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Golden-winged Warblers (Vermivora chrysoptera) are declining in the eastern portion of their range partially due to a loss of shrub-scrub and early successional habitat. We surveyed Golden-winged Warbler abundance in shrub swamp, young aspen (Populus spp.), heavily thinned hardwood, jack pine (Pinus banksiana), and two edge cover types (i.e., swamp/aspen and swamp/mature) in 2002–2004 in northern Wisconsin. Golden-winged Warbler abundance was greatest in young aspen stands (1–10 years of age) and least in the swamp/ mature edge cover type. Abundance did not differ among years in any of the cover types. Aspen stem density was positively related to Golden-winged Warbler abundance among stands. The presence of Golden-winged Warblers within stands, at the sampling station scale, was positively correlated with aspen stem density, the amount of low woody cover, and ground vegetation. The most effective way to manage for this species in the north central portion of its range may be through the creation of young aspen forests and by maintaining shrub-scrub habitat.
Availability of food resources is an important factor in avian habitat selection. Food resources for terrestrial birds often are closely related to vegetation structure and composition. Identification of plant species important in supporting food resources may facilitate vegetation management to achieve objectives for providing bird habitat. We used fecal analysis to describe the diet of adult Wilson's Warblers (Wilsonia pusilla) that foraged in the understory of Douglas-fir (Pseudotsuga menziesii) forests in western Oregon during the breeding season. We sampled arthropods at the same sites where diet data were collected, and compared abundance and biomass of prey among seven common shrub species. Wilson's Warblers ate more caterpillars (Lepidoptera larvae), flies (Diptera), beetles (Coleoptera), and Homoptera than expected based on availability. Deciduous shrubs supported higher abundances of arthropod taxa and size classes used as prey by Wilson's Warblers than did evergreen shrubs. The development and maintenance of deciduous understory vegetation in conifer forests of the Pacific Northwest may be fundamental for conservation of food webs that support breeding Wilson's Warblers and other shrub-associated, insectivorous songbirds.
We identified arthropods in fecal samples from 56 Southwestern Willow Flycatchers (Empidonax traillii extimus) at three localities in Nevada and Arizona with different plant communities during the 2004 breeding season. We concurrently collected arthropods in flight with Malaise traps and on different plant species by sweep net. These potential prey were identified to Order and counted. Fecal samples contained 57 taxa of spiders and insects including 32 families in 8 Orders. Flycatchers consumed similar diversities (numbers of taxa), but different taxonomic compositions (abundances in Orders) of arthropods among localities. Diets of E. t. extimus more closely resembled compositions of arthropods swept from plants than those trapped in flight with Malaise traps. Fecal samples at Upper Pahranagat Lake in southern Nevada contained arthropod compositions most related to those swept from Salix gooddingii. Fecal samples at the Virgin River near Mesquite in southern Nevada, where Salix exigua and naturalized Tamarix ramosissima grow, contained arthropod compositions most related to those swept from S. exigua. Fecal samples at Topock Marsh in western Arizona contained arthropod compositions most related to those swept from T. ramosissima, the dominant vegetation. The relation between flycatcher diet and arthropod composition on plants was least at Topock Marsh, suggesting prey from other communities are important in supplementing the fauna that develop on introduced Tamarix. The diverse diet of Southwestern Willow Flycatchers may take advantage of the increased nitrogen and sulfur contents of spiders and predaceous insects.
We collected diet data at 12 Ferruginous Hawk (Buteo regalis) and 14 Swainson's Hawk (B. swainsoni) nests in a short-grass prairie and agricultural community in the panhandle area of northwest Texas and southwest Oklahoma, and in northeastern New Mexico during the 2003–2004 breeding seasons. We documented 959 Ferruginous Hawk and 1,058 Swainson's Hawk prey deliveries during ∼5,618 hrs of video monitoring. Ferruginous Hawks delivered 10.0 ± 0.7 (x̄ ± SE) prey species per nest and typically larger prey. Swainson's Hawks delivered 13.4 ± 1.1 prey species per nest and typically smaller prey. There was a dietary overlap (Simplified Morisita Index [CH]) of 0.31 in prey species delivery frequency and 0.56 in prey species' biomass. Ferruginous Hawks made 4.6 deliveries/day at 480 g/delivery whereas Swainson's Hawks delivered smaller prey items (147 g/delivery) but more frequently (7.0 deliveries/day). Deliveries/day and mass/day increased with increasing brood sizes of both species, but deliveries/day/nestling and mass/day/nestling decreased. Provisioning rates did not vary significantly over the nestling period. These data represent the most accurate diet quantification to date for Ferruginous and Swainson's hawks. Ferruginous Hawks used a larger array of prey types than shown in other studies based on indirect diet analysis methods. The low interspecific diet overlap suggests that prey is partitioned, which may facilitate the well-documented sympatric distribution of the two species.
We quantified nesting-site habitats for sympatric White-tailed Hawks (Buteo albicaudatus) (n = 40), Red-tailed Hawks (B. jamaicensis) (n = 39), and Crested Caracaras (Caracara cheriway) (n = 24) in the Coastal Sand Plain of south Texas. White-tailed Hawks and Crested Caracara nest sites occurred in savannas, whereas Red-tailed Hawk nest sites occurred in woodlands on the edge of savannas. White-tailed Hawk nest sites were in shrubs and trees that were shorter (3.5 ± 1.0 m) and had smaller canopy diameters (5.5 ± 2.1 m) than those of Red-tailed Hawks (10.1 ± 2.0 m, 13.7 ± 5.8 m) and Crested Caracaras (5.6 ± 1.7 m, 8.5 ± 3.5 m). Red-tailed Hawk nest sites had higher woody densities (15.7 ± 9.6 plants) and more woody cover (84 ± 19%) than those of White-tailed Hawks (5.6 ± 5.8 plants, 20 ± 21%) and Crested Caracaras (9.9 ± 6.7 plants, 55 ± 34%). Crested Caracara nest sites were in dense, multi-branched shrubs composed of more living material (97 ± 3%) than those of White-tailed (88 ± 18%) and Red-tailed hawks (88 ± 18%). Nest sites of White-tailed Hawks, Red-tailed Hawks, and Crested Caracaras were similar to random samples from the surrounding habitat indicating that preferred nesting habitat was available for each of these species at least within 60 m of active nest sites. Nest tree height, along with woody plant and native grass cover best discriminated nest sites among the three raptor species. There was no overlap at Red-tailed and White-tailed hawk nest sites in vegetation structure, while Crested Caracara nests were in habitat intermediate between the two other species. Partitioning of nesting habitat may be how these raptor species co-exist at the broader landscape scale of our study area in the Coastal Sand Plain of Texas.
We report three cases of hybridization between wild Swainson's Hawks (Buteo swainsoni) and Red-tailed Hawks (B. jamaicensis) identified by using nuclear and mitochondrial DNA markers. The hybrid individuals were field-identified as Swainson's Hawks and sampled from Alberta, Canada (n = 2) and Utah, USA (n = 1). Nineteen nuclear microsatellite loci were used in a factorial correspondence analysis to create genotypic clusters of 468 Red-tailed and 357 Swainson's hawks. Three suspected hybrids were identified by an intermediate genetic position between the genotypic clusters of the two species, indicating a hybridogenetic composition. We examined mitochondrial control region sequence data to identify the maternal background of the putative hybrids; two of the hybrid specimens had Red-tailed Hawk mtDNA haplotypes and the third a Swainson's Hawk haplotype. These results suggest that hybridization between these two species may occur in their shared breeding range and can result in reciprocal hybrid offspring, barring any social, behavioral, or biological isolating mechanisms.
Numerous researchers have investigated survival of Mallard (Anas platyrhynchos) ducklings, but few have modeled survival of ducklings radio-marked at hatch relative to time-dependent factors. We estimated survival of 48 radio-marked ducklings for two study sites (Oakwood and Mickelson) in eastern South Dakota during summers 1998–1999. Our best-approximating model of survival indicated duckling age, study site, precipitation, and the interaction of study site and precipitation influenced survival. Survival of ducklings to 30 days was 0.42 at Oakwood (95% CI, 0.13–0.67) and 0.77 at Mickelson (95% CI, 0.42–0.92). Duckling mortality was 31.9 and 1.6 times more likely for each 1 cm of precipitation at Oakwood and Mickelson, respectively. We suggest this difference was partially attributable to greater cover of emergent vegetation at Mickelson, which potentially reduced body heat loss via evaporative cooling. Our best model also indicated daily survival increased with duckling age. Models containing daily minimum temperature received little support (wi ≤ 0.01) indicating the covariate had negligible influence on daily survival of ducklings.
The social behavior of free-living male Tibetan Eared-pheasants (Crossoptilon harmani) is described during their breeding season at a site near Lhasa, Tibet. Four types of male-male interactions were identified. (1) Mate guarding. A male maintained vigilance behavior near his partner. (2) Evading. A male urged the female to avoid other breeding males. (3) Lateral display. A male laterally presented his body to another male and the latter postured submissively. On a few occasions, displaying males escaped alone and dominant males attempted to copulate with mates of these males. (4) Driving. A male violently drove off any males that came too near his mate. These behavioral types emerged as pair members associated in groups in early spring, became extensive as pair bonds intensified, and disappeared with hatching. Paired males occasionally displayed to subadult males, but no display activity was observed between subadult males. These interactions were unidirectional for a group in which all male members were individually identified and revealed a linear dominance hierarchy among the males. I believe that mate-guarding was to detect and evading was to escape the high-ranking males, which potentially obtained (through displaying to lower-ranking males) extra-pair copulations. Advertising quality to impress/intimidate opponents and to attract additional females is likely the underlying reason for male-male display. My observations provide an interesting example of how males behaviorally respond to conflict between gregariousness and maintenance in a socially monogamous mating system.
The Yellow-shouldered Parrot (Amazona barbadensis) has a disjunct geographical distribution and the smallest population of the species inhabits La Blanquilla Island in the southern part of the Caribbean Sea. We conducted field work from 1993 to 1998 to gather information on the natural history and population status of this parrot on La Blanquilla. We compared that information with similar data gathered previously from Margarita Island. We found three communal roosts on La Blanquilla and estimated the parrot population to be ∼100 individuals. We found an average of 8.8 ± 3.6 active nests/year; all nests were in the central and western parts of the island, mainly in tree cavities of Guaiacum officinale. Nests on La Blanquilla Island were closer to the ground than nests on Margarita Island. The breeding season on La Blanquilla Island started later and clutch size was lower (2.24 ± 0.95 eggs/nest) than on Margarita Island. Parrots were observed foraging on 12 plant species; most observations involved consumption of the fruit of Casearia tremula (Flacourtiaceae). The main threats to Yellow-shouldered Parrots on La Blanquilla are predation and illegal poaching. Survival of the Yellow-shouldered Parrot on La Blanquilla Island is uncertain because of small population size and increasing threat levels.
We report on the ornithological results of the first rapid biodiversity survey in the BX-044 polygon, one of the largest open vegetation enclaves in southern Amazonia, in the Brazilian states of Amazonas and Rondônia. Three-hundred and thirty species were recorded in all habitats surveyed, including closed (terra-firme, riparian, gallery, and campinarana forests) and open (cerrado and grassland) vegetation types. Over 90% (298) of all species were not shared between closed and open habitat types emphasizing the importance of inter-habitat diversity to the overall species richness recorded. Significant range extensions were documented for 34 species (30 of which were associated with the cerrado biome). Open vegetation enclaves contribute significantly to local avian species richness in Amazonia in addition to supporting species with special relevance to conservation with ranges centered in the cerrado, currently one of the most threatened biomes of South America. Conservation of Amazonian cerrado enclaves offers the unique opportunity to combine preservation of areas with high inter-habitat diversity with establishment of a complementary network of conservation units directed at preserving the cerrado biome throughout South America. Urgent steps must be taken to protect Amazonian open vegetation enclaves, which are still conspicuously under represented in the network of Brazilian conservation units, despite the fairly recent expansion of agriculture into these areas.
Effects of scale on relationships between organisms and their environment are of considerable contemporary interest. We evaluated Breeding Bird Survey data and landscape measures derived from aerial photographs to examine how relationships changed over a continuous range of 16 spatial scales. Analyses incorporated 1985–1994 data (average number of birds/stop/yr) for eight flycatcher species (Tyrannidae) for each of 50 stops on 198 Breeding Bird Survey transects in the Central Plains. Associations of bird abundances with landscape variables changed gradually with small changes in scale. Edge density had significant associations with abundances of Eastern Phoebes (Sayornis phoebe), Great Crested Flycatchers (Myiarchus crinitus), and Western Kingbirds (Tyrannus verticalis) suggesting this landscape characteristic is important for certain breeding flycatcher species. Fractal dimension and principal component II, the latter reflecting amounts of closed forest versus open country, exhibited the highest correlations with abundances of the greatest number of species. Correlations of abundances and landscape variables were highest at larger spatial scales, 17- to 50-stop segments (i.e., 13.7 and 40.2 km in length, respectively). Evaluating more than 2–3 spatial scales can provide insight into relationships of abundance of a species with potentially influential environmental factors. These analyses allow the data to indicate the most appropriate scale or scales for a particular study, rather than depending entirely on a researcher's subjective perception of what scales are important to a given species.
Interspersion is a key habitat component related to marsh bird abundance, but is not easily quantified. We used Fragstats 3.3 and aerial photos to measure interspersion within wetlands as m/ha of interface between vegetation and water (i.e., edge density). We then related edge density and other factors (marsh area, cover-to-water ratios, marsh area within 5 km) to the abundance of marsh birds on 16 emergent wetlands in New York during 2005. Abundance was assessed via call broadcast surveys for American Bittern (Botaurus lentiginosus), Least Bittern (Ixobrychus exilis), Pied-billed Grebe (Podilymbus podiceps), Sora (Porzana carolina), and Virginia Rail (Rallus limicola). Interspersion, as measured by edge density, was the best predictor of abundance for all species but Pied-billed Grebe (r2 = 0.30–0.71). Vegetation and water interspersed in a spatially complex pattern likely increases breeding diversity and density of marsh birds. Modern spatial analysis programs provide opportunities to quantify interspersion without intensive field work or calculations, which can lead to more accurate research and management efforts focused on marsh birds.
Fire suppression has resulted in a greater density of ponderosa pine (Pinus ponderosa) in grassland and shrub-steppe habitats potentially reducing habitat quality for declining grassland and shrub-steppe birds. Birds were surveyed at 10 shrub-steppe sites in the southern Okanagan Valley of British Columbia to examine whether encroachment of pine affected grassland and shrub-steppe birds. Encounter rates did not differ between years and were combined for a total of 4,281 sightings and 80 species. Sites with more ponderosa pine had a greater diversity of birds. Grassland and shrub-steppe birds as a group declined with increasing numbers of trees. Forest and open woodland birds increased in number as did generalist birds. These results support conservation efforts to reduce conifer densities in shrub-steppe habitats to benefit associated declining bird populations.
I analyzed the relationship between spring temperature and arrival date for 105 species using over 32,000 arrival records of migratory breeding birds in Maine collected by a volunteer network between 1994 and 2005. I used quantile regression analysis, testing three different quantiles (0.1, 0.25, 0.5). Only 69 of 315 regressions yielded a significant negative relationship. Five species showed significant regressions for all three quantiles and 15 showed significant regressions for two quantiles. Quantile regressions of arrival date with a hemispheric measure of climate variability, the North Atlantic Oscillation index, produced only 63 statistically significant regressions for the three quantiles. Seven species and 12 species had significant regressions with three and two quantiles, respectively. Overall, 60 species had at least one significant relationship with a climatic variable. These results indicate the arrival dates of most migratory breeding birds in Maine show a modest relationship with the significant temperature variability seen over the 12-year study period. The data suggest the response of migratory birds in Maine to global warming impacts will be a gradual process.
This study presents 11 years of nesting success and phenology data for Black Swifts (Cypseloides niger) at Box Canyon in Ouray, Colorado. Nest data were recorded on a near-daily basis for 160 nest attempts. Nesting success was 72% and mean and extreme dates of nesting events, including arrival, egg-laying, onset of incubation, hatching, and fledging are reported. On average, Black Swifts arrived on 13 June, egg laying started on 28 June, incubation started on 1 July, hatching occurred on 26 July, and fledging occurred on 13 September. The average incubation period was 26 days and the nestling phase was 48 days. In seven instances, a second egg appeared after loss of the first egg and, in one case, a third egg appeared. It was not possible to ascertain whether second or third eggs represented a renesting attempt or nest usurpation.
The Mariana Swiftlet (Aerodramus bartschi) on Saipan lays a single white egg which is incubated for 22.95 days (range 17–30 days). Newly hatched nestlings are naked and weigh 1.11 g (range 1.0– 1.2 g). Nestlings grow slowly, reaching asymptotic weight on day 29 and fledging after 46.8 days (range 40– 55 days). Post-asymptotic weight recession is ±2% and nestlings fledge at slightly above adult weight of 8.01 g. Wing and tail length are >94% of adult size at fledging. Low clutch size, slow chick growth, and extended nestling period are characteristic of other species of swiftlets and may represent food limitation in these diminutive aerial insectivores.
We used Mayfield logistic regression and an information-theoretic approach to examine habitat characteristics associated with nesting success of Wood Thrushes (Hylocichla mustelina) across an urban to forested gradient in southwestern Pennsylvania in 2003 and 2004. Both nest placement and number of understory stems provided equally plausible models. Mayfield success was 20% higher for nests >3 m above ground level while dense understory was associated with low nest height. Wood Thrush nests in the forest interior averaged 2 m higher with a third less understory than edge nests. Urbanization and distance to the forest edge were not useful predictors of Wood Thrush nest success. The analysis was confounded by low breeding density at the most urbanized sites, but we found moderate success (42%, n = 63) across a fragmented landscape with minimal core forest area. Interior nests in a large contiguous forest were twice as successful (60%, n = 31) compared to edge nests (25%, n = 33) adjacent to a small housing development. We do not know the mechanism underlying increased predation of low understory nest sites that we observed. The ability of Wood Thrushes to see and/or effectively attack a predator in the area may be important for nest defense; changes in the predator community associated with forest edges may also explain differences in nest success. The relationship between nest placement, nest defense, and the predator community needs further study.
We experimentally parasitized nests of the Village Weaver (Ploceus cucullatus) in Hispaniola using real and artificial eggs made from wood and modeling clay. Artificial eggs were similar in size and shape to real weaver eggs and were coated with acrylic paint and glazed. Real eggs were actual weaver eggs taken from Village Weaver nests. Experimental parasitic eggs (1) mimicked natural weaver eggs, (2) differed in color only, (3) differed in spotting only, or (4) mimicked Shiny Cowbird (Molothrus bonariensis) egg color and spotting pattern. Parasitized nests were checked after 2–6 days. Real eggs were ejected from weaver nests with increasing frequency as they became less similar to the eggs in the nest with cowbirds eggs having the highest rejection (81%). However, for artificial egg types there were no significant within-composition differences in patterns of rejection. Clay eggs were usually ejected from the nests, whereas nests containing wood eggs often ended empty, or with only the artificial egg remaining in the nest. These patterns may reflect the differential ability of weavers to recognize and remove foreign eggs of different compositions from their nests. Researchers undertaking egg-rejection experiments should use real eggs either in addition or in place of artificial eggs to assess the cost of rejection and the coevolutionary relationships between parasite and host.
Canada Warblers (Wilsonia canadensis) are one of the last warblers to arrive in breeding areas in northern Alberta and one of the first to depart in autumn resulting in a condensed breeding chronology relative to other locally breeding wood warblers. Males arrived before females during spring migration, while in autumn, adult females departed prior to males. Second-year males arrived later (P = 0.029) than after-second year males. Adult males departed later (P = 0.015) than adult females. Hatch-year birds departed after adult females but prior to adult males. Female Canada Warblers remained in breeding areas for 62 days while males remained 72 days. These data provide the shortest documented breeding site occupancy estimate for any bird that shows a post-nuptial molt. The short time spent in breeding areas may impose energetic constraints that influence breeding, molt, and survival, particularly for females.
Swainson's Thrushes (Catharus ustulatus) migrate widely throughout North and Middle America. In the Caribbean, the species is known to occur only in the western-most Greater Antilles, and there only as a rare migrant. We captured and visually detected migrant Swainson's Thrushes beginning in 2000 at a banding station on Guana Island, British Virgin Islands. The majority of thrushes captured were adults (79%) and most had no (71%) or little fat (12%) reserves at time of capture; 61% were classified as being in emaciated or poor condition. The poor physiological conditions may have resulted from longer over water flights rather than island hopping.
Diurnal variations in body mass and visible fat scores were measured for seasonally acclimatized Mountain Chickadees (Poecile gambeli) and Juniper Titmice (Baeolophus ridgwayi) to examine if they undergo winter fattening. Body mass varied with time of day and was highest in evening for both species in summer and winter. Body mass, expressed as percent mass increase from morning to evening, was 7.3% for summer chickadees, 7.6% for summer titmice, 9.1% for winter chickadees, and 6.1% for winter titmice. Body mass was not significantly higher in winter-acclimatized birds compared to summer-acclimatized birds. Visible fat scores were significantly elevated in winter-acclimatized Mountain Chickadees relative to summer. Mountain Chickadees and Juniper Titmice appear to have seasonally constant body mass rather than undergoing winter fattening. These data are similar to other North American species in the family Paridae but contrast with data on European parids.
We report a massive inland displacement of petrels, particularly female Atlantic Petrels (Pterodroma incerta) in southern Brazil, after Hurricane Catarina, the first ever reported hurricane in the South Atlantic Ocean. At least 354 petrels were affected and were found in 26 different locations, up to 420 km from the coast and 1,100 m above sea level. Birds were in heavy molt and near starvation, which probably contributed to their displacement and mortality.
We report observations of a population of Military Macaws (Ara militaris) within the Tehuacán-Cuicatlán Biosphere Reserve in northern Oaxaca, Mexico during 2002–2004. Macaws used a series of barrancas for roosting and nesting, and foraged widely in surrounding areas. Most of the population of ∼100 individuals could be counted flying to or from the major roosting areas of El Sabino Canyon and Barranca de Las Guacamayas. Reproduction appeared to be restricted to vertical cliffs of El Sabino Canyon. Most movements were associated with seasonal foraging and depended upon availability of fruits.
We documented the juvenal plumage of the Green-breasted Mountain-gem (Lampornis sybillae) during mist-netting operations in the cloud forest at La Tigra National Park, Honduras from February to April 2006. A recently-fledged juvenile of this species was caught on 17 March and, contrary to previous suggestions, we found the throat and breast were mottled green. Ninety-eight immature mountain-gems intermediate between this juvenal plumage and that of adults were also caught during our study. Both males and females of the Green-breasted Mountain-gem apparently begin replacing juvenal throat feathers soon after fledging and prior to molting flight feathers. A high capture rate of young hummingbirds at the end of the dry season, including recent fledglings and individuals showing only traces of juvenal plumage, suggests a protracted breeding season that we estimate to last at least from November through March. We also caught adults in a variety of stages of flight-feather molt, perhaps part of a transition from breeding; molting in our population is estimated to span at least an 8-month period.
Georgia land lottery maps from the 1820s reveal two tree species, water oak (Quercus nigra) and sweetgum (Liquidambar styraciflua), were formerly limited to major floodplains in the Piedmont and Coastal Plain. These species are now common in upland sites as a result of past land use and disruption of fire regimes. We investigated the effect this invasion had on breeding bird diversity in upland mixed pine (Pinus spp.) stands based on 90 point counts conducted in spring 2005. Half of these stands had no water oak or sweetgum (open stands) and half had a minimum of 25% of their basal area as water oak and/or sweetgum (invaded stands). Bird species richness and abundance were 42 and 41% lower, respectively, in invaded stands. Thirty-five bird species had more than 20 records and were tested for an association with invaded stands. No species were positively associated with invaded stands while 10 were negatively associated with invaded stands; these were mostly grassland pine savanna and shrubland bird species of high conservation value. Invasion of upland pine forest by these native tree species is similar to invasion by exotic species, and appears to disrupt ecosystem function causing declines in bird diversity.
Turkey Vultures (Cathartes aura) in southern and south-central Saskatchewan first nested in deserted houses in 1982. This new behavior across the Aspen Parkland and Boreal Transition ecoregions became more common in the mid-1990s as vultures increased and occupied new territory. We documented 126 nestings, which produced 185 young in 74 deserted buildings during 2003–2006. The mean number of young fledged per successful nest (1.7) was similar to that recorded in other parts of its range.
Vigilance is especially important in colonial socially monogamous birds during the nesting season as nest materials, offspring, and mates are vulnerable to theft, depredation, and extra-pair copulations, respectively. We found that when both members of a mated pair of Yellow-crowned Night-herons (Nyctanassa violacea) were at the nest they faced in opposite directions in 73% of observations, which was significantly more often than would be expected by chance (P < 0.0001, χ21 = 33.3). This behavior may improve vigilance against intruders from all directions. When an extra-pair conspecific was present at the nest of a mated pair, members of the pair were significantly more likely to orient in the same direction towards the conspecific rather than face opposite directions. In 95% of all cases in which an extra-pair conspecific was present, at least one member of the mated pair faced it, indicating that extra-pair conspecifics are perceived as threats by nesting pairs.
Kori Bustards (Ardeotis kori) are polygynous and males display singly or in loose lek formations to females during the breeding season. A new display, head tossing, has been observed on repeated occasions by five different males (all Ardeotis kori struthiunculus) in the Smithsonian National Zoological Park, Dallas Zoo, and San Diego Wild Animal Park. This display has not been reported for A. k. kori or in any other Ardeotis species. Trained behavior watchers recorded detailed observations of a male bustard's booming behavior and frequency in 2004 and 2005; over the 2 years they collected 407 hrs of booming data. Head tossing occurred when the male rapidly threw his head backward onto his back. The head tossing display further exposed the white neck feathers and the motion of head tossing was extremely visible. Head tossing was followed by a cessation of booming or was a transition between additional booming sessions. Head tossing primarily occurred at the end of a six-boom calling bout (90% of the time) and was observed infrequently (less than 2% of all booming bouts). Head tossing appears to occur predominantly during the early phases of the breeding cycle and may function as a territorial marker directed at other males, and potentially provides information about the rank of the displaying male.
Northern Hawk Owls (Surnia ulula) have been reported to cache prey during the breeding season for later consumption, but detailed reports of prey caching during the non-breeding season are comparatively rare. We provided prey to four individual Northern Hawk Owls in wintering areas in northeastern Minnesota during 2001 and 2005 and observed their caching behavior. These owls cached 93% (n = 14) of prey items presented to them and consumed one item immediately after capture. A number of bird species relocate stored food by remembering the spatial locations of caches. Prominent landmarks (dead trees larger than the surrounding vegetation, sites concealed in the snow next to a utility pole or clump of grass) or sites near them were often selected for caching by Northern Hawk Owls and likely facilitate relocation of stored prey. Prey caching during winter allows exploitation of temporary increases in prey abundance and may aid in survival during times of food shortage or adverse weather.
We report observations of Willets (Catoptrophorus semipalmatus) using White Ibis (Eudocimus albus) as “beaters” to disturb prey and kleptoparasitizing (stealing) prey from them. Our observations occurred at J. N. “Ding” Darling National Wildlife Refuge on Sanibel Island, Florida on 8 December 2004. We observed these behaviors in four White Ibis-Willet pairs and describe one instance in detail and document it with photographs. To our knowledge this is the first documentation of a Willet using other birds as beaters and the first case of Willets stealing from White Ibis, although many records exist of Willets stealing from other shorebirds. We believe the use of beaters by Willets may be an under-reported foraging behavior.
We report a Gray Catbird (Dumetella carolinensis) reusing a Northern Cardinal (Cardinalis cardinalis) nest in the same breeding season. The Northern Cardinal nest failed during incubation on 19 June 2006, but the Gray Catbird nest was successful, fledging three young on 31 July 2006. Nest site availability does not appear to be the reason for reuse of the nest. Time constraints late in the breeding season may result in use of old nests.
We report predation by an American Crow (Corvus brachyrhynchos) of a bat in flight. We observed an aerial attack of a little brown bat (Myotis lucifugus) by a crow, followed by consumption of the prey item. American Crows are reported to have a wide variety of foraging strategies and food items; consumption of bats, in general, has not been reported among them.
I report the first mid-winter specimen of a Flammulated Owl (Otus flammeolus) from within the USA breeding range of the species, an adult male found freshly dead on 2 January 1996 at Santa Fe, New Mexico following the season's first snowstorm. This event, plus an additional specimen found dead in late autumn within the New Mexico breeding range, supports the argument this species appears unable to successfully overwinter in its USA breeding range.