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The Golden-crowned Kinglet (Regulus satrapa) is the smallest insectivorous bird that overwinters in boreal forests across North America from Alaska to Nova Scotia, where nights may last 16 h and nighttime temperatures may fall below −40° C. I here provide the first documentation of Golden-crowned Kinglets huddling in the field during winter on open branches. The birds forage until darkness and do not necessarily come back every night to the same site. Traveling in groups and huddling where they end up in the darkness compensates for small body size and potential compromises in foraging time.
We present the first account of nesting biology for the Neotropical suboscine genus Laniocera by describing the nest and eggs of the Cinereous Mourner (L. hypopyrra) based on observations made in the Peruvian Amazon during 2001. The cup-shaped nest was in mature floodplain forest among the branches of an epiphytic fern in a small tree 1.8 m above the ground, and contained two buffy eggs with chocolate brown blotches and spots. These observations demonstrate that Laniocera is not a cavity nester, supporting its removal from the myiarchine flycatchers and previous suggestions of a close relationship to the genus Schiffornis.
During 1996–2000, I studied the nesting ecology of Sprague's Pipits (Anthus spragueii), Clay-colored Sparrows (Spizella pallida), Savannah Sparrows (Passerculus sandwichensis), Baird's Sparrows (Ammodramus bairdii), Chestnut-collared Longspurs (Calcarius ornatus), and Western Meadowlarks (Sturnella neglecta) on 47 native mixed-grass prairie pastures in southern Saskatchewan. Predation was the primary cause of nest failure and occurred at a similar frequency among the six species. Nest success and productivity varied among years and was lowest during 1997, the year of a substantial increase in meadow vole (Microtus pennsylvanicus) populations in southern Saskatchewan. Nest predation was most severe during the nestling stage with daily survival rates typically lower than those of the incubation period. Brown-headed Cowbirds (Molothrus ater) parasitized nests of all six species, with 5–29% of host nests containing cowbird eggs. Savannah Sparrows, Clay-colored Sparrows, and Western Meadowlarks incurred the highest frequency of brood parasitism. Parasitized hosts experienced lower productivity due to a combination of reductions in clutch size, hatching success, and fledging success. Overall, brood parasitism by cowbirds cost these birds between 1.3 and 2.2 young per successful nest. These results support the general contention that nest predation is the primary factor influencing grassland songbird reproductive success.
Recent success of Eastern Wild Turkey (Meleagris gallopavo silvestris) reintroductions across southern Ontario has prompted wildlife managers to investigate the potential of extending the northern limit of this subspecies' range. We monitored the survival and reproduction of introduced Wild Turkeys on the Precambrian Shield in central Ontario during 1999–2001. Mean annual survival of 39 radio-tagged hens was 0.288 ± 0.057 SE. Summer and winter survival rates differed between the first and second years of the study. Spring and fall survival rates did not differ significantly between years. Reproductive parameters that characterized the population included a nesting rate of 0.588, mean clutch size of 10.0 eggs/nest, nest success of 0.500, hatching rate of 0.81, hen natality rate of 1.18 females hatched/female, poult survival of 0.54, and fall recruitment of 0.63 juvenile females/breeding hen. Success of the pilot Wild Turkey introduction in central Ontario was compromised by high predation, low numbers of introduced birds, and a prolonged period of deep snow during 2000–2001.
Effective management of Ruffed Grouse (Bonasa umbellus) populations requires a full understanding of chick production. Previous reports of nest survival for Ruffed Grouse are biased because they did not account for successful nests being more likely to be found, and the role of habitat quality in determining nest survival is unknown. We determined survival rates of Ruffed Grouse nests in northern lower Michigan using the less biased Mayfield estimator, defined differences between first and second nests, and compared the local habitat characteristics of successful and unsuccessful nests. Median hatching dates were 10 June for first nests (n = 34) and 1 July for second nests (n = 6). First nests had a lower survival rate (0.442, 95% CI = 0.270–0.716), a higher mean clutch size (12.7 eggs ± 0.3 SE), and higher egg hatching rate (0.960, 95% CI = 0.900–0.997) than did second nests (nest survival = 0.788, 95% CI = 0.491–1.00; clutch size = 7.3 eggs ± 0.3 SE; and hatching rate = 0.826, 95% CI = 0.718–0.925). Nest survival, annual production (3.4 hatchling females/adult female, 95% CI = 2.3–5.0), and fall recruitment (1.0 juvenile females/adult female, 95% CI = 0.3–2.4) were less than previously reported estimates. Habitat characteristics at nest sites varied widely and did not differ appreciably between successful and unsuccessful nests.
The Swainson's Warbler (Limnothlypis swainsonii) is a locally distributed and relatively uncommon Neotropical migrant songbird that breeds in the bottomland forests of the southeastern United States and spends the nonbreeding season in the Caribbean Basin. Populations of Swainson's Warblers have declined during recent decades as bottomland forests have come under increasingly intensive management and large areas have been converted to other land uses. We examined the habitat around song perches used by male Swainson's Warblers at Big Hammock Wildlife Management Area, a managed bottomland forest along the Altamaha River in Tattnall County, Georgia. We quantified 20 features of habitat structure in areas occupied by Swainson's Warblers (occupied plots) and two sets of controls: unoccupied plots adjacent to occupied plots (adjacent control plots) and unoccupied plots throughout the management area (general control plots). Occupied plots and adjacent control plots both differed in structure from the general control plots. We detected no significant differences, however, in vegetation structure between occupied plots and adjacent control plots. General control plots tended to have a greater number of trees, greater basal area, and a complete canopy, whereas occupied and adjacent control plots had high densities of small stems, cane, herbaceous ground cover, and leaf litter; this latter pattern is typical of documented Swainson's Warbler breeding habitat. Lack of significant differences in vegetation structure may be due to great variation in habitat structure around song perches, small sample size, or scarcity of Swainson's Warblers. Future research should focus on quantifying habitat characteristics around nest sites, song perches, and feeding areas. Our results suggest that management of bottomland habitats by thinning forests and encouraging regeneration of canebrakes is needed for successful conservation of Swainson's Warblers.
We used point counts and nest monitoring to compare avian community composition and nesting success in thinned and unthinned stands of commercially managed Sierran mixed conifer forest. We conducted point counts and monitored 537 active nests of 37 species on 10 study plots during three consecutive breeding seasons in the northern Sierra Nevada. All 10 study plots had experienced a similar long term management history that included fire suppression and single-tree selection logging, but five of the plots also underwent a protocol of combined commercial and biomass thinning 5–8 years prior to the beginning of the study. Pooling species by nest substrate, we found that detections of ground-nesting bird species were similar on thinned and unthinned plots, but we detected canopy-, cavity-, and especially shrub-nesting species much more frequently on the thinned plots. Nest success rates were not statistically different between thinned and unthinned plots for ground-, shrub-, canopy-, or cavity-nesting species. Thinned stands were characterized by significantly less canopy cover, significantly lower density of small and medium conifers, and significantly greater understory cover and deer brush (Ceanothus integerrimus) cover than the unthinned stands. We surmise that the thinning protocol stimulated vigorous shrub growth, and conclude that forest conditions associated with a relatively open canopy and a well-developed shrub understory are highly beneficial to numerous breeding bird species in the Sierran mixed conifer community, including many species that may not nest or forage in the understory. Forest thinning that promotes vigorous shrub growth may correlate with an increased abundance of nesting birds, at least within stands affected by historical fire suppression and single-tree selection logging.
During spring 2000, we captured five adult female Broad-winged Hawks (Buteo platypterus) in northcentral Minnesota and western Maryland and fitted them with satellite-received radio tags. The migrating hawks left their nesting areas about 10–15 September and moved south toward eastern Texas. They followed the Gulf Coast through Mexico and an inland course through Central America to their wintering areas. Mean fall migration distance for four hawks was about 7,000 km, and for three hawks the mean fall migration time was about 70 days and mean fall migration rate was about 100 km/day. Three hawks arrived on their wintering areas from about 15 October to 15 December. Wintering areas for four hawks were in Panama, Venezuela, Brazil, and Peru, between 08° 25′ N, 80° 54′ W and 11° 00′ S, 67° 07′ W. We tracked one hawk for her entire spring migration, and two hawks showed fidelity to their nest areas.
We examined the timing and intensity of body molt in relation to stage of remige growth for postbreeding adult male Long-tailed Ducks (Clangula hyemalis) off the coast of northern Alaska. During this period, remige and rectrix feathers are molted simultaneously with body feathers during the prebasic molt, which results in a period of increased energetic and nutritional demands. We collected birds from late July through mid-August and recorded intensity of molt in eight regions: head and neck, back and rump, greater coverts, lesser coverts, flank and sides, breast, belly, and tail. Using nonlinear regression, we estimated the peak intensity and variation for each region in relation to ninth primary length. We found little evidence of molt in the head and neck region. The greater and lesser coverts, and back and rump reached peak molt intensities earliest and were followed by tail, breast, and belly. Molt intensity in the flank and side region was highly variable and indicated a more prolonged molting pattern in relation to other regions. While body molt occurs simultaneously with wing molt, we found that molt among regions occurred in a staggered pattern. Long-tailed Ducks may employ this staggered molting pattern to minimize the energetic and nutritional requirements of molt.
We studied nocturnal and diurnal behavior of breeding American Avocets (Recurvirostra americana) at the Jay Dow, Sr. Wetlands in the northwestern Great Basin, USA. Seven-day observation periods were centered on two full moons when ambient light was maximal and auxiliary lighting unnecessary. We recorded avocet density, habitat use, interbird distances, and behavior three times daily (beginning at 07:00, 15:00, 23:00 PST) for 14 days. We calculated the mean proportion of individuals within flocks engaged in four behavior classes (foraging, copulating, agonistic, other). Foraging birds were further subdivided by technique (pecking, dunking, scything). Avocets copulated with similar frequencies during the morning, afternoon, and night. Avocets were more aggressive and closely spaced at night than during day. The full repertoire of behaviors seen during daylight also occurred at night, though frequencies of particular behaviors, flock location, and interbird distances varied among morning, afternoon, and nighttime observations. The role of nocturnal reproductive behavior should be assessed in species generally perceived as being diurnal.
Individuals in a number of bird species have the opportunity to maintain contact with their mates during nonbreeding periods. This contact may be important to synchronize the partners' reproductive cycles before breeding begins. As a first step toward exploring the function of pair bond maintenance in nonbreeding birds, I studied the behavior of three pairs of Pileated Woodpeckers (Dryocopus pileatus) and an unpaired male at roost sites during autumn. At dawn and dusk, paired individuals exchanged visual, vocal, and other acoustical signals identical to those given during the breeding season. Demonstration tapping away from a nest is reported here for the first time. The possible function of these behaviors may be related to monitoring the partner's condition and investing in the pair bond to enhance future reproductive success.
During three field seasons in southwestern Madagascar we made opportunistic observations and tape recordings of the sounds produced by the Long-tailed Ground-roller (Uratelornis chimaera; Brachypteraciidae). Here we present new information on vocal behavior in this species and provide the first documentation of display and nonvocal production of sound by any ground-roller.
I observed an apparent coordinated attack by a mated pair of Florida Scrub-Jays (Aphelocoma coerulescens) on a black racer (Coluber constrictor) in southcentral Florida. Depending upon their size, snakes can be either prey or predators of scrub-jays. This medium-sized snake may have been large enough that one bird could not safely subdue it. By coordinating their attack, the birds were able to kill and feed on the snake. This appears to be an example of pair hunting. The cooperative hunting technique, in which two mated birds perform coordinated movements, enables the pair to attack otherwise prohibitively large prey. Both members of the attack benefit by eating the prey. Cooperative hunting has only rarely been described in passerines.
On 21 June 2002 we observed mixed flocks of Great Egrets (Ardea alba) and Snowy Egrets (Egretta thula) foraging aerially on shad (Dorosoma sp.) forced to the surface by foraging white bass (Morone chrysops) at the Richland-Chambers Reservoir in Freestone County, Texas. These events occurred over open water ranging from 3–12 m deep during a 2-h period of observation. Egrets foraged exclusively by hovering about 3–5 m above the water and then dipping to capture shad. Foraging behavior was interspersed with intervals of vigilance on a nearby shoreline. Here we provide a detailed record of the temporarily exclusive use by egrets of this rare foraging method in fresh water, in water of such depth, and on live schooling prey over open water.
This report presents experimental data on the transport of vertebrate prey by the Northern (Great Grey) Shrike (Lanius excubitor). The species is known to use three modes of transport: carrying prey exclusively with the bill, exclusively with the feet, and by transferring the prey from bill to feet while in flight. Shrikes often transport their prey a short distance from the point of capture (initial distance), followed by the longer flight to the impaling site (long distance). We found that the overall distance (initial plus long) and long distances, but not the initial distance, decreased with increasing prey weight. Greater weight of the prey coincided with reduced use of bill-only transport. The results reveal that Northern Shrikes are well adapted to carry their most common vertebrate prey, voles of the genus Microtus.
We report three unusual cases of predation in which birds of insectivorous or omnivorous species preyed upon smaller birds in El Salvador, Central America. A Squirrel Cuckoo (Piaya cayana) fed on a netted Indigo Bunting (Passerina cyanea); a Blue-and-white Mockingbird (Melanotis hypoleucus) chased, killed, and carried off a probable juvenile Rufous-collared Sparrow (Zonotrichia capensis); and a Black-headed Saltator (Saltator atriceps) fed on a netted Cinnamon Hummingbird (Amazilia rutila). Preying upon birds has not been reported previously in any of these species. Evidence suggests that the Squirrel Cuckoo and the Blue-and-white Mockingbird may prey on small birds or other vertebrates with some regularity, while the saltator may have consumed the hummingbird due to non-natural conditions.
I report observations of fruit consumption by Magellanic Woodpeckers (Campephilus magellanicus) and an opportunistic predation on a lizard (Liolaemus sp.) by an adult male. During normal feeding activities, the woodpecker snatched from a bark crevice of a lenga (Nothofagus pumilio) tree a lizard, which he then beat until stunned or dead, before flying off carrying the reptile. Frugivory, although undocumented for this species, is widespread among picids. Conversely, this apparently first observation of a Magellanic Woodpecker preying on another vertebrate adds to a few known cases of vertebrate predation by woodpeckers.
I observed a male Brown-headed Cowbird (Molothrus ater) attack and kill a nestling of an unidentified passerine in a grassland field in Day County, South Dakota, in June 2000. The killing or removal of nestlings by female cowbirds has been reported by others, but this behavior has not been documented previously in male cowbirds.
I present the second record of Shiny Cowbird (Molothrus bonariensis) parasitism of the Black-chinned Siskin (Carduelis barbata). The last recorded observation was in 1929. This also represents the northernmost nesting record of the Black-chinned Siskin.
We studied parental care in the Great Kiskadee (Pitangus sulphuratus) in a suburban residential area in Buenos Aires Province, Argentina, from September through December, 1998. Our data suggest that the dominant breeding system of the Great Kiskadees on our study site is social monogamy. Both male and female were involved in territory defense, nest building, and feeding the young. The female alone incubated the eggs and brooded the nestlings. Male and female visitation rates to the nest during the nestling period were similar.