean Sea during fall migration in 2003 was 2,981. This may pose a significant, additional, anthropogenic source of mortality that warrants further investigation, particularly because impacts could be minimized if this source of avian mortality is recognized.
I report the first sighting of Aplomado Falcon (Falco femoralis) for Puerto Rico and all of the West Indies. I observed a single individual at Laguna Cartagena National Wildlife Refuge (southwestern Puerto Rico) on 15 January 2008; the individual stayed until 25 January 2008. Photographs establishing the bird's identity were obtained during prolonged periods of observation by several observers.
We report observations of Blue Jay (Cyanocitta cristata) mortality in idle lobster traps stored on Merepoint Neck in the Town of Brunswick, Maine. Three of nine individual Blue Jays found inside the traps were alive but emaciated. Each of the live Blue Jays was seen picking off and swallowing pieces of pectoral muscles from Blue Jay carcasses also inside the traps. We could not find literature describing or warning of the attractive nuisance posed to birds by improperly stored fishing gear, such as lobster traps. Our observations identify a previously undocumented threat to local bird populations, and likely the first documentation of adult-adult cannibalism for the Blue Jay. We suggest some simple solutions to mitigate avian mortality due to improperly stored fishing gear.
We report five instances of small birds mobbing Common Nighthawks (Chordeiles minor). In each case, the nighthawk was roosting in a tree during daytime and was mobbed by a group of birds in a manner typical of that directed toward an avian predator. We found only four previously published accounts of perched caprimulgiforms being mobbed. Mobbing birds probably mistake caprimulgiforms for owls because of convergence in plumage coloration and pattern between these two groups of crepuscular-nocturnal birds.
Communal winter roosts of American Crows (Corvus brachyrhynchos) often occur in urban areas and may number in the thousands of individuals. We documented the distribution of urban roosts of American Crows in central Ohio and, on 12 January 2010, we observed a roost of ∼2,500 individuals with ∼250–300 birds roosting on the ground. The ground roosting birds remained stationary for the entire observation period of ∼45 min indicating this location was not a stopover site. This behavior may increase thermoregulatory benefits during cold nights assuming decreased predation threats in urban environments. We suggest urban ground roosting behavior by crows may be adaptive in colder environments.