Palaeospiza bella was described as an oscine songbird in the late 19th century. The late Eocene age of the holotype specimen would make it the oldest Northern Hemisphere record of the Passeriformes. However, few recent workers have accepted the placement of P. bella within Passeriformes, and the higher relationships of this fossil have remained controversial. We show that P. bella is a member of the Coliiformes (mousebirds) and represents the latest North American occurrence of a clade with an exclusively African extant distribution. Coliiformes are now known from the latest Paleocene to the approach of the Eocene-Oligocene boundary in North America. We present a redescription of P. bella and a new phylogenetic analysis of fossil and living Coliiformes based on a matrix including 49 characters and 18 ingroup taxa. The results of this analysis place P. bella in Colii, the clade comprising taxa more closely related to Coliidae (crown mousebirds) than to the extinct Sandcoleidae. The oldest stem-group Coliiformes are late Paleocene (about 56.2–56.6 Ma) in age. However, no fossil taxon can be confidently placed within the crown clade Coliidae at present. Phylogenetic results imply that a minimum of three mousebird dispersals from Europe to North America occurred during the Early Cenozoic. Review of the early Eocene fossil Eocolius walkeri from the London Clay shows that this taxon lacks convincing coliiform synapomorphies and should be removed from the clade.

We used museum specimens to describe the timing and location of the postbreeding molt in Western Kingbird (Tyrannus verticalis), an insectivore that breeds in arid lowlands of western North America, where late summer conditions are exceedingly dry. Like many other western migrants, adult Western Kingbirds depart their breeding grounds and move to molt in the Mexican monsoon region. By contrast, juveniles stay on the breeding grounds in late summer, delaying their eccentric primary molt and body molt until after undertaking part of their fall migration. The high number of juvenile specimens collected on the breeding grounds in late summer confirms that the decrease in adults, measured as the percentage of all Western Kingbirds that are adults, is not an artifact of inactive collectors. We also demonstrate adult departure using museum databases to calculate the percentage of all passerines collected in breeding areas outside the southwestern molting grounds that were adult Western Kingbirds. The close correlation between these indices validates the use of total number of passerines as an index of the collecting effort targeting a specific passerine. Our results provide another example of the importance of the Mexican monsoon region for molting passerines, highlighting the need to preserve habitat in this region.

We live-trapped and banded Brown-headed Cowbirds (Molothrus ater, n = 1,722 individuals) to evaluate sex ratios and survival probabilities during the breeding season at the San Juan Basin Research Center, La Plata County, Colorado, from 1992 to 1999. For adult Brown-headed Cowbirds, sex ratios varied significantly among years, and sex ratios were always male-biased within a year. In hatch-year (HY) cowbirds, and within years, sex ratios were similarly male-biased, but there was no difference among years in HY sex ratios. Using the program MARK, for adult females, second-year (SY) males, and after-second-year (ASY) males, the most parsimonious model, suggested that some variation occurred among these groups in individual survival probability (φ;) to the next year after the initial year of capture and in all following years. However, this model indicated no differences among these groups to best describe the probability of recapturing an individual (P). For HY individuals, analyses in MARK indicated that the most parsimonious model, did not include any differences in survival probability between the sexes, and survival probability was constant for the cohorts and periods examined. We also found some evidence that the residency status of adult Brown-headed Cowbirds potentially affected their frequency of recapture in the following year. In adults, the male-biased sex ratios that we observed were very likely the result of decreased survival probability of adult females compared with both SY and ASY males. Additionally, the male-biased sex ratios of adults may have already begun to develop in HY individuals.

We estimated apparent annual survival probability of adult Purple Martins (Progne subis) using a 14-year data set from a population in northwestern Pennsylvania. We modeled age, sex, and year effects on adult survival using known-age birds (585 males and 392 females) first banded or resighted as one-year-olds in two core breeding colonies. We resighted banded birds at (1) the two core breeding colonies, (2) other breeding colonies within 50 km of the core colonies, and (3) a large premigratory roost that attracts adult Purple Martins from colonies ≤200 km away. Apparent annual survival probability for one-year-olds increased by 0.08 when we included encounters outside the core colonies. Survival probability for older males and females was largely unaffected, a result of their high breeding-site fidelity. The model with age-specific survival (1 year old, 2–4 years old, ≥5 years old) and an age*sex interaction had the strongest support when all encounters were included. Apparent annual survival of one-year-old females (0.48 ± 0.03 [SE]) was lower than that of one-year-old males (0.59 ± 0.02), but we detected no sex differences in survival among older birds (2–4 years old: females, 0.64 ± 0.02; males, 0.62 ± 0.02). We found evidence of senescence, because birds at least five years old had lower apparent survival (females: 0.51 ± 0.06; males: 0.52 ± 0.05). Fully time-dependent models had low support, including those evaluating the relationship between annual variation in prevalence of West Nile virus and the El Niño Southern Oscillation Index, a key climate variable.

In an urban landscape, population viability may require successful movement of recently fledged birds between habitat patches, yet postfledging movements are rarely studied. We used radiotelemetry to track 26 American Robin (Turdus migratorius), 15 Swainson's Thrush (Catharus ustulatus), 46 Spotted Towhee (Pipilo maculatus), and 35 Song Sparrow (Melospiza melodia) fledglings across the urban gradient of the Seattle metropolis, to document the relative use of specific features of the built and forested environment and to correlate land-cover metrics with survival during the postfledging period. Survival of postfledging birds, other than American Robins, was high, and the effects of land cover on survival were limited. Across species, we observed lower survival in forested areas than in the suburban lands around them, but this may have been a function of fledgling age. Once juvenile birds became independent, they often moved into suburbs without increased risk of death. We found little consistency in relative habitat use within species, with the exception of American Robins, which used suburban residential areas more than forested areas. However, resource use by the other species was context-specific: (1) use of residential areas by Song Sparrows was highest where this habitat was least common, (2) use of forested areas by Spotted Towhees decreased with increasing level of urbanization, and (3) use of heavy-medium urban areas by Swainson's Thrush decreased with increasing abundance of roads.

We evaluated hypotheses explaining risk of predation by American Black Bear (Ursus americanus) at 418 Yellow-bellied Sapsucker (Sphyrapicus varius) and Hairy Woodpecker (Picoides villosus) nests, on the basis of nestling begging and nest-site habitat features in Algonquin Provincial Park, Ontario. Ninety-three percent of Yellow-bellied Sapsuckers in stands dominated by Sugar Maple (Acer saccharum) nested in Sugar Maple or American Beech (Fagus grandifolia) trees that were dead or in declining health, whereas 86% of Yellow-bellied Sapsuckers in stands dominated by aspen (Populus spp.) nested in Quaking Aspen (P. tremuloides) that were in declining health. Black Bears depredated 17% of 315 nests of Yellow-bellied Sapsuckers in Sugar Maple stands, which accounts for 71% of all Yellow-bellied Sapsucker nest failures. Only 1 (2%) of 46 Hairy Woodpecker nests in the same Sugar Maple stands was depredated by a bear. None of 51 Yellow-bellied Sapsucker nests in aspen stands was depredated. In Sugar Maple stands, daily nest survival of Yellow-bellied Sapsucker nests was lowest when nestling begging calls were loudest and carried the farthest, in more recently harvested stands, and in trees other than American Beech (mostly Sugar Maple). Nest substrates were hardest at Hairy Woodpecker nests, followed by successful Yellow-bellied Sapsucker nests in American Beech and Quaking Aspen; Yellow-bellied Sapsucker nests were softest in stands that had been harvested within the past 30 years. Our study suggests that the risk of predation by American Black Bears at woodpecker nests is a combined function of nestling begging calls, which attract bears to the nest, and nest habitat characteristics, which influence accessibility to the interior of the cavity.

Dispersal is a key process in the metapopulation dynamics and genetic structure of spatially segregated populations. However, our knowledge of avian dispersal, particularly in migratory passerines, remains limited. We studied dispersal of Bobolinks (Dolichonyx oryzivorus) and Savannah Sparrows (Passerculus sandwichensis) to determine whether agricultural management practices affected dispersal patterns and habitat selection. From 2002 to 2006, we banded adults and nestlings on six focal hay fields and two pastures in the Champlain Valley of Vermont and New York and searched for banded birds within 1.5 km of Vermont field sites during two years. Natal dispersal distances were greater than breeding dispersal in both species, and breeding dispersal distances of Bobolinks were greater than those of Savannah Sparrows. Site fidelity was high in both species, with >80% of detected adults and ∼30% of detected natal dispersers returning to the same field in subsequent years. During natal dispersal, movement was random with respect to habitat quality. Adult Bobolinks dispersed to fields with annual reproductive rates greater than or equal to those of their original field; by contrast, adult Savannah Sparrows were more likely to move to or remain in low-quality habitats. During breeding dispersal, strong site fidelity took precedence over the effect of the previous year's nest success on the probability of dispersal, particularly for Savannah Sparrows. Site fidelity has implications for management of agricultural fields because consistency of cropping patterns and cutting dates are important for maintaining populations of these species.

La dispersión es un proceso clave que afecta la dinámica de metapoblaciones y la estructura genética de poblaciones segregadas espacialmente. Sin embargo, nuestro conocimiento de la dispersión de aves es limitado, particularmente para pájaros migratorios paserinos. Estudiamos la dispersión de Dolichonyx oryzivorus y Passerculus sandwichensis para determinar si las prácticas de manejo agrícola influyen sobre los patrones de dispersión y selección de hàbitat. De 2002 a 2006, marcamos adultos y polluelos en seis campos de heno y dos potreros en el valle Champlain de Vermont y Nueva York, EE.UU., y buscamos pájaros marcados en un radio de 1.5 km alrededor de los campos de Vermont durante dos años. Las distancias de dispersión natal fueron mayores que las de dispersión reproductiva en las dos especies, y las distancias de dispersión reproductiva de D. oryzivorus fueron mayores que las de P. sandwichensis. La fidelidad al territorio fue alta en las dos especies, debido a que más del 80% de adultos encontrados y aproximadamente el 30% de los dispersores natales volvieron al mismo campo en años posteriores. El movimiento en la dispersión natal fue aleatorio con respecto a la calidad del h´bitat. Los adultos D. oryzivorus se dispersaron a otros campos con tasas reproductivas anuales mayores o iguales a las de su campo original; en contraste, fue más probable que los adultos P. sandwichensis se movieran o se quedaran en hàbitats de baja calidad. En la dispersión reproductiva, el efecto que el éxito reproductivo en años anteriores tuvo sobre la probabilidad de dispersión fue menor que la firme fidelidad al territorio, especialmente en P. sandwichensis. La fidelidad al territorio tiene implicaciones para el manejo de los campos agrícolas, porque la consistencia de los patrones de cultivo y las fechas de corte son importantes para mantener poblaciones de estas especies.

Offspring quality is an important issue in avian life-history theory, particularly with regard to birds that have low reproductive rates and extended parental care. Offspring mass has been identified as an indicator of quality in several bird species. These studies have shown that nestling mass is predictive of offspring survival outside the nest, but few studies have considered the role of fledgling mass. Mass during the fledgling period may change and influence juvenile survival. Fledgling mass may be especially relevant for tropical birds that have very long fledgling periods during which food conditions randomly or seasonally change. Here, we show that fledgling mass predicts juvenile survival in the Hawaii Akepa (Loxops coccineus coccineus), an endangered Hawaiian Honeycreeper with high annual adult survival and a two-egg clutch. Juvenile survival of Hawaii Akepa approximated a trimodal pattern of no survival, low survival, and high survival that corresponded to ascending mass classes. Fledglings in the highest mass class had an apparent juvenile survival probability that was more than double that of fledglings of the lower mass classes and that was statistically indistinguishable from survival rates of adults. This mass-dependent juvenile survival has important implications for understanding the life-history evolution and population biology of the Hawaii Akepa and perhaps of other tropical birds.

La calidad de las crías es un aspecto importante de la teoría sobre las historias de vida de las aves, particularmente para las que presentan tasas reproductivas bajas y cuidado parental extendido. La masa de las crías ha sido identificada como un indicador de la calidad en varias especies de aves. Esos estudios han mostrado que la masa de los pichones predice la supervivencia de las crías fuera del nido, pero pocos estudios han considerado el papel de la masa de los volantones al momento de abandonar el nido. La masa durante el período de emplumamiento puede cambiar e influenciar la supervivencia de las aves jóvenes. La masa de los volantones podría ser especialmente relevante para las aves tropicales que tienen períodos de emplumamiento muy largos, durante los cuales las condiciones cambian aleatoria o estacionalmente. En este estudio demostramos que la masa de emplumamiento predice la supervivencia de las aves jóvenes en Loxops coccineus coccineus, una especie de mielero hawaiano amenazada que presenta una supervivencia anual de los adultos alta y una nidada de dos huevos. La supervivencia de los jóvenes se aproximó a un patrón trimodal de no supervivencia, supervivencia baja y supervivencia alta, que correspondió a una escala creciente de clases de masa. Los volantones en la clase de masa más alta presentaron una probabilidad de supervivencia aparente de más del doble en comparación con la de los volantones de las clases de masa menores, y su tasa de supervivencia fue estadisticamente indistinguible de la de las aves adultas. Esta supervivencia dependiente de la masa en las aves jóvenes tiene implicaciones importantes para entender la evolución de la historia de vida y la biología poblacional de L. c. coccineus y quizás de otras aves tropicales.

Using microsatellite markers and mitochondrial DNA (mtDNA) sequences (cytochrome oxidase 1 gene), we estimated levels of genetic structuring among nine Magellanic Penguin (Spheniscus magellanicus) colonies distributed throughout three major reproductive regions of the South Atlantic Ocean. Overall, breeding colonies showed relatively high levels of genetic diversity at both nuclear and mtDNA markers (mean heteorzygosity: H_e = 0.598; mean allelic diversity: A = 7.11; mtDNA haplotype diversity: h = 0.812). A hierarchical analysis of molecular variance based on microsatellite data showed limited genetic structuring of breeding colonies, with 99% of the variation explained by differences among individuals and 0.7–1.0% attributed to differences among the three regions. The mtDNA analysis revealed higher levels of genetic structuring, with 3.43% of the variation explained by regions and 2.24% explained by colonies within the regions. Furthermore, a Mantel test revealed a significant association between geographic and genetic distances among colonies. The limited genetic structuring we detected is likely a result of (1) population intermixing through natal dispersal and (2) the large effective sizes of the reproductive colonies, both of which prevent genetic differentiation at neutral markers, balanced with (3) the regional association of breeding colonies to distinct feeding grounds and (4) a recent expansion of the population. Our results suggest that the demographic dynamics of breeding colonies of Magellanic Penguins may be framed under a metapopulation model, in which colonies with large numbers of breeding pairs could be considered “source” populations for maintaining the overall abundance of this species in the Atlantic Ocean.

Many species of birds lay clutches that include eggs of varying sizes. Smaller eggs laid late in a clutch may facilitate brood reduction when there is insufficient food, whereas larger eggs may offset the disadvantage of late-hatching chicks when hatching is asynchronous. Alternatively, egg size may not be adaptive but may reflect energetic constraints on females. Magellanic Penguins (Spheniscus magellanicus) usually lay clutches of two eggs that are similar in size. In 5.1% of clutches (n = 7,085; 1983–2006), the volume of the smaller egg was <88.8% of the volume of the larger egg. We wondered whether this was possibly an adaptive trait. We found that laying a dimorphic clutch was costly and not adaptive. Eggs in dimorphic clutches failed to hatch 30% of the time, even if the eggs were larger than average. Eggs in normal clutches failed to hatch only 8% of the time. When both eggs hatched, no chicks fledged from 68% of dimorphic clutches, whereas no chicks fledged from 62% of normal clutches (G = 8.2, P = 0.02). Laying a dimorphic clutch is not a trait; females that laid a dimorphic clutch did not always lay dimorphic clutches and commonly laid eggs of similar size in other years. We did not find evidence of a constraint on females, in terms of body condition, age, laying date, persistence of the mate, or environmental conditions inferred from mean annual reproductive success. Dimorphic clutches are not adaptive and appear to be noise in the system.

We used radiotelemetry, habitat sampling, camera trapping, and line-transect surveys to explore movement patterns, distribution, and abundance of Great Argus Pheasants (Argusianus argus) in Sumatra, Indonesia. We radiotracked six adult and one subadult males. Territories averaged 14.5 ± 8.5 ha, and home-range size did not vary by month or by relative abundance of selected plant foods. Daily travel distance (849 ± 211 m) varied significantly between months but did not reflect changes in plant foods. Territories were used almost exclusively by resident males. Males preferentially used undisturbed forest (habitat I). Vegetation structure at male display sites and random points indicated that display sites were located in undisturbed forest, with few lianas and small leaf size on trees adjacent to the display site. Between 1998 and 2001, we conducted five line-transect surveys in conjunction with camera-trap surveys. Density estimates of calling males varied from 0.4 to 2.5 males km^-2, and the total density estimate ranged from 0.9 to 3.7 birds km^-2. Density estimates increased substantially between 1998 and 2001, reflecting recovery from depressed densities after the 1997–1998 El Niño drought. Habitat occupancy estimates varied from 25% to 38% but were not significantly different over time. The proportion of occupied habitat was similar to the proportion of habitat I. We conclude that Great Argus Pheasants prefer undisturbed forest and rarely use other habitat even as population density increases. Restricted movements and habitat preference may limit the ability of Great Argus Pheasants to colonize forest fragments.

Two subspecies of Northern Flicker (Colaptes auratus), Yellow-shafted Flicker (C. a. auratus) and Red-shafted Flicker (C. a. cafer), form a hybrid zone that stretches the length of North America and is apparently stable. The most widely accepted hypothesis for the zone, the “bounded-hybrid superiority” hypothesis, predicts that the fitness of hybrids should be equal to or higher than that of parental types within the hybrid zone. We compared the reproductive performance at various stages of the reproductive cycle among Northern Flickers of different phenotypes at a location in the hybrid zone in which individuals are predominantly reddish. Individuals with red and yellow coloring showed similar levels of aggression toward taxidermy models of pure Red-shafted and Yellow-shafted flickers, and there was no association between phenotype (color class) and the likelihood of winning agonistic contests. In addition, the color of the male and female parents was not related to nest initiation date, clutch size, hatching success, risk of predation, or number of fledglings. These results do not support the tension-zone model, which predicts lower fitness of hybrids, but neither do they strongly support the concept of hybrid superiority, because all phenotypes had equivalent reproductive success. Annual changes in selection pressure, such as those caused by weather, could mask fitness differences between red and yellow individuals measured at a single geographic location and result in a hybrid zone that is variable in location and width over time.

Comparing the patterns of population differentiation among genetic markers with different modes of inheritance can provide insights into patterns of sex-biased dispersal and gene flow. The Blue-and-yellow Macaw (Ara ararauna) is a Neotropical parrot with a broad geographic distribution in South America. However, little is known about the natural history and current status of remaining wild populations, including levels of genetic variability. The progressive decline and possible fragmentation of populations may endanger this species in the near future. We analyzed mitochondrial DNA (mtDNA) control-region sequences and six microsatellite loci of Blue-and-yellow Macaws sampled throughout their geographic range in Brazil to describe population genetic structure, to make inferences about historical demography and dispersal behavior, and to provide insight for conservation efforts. Analyses of population genetic structure based on mtDNA showed evidence of two major populations in western and eastern Brazil that share a few lowfrequency haplotypes. This phylogeographic pattern seems to have originated by the historical isolation of Blue-and-yellow Macaw populations ∼374,000 years ago and has been maintained by restricted gene flow and female philopatry. By contrast, variation in biparentally inherited microsatellites was not structured geographically. Male-biased dispersal and female philopatry best explain the different patterns observed in these two markers. Because females disperse less than males, the two regional populations with well-differentiated mtDNA haplogroups should be considered two different management units for conservation purposes.

Birds that live in family groups and cooperatively defend the family's territory are currently recognized as cooperative breeders only if helpers assist with chick rearing. We observed breeding Kagus (Rhynochetos jubatus) and video-monitored nests to determine whether help with feeding or family size affected their reproductive success. During >5,500 h of nest monitoring, helpers never provided parents or chicks with food. The reproductive success of families increased with group size nonetheless. Family size affected breeding success more than habitat-related parameters. Nonbreeding Kagus reacted to playback calls as often as breeding birds did. Observations of territorial fights gave additional evidence that nonbreeding group members help defend the family's territory and can, therefore, improve reproductive success. Our results suggest that cooperative territory-defense was the most important factor that increased the breeding success of Kagus. We propose that group territoriality should be considered a form of cooperative breeding.

Recent hybridization has been reported between the Herring Gull (Larus argentatus) and Glaucous Gull (Larus hyperboreus; the larger of the species) in Iceland, after the arrival of Herring Gulls around 1925. We used samples of both species from various locations in Iceland and from three periods spanning >40 years. To analyze the nature of hybridization and the extent of introgression between the species, we compared morphological variation using genetic information based on microsatellite and mtDNA data. Both comparisons of single traits and multivariate analysis pointed to hybridization and introgression. Variation in genetic markers and morphological traits revealed two distinct groups, connected by a number of intermediates. A discrepancy in classification based on genetic or morphological information revealed introgression. Variation within each species reflected the effect of hybridization; for example, individuals with less pigmentation (i.e., more hyperboreus-like) tend to be larger. The differences we observed among samples and periods reflect changes in the overlap of the populations' distributions.

We tested female Common Canaries' (Serinus canaria) preferences for “sexy phrases” of different durations. Two groups were used: (1) females raised in acoustic isolation and (2) females raised in “normal” acoustic conditions. We presented sexy phrases to both groups and counted their copulation-solicitation displays to determine their preference for the length of these stimuli. Females of both groups gave more copulation-solicitation displays in response to the longest sexy phrases presented. Our results indicate that the duration of sexy phrases is an important acoustic cue for female Common Canaries, as is total song duration in many species; this preference can be explained by theories of sexual selection. Moreover, responses of both experienced and inexperienced females are similar, which indicates that experience does not influence the females' preference for long sexy phrases. These preferences could come from predispositions, as is the case for many acoustic parameters of sexy phrases.

Migratory species are of increased conservation concern because of their reliance on multiple, geographically disjunct habitats. An understanding of how long-term ecological processes and contemporary population genetic patterns are related is critical for effective management and conservation of such species. Combining traditional long-term census and mark-recapture data with temporally focused molecular genetic data can help inform these efforts. We used 24 years of banding data, 15 years of migration counts, and molecular genetic data from 17 microsatellite loci to describe the migration phenology, direction, and population connectivity of Red-tailed Hawks (Buteo jamaicensis) migrating through the Marin Peninsula, California. Count data indicated two distinct peak periods of movement across years: 15 August-30 September and 1 October-30 November. Band-encounter data from these two periods revealed a significant difference in movement: individuals in the early period of migration (15 August-30 September) displayed little net movement, whereas individuals from the second period (1 October-30 November) showed directional, southward movement. Finally, molecular genetic data suggest that the early-season period primarily involves a population from central California, whereas the second period includes both individuals from central California and individuals from desert regions of the Intermountain West. These analyses provide important information for interpreting long-term Red-tailed Hawk count and banding data and offer an example of how traditional population-monitoring methods can be combined with molecular genetic markers.

The Little Penguin (Eudyptula minor), a colonial-nesting seabird that is widespread in New Zealand and southern Australia, has high dispersal potential but exhibits regional variation in morphology, coloration, and breeding phenology. We present a distribution-wide survey of mitochondrial DNA variation in the Little Penguin to document phylogeographic relationships and genetic structuring and to test for concordance with intraspecific taxonomy. Phylogeographic structuring was absent among Australian colonies (27 localities, 94 individuals), but the distribution of haplotypes among colonies was significantly nonrandom (ϕ_ST = 0.110, P < 0.01). The Australian individuals exhibited close phylogenetic relationships with a subset of New Zealand birds (4 localities, 22 individuals), whereas the remaining New Zealand birds (20 localities, 106 individuals) were phylogenetically distinct, with ≥7% sequence divergence, and exhibited greater levels of genetic variation and geographic structuring (ϕ_ST = 0.774, P < 0.05). These patterns are consistent with earlier suggestions of an origin in New Zealand followed by recent colonization of Australia and back-dispersal to New Zealand. Extinction and re-establishment processes may have been important factors in the development of genetic structuring across a range of spatiotemporal scales. The genetic data are consistent with suggestions that a single subspecies exists in Australia, but not with the subspecies distributions within New Zealand that have been suggested on the basis of morphology and coloration.

El pingüino Eudyptula minor es un ave marina que anida en colonias y que se distribuye ampliamente en Nueva Zelanda y en el sur de Australia. Esta especie presenta un alto potencial de dispersión pero presenta variación regional en su morfología, coloración y fenología reproductiva. Presentames un muestreo de la variación del ADN mitocondrial que abarca toda el área de distribución de esta especie para documentar sus relaciones filogeográficas y estructuración genética y también para probar la concordancia con la taxonomía intraespecífica. No existió estructuración filogeográfica entre las colonias australianas (27 localidades, 94 individuos), pero la distribución de los haplotipos entre las colonias fue significativamente diferente a la esperada por azar (ϕ_ST = 0.110, P < 0.01). Los individuos australianos exhibieron relaciones filogenéticas cercanas con un subgrupo de aves de Nueva Zelanda (4 localidades, 22 individuos). Las demás aves de Nueva Zelanda (20 localidades, 106 individuos) fueron filogenéticamente diferentes (≥7% de divergencia en sus secuencias) y exhibieron un mayor grado de variación genética y estructuración geográfica (ϕ_ST = 0.774, P < 0.05). Estos patrones son consistentes con estudios anteriores que sugirieron un origen en Nueva Zelanda seguido por una colonización más reciente hacia Australia, con un nuevo evento de dispersión hacia Nueva Zelanda. Los procesos de extinción y restablecimiento pueden haber sido factores importantes en el desarrollo de la estructuración genética a través de un amplio rango de escalas de espacio y tiempo. Los datos genéticos son consistentes con la sugerencia de que existe una única subespecie en Australia, pero no con la distribución de las subespecies que ha sido sugerida en Nueva Zelanda con base en la morfología y la coloración.

The zone of secondary contact between Herring Gulls (Larus argentatus) and Caspian Gulls (L. cachinnans) in central Poland is characterized by high levels of introgreeRzemyscular mars several phenotypic characters, with the exception of bare-parts coloration. These patterns suggest a role for coloration as a premating isolating barrier between these species. We investigated the degree of reproductive isolation in this zone of secondary contact by testing three hypotheses: (1) postmating isolation is weak or absent, (2) a partial premating isolation is present, and (3) orbital-ring color or another closely correlated trait is involved in premating isolation, which explains the signal of disruptive selection previously observed (a lower degree of introgression). We also investigated whether differences in breeding phenology could contribute to premating isolation. We found no evidence of postmating isolation, but premating isolation occurred: heterospecific pairs were significantly scarcer than expected under random mating. This assortative mating is best explained by a combination of divergent breeding phenology and mate choice influenced by orbital-ring color. However, because the differentiation in orbital-ring color between L. argentatus and L. cachinnans is incomplete and their breeding periods overlap, premating isolation is only partial. That a previous study found a high level of genetic introgression between these species suggests that reinforcement can occur only in association with sufficiently strong postmating isolation.

Because of the continuing loss of native grasslands, many shorebirds that breed in the temperate zone have become increasingly dependent on non-native grasslands associated with farming for breeding habitat. But invasive land-management in non-native grasslands has placed ground-nesting shorebirds at considerable risk. We studied the reproductive success of Long-billed Curlews (Numenius americanus) breeding in northeastern Nevada, in a landscape dominated by hay fields, between 2003 and 2006. Observed nest density was as high as 9 nests per 100 ha, and mean nest success was 31%, with considerable interannual variation. Predation, predominantly by large mammalian predators such as Coyotes (Canis latrans), was the greatest cause of nest failure in Long-billed Curlews. Flooding of nests during irrigation of hay fields and trampling and disturbance by cattle also affected nest success, albeit to a lesser degree. Fledging success of radiomarked chicks averaged 47%, and hay fields were the preferred brood-rearing habitat, especially in dry years. Mammalian predation was the greatest cause of chick mortality, whereas ranching activities had no noticeable effect on chick survival. In all years, Long-billed Curlews exhibited a high propensity for renesting after a first nest failure. After taking renesting into account, per-female nest success averaged 45% and mean annual productivity was 0.70 female chicks hatched and 0.33 female chicks fledged per breeding female. These results suggest that despite potential negatives associated with high land-management intensity, hay fields in northern Nevada can be of great value in conservation of the Long-billed Curlew.

There is widespread evidence that individuals within and among host populations are not evenly parasitized by Common Cuckoos (Cuculus canorus). We first investigated whether the song and nest size of a host species, the Great Reed Warbler (Acrocephalus arundinaceus), reveal information on parental abilities and level of defense against Common Cuckoos. Second, we analyzed whether female Common Cuckoos' preference for host nests is predicted by the degree of song expression and the nest size of the host. Earlier-breeding hosts built bigger nests, were more active singers, and had less rich syllable repertoires than late breeders. Host nestlings raised in a big nest received more feedings than those raised in a small nest. Host males that were active singers were paired with females that built bigger nests. All host pairs rejected nonmimetic artificial eggs, but those with a big nest were more prone to reject natural Common Cuckoo eggs. Thus, Great Reed Warbler pairs with a big nest were more willing to feed nestlings, but also had higher discriminatory abilities against Common Cuckoo eggs, than those with a small nest. These findings, and female Common Cuckoos' inability to capture the information provided by Great Reed Warblers' sexual signals, may explain why the females followed a simple rule of selecting the more visible host nests in the population.

Distance sampling is usually preferred over uncorrected point counts for surveys of forest birds, but rarely has its accuracy been assessed against known numbers, particularly in tropical forests. We compared density estimates of eight species of breeding bird—Black-naped Monarch (Hypothymis azurea), Hill Blue Flycatcher (Cyornis banyumas), White-rumped Shama (Copsychus malabaricus), Puff-throated Bulbul (Alophoixus pallidus), Abbott's Babbler (Malacocincla abbotti), Puff-throated Babbler (Pellorneum ruficeps), White-browed Scimitar Babbler (Pomatorhinus schisticeps), and White-bellied Yuhina (Yuhina zantholeuca)—obtained through color-banding, nest finding, and territory mapping with those derived from distance methods in evergreen forest in northeastern Thailand. We also assessed the availability of birds to be detected using a closed-capture model and incorporated this with point-transect distance sampling. Abundance estimates from territory mapping and distance sampling were highly correlated, but biased for two species using line transects and five species using point transects. Six of the seven biased estimates were biased low. Probabilities of detection were not significantly different between lines and points, and there was no significant difference in the overall accuracy between methods. Accounting for observer differences improved density estimates but reduced precision. The variance in accuracy was mostly related to the behavior of the different species. Adjusting for availability did not improve the overall accuracy of the estimates, because of the low singing rates of tropical birds. Nonetheless, distance sampling provided relatively robust estimates despite the near total dependence on aural cues. Violations of distance-sampling assumptions may be frequent in heavily forested habitats, where both availability for detection and probability of detection on the transect line (or point) are likely to be <1.