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Grassland passerines are purported to tolerate parasitism by Brown-headed Cowbirds (Molothrus ater) because of adaptations by cowbirds that constrain egg discrimination and removal by their hosts, i.e., evolutionary equilibrium, rather than because of an absence of these defensive behaviors, i.e., evolutionary lag. We tested these hypotheses by experimentally parasitizing six grassland species with cowbird-like eggs and non-mimetic (blue) eggs in south-central Saskatchewan. Sprague's Pipits (Anthus spragueii), Vesper (Pooecetes gramineus), Savannah (Passerculus sandwichensis), and Baird's (Ammodramus bairdii) sparrows, and Chestnut-collared Longspurs (Calcarius ornatus) accepted all or nearly all cowbird eggs, but ejected or attempted to eject between 9 and 20% of blue eggs with 54% of rejected eggs not removed from the nests, i.e., failed ejection attempts. Western Meadowlarks (Sturnella neglecta) ejected an intermediate number of cowbird eggs (67%) and most blue eggs (92%), none of which was recovered. Ejection of non-mimetic eggs versus cowbird eggs by each species suggests that similarity in appearance of cowbird eggs and hosts' eggs impeded discrimination and may represent a form of cowbird egg mimicry. The low number of blue eggs ejected by five of the six species, their failure to remove these eggs from the nest sites, and the damage wrought on some hosts' eggs during ejection suggest the morphology of cowbird eggs also constrains ejection behavior. These results support the evolutionary equilibrium hypothesis as the better explanation for acceptance of cowbird parasitism observed in these grassland passerines.
We describe egg characteristics, and analyze between and within clutch variation in egg size and mass in a natural population of Greater Rheas (Rhea americana). We assess the effect of this variation on nesting success and egg success. Yolk represented 29.5% of egg mass whereas albumen was 63.9%. Yolk mass increased with egg width but not with egg length, while mass of albumen increased mainly with egg length. The largest and smallest eggs were 10.3% larger and 25.3% smaller, respectively than mean intra-clutch values. The widest egg was 11.9% wider while the narrowest egg was 20.5% narrower than mean intra-clutch values. There was a significant decrease in egg size between clutches during the breeding season as a result of a decrease in egg length. There was no effect of laying order on intra-clutch variation in egg size, but we detected an increase in the variation of egg length within clutches with clutch size. We did not detect a relationship between egg size and nesting success, and between egg size and egg success. The relatively low intra-clutch variation in egg size and lack of effect of egg size on hatching success do not support the hypothesis that females invest in eggs according to expected chick fitness.
The classification of New World martins (Progne) has a convoluted history because taxonomists have relied on plumage traits that vary continuously across populations. We estimated the phylogeny of Progne by analyzing mitochondrial cytochrome b DNA sequences of 27 individuals of eight of the nine species (10 subspecies) and nuclear β-fibrinogen intron 7 sequences of 20 individuals of six species (8 subspecies). The Brown-chested Martin (P. tapera) is sister to other Progne species. The Middle American taxa—Sinaloa Martin (P. sinaloae), Cuban Martin (P. cryptoleuca), Caribbean Martin (P. dominicensis), and Central American populations of Gray-breasted Martin (P. chalybea)—form a well supported clade. This group is distinct from Purple Martin (P. subis), which has no particularly close relatives. All four Middle American taxa appear to be good species, although Cuban and Caribbean martins could be merged in view of their similar plumage and low genetic divergence (1.2%). Two of the South American taxa, the Peruvian Martin (P. murphyi) and Southern Martin (P. elegans), are also distinct species. We did not examine the Galapagos Martin (P. modesta) for lack of DNA, but it is likely to be a good species as well. An unexpected result of the study was that Gray-breasted Martin appears polyphyletic; its South American populations are closer to the Southern Martin than to its Central American populations.
We explored distributions of Asian nuthatch species in ecological and geographic space using ecological niche modeling based on occurrence data associated with specimens and observations. Nuthatches represent a well-defined clade occurring throughout the Northern Hemisphere, but are most diverse in southern Asia where 15 of the 24 species occur and where the lineage is believed to have evolved. Species richness was focused in a narrow east–west band corresponding to the forested parts of the Himalayas with a maximum number of nine species predicted present in these foci. The distributional predictions have a mid-elevation focus with highest species diversity between 1,000 and 2,000 m. Niche breadth and volume were positively related, but accumulation of distributional area (niche volume) decreased with additional environmental combinations (niche breadth). The extent of potential range filling, a measure of distributional disequilibrium, was connected with montane habit (R2 = 0.422) indicating that montane situations limit the distributional potential of species.
Estimates of local abundance for declining species provide important information necessary for conservation measures. We estimated the density and abundance of Mountain Plover (Charadrius montanus) in Phillips and Valley counties in north-central Montana in 2004 using distance sampling methodology. Sampling efforts were stratified to include active prairie dog (Cynomys sp.) colonies, an Area of Critical Environmental Concern (ACEC) specifically established for Mountain Plover, and all other habitats. The density of plovers was greatest on prairie dog colonies (7.20 ± 0.42 [SE] plovers/km2) and much lower on both the ACEC (1.60 ± 0.31 plovers/km2), and all other habitats (0.07 ± 0.01 plovers/km2). An estimated 1,028 (95% CI = 903–1,153) plovers inhabited this region in 2004, most (74%) on prairie dog colonies. Our results highlight the importance of prairie dog colonies to plovers in this region and suggest that as much as 10% of their continental population may breed in north-central Montana.
Three species of Buteo hawks nest sympatrically in the southern Great Plains of the United States. Dietary overlap among them is broad and we tested the hypothesis these species partition their breeding habitat spatially. We compared land cover and topography around 224 nests of the three species breeding in shortgrass prairie in 2004 and 2005. Red-tailed Hawks (Buteo jamaicensis) nested almost exclusively in riparian timber surrounded by prairie (95% prairie land cover around nests) and disproportionately used areas with greater topographic relief within prairie landscapes. Swainson's Hawks (B. swainsoni) commonly nested in low-relief areas dominated by small-grain production agriculture but generally used habitats in proportion to availability. Most nest sites of Ferruginous Hawks (B. regalis) were in prairie (78% prairie land cover around nests), but some were in areas that were at least partially agricultural. Ferruginous Hawks had at least two times more sand sagebrush (Artemisia filifolia) around their nests than their two congeners. We conclude that sympatric breeding Buteos on the southern Great Plains spatially partitioned nest sites according to subtle differences in land cover and topography.
Vocal mimics that produce large repertoires of song types, such as in the Mimidae, have unique challenges discriminating songs of conspecifics from those of other mimids in areas where these species co-occur. We investigated cues used by Northern Mockingbirds (Mimus polyglottos) in discriminating their songs from songs of a sympatric mimid, the Brown Thrasher (Toxostoma rufum). We presented territorial mockingbirds with four playback treatments in which either mockingbird song types or thrasher song types had either a standardized mockingbird repetition pattern (5 repetitions) or a standardized thrasher pattern (2 repetitions). Four measures (time within 2 m of speaker, latency to approach, closest approach, and number of flights) were used to estimate a subject's response to each playback. Subjects responded significantly more strongly to mockingbird song types in a mockingbird repetition pattern than to thrasher song types in either repetition pattern. Responses to mockingbird song types in a thrasher repetition pattern elicited intermediate responses. Thus, mockingbirds can distinguish conspecific songs from Brown Thrasher songs based on song types alone regardless of their repetition pattern, although repetition pattern still appears to have a role in conspecific recognition. Brown Thrasher song includes a significantly broader frequency range than mockingbird song, which may allow direct discrimination. Our results suggest cues used by mimids in species discrimination are not necessarily the same as those used by human observers.
Smaller species are less likely to maintain families (or other forms of social groups) than larger species and are more likely to be displaced in competition with larger species. We observed mixed-species flocks of geese in southwest Louisiana and compared frequencies of social groups and success in social encounters of Lesser Snow Geese (Chen caerulescens caerulescens; hereafter Snow Geese) with that of the smaller, closely-related Ross's Geese (C. rossii). Less than 7% of adult and <4% of juvenile Ross's Geese were in families, whereas 10–22% of adult and 12–15% of juvenile Snow Geese were in families. Snow Geese won 70% of interspecific social encounters and had higher odds of success against Ross's Geese than against individuals of their own species. The larger Snow Geese maintain families longer than Ross's Geese, which probably contributes to their dominance over Ross's Geese during winter. Predator vigilance probably is an important benefit of mixed flocking for both species. We suggest the long-standing association with Snow Geese (along with associated subordinate social status) has selected against family maintenance in Ross's Geese.
Common Goldeneyes (Bucephala clangula) and Hooded Mergansers (Lophodytes cucullatus) are common cavity-nesting ducks but the importance of fast-flowing rivers as suitable nesting habitat may have been overlooked. We monitored the use of >90 nest boxes installed along a boreal forest river over a 5-year period. A high nest box occupancy rate was reached in the second year (40%) and was maintained thereafter (48 to 55%). On average, 35 nest boxes were occupied by goldeneyes and 11 by mergansers each year. Laying date was similar between the two species but merganser nests hatched slightly later. Both species had similar clutch sizes but merganser nests contained more eggs than goldeneye nests when heterospecific parasitic eggs were included. On average, 16% of goldeneye nests were parasitized by mergansers, and 49% of merganser nests were parasitized by goldeneyes. Density of suitable natural cavities in the area was relatively low suggesting the high occupancy rate of nest boxes may be a response to lack of suitable cavities. Nest box use was positively related to the total surface area of ponds in the vicinity and negatively to distance to the river. Use of nest sites along fast-flowing rivers appears to be an opportunistic strategy and may be dependant on the presence of nearby ponds and lakes.
Red-breasted Mergansers (Mergus serrator) commonly breed in estuaries, but little is known about their brood-rearing in coastal environments. We measured daily movements and habitat use of radio-marked (n = 17) female Red-breasted Mergansers with broods originating from coastal barrier islands at Kouchibouguac National Park, New Brunswick, Canada from 2002 to 2004. Primary brood movements from nest sites to initial rearing areas were often extensive, averaging 3.5 km (n = 15), since many broods crossed Saint-Louis Lagoon to continental rearing sites. Broods remained mobile throughout the rearing period and there was little difference in daily movements between age class I (days 1–10 post nest exodus), class II (days 11–20), and class III (>20 days) broods. Broods frequented shallow (x̄ = 51 cm, 95% CI: 44–58 cm, n = 191 locations), nearshore (x̄ = 47 m, 95% CI: 33–60 m, n = 157 locations) waters that often supported submergent eel grass (Zostera marina). Broods selected estuarine intertidal regions in Saint-Louis and Kouchibouguac lagoons, as well as wetlands at the mouths of tidal streams. Few broods were found in tidal river and marine habitats. Continental estuarine intertidal, tidal stream, and saltmarsh habitats were preferred by age class I broods whereas estuarine intertidal and subtidal habitats were preferred by age classes II and III. This study highlights the importance of estuarine habitats in lagoons and tidal streams for brood-rearing Red-breasted Mergansers in eastern New Brunswick.
We compared growth rates of Black Brant (Branta bernicla nigricans) goslings from two dispersed nesting aggregations to those from the large Tutakoke River Colony on the Yukon-Kuskokwim Delta, Alaska during summers, 1999 and 2000. Approximately 20% of the Black Brant population on the Yukon-Kuskokwim Delta, Alaska nests outside of the four major colonies. Dispersal to these outlying breeding locations is hypothesized as a mechanism by which individuals reduce the negative effects of density dependence associated with major colonies. Growth rates of goslings varied among brood rearing areas both associated with dispersed nesting aggregations (n = 4) and associated with the Tutakoke River Colony (n = 7). Mean mass of goslings, adjusted for age, from brood rearing areas associated with dispersed nesting aggregations ranked sixth, eighth, and ninth of nine brood rearing areas sampled in 1999, and sixth and ninth of nine brood rearing areas sampled in 2000. Mean age-adjusted mass of goslings with the largest mass were 198 and 139 g lighter, respectively, from brood rearing areas associated with a dispersed nesting aggregation than those from brood rearing areas associated with the Tutakoke River colony in 1999 and 2000. Our findings suggest that goslings from dispersed nesting aggregations we sampled are unlikely to have an advantage over goslings from a major colony with respect to survival, adult body size, and recruitment.
Curassows (Cracidae) are important components of the avian biomass in neotropical frugivorous bird communities. However, their feeding habits and ecological role remain unclear. We identified the diet of wild Yellow-knobbed Curassow (Crax daubentoni) based on analyses of feces and direct observations from November 2001 to July 2002 in a tropical dry forest in central Venezuela. We also analyzed stomach contents from specimens collected in different localities throughout the Llanos region. The diet of curassows included fruits (41 and 49% of dry weight in feces and stomach contents, respectively), seeds (15 and 48%), leaves (39 and 0.7%), minerals (stones, earth; 4.3 and 1.1%), and small proportions of flowers, roots, fungus, seedlings, and invertebrates (insects, Order Coleoptera), each <1% of total dry weight. Curassows fed on 26 plant species from 21 families. When food resources for frugivores are scarce during the dry season (Nov–Apr), 47–50% of the diet was a single species (Guazuma ulmifolia, Sterculiaceae) indicating this species can be critical for curassow survival. An increase in consumption of leaves and invertebrates was observed in the rainy season (May–Jul). Most seeds observed in feces (93%; n = 5,408; range = 1–10 mm) were intact suggesting that curassows could have an important role as seed dispersers in this tropical ecosystem.
We examined the influence of landscape configuration created by forest regeneration practices on distribution of Whip-poor-wills (Caprimulgus vociferous) during the breeding season by comparing relative abundance and space use between forest areas (stands ≥ 17 years of age) and regenerating forest edges (regeneration stand ≤ 6 years of age adjacent to forest area). Regenerating forest edges contained greater (P < 0.001) abundance of Whip-poor-wills (x̄ ± SE = 2.4 ± 0.30 birds/10 ha) than forest areas (0.8 ± 0.11 birds/10 ha). Eighty-four percent of detections at regenerating forest edges were from within the regenerating stand. However, Whip-poor-wills within regenerating stands were detected within 100 m of the forested edge with a greater probability (P < 0.001) than expected by chance. The positive response of Whip-poor-wills to forest edges is likely due to proximity and use of foraging habitats. The relatively high number of habitat openings created by some forest regeneration practices provide Whip-poor-wills with foraging opportunities not present in less intensively managed forest systems. Forest management for Whip-poor-wills should consider harvest strategies that maintain the availability of regenerating patches in close proximity to mature forests.
We documented the effects of hurricane Wilma (2005) on Chimney Swift (Chaetura pelagica) using data from the Québec Chimney Swift Survey Program and observations of swift mortality during migration. Hurricane Wilma developed in the Caribbean and followed the eastern coast of North America, moving over areas used extensively by migrating birds. Thousands of birds and, among them, Chimney Swifts, were caught and carried by the storm as far as Atlantic Canada and western Europe. At least 727 swifts were reported dead. Chimney Swift numbers in the province of Québec, Canada, declined significantly the following year, suggesting adverse consequences of the hurricane on this population over a large area. Roost counts declined by an average of 62%; the total Chimney Swift population decreased by approximately 50%. These results suggest that hurricanes can reduce the breeding population size of some migratory bird species.
We examined annual and seasonal home ranges of 41 Red-cockaded Woodpecker (Picoides borealis) groups from 1997 to 1999 in a Mississippi loblolly (Pinus taeda) and shortleaf (P. echinata) pine forest. Adaptive kernel annual home-range estimates (x̄ = 43.1 ± 6.3 ha) were more conservative than maximum convex polygon estimates (x̄ = 58.4 ± 4.5 ha). Mean non-nesting season home ranges were 15–20 ha greater than nesting season home ranges. Home ranges were smaller during nesting and increased during the post-fledging period. Compositional analysis revealed that Red-cockaded Woodpeckers selected habitats disproportionate to their availability annually and seasonally. Red-cockaded Woodpeckers selected pine sawtimber, pine poletimber, pine regeneration, and hardwood sawtimber habitats in that order. Home range appears to be a factor of landscape composition and inversely related to habitat quality.
Populations of Golden-winged Warblers (Vermivora chrysoptera) are declining dramatically in eastern North America. Success of conservation efforts will rely largely upon identification and management of suitable anthropogenic habitats (e.g., harvested forest and utility rights-of-way [ROWs]). We assessed habitat quality among three habitat types in central Pennsylvania by comparing population density, nesting success, and productivity among 1-ha patch clearcuts (clearcut area), a 60-m-wide utility ROW (wide ROW), and a 20-m-wide utility ROW (narrow ROW) in 2002 and 2003. Golden-winged Warblers did not use any portion of the narrow ROW that occurred outside the clearcut area. Density (territories/ha) did not differ either year (all P ≥ 0.20) between used sectors of the clearcut area (0.47, 0.50) and the wide ROW (0.71, 0.79). Overall nesting success (successful nests/total nests) was not independent (P = 0.012) of habitat type (58% in the clearcut area, 15% in the wide ROW). Overall productivity (young fledged/nesting territory) was greater (P = 0.026) in the clearcut area (2.38) than in the wide ROW (0.57). Our study raises important questions about the suitability of utility ROWs for Golden-winged Warblers.
Regional droughts have far-reaching, substantial, and easily recognizable impacts on populations and the environment. One component of these impacts that is not widely recognized is impairment of immune function by drought-related physiological stress. We studied cell-mediated immune function of cavity-nestling Western Bluebirds (Sialia mexicana), Ash-throated Flycatchers (Myiarchus cinerascens), and Violet– green Swallows (Tachycineta thalassina) at Los Alamos, New Mexico. There was a dramatic decrease in the cell-mediated immune responsiveness of developing nestlings associated with unusually dry conditions. Adult Western Bluebirds captured in 2002 weighed 7% less than in all previous years and average clutch size for all three species was reduced by 21% in 2002. Nestling body mass was also reduced for flycatcher and bluebird nestlings in 2002 compared to all other years. Survival to fledging age was lower overall during the drought years of 2000–2002 compared to the first 3 years of the study.
We investigated the relationship between grassland breeding bird densities and both grazing and available moisture in the central Platte River Valley, Nebraska between 1980 and 1996. We also compared species richness and community similarity of breeding birds in sedge (Carex spp.) meadows and mesic grasslands. Densities of two species had a significant relationship with grazing and six of seven focal species had a significant relationship with available moisture. Bobolink (Dolichonyx oryzivorus) and Brown-headed Cowbird (Molothrus ater) densities were lower in grazed plots compared to ungrazed plots, whereas Red-winged Blackbird (Agelaius phoeniceus) densities were greater in sedge-meadow plots compared to mesic grassland plots. Bobolink, Dickcissel (Spiza americana), and Brown-headed Cowbird were negatively associated with available moisture with breeding densities peaking during the driest conditions. Our results suggest that wet conditions increase species richness for the community through addition of wetland-dependant and wetland-associated birds, but decrease densities of ground-nesting grassland birds in wet-meadow habitats, whereas dry conditions reduce species richness but increase the density of the avian assemblage. We propose that wet-meadow habitats serve as local refugia for grassland-nesting birds during local or regional droughts.
We compared the structure of riparian willow (Salix spp.) habitat and songbird diversity across two regions of the Greater Yellowstone Ecosystem: Gallatin National Forest and Yellowstone National Park in the north and Grand Teton National Park in the south. The average height of willows was greater (151 vs. 65.9 cm) in the Teton region, and the average density of willows was greater (45.2 vs. 26.1%) in the Gallatin. The average height of willows was the most important variable explaining songbird species richness and abundance across these two regions. Songbird richness and abundance was greater (6.1 vs. 3.1 species; 11.7 vs. 5.6 individuals) in the Teton region. Larger patch size in the Tetons could be a factor contributing to the higher level of diversity but was not statistically significant. Individual species responses to habitat structure varied based on the nesting height preference of the species. Species that nest above the ground or in taller vegetation had abundance positively correlated with average willow height (Yellow Warbler [Dendroica petechia] P < 0.001; Fox Sparrow [Passerella iliaca] P = 0.001). Yellow Warbler, Willow Flycatcher (Empidonax trailii), Fox Sparrow, and Common Yellowthroat (Geothylpis trichas) all had higher abundances in the Teton sites. The difference in willow habitat structure across these regions is likely influenced by historic differences in elk (Cervus elaphus) browsing in the northern regions of the Greater Yellowstone Ecosystem.
We investigated relationships between riparian bird abundance and local vegetation characteristics and habitat features across the Sacramento/San Joaquin Valley, California. Number of detections was analyzed for each of 21 species from point count surveys over a 4-year period at 22 sites from three regions (Sacramento River, Cosumnes River, and San Joaquin River) in relation to 16 measures of habitat and vegetation composition within 50 m of 184 survey points. Tree variables, including tree height and trunk diameter, were often important, as was specific composition of tree species, especially Fremont cottonwood (Populus fremontii) and valley oak (Quercus lobata). Effects of mugwort (Artemisia douglasiana) and blackberry (Rubus spp.) were generally positive. The median partial R2 due to vegetation/habitat characteristics was 16% after controlling for regional differences in abundance per species. Comparisons of model results at the local versus regional scale revealed spatial variation in bird abundance was independent of spatial variation in habitat variables. The effect of a habitat variable differed among the three regions for 11 of 16 variables. Models that used one or more of the first three principal components (extracted from the 16 vegetation and habitat variables) had substantially lower predictive ability than models built using individual variables. The results emphasize the importance of both understory vegetation and tree characteristics at different spatial scales. Local vegetation and habitat characteristics are important in explaining variation in local abundance, but there is a need to develop models specific to each subregion.
We provide the first description of the eggs, breeding biology, and natural history of the Ochre-breasted Brush Finch (Atlapetes semirufus). We found 37 nests over four breeding seasons (2004– 2007) in Yacambú National Park, Venezuela. Nesting activity started in late April and continued until early June suggesting single-brooded behavior despite a typical tropical clutch size of two eggs (x̄ = 1.89) that were laid on consecutive days. Egg mass averaged 3.38 g and 11.6% of adult female mass. The incubation and nestling periods averaged 14.9 and 10.5 days, respectively. Only females incubated and the percent time they spent incubating did not change between early and late incubation. Females brooded 42.7% of the time when nestlings were 2 days of age and 20.5% when 9 days of age. Both parents provisioned young at a low rate (3.9 trips/hr) and nestling growth rate (k = 0.45) was also slow. Nest predation rates were relatively high with daily mortality rates of 0.058 and 0.067 during incubation and nestling stages, respectively.
We provide a detailed report on the reproductive biology of the Red-ruffed Fruitcrow (Pyroderus scutatus granadensis). Eight nests were found between 2003 and 2007 in tropical montane cloud forest in Yacambu National Park, Lara, Venezuela. All nests were near streams in steep drainages. Nests consisted of twigs arranged in a cupped platform. Clutch size was a single egg and the average incubation period (n = 3) was 22.3 days. Nest attentiveness during incubation averaged [± SE] 76.3 ± 1.86% and increased only slightly across stages (early, middle, late). On-bout and off-bout durations were relatively similar across incubation stages. A nestling period of 35 days was recorded for one nest and feather pin-break was estimated to occur at day 19. Brooding attentiveness during the early nestling period averaged 62.5 ± 6.41%, and the adult ceased brooding at about feather pin-break. Food delivery rates increased with nestling age. Food provisioning consisted mostly of insects (66.7%) and lizards (25%) with fruit comprising only 8.3% of the nestling diet at early stages. Provisioning changed to mostly fruit (82.4%) and some insects (17.6%) in late stages of the nestling period.
Little information is available on nesting of Golden Swallow (Tachycineta euchrysea), a threatened species that occurs only on the island of Hispaniola. We report on six nests discovered and monitored in abandoned bauxite mines in the Sierra de Bahoruco of the Dominican Republic. Nests were in cavities of the vertical walls of these pit mines. Clutch sizes consisted of 2–4 eggs and the nestling stage lasted between 21 and 24 days with both parents provisioning the brood. Three of the six nests were depredated by introduced mammals. We compare our observations of Golden Swallow nesting success to nesting studies of congeneric swallows and emphasize the potential conservation importance of a nest box placement and monitoring program on Hispaniola.
I report a nest, nestling care, and the breeding season of the Spangled Cotinga (Cotinga cayana) near Saül, French Guiana. The open cup nest was found on 20 October 2007 with a 15–20 days old nestling, ∼12 m above ground in a yellow mombin tree (Spondias mombin). Nest activities were followed during 4 days, from dawn to dark. The nestling's plumage had a scaled color pattern like that of the female, but was paler gray. The female left the nest between 0600 and 0630 hrs in the morning, and provisioned the nestling 6–8 times a day. Food items delivered to the nestling were mainly bluish to blackish fruits, ∼6–7 mm in diameter, but also included a ∼6 cm cricket (Orthoptera) and a ∼10 cm lizard. The female arrived for a last provisioning between 1630 and 1710 hrs, after which she stayed with the nestling until morning. This and other records of breeding Spangled Cotingas suggest that nesting coincides with the dry season.
We describe characteristics of nest sites, nests, and the first report of the eggs and incubation behavior of the Grey-headed Bullfinch (Pyrrhula erythaca). We found nine nests in coniferous forest during June and July 2003 at Lianhuashan Natural Reserve in central China. Only the female built the nest, but her mate remained in close attendance. Nests were cup shaped and built on horizontal branches of coniferous trees, 1.3–16.0 m above ground. Clutch size was three eggs (n = 3); the eggs were white in color and spotted with reddish brown. Only the female incubated and averaged 85% nest attendance. On-nest and off-nest bouts (x̄ ± SD) were 31 ± 17 min and 4 ± 5 min, respectively. Egg color, egg size, and clutch size were similar to those reported for other bullfinches, but nest materials differed slightly.
The genus Sporophila (Emberizidae) comprises species of small finches characterized by marked sexual dichromatism, which in birds is positively associated with extent of female bias in parental care. We analyzed differences in parental care in Tawny-bellied (S. hypoxantha) and Rusty-collared (S. collaris) seedeaters. We video-recorded nest activity during incubation and when young were 2–4 and 7–9 days of age. Females of both species built the nest and incubated the eggs alone. Female Tawny-bellied Seedeaters: (1) incubated 59% of the time, (2) had a higher frequency of nest visits than males when chicks were 2–4 days of age, and (3) their visits were longer because after feeding they remained in the nest brooding the chicks. There were no gender differences in frequency of nest visits when chicks were 7–9 days of age, but visits of females were longer than those of males. Female Rusty-collared Seedeaters: (1) incubated 51% of the time and (2) had a higher frequency of nest visits when chicks were 7–9 days of age. Both males and females brooded chicks and there were no gender differences in frequency and length of nest visits when chicks were 2–4 days of age. Parental care in both species is female biased, but the extent of male care is slightly higher in Rusty-collared than in Tawny-bellied seedeaters.
We review the published information on postnatal growth rates of hummingbirds (13 species), and report previously unpublished records for nine additional trochilid species. The allometric relationship based on the log10-transformed data of K (logistic growth rate constant) and body mass has a slope of −0.313 and an intercept of −0.346 (n = 22; r2 = 0.18; P = 0.049). The allometric relationship has a slope of −0.366 and an intercept of −0.327 (n = 20; r2 = 0.30; P = 0.013) if the two Nearctic records are excluded. Visual inspection suggests that higher K-values occur in Nearctic hummingbirds (x̄ = 0.422; n = 2) compared to Neotropic species (x̄ = 0.269; n = 20). We suggest a revival of studies collecting basic life history information such as postnatal growth rates of birds, especially of tropical taxa.
I describe previously unknown begging calls and displays of a fledgling Rusty-breasted Cuckoo (Cacomantis sepulcralis) fed by a Pied Fantail (Rhipidura javanica) in Singapore. The cuckoo emitted two types of begging calls: (1) ‘host-absent begging call’ (loud ‘tsi’ repeated at 1-sec intervals) and (2) ‘standard’ begging call in the presence of the Pied Fantail (wheezy ‘seeee’ repeated 1–2 times/sec). The fledgling also performed the ‘wing-shake begging’ display, i.e., it raised one of its wings at a time towards the approaching Pied Fantail. This display was similar to that of the best studied brood parasite, the Common Cuckoo (Cuculus canorus). The structure of both types of begging calls of the Rusty-breasted Cuckoo was different in comparison to the Common Cuckoo and relatively more similar to some other closely related species of the genus Cacomantis.
Recent observations of the Red Owl (Tyto soumagnei) in Madagascar demonstrated that it inhabits dry deciduous forest, and roosts on rock ledges and in cave entrances in the extreme north of the island. We observed a Red Owl at a sinkhole site in the Réserve Spéciale d'Ankarana, found evidence of its use of an additional cave, and collected its pellets in three separate dry seasons between 2000 and 2003. Tsingy tufted-tailed rats (Eliurus antsingy) constituted almost 50% of the total prey mass of Red Owls at Ankarana. Their diet at Ankarana differed from that of Red Owls from Masoala in the humid northeast of Madagascar, as the Ankarana pellets contained insects, frogs, and numerous geckos. Red Owls appear to consume more native than introduced rodents and do not appear to prey upon birds or bats like other large owls on the island. Forest degradation could reduce densities of tufted-tailed rats and could be a conservation threat to this owl.
I examined bird population responses to a managed forested landscape resulting from management for Ruffed Grouse (Bonasus umbellus) habitat in central Pennsylvania during three consecutive springs, 2005–2007. The number of bird species increased from 2001–2002 (n = 40) to 2005–2007 (n = 46). Abundance of all species combined declined (0.10 ≥ P ≥ 0.05), perhaps because the area was more heterogenous in 2001–2002 than in 2005–2007. Red-eyed Vireo (Vireo olivaceus) was the most common species in both 2001–2002 and 2005–2007. Six of the 20 common species were detected only in the treated sector in both periods; none was specific to the reference sector. Despite increased forest maturation, no populations of early successional bird species declined (P ≤ 0.05) between periods, but populations of three other species did. Management of the Barrens Grouse Habitat Management Area for Ruffed Grouse habitat did not have a profound effect on bird populations from 2001–2002 to 2005–2007 subsequent to the last cutting cycle.
The choice of fruits by an avian frugivore is affected by choices it makes at multiple hierarchical levels (e.g., species of fruit, individual tree, individual fruit). Factors that influence those choices vary among levels in the hierarchy and include characteristics of the environment, the tree, and the fruit itself. Feeding experiments with wild-caught birds were conducted at El Tirol, Departamento de Itapúa, Paraguay to test whether birds were selecting among individual fruits based on fruit size. Feeding on larger fruits, which have proportionally more pulp, is generally more efficient than feeding on small fruits. In trials (n = 56) with seven species of birds in four families, birds selected larger fruits 86% of the time. However, in only six instances were size differences significant, which is likely a reflection of small sample sizes.
We followed the fate of nests of Rio Grande Wild Turkeys (Meleagris gallopavo intermedia) on the Edwards Plateau of Texas during 2006 and 2007 using motion-activated digital cameras on a subset of nests to evaluate the frequency of nest predation and to identify nest predators. Predation was the primary cause of loss for nests with cameras, accounting for 57 and 65% in 2006 and 2007, respectively. Predation for nests without cameras also was high (69 and 65% for 2006 and 2007, respectively) suggesting the cameras did not increase the probability of nest failure. We documented partial-and multiple-predator events that could result in misidentification of nest predators. Our results provide insight into nest predator communities and confirm that multiple predator events occur with regularity in the wild.
We sampled 100 Cliff Swallows (Petrochelidon pyrrhonota), just after arrival in Nebraska breeding areas, to ascertain if migrating birds re-introduce Buggy Creek virus (BCRV; Togaviridae) to north-temperate localities in spring. Most birds sampled were previously banded and were known to have used parasite-free nesting colonies in past summers and/or were seronegative to BCRV; thus, they were unlikely to have been previously exposed to the virus in their breeding areas. None of the birds had evidence of viral RNA in blood, as measured by RT-PCR. These results are consistent with other studies that have shown little evidence that migratory birds re-introduce arboviruses to temperate localities between years.
On 25 August, 2007, a Marbled Godwit (Limosa fedoa) was struck by a Southwest Airlines Boeing 737 at 3,700 m. The bird was identified by examination of feather remains recovered from the aircraft and represents an altitude record for this species.