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The extinct drepanidine genus Ciridops is known from five historically taken specimens of Ciridops anna from the island of Hawaii, the last in 1892, and from fossil populations on Molokai, Oahu, and Kauai. The origins of the historical specimens and the taxonomic history of the genus are reviewed. The plumages of C. anna are interpreted as highly sexually dimorphic (red males vs. greenish females); the juvenile plumage of males included brownish feathers that appear to have been retained and mixed with the incoming definitive plumage. The thigh musculature and pelvic and hindlimb osteology show that the strong legs and feet of Ciridops were probably used to move plant debris in search of insects. The closest living analog may be the Yellowhead (Mohoua ochrocephala) of New Zealand. Analysis of stomach contents of the single fluid-preserved specimen of C. anna disclosed remains of insects that are widely distributed in Hawaiian forest ecosystems. The traditionally claimed association of Ciridops anna with palms of the genus Pritchardia suggests that Ciridops may have fed in the accumulated debris in the axils of palm leaves. The patchy distribution of fossils of Ciridops may result from the birds being associated with nearly pure stands of Pritchardia that were in turn patchily distributed. Vulnerability of Pritchardia to introduced seed predators, including rats and humans, and to destruction of lowland habitats by cutting and burning, may have caused the prehistoric extinction of Ciridops on all islands except Hawaii.
The endemic solitaire, ‘Ōma‘o (Myadestes obscurus), is common in windward forests of Hawai‘i Island, but has been historically extirpated from leeward forests. The last detections of ‘Ōma‘o on the leeward side of the island were in woodland habitat on the western flank of Mauna Loa in 1978. ‘Ōma‘o were detected in woodland habitat in relatively low densities during a 2010 forest bird survey of Hawai‘i Volcanoes National Park. The source of the population is unknown. It is probable they originated from a documented but unsurveyed population of ‘Ōma‘o in scrub alpine lava. Alternatively, the birds may have persisted undetected for nearly 35 years, or expanded from windward mesic forests on southeast Mauna Loa. There is no evidence ‘Ōma‘o recolonized the wet mesic forests of leeward Mauna Loa. The ‘Ōma‘o can occupy diverse native habitats compared to other species in the Hawai‘i Myadestes genus, of which most species are now extinct. The connectivity of each population is not understood but we assume there are significant geographic, physiological, and behavioral barriers for scrub alpine and wet mesic forest populations. The expansion of ‘Ōma‘o to leeward woodlands is encouraging as the species is Hawai‘i Island’s last native frugivore capable of dispersing small and medium sized seeds of rare angiosperms, and could have an important role in re-establishing ecosystem function.
We documented unusual variation in the sequence of primary replacement during the prebasic molt of Rufous Fantails (Rhipidura rufifrons) captured in 2009 and 2010 on Saipan, Northern Marianas Islands. Most captures (62%) followed a typical replacement sequence, starting at the proximal primary (P 1) and proceeding distally to the outermost primary (P 10), but some individuals (38%) commenced molt from medial feathers, either P 2, P 3, or P 4 with replacement proceeding bidirectionally from the point of origin in multiple molt series. The distribution of centers for medial origin was P 2 (3%), P 3 (77%), P 3 and/or P 4 (12%), and P 4 (8%), indicating this pattern was distinct from the typical (P 1) pattern and the commencement point was not fixed to a specific primary. Females and individuals undergoing the second prebasic molt were more likely to have a center among primaries 2–4 than males and older birds. Two females that showed a center at P 1 during molt in 2009 showed a center at P 3 or P 4 during molt in 2010 represented exceptions to this finding but also indicated the starting point could vary inter-annually in an individual. Multiple molt series among primaries are poorly documented in passerines and we provide the first evidence for this molting strategy in the Rhipiduridae. Our results suggest a molt center among primaries 2–4 in younger and female Rufous Fantails may have evolved to enable more-rapid replacement of primaries while maintaining better foraging ability among selectively disadvantaged individuals.
The winter distribution of neotropical seedeaters (Sporophila spp.) known as capuchinos is poorly known. There are difficulties to understanding their migration patterns: fieldwork is lacking in their wintering areas, their ‘eclipse’ plumages often make it difficult to identify species, different species share habitats during winter, and there is little or no genetic differentiation of several forms. Vocalizations display a geographic signature (i.e., diagnostic acoustic features that are found in a limited area during the breeding period) and can be useful as indicators of a specific geographic origin of a wintering bird. I present data that: (1) demonstrates that non-breeding male Dark-throated Seedeater (S. ruficollis), Rufous-rumped Seedeater (S. hypochroma), and Tawny-bellied Seedeater (S. hypoxantha) in wintering areas can be assigned to a particular distant breeding population based on vocalizations; (2) evaluate the potential contribution of vocal variation in other capuchinos to understand their migratory movements; and (3) use vocalizations to unravel migration patterns of capuchinos. Non-breeding males of S. ruficollis from the Entre Rios regiolect were recorded in Cerrado habitat close to Vila Bela da Santíssima Trindade, Brazil and in the Beni savannas close to Trinidad, Bolivia, S. hypochroma from the Corrientes regiolect was recorded close to Vila Bela da Santíssima Trindade, and S. hypoxantha from the Entre Ríos regiolect was recorded close to Trinidad. Linking breeding and non-breeding areas through song-types is important to understand the evolutionary ecology and to promote conservation of these tiny long-distance flyers.
We placed light-level geolocators on 17 Rusty Blackbirds (Euphagus carolinus) in 2009 to track their migrations from nest sites near Anchorage, Alaska to wintering areas and back. We recaptured three of these birds in 2010 and found they departed breeding areas during the first half of September, spent 72–84 days migrating to overwintering areas, but only 16–30 days on their northward migration to Alaska. Birds took similar Central Flyway routes on southward and northward migrations, which were not previously described for this species. The birds used a series of stopover sites across the prairie region from southern Saskatchewan to Iowa over a 4 to 5 week period on their southward migration to wintering areas that spanned from South Dakota to northern Louisiana. We found upon recapture in 2010, the geolocator attachment harnesses had abraded the surrounding feathers on all three birds. This coupled with the low return rate (18%) for instrumented birds indicates a better harness method must be developed before this technology is more widely used on Rusty Blackbirds.
We equipped five Black-necked Cranes (Grus nigricollis) with satellite transmitters between February and November 2009 to investigate their migration routes between breeding areas and wintering area at Napahai Marsh (3,260 m asl), China. We identified the Shaluli Mountain region (southwest Sichuan), including Daocheng, Litang, Baiyu, and Xinlong counties as a new breeding area with a mean elevation of 4,330 m asl. Four of five tracked cranes spent the summer in Daocheng County. The fifth crane was there briefly and then moved north to Baiyu and Xinlong counties. The distance between Napahai Marsh and Daocheng County (∼180 km) is one of the shortest migration routes among crane species, but covered an elevation increase of ∼1,200 m. The migration route of the fifth crane was ∼400 km in length and occurred over 2 or 5 days in spring 2009 and 2010, respectively, and 19 days in fall 2009 with five stopovers.
Population composition of Aechmophorus grebes was investigated in Utah and the occurrence of possible intermediates between Western (Aechmophorus occidentalis) and Clark's (A. clarkii) grebes was assessed. Individuals with clearly intermediate traits represented an aggregated 6.5% (43 individuals) in the populations investigated while another 7.6% (46 individuals) did not entirely conform to the description of Aechmophorus grebes provided by Storer and Nuechterlein. The number of intermediates has increased in Utah in comparison to historical data. A similar survey in California and Oregon in 2009 also found increased percentages of intermediates. The results a priori contradict growing reinforcement of incompatibilities between both Aechmophorus grebes. Western and Clark's grebes in these major areas of sympatry appear to interbreed as frequently as in areas of relative allopatry. No evidence against assortative mating was found. Hybridization for Aechmophorus grebes may reflect adaptive mate choice rather than a mistake. Introgressive hybridization may be important and mask real rates of hybridization.
We examined support for the hypothesis that abundance of Cerulean Warblers (Setophaga cerulea) increases with percentage of bottomland and upland forest, and decreases with percentage of developed land at a local-habitat scale (within a 250-m buffer) and increases with percentage of all forest at a landscape scale (within a 10-km buffer). We conducted surveys along 16 rivers in Missouri and Arkansas from 1999 to 2006 and related habitat and landscape factors to counts of Cerulean Warblers in 123 5-km segments on these rivers. We detected 576 singing male Cerulean Warblers and found support for both local and landscape effects on Cerulean Warbler abundance. Model fit was good with an average correlation of 0.841 between predicted and observed values based on an eight-fold cross-validation procedure. The abundance of Cerulean Warblers increased 390.7, 8.7, and 4.1 times across the observed range of forest within 10 km, bottomland forest within 250 m, and upland forest within 250 m, respectively. Conservation and research need to address large-scale forest patterns in addition to local habitat for Cerulean Warblers. Further research is needed on abundance patterns across riparian and upland forests and demographic rates in this part of their range.
We studied the nesting ecology of Swainson's Warblers (Limnothylpis swainsonii) in Britton's Neck, South Carolina, USA and found 144 nests of which 78 were active. Nest initiations followed a bimodal distribution. Clutches averaged (± SE) 3.19 ± 0.20 eggs and 2.50 ± 0.33 fledglings per nest. The Mayfield nest success estimate for a 23-day cycle was 50%. Logistic exposure models indicate nest success to be most impacted by Brown-headed Cowbird (Molothrus ater) nest parasitism, nest age, and distance to the nearest swamp. Unparasitized nests that were younger in age and further from a swamp had the highest daily survival rates. Ten percent of nests were parasitized by Brown-headed Cowbirds with a 26% reduction in Swainson's Warbler hatching and an 89% reduction in fledgling production. Multiple brooding was observed in 21% of 2000 and 2001 Swainson's Warbler nests. Vines, such as greenbrier (Smilax spp.), were the most common substrate used for nesting, although two-thirds of the nests contained cane (Arundinaria tecta and A. gigantea) within a 5-m radius.
We installed nest boxes for Thorn-tailed Rayaditos (Aphrastrura spinicauda) and monitored their use in a Monterrey pine (Pinus radiata) plantation in the Maule Region, southcentral Chile. Thirty-four breeding pairs built nests in boxes, of which 75% began laying eggs. Nest establishment began in early September and construction lasted 12.8 ± 4.9 days (n = 23). Rayaditos used mainly pine needles, together with mosses, epiphytes, herbs, and animal hair in their nests. Clutch size ranged from two to four eggs (mode = 3) that were incubated for 15.8 ± 1.2 days. Brood size negatively affected mass of nestlings, but was positively related to mass of the parents. Adults had higher body mass and built larger nests than those reported previously for the species on Chiloé Island, where broods are larger and the incubation period is shorter. The provision of artificial cavities allowed Thorn-tailed Rayaditos to nest in the pine plantation. Nest boxes combined with other management tools, such as maintaining snags and understory enhancement, may be important factors in mitigation of negative effects of pine plantations on secondary cavity-nesting birds.
We report the first description of the nest, eggs, and nesting phenology of the Cozumel Vireo (Vireo bairdi), a passerine species endemic to Isla Cozumel, México. We discovered three nests of this species in 2009. These open-cup nests were woven onto branches and hung beneath forks. Clutch size was 2–3 eggs, and eggs were ovate and had a white ground color with reddish-brown flecks. These characteristics of nests and eggs are similar to those of most other Vireo spp., including other West Indian members of the Vireo subgenus. Breeding activities, including egg-laying, incubation, and nestling and post-fledging provisioning occurred from May to July 2009. We estimated the length of incubation to be ∼14 days and length of the nestling stage to be 11–12 days. Much of the Cozumel Vireo's breeding biology remains unknown and further study of this single-island endemic is needed.
Twelve Black-capped Chickadees (Poecile atricapillus) were captured and presented with a stuffed Eastern Screech-Owl (Megascops asio) model in areas containing and historically lacking persistent screech-owl populations (n = 4 and 8 chickadees, respectively) to assess whether ‘chick-a-dee’ calls have a site-specific structure for this dangerous, regionally sympatric predator. These learned vocal signals are used in various circumstances and one context is to denote information about predator threat level with numerous short and frequent D notes designating high threat. Average number of D notes per call was 4.4 where chickadees co-occurred with screech-owls but, in areas lacking them, the average was 2.3. Duration of the first D note and time between D notes were, respectively, 36% and 44% longer in areas without screech-owls. Diminution of predator recognition remains plausible but we present evidence that suggests chickadees elicit a threat-inappropriate call structure in areas lacking screech-owls because they have not learned the vocal repertoire for this predator and that nuances in ‘chick-a-dee’ calls convey predator-specific identity.
The Red-tailed Hawk (Buteo jamaicensis) is a top predator of upland ecosystems in the Greater Antilles. Little information exists on the ecology of the insular forms of this widely distributed species. We studied movements and resource use of the Red-tailed Hawk from 2000 to 2002 in the montane forests of northeastern Puerto Rico. We captured 32 and used 21 radio-marked Red-tailed Hawks to delineate home range, core area shifts, and macrohabitat use in the Luquillo Mountains. Red-tailed Hawks in the Luquillo Mountains frequently perched near the top of canopy emergent trees and were characterized by wide-ranging capabilities and extensive spatial overlap. Home range size averaged 5,022.6 ± 832.1 ha (305–11,288 ha) and core areas averaged 564.8 ± 90.7 ha (150–1,230 ha). This species had large mean weekly movements (3,286.2 ± 348.5 m) and a preference for roadside habitats. Our findings suggest fragmentation of contiguous forest outside protected areas in Puerto Rico may benefit the Red-tailed Hawk.
We observed an active nest of the Grey-bellied Hawk (Accipiter poliogaster) in the mixed rainforest of southern Brazil during the 2011 breeding season. The nest was a platform built in the branches of the upper part of a Paraná pine (Araucaria angustifolia). The clutch size was two eggs, but only a single nestling survived and left the nest, ∼49 days post-hatching. The fledgling was fed by adults at the nest for at least 90 days post-hatching. Only the adult female incubated the eggs and brooded the nestlings. Both female and male provided nest defense, the former up to 50 m from the nest and the latter at 50 to 200 m. Only the male hunted and only the female fed the nestlings. The identified prey brought to the nest by the male included eight birds and one young armadillo. Five voice types were identified: one alarm call, three food-related calls (performed by adults), and one food-begging call (performed by the fledgling). The type of habitat where the nest occurred suggested this poorly known species can possibly survive in disturbed areas. It seems to be naturally rare and its' shy behavior contributes to its low detection.
We used collection of prey remains, direct observations of hawks with prey, and video cameras at two nests to assess frequency of occurrence and biomass of prey species taken by breeding Cooper's Hawks (Accipiter cooperii) in Victoria, British Columbia, Canada during 1995–2010. Small (≤ 27 g) to medium-size (28–91 g) bird species contributed the majority (79–94%) of prey recorded from collection of 3,231 prey remains, 437 direct observations, and 783 video items at 87 nest sites. Avian prey contributed over half of prey biomass recorded in direct observations and video data (67% and 93%, respectively). One native and two introduced species provided most (> 85%) prey recorded in all samples in which birds were identified to species: American Robin (Turdus migratorius), European Starling (Sturnus vulgaris), and House Sparrow (Passer domesticus). Introduced species were an important component of the diet, contributing over half of items identified in all samples. There was a temporal shift in age of prey used: the early-season diet (Mar–Apr) was comprised of adult birds and subadult mammals, while avian young of the year dominated the diet from late May until the end of the breeding season (70–100% of identifiable items). Mammals were inconsequential in terms of frequency and biomass except at nests (6 of 87) on or near the University of Victoria campus where nearly all European rabbit (Oryctolagus cuniculus) prey was recorded.
We examined nestling Red-shouldered Hawks (Buteo lineatus) in 56 nests (147 nestlings) in suburban southwestern Ohio and in 25 nests (67 nestlings) in rural forested Hocking Hills in south-central Ohio, ∼180 km east of southwestern Ohio. Fifteen of 25 nests in Hocking Hills had Protocalliphora avium larvae on one or more nestlings and/or pupae in the nest material. Nineteen nestlings had larvae in one or both ears, an additional 14 had evidence of larvae outside the ears, 32 were not visibly parasitized, and two were not examined or their status was not reported; in contrast, no nests and no nestlings were parasitized in southwestern Ohio. Reproductive rate (young fledged/nest) did not differ between southwestern Ohio and Hocking Hills (2.4 ± 0.1 young/nest at southwestern Ohio vs. 2.7 ± 0.2 at Hocking Hills; P = 0.214). Parasitized nests at Hocking Hills were no more likely to have been used in the previous breeding season than non-parasitized nests (χ2 = 0.903, P = 0.342, n = 22). Similarly, number of young fledged/nest at parasitized nests did not differ from that at non-parasitized nests within Hocking Hills (U = 75.0, P = 1.00, n = 25; mean (± SE) number of young = 2.7 ± 0.3 vs. 2.7 ± 0.3 at parasitized and non-parasitized nests, respectively). The Protocalliphora loads we observed did not appear to have a negative effect on the fledging rate of nestling Red-shouldered Hawks; however, we did not assess any other potential effects of parasitism.
Hematocrit, the percentage of packed red blood cells in blood, has been used as a measure of avian condition. We investigated the relationship between hematocrit and condition in a wild, breeding population of adult European Starlings (Sturnus vulgaris), and their nestlings (at 5- and 11-days post hatch). Hematocrit was not correlated with condition in adults or nestlings at either 5- or 11-days post-hatch. Adult males and females had similar hematocrit values. Hematocrit increased with age; adults had significantly higher hematocrit than both 5- and 11-day old nestlings, and 11-day old nestlings had significantly higher hematocrit than when they were 5 days of age. Hematocrit was not correlated with sampling date, ambient temperature, or relative humidity level, but was positively correlated with sampling time in the day for nestlings (but not adults). Our findings caution against using hematocrit as a measure of condition in birds.
Relocation by dependent young is a survival strategy that occurs among a wide range of taxa. The Common Nighthawk (Chordeiles minor) lays its eggs on bare substrate and, once hatched, nestlings may relocate to new sites daily. We located and monitored eight Common Nighthawk nests in Grand Teton National Park, Wyoming, quantified inter-use-site distances in relation to nestling age, and calculated a nestling growth rate curve. Common Nighthawk nestlings grow in a nearly linear fashion. Nestlings moved up to 48 m in a single day and larger, older nestlings tended to move greater distances between daily use-sites.
The ecological nesting requirements of Northern Black Swifts (Cypseloides niger borealis) have been well documented, but little information exists regarding the microclimate at Black Swift nests. We placed 42 data loggers at 10 occupied Black Swift colonies between 2006 and 2010 to measure and record temperature and relative humidity, resulting in 19,181 usable records. Median temperature and relative humidity at nine Colorado and New Mexico sites were 9.4 °C and 89.7%, respectively, and at one California site were 13.4 °C and 92.8%, respectively. Values were quite stable throughout the breeding season with slight changes reflecting the ambient temperature and humidity of the surrounding macroclimate. These baseline data may prove useful for conservation of this species, especially if predicted global climate changes occur.
Previous Chimney Swift (Chaetura pelagica) trapping efforts relied on chimney-top box traps at large roost sites, which were disruptive and inefficient when targeting individual birds. I designed a hoop net for use at nest chimneys to trap individual breeding birds. I caught 13 swifts at 11 different sites in Guelph, Ontario, Canada over two summers with no site abandonment. This trap is superior for trapping individuals because it: (1) can be deployed quickly without scaling the chimney, (2) will work on chimneys of different sizes and shapes, and (3) minimizes disturbance to birds. My results indicate this net is an efficient, safe, and relatively simple method of trapping individual Chimney Swifts at their nest chimneys.
Inter- and intra-specific competition are known to influence feeding decisions, but relatively little research has investigated how inter- and intra-sexual interactions can impact foraging. We studied foraging preferences of male and female Northern Cardinals (Cardinalis cardinalis) during winter and found they preferred sunflower seed to safflower seed when presented with paired feeders in the absence of conspecifics. Male cardinals avoided feeders occupied by other males and approached feeders occupied by females, regardless of feeder contents. Female cardinals avoided other females and especially males when choosing feeders. These changes in foraging behavior by male and female cardinals as a result of conspecific presence indicate inter- and intra-sexual interactions alter the attractiveness of a high or low energy food source.
We report observations of Thick-billed Euphonias (Euphonia laniirostris) and a Golden-faced Tyrannulet (Zimmerius chrysops) kleptoparasitizing nest material from Red-faced Spinetail (Cranioleuca erythrops) nests in Antioquia, Colombia. Thick-billed Euphonias (12 ± 1 m, n = 11 encounters) and Golden-faced Tyrannulets (10 ± 1 m, n = 19) at our study site typically foraged at similar heights as the Red-faced Spinetail nests they parasitized (9 m for both nests), consistent with the idea that a kleptoparasite might steal material from nests in its home stratum to avoid predation risk associated with descending to the ground in search of nest material. We encourage ornithologists to continue reporting instances of nest material kleptoparasitism so its prevalence in birds can be rigorously assessed.
The Tody Motmot (Hylomanes momotula) has a fragmented range throughout Central America. I present evidence from audio recordings for a new location for this species in Costa Rica. Individuals detected likely represent a previously undiscovered population in the foothills of the Caribbean Slope of the Tilarán Mountains. A small population of Tody Motmots could easily be overlooked in foothill forests drained by the Jamaical, San Lorencito, and San Lorenzo rivers, which are exclusively on private land.
Red-tailed Hawks (Buteo jamaicensis) usually hunt from a perch and swoop down on prey. I observed a novel foraging strategy in which the bird deliberately, and successfully, attacked and deconstructed nests of squirrels to flush or capture prey in an urban environment.
We examined differences in microhabitat use between Boreal (Poecile hudsonicus) and Black-capped chickadees (P. atricapillus) where they co-occur near Marquette, Michigan, USA. Twenty-four Boreal and 37 Black-capped chickadees were followed during 60 hrs of field observation. Boreal Chickadees foraged only in three conifer species, 76% of which were black spruce (Picea mariana), while Black-capped Chickadees foraged widely across six coniferous and three deciduous tree species. Analysis of foraging data categorized by zones within conifer trees indicated high niche overlap (0.676) between Boreal and Black-capped chickadees across all foraging zones. Individual comparisons on a zone-by-zone basis revealed a significant difference in foraging occupancy in the medial portion of the crowns of conifer trees (P = 0.0002). Our results indicate exclusive use by Boreal Chickadees of dense medial foliage within the top 3 m of conifer crowns.