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Movement ecology and demographic parameters for the Common Merganser (Mergus merganser americanus) in North America are poorly known. We used band-recovery data from five locations across North America spanning the years 1938–1998 to examine migratory patterns and estimate survival rates. We examined competing time-invariant, age-graduated models with program MARK to study sources of variation in survival and reporting probability. We considered age, sex, geographic location, and the use of nasal saddles on hatching year birds at one location as possible sources of variation. Year-of-banding was included as a covariate in a post-hoc analysis. We found that migratory tendency, defined as the average distance between banding and recovery locations, varied geographically. Similarly, all models accounting for the majority of variation in recovery and survival probabilities included location of banding. Models that included age and sex received less support, but we lacked sufficient data to adequately assess these parameters. Model-averaged estimates of annual survival ranged from 0.21 in Michigan to 0.82 in Oklahoma. Heterogeneity in migration tendency and survival suggests that demographic patterns may vary across geographic scales, with implications for the population dynamics of this species.
Seaside Sparrows (Ammodramus maritimus) nest at varying population densities, and breeding pairs may occupy either large, all-purpose activity spaces or small nesting territories, foraging in undefended areas separate from the nest site. We determined the prevalence of extra-pair paternity in a large, socially monogamous population of Seaside Sparrows nesting in small, overlapping territories. We used six microsatellite DNA markers and a likelihood-based approach to paternity assignment. Five of 47 chicks (11%) in three of 18 broods (17%) in this population were sired by extra-pair males. Although this is the first study of the genetic mating system in the genus Ammodramus, the rate of extra-pair paternity we observed is lower than in most other New World emberizines. As the first measurment of extra-pair paternity in Seaside Sparrows, this study provides a baseline for comparative studies of how extra-pair paternity is influenced by the wide variation in nesting density and territoriality found in Seaside Sparrows. These results, from a socially monogamous sparrow may also provide a context for studies of unusual mating systems in other salt-marsh nesting birds.
Birds killed by colliding with towers and windows were studied to describe the type and extent of injuries and, more precisely, to suggest the actual cause of death. A total of 502 specimens (247 tower kills, 255 window kills) were dissected, radiographed, and examined. Tower and window collision categories were further subdivided to consider age (subadult versus adult) and weight (<39 g, sparrow-size or smaller, versus > 39 g, cardinal size or larger) differences in injury and differential vulnerability. Injuries were classified as superficial, subdermal, or skeletal fractures. Comparisons of injuries between tower- and window-killed specimens indicate that the consequences of these two types of collisions are similar. Subdermal injuries were more severe in tower kills than in window kills. Subadults experienced more severe subdermal injuries than adult tower and window casualties. Among window kills, larger birds had more severe subdermal injuries than smaller birds. Collision victims may show blood or fluid in the mouth or nose cavities (30–60%), almost all have subdermal intracranial hemorrhaging (98–99%), and most lack any evidence of skeletal fractures (82–91%). Histological examination of the brain of two specimens revealed blood pools in the cerebrum and cerebellum. The extravascular bleeding in and around the brain is probably the actual cause of death in collision fatalities. Treatment to reduce brain edema if administered within 6–8 h shortly after impact can save some strike casualties.
Anting is a widespread but poorly understood behavior in which birds apply ants or other organisms or objects to their plumage or skin. I observed two instances of active anting in the ‘Elepaio (Chasiempis sandwichensis), a monarch flycatcher endemic to the Hawaiian Islands, one involving a garlic snail (Oxychilus alliarius) and the second involving a fruit of Brazilian pepper or Christmas berry (Schinus terebinthifolius). On both occasions the ‘Elepaio held the object in its bill and wiped it on its body then preened, but did not eat the object. Chemical compounds contained in each species are known to have antibiotic properties, suggesting the purpose of the anting was to control parasites or pathogens. There are no native ants in Hawaii, and neither the garlic snail nor Brazilian pepper is native to Hawaii.
We developed an identification setup enabling automatic detection of the passage of free-living King Penguins implanted with small radio frequency transponders at Possession Island, Crozet Archipelago. An unique feature of the system is the use of antennas allowing automatic detection and identification on pathways up to 8-m wide without the use of flipper bands. We present results on demographic parameters of the King Penguin, and we found an unexpectedly survival rate of immature penguins. Such an identification system can be used for other birds, mammals, or reptiles that use regular pathways.
Populations of Henslow's Sparrows (Ammodramus henslowii) are declining, and loss of habitat is a likely factor. Coal mine reclamation has created grassland habitat in Kentucky and elsewhere, and information is needed concerning the use of these areas by Henslow's Sparrows. We compared the behavior and ecology of populations on reclaimed sites and non-mined sites in west-central Kentucky during the 2000 and 2001 breeding seasons. Territories were smaller on the reclaimed sites than unmined sites, perhaps due to differences in habitat quality. Insect sweeps revealed more prey biomass on reclaimed sites than unmined sites. Twenty-eight of 48 nests (58%) fledged at least one young, and nesting success was similar on reclaimed and unmined sites. Mean clutch size was 3.75, with no difference between reclaimed and unmined sites. Similarly, the mean number of fledglings per nest was similar on reclaimed and unmined sites. Multivariate analysis revealed differences in the characteristics of vegetation on reclaimed areas and unmined areas. Reclaimed areas had more grass cover and greater vegetation density, probably due to differences in management history (i.e., mowing or burning) and species composition. Our results indicate that the nesting success of Henslow's Sparrows on reclaimed surface mines in Kentucky is comparable to that on unmined areas. As such, the thousand of hectares of reclaimed surface mines in Kentucky and elsewhere could play an important role in stabilizing populations of Henslow's Sparrows.
Conservation strategies for Neotropical migratory birds have emphasized identification and preservation of habitats in which populations are reproducing above replacement rates. In 2000–2001, we monitored 141 Acadian Flycatcher (Empidonax virescens) nests in the extensively forested Blue Ridge Mountains in Virginia to assess the site's potential to host “source” populations of this common species. Our estimates of reproductive success, unlike most studies, incorporated the nesting behavior of marked females followed throughout the breeding season. Despite the presence of Brown-headed Cowbirds (Molothrus ater) in a nearby 15-y-old clearcut and in open areas of a summer camp, we found no parasitized nests. Overall, the predation rate was 41%, 2.5 fledglings were produced per successful nesting attempt, and seasonal fecundity approached two female fledglings per adult female per season. Given return rates (minimum survival rates) of 52% at our study site, our measured levels of reproductive success are sufficient to classify the Blue Ridge Mountains as a potential “source” for Acadian Flycatchers. Our data contrast sharply with those collected from landscapes with high levels of forest fragmentation in the midwestern and southeastern U.S., where even relatively large patches of forest appear to host “sink” populations of Acadian Flycatchers.
The importance of many of Mexico's wetlands for waterbirds remains poorly assessed, and this is an obstacle in planning their conservation. Between Marismas Nacionales, Nayarit, and the center of the state of Guerrero, a span of roughly 1150 km on the Pacific coast of Mexico, there is only large coastal wetland: Laguna de Cuyutlán and its associated wetlands in the state of Colima. We studied the waterbirds that used this area during the non-breeding season, from September 1996 to March 1997. We surveyed birds on eight occasions from 11 stations that included different combinations of mudflats, water pools, shallow water, deep water, and mangroves. Throughout the study we counted 54,370 individuals of 57 species of waterbirds, but 11 species accounted for 90% of all individuals. The total number of individuals exhibited strong seasonal variation, although peaks in abundance reflected variations of only a few species. Waterbirds differed greatly in their use of different sites. The site with the most individuals, but not with the most species, had a combination of mudflats, shallow water, and deeper water. The poorest sites where those associated with a thermoelectric facility. We cannot extrapolate our numbers to the entire wetland complex, but the overall numbers of waterbirds suggest that the area be considered an Área de Importancia para la Conservación de las Aves. The two economic activities in Cuyutlán, fishing and salt production, do not seem to pose direct threats to waterbirds.
Although nocturnal habitats are often critical to avian survival, they are relatively unstudied. Nocturnal roost habitat selection may be particularly important for Ruffed Grouse (Bonasa umbellus) broods, which experience high mortality due to predation and exposure in the first few weeks after hatching. Because these habitats may have important consequences for Ruffed Grouse productivity and abundance, and little is known about them, we assessed nocturnal roost habitat selection of Ruffed Grouse broods and the influence of habitat features on brood survival in central Pennsylvania. Roost use changed through time, with grouse broods roosting on the ground in the first five weeks after hatching and arboreally thereafter. Broods selected roost sites with greater deciduous canopy cover, coarser woody debris, and more concealing cover than at random sites. Habitat did not differ between ground and arboreal roosts. Brood survival declined from a mean 0.90 in the first week to 0.38 through the fifth week and was negatively affected by increasing stem density. Roost use is likely determined by developmental constraints on the thermoregulatory ability of chicks, while habitat selection reflects a compromise between diurnal habitat needs and behavioral adaptations that reduce exposure to nocturnal predators.
Our understanding of the frequency of brood amalgamation in the Northern Bobwhite (Colinus virginianus) is largely anecdotal. Information on it is important in understanding survival and reproduction. We captured entire bobwhite broods at 3–4 and 10–12 d of age and individually marked each bobwhite chick within a brood. Broods were considered amalgamated if novel unmarked or marked individuals or significant differences in body mass or flight ability among chicks were observed. During 2002, minimum frequencies of brood amalgamation within bobwhite broods were 6.7% at 3–4 d and 20.7% for 10–12 d-old broods. During 2003, minimum frequencies of brood amalgamation ranged from 0.0% at 3–4 to 22.2% for 10–12 d-old broods. Our results indicate bobwhites exhibit higher rates and earlier onset of brood amalgamation than previously documented among the Galliformes. Causes of brood amalgamation in bobwhite may differ from those proposed for waterfowl due to the bobwhite's limited mobility, short lifespan, gregarious behavior, and resulting potential for relatedness among individuals. Molecular techniques should be used to assess the effects of inclusive fitness losses and gains among bobwhites that donate and receive chicks. Bobwhite researchers should recognize the potential bias in chick survival estimates caused by high rates of brood amalgamation.
Dusky Flycatchers (Empidonax oberholseri) nesting in a mixed conifer-aspen woodland in southern Utah occurred at a breeding density of 0.44 territories/ha. Females began laying first clutches 1–26 June; adults fed nestlings (in renesting attempts) as late as mid August. Mean clutch size was 3.8 eggs in first clutches and 3.6 eggs overall. Incubating females spent 90% of daylight hours on the nest, where they were fed by males 1.1 times/ hour. Incubation lasted 14–16 d; nestlings remained in the nest 15–17 d. Thirteen of 32 nests (40.6%) were successful in producing at least one fledgling, with successful nests producing 2.7 young/nest. Based on exposure, probability of a nest surviving from egg laying to fledging was 0.40. Predation accounted for 84.2% of nest failures; brood parasitism by a Brown-headed Cowbird (Molothrus ater) occurred at one nest.
Using data on the extent of prebasic molt in known-aged adult and first-winter Western Bluebirds (Sialia mexicana), we assessed the accuracy of the molt limit as a tool for ageing birds. Sixty-nine known-aged birds were examined over the winter 2002–2003 in upper Carmel Valley, California. We also examined 29 breeding males in spring 2004 to assess the accuracy of this method for ageing birds during the breeding season. All birds were aged correctly using molt limit as the defining characteristic. We found that all first-winter birds had replaced 2–8 greater secondary coverts, while adults had replaced all wing coverts. We observed no significant sexual variation in the extent of first prebasic molt. These results indicate that the extent of prebasic molt is a highly reliable means of ageing birds in this population.
Chungungo, Tilgo, and Pájaros are small, uninhabited islands within 30 km of the coast of north central Chile. Based on surveys conducted in January 2002 and 2003, we observed 32 marine and terrestrial species of birds that nest, feed, and/or roost on these islands. Seven of these species are considered Endangered, Vulnerable, or Insufficiently Known according to Chilean and other international standards. These islands serve as important sites for these species and should be given adequate protection.
A short-term color-marking technique suitable for non-breeding birds was developed by altering a common method used to mark incubating birds. A dye paste was spread on the ground at resting sites used by Herring (Larus argentatus) and Great Black-backed (L. marinus) gulls. Gulls first contacted dye by walking, standing, or sitting in the paste. When preening, birds transferred small amounts of dye over their feathers, creating unique patterns. Marks remained visible an average of 27 d.