The Variable Antshrike (Thamnophilus caerulescens) is arguably the most polytypic thamnophilid, with males ranging from almost entirely jet black to nearly white. The four subspecies that occur in Bolivia are strikingly divergent in male plumage: T. c. aspersiventer (black with white-barred belly), T. c. connectens (black back and bib with white belly), T. c. dinellii (gray throat and back with rufous belly), and T. c. paraguayensis (light gray with white belly). To assess the genetic structure of those taxa in Bolivia, sequence variation at the mitochondrial cytochrome-b gene was screened in 126 individuals collected across transects spanning the plumage and vocal variation in the four forms. A 95-km-wide cline in haplotype frequencies from T. c. aspersiventer to T. c. dinellii was centered in the Serrania Cochabamba across an ecotone from humid to dry Andean foothill habitats. Thamnophilus caerulescens connectens is not a valid taxon, instead representing an introgressed population near the dinellii tail of the T. c. aspersiventer-T. c. dinellii hybrid zone. Although direct contact between T. c. dinellii and T. c. paraguayensis remains undocumented, the mitochondrial data were consistent with introgression along a broad cline extending across most of southern Bolivia. Overall, the transitions in mitochondrial frequencies were remarkably concordant with clinal changes in vocalizations among those same populations (Isler et al. 2005). Both studies highlight the need for increased sampling, in both the geographic extent and number of individuals per population, to address adequately the potential for clinal variation between populations that are not isolated geographically. A more restricted sampling design in the present study might have led to the erroneous conclusion that T. c. aspersiventer, T. c. dinellii, and T. c. paraguayensis have reciprocally monphyletic mitochondrial lineages, making them full species according to some species concepts.

In avian taxa in which vocalizations are considered innate, such as suboscine passerines, vocal characters are increasingly being used to help determine whether populations have achieved species status. In comparing vocal characteristics of distant populations, however, one must be concerned with the possibility of character gradation through intermediate populations. The first quantitative study of a species in a suboscine family to test for clinal vocal variation, our vocal study found clinal variation in the pace (number of notes per second) of male loudsongs, and revealed that the geographic pattern of the clines was consistent with genetic variation found in the companion molecular study (Brumfield 2005). The result underscores the necessity of searching for intermediacy when analyzing vocalizations of geographically distant populations. Furthermore, given that male loudsong pace was the only vocal character that varied across the intergrading populations, the result also provides support to the guideline that one should expect thamnophilid species to differ in at least three vocal characters (Isler et al. 1998) and indicates that this degree of vocal character differences can be a valuable “yard stick” in determining which thamnophilid populations have achieved biological species status.

We describe Scytalopus stilesi, an overlooked species of tapaculo endemic to Colombia, on the basis of a series of eight specimens taken in 2002 and comparative analyses of its vocalizations, mitochondrial DNA sequences, and distribution. The new species ranges in the northern half of the Cordillera Central of the Colombian Andes in the Departments of Antioquia, Caldas, and Risaralda, in cloud forests between 1,420 and 2,130 m above sea level. The song, calls, and female song of the new species differ distinctly from those of all other known Scytalopus taxa. Phylogenetic analyses based on sequences of the cytochrome-b gene strongly suggest affinities with S. robbinsi of southwestern Ecuador and with two as-yet-undescribed tapaculos from the Colombian Andes. Scytalopus stilesi coexists locally with, though it is ecologically segregated from, S. atratus, S. latrans, and S. spillmanni. The mid-elevation premontane wet forests to which the new species is restricted have been subject to severe deforestation and fragmentation. The species is, however, relatively common in continuous mature-forest remnants, large primary-forest fragments, riparian forests, and tall secondary-forest patches. We employed a geographic information system (GIS) approach to model the potential distribution of the new species and assess its conservation status under the International Union for the Conservation of Nature (IUCN) criteria. Scytalopus stilesi does not qualify as threatened according to those criteria, but it should be regarded as near threatened. The new species coexists with numerous threatened bird species that are in need of more effective conservation.

We assessed the effects of range disjunction, migratory habit, coloniality, and habitat structure on the genetic differentiation of North American Burrowing Owl (Athene cunicularia) populations. Burrowing Owls in North America comprise two forms or subspecies: A. c. floridana in Florida, separated by ∼1,500 km from the western form, A. c. hypugaea, which ranges from Texas to California and north to southern Canada. Burrowing Owls tend to be loosely colonial, and both the Florida populations and southerly populations of A. c. hypugaea from California to Texas are nonmigratory. To assess genetic structure, we examined 201 individuals from nine western and six Florida populations at seven highly variable microsatellite DNA loci. Mean gene diversity (H_exp) was higher in the west than in Florida (0.539 and 0.341, respectively; P < 0.05). Populations within subspecies were essentially panmictic (A. c. floridana: θ = 0.038, ρ = 0.014; A. c. hypugaea: θ = 0.014, ρ = 0.009) and even genetic differentiation across subspecies was modest (θ = 0.051, ρ = 0.014). Nevertheless, the western and Florida forms were easily distinguished by any of several criteria, such as allelic absences in Florida, assignment tests, and well-supported branches on the inferred phylogenetic tree. Genetic differentiation was at least twice as great in resident Florida (θ = 0.038) and California (θ = 0.021) populations as in migratory western populations (θ = 0.012), though 95% confidence intervals of theta estimates overlapped. We found no evidence of a genetic bottleneck that would result in evolutionary disequilibrium within subspecies. In the west, high observed heterozygosity values and evidence of gene flow suggest that population declines and patchy habitat, which currently imperil this species throughout much of its range, have not led to inbreeding or biologically meaningful genetic differentiation among the sampled populations.

The many hazards that await birds along their migratory routes may negatively affect their survival, especially among newly fledged young. We estimated survival of young Greater Snow Geese (Chen caerulescens atlantica) during fall migration from the High Arctic to temperate areas and examined factors affecting their survival over a five-year period, using two approaches. First, each year (1993–1997), we banded fledglings and adults in mid-August, just before their departure from Bylot Island in the High Arctic (Nunavut, Canada), and again at an important staging area 3,000 km to the south at the Cap Tourmente National Wildlife Area (Québec, Canada) in October; recovery data from those two banding periods allowed estimation of survival during fall migration. Second, we visually determined brood size of neck-banded females before and after the main portion of the migratory flight, to estimate survival of young. The two approaches yielded similar survival estimates and showed the same interannual variation, thus suggesting that estimates were reliable. Mortality of young shortly after fledging and during the fall migration was high, compared with that of adults (monthly survival 0.662 in young vs. 0.989 in adults). However, mortality of young after migration was similar to that of adults (monthly survival 0.969 in young vs. 0.972 in adults). Migration survival of young varied considerably among annual cohorts (range of 0.119–0.707 over five years), and most of the mortality appeared to be natural. Survival was especially low in years when (1) temperatures at time of fledging and start of migration were low (i.e. near or below freezing), (2) mean body mass of goslings near fledging was low, or (3) mean fledging date was late. Our results suggest that migration survival of young is affected by a combination of several factors (climatic conditions, body mass, and fledging date) and that survival is reduced when one of those factors intervenes.

The Cerulean Warbler (Dendroica cerulea) is a species of conservation concern in eastern North America, where declines in its population have been documented over the past several decades. A high proportion of the population occurs in forested areas of southern West Virginia, where it may be threatened by loss and degradation of forested habitat from mountaintop mining and valley fill (MTMVF). We examined, from a landscape perspective, the effects of forest fragmentation (in particular, effects of fragment size and response to edges) on Cerulean Warblers, using territory mapping techniques and geographic information system (GIS) technology in portions of four counties in southwestern West Virginia. We quantified landscape characteristics from digitized aerial photographs and measured microhabitat characteristics on spot-mapping plots. Territory density of Cerulean Warblers was 4.6 territories per 10 ha in intact forest and 0.7 territories per 10 ha in fragmented forest. The best habitat model included both landscape and microhabitat variables and indicated that territory density increased with increasing snag density, percentage of canopy cover >6–12 m and >24 m in height, and distance from mine edge. Models for predicting microhabitat use at the territory level were weak, indicating that microhabitat characteristics of territories were similar to habitat available on spot-mapping plots. The species did not appear to avoid internal edges, such as natural canopy gaps and open-canopy or partially open-canopy roads. Territory placement on ridges was greater than expected, and in bottomlands (ravines) and midslopes less than expected, given availability. Fifty percent of all territories were on ridges. Preference for ridges suggests that MTMVF may have a greater effect on Cerulean Warbler populations than other sources of forest fragmentation, given that ridges are removed in MTMVF. Our data indicate that Cerulean Warblers are negatively affected by mountaintop mining from loss of forested habitat, particularly ridgetops, and from degradation of remaining forests, as evidenced by lower territory density in fragmented forests and lower territory density closer to mine edges.

Egg size is a particularly important life-history trait mediating maternal influences on offspring phenotype. Females can vary their egg-size investment in relation to environmental circumstances, their own breeding condition, and the quality of their mate. Here we analyzed inter- and intraclutch variation in egg size in the Collared Flycatcher (Ficedula albicollis) on the basis of eight years of data. According to our results, mean egg size increased with female condition, but did not differ among young, middle-aged, and old females. The male’s age, body size, and forehead patch size did not influence egg size; thus, we found no evidence for differential investment in egg size in relation to male quality. We found no effect of laying date on egg size when controlling for ambient temperature during the egg formation period, yet temperature had a significant effect on egg size. That result indicates proximate constraints on egg formation. Furthermore, we report on annual differences in intraclutch egg-size variation. Egg size increased within clutches in years with a warm prelaying period; whereas in years when the weather during that period was cold, there was no significant intraclutch trend. Proximate considerations seem to explain the observed patterns of intraclutch egg-size variation; however, we cannot reject the adaptive explanation. Mean egg size and intraclutch egg-size variation were unrelated to clutch size. Therefore, we found no evidence for a trade-off between size and number of eggs within a clutch.

The need for fresh water may affect growth and survival of young waterfowl, including ducklings of sea ducks that are routinely raised in coastal marine habitats. We studied the influence of water salinity on growth and survival of Common Eider (Somateria mollissima) ducklings collected from nests on Southampton Island, Nunavut, Canada, in July 2001 and 2002. In 2001, 50 ducklings were partitioned into five groups (n = 10) and assigned a water salinity treatment for 6.5 days. Treatments included fresh water (<1 ppt NaCl), brackish water (11 ppt or 21 ppt), seawater (33 ppt), and a mixed regime (<1 ppt for 12 h, followed by 33 ppt for six days). In 2002, the experiment was replicated twice with different ducklings. Overall, growth rates were negatively correlated, and mortality rates positively correlated, with water salinity: 3%, 17%, and 60% of ducklings died in the <1-ppt, 11-ppt, and 21-ppt treatment groups, respectively; and 100% died in the 33-ppt and mixed-regime groups. The results confirm that fresh water is required for growth and survival of Common Eider ducklings immediately after hatch, which suggests that sources of fresh water in brood-rearing areas are an important requirement for successful reproduction.

Various studies have shown that experiments on nest defense and enemy recognition (e.g. recognition of adult brood parasites) can be confounded by many factors. However, no study has described a confounding effect of control dummy type. Here, I show experimentally that the choice of control dummy may influence the results of an experiment and lead to erroneous conclusions. I tested recognition abilities of the Blackcap (Sylvia atricapilla), currently a host rarely used by the Common Cuckoo (Cuculus canorus). Blackcaps responded very differently to two kinds of control dummies: they ignored the Eurasian Blackbird (Turdus merula) dummy, but attacked the Rock Pigeon (Columba livia) dummy as frequently as they attacked the Common Cuckoo. The differing results may be explained by the fact that the Rock Pigeon is more similar to the Common Cuckoo than the Eurasian Blackbird is, and consequently elicited more aggressive behavior than the latter. Thus, absence of discrimination in enemy-recognition studies may reflect a methodological artifact resulting from varying abilities of particular hosts to discriminate along a continuum of recognition cues. This result has serious methodological implications for further research on enemy recognition and aggression in general: a control dummy should not be too similar to the dummy brood parasite; otherwise, the chance of detecting existing recognition abilities is low. Further, I argue that coevolution only increases pre-existing aggression in the particular host species. Therefore, increment analysis (assessing changes in host antiparasitic responses during the nesting cycle while controlling for background aggression to control dummies) provides a more accurate picture of hosts' recognition abilities than the traditional approach (when the total level of antiparasitic response is analyzed).

We studied fat stores in passerine migrants at a high-latitude site in Fairbanks, Alaska (64°50'N, 147°50'W). We examined fat-deposition strategies during the final (spring) and initial (autumn) stages of long-distance migration, 1992–1998, to (1) improve understanding of geographic fat-deposition patterns by adding a high-latitude perspective; (2) determine whether there are age-related differences in fat-deposition strategies in autumn; and (3) test the “spring fatter” hypothesis of seasonal fat-deposition, which suggests that migrants should carry more fat in spring when they near their breeding areas than in autumn when they depart. Our analyses examined factors affecting daily fat scores during migration and compared between-season differences in fat stores among a total of 18,685 individuals of 16 migrant species. In autumn, adults had higher visible subcutaneous fat scores than immatures in 11 of 16 species. However, in all but two species, those differences were attributable to the effects of overnight low temperature, day length, and time of day, rather than age, probably because of later departures by adults. Fat scores were higher in autumn than in spring in 6 of 16 species, and body-condition indices were higher in autumn in 5 of 16 species. Only one species showed higher fat scores in spring, but that difference was not reflected in a seasonal comparison of body- condition indices. No species arrived with high fat loads in spring, and generally low fat levels in autumn suggest that high-latitude passerine migrants in North America are paying most of the energetic costs of long-distance migration with resources obtained en route to their wintering grounds. Among passerine migrants near these high-latitude breeding grounds, seasonal fat-deposition strategies appear to be responding to energetic needs at the level of daily maintenance, rather than to hypothesized insurance needs in spring or to the forthcoming needs of a long- distance migration in autumn.

The Aquatic Warbler (Acrocephalus paludicola) has a unique mating system. Males are free of any parental duties and can fertilize many females during a single breeding season. Females also usually copulate with more than one male, and nestlings in a single nest may be sired by as many as five males. Paternal success of 33 Aquatic Warbler males in a Polish population was determined by microsatellite polymerase-chain-reaction analysis. Males infected by blood parasites (trypanosomes) sired fewer offspring, weighed less, and probably arrived later to breeding grounds than uninfected males. Number of nestlings sired by a male correlated positively with its fat deposits and wing length. These findings indicate that male body condition directly influences paternal success. Number of sired nestlings per individual male ranged from one to eight. Reproductive success among males was uneven, with six males (18%) fathering 44% of nestlings in the study area. Males with high reproductive success arrived at the breeding grounds earlier in spring than males with low reproductive success.

Females of some bird species “steal“ the parental care of other breeding individuals by laying eggs parasitically in their nests. In most populations, conspecific brood parasites lay parasitically before laying in their own nests. By contrast, in a young and expanding Common Moorhen (Gallinula chloropus) population, 17.4% (n = 8) of brood parasites laid parasitically when their own clutches were currently being incubated, and 13.1% (n = 6) laid parasitically when they were tending to their young. This result differs from previous data on conspecific brood parasitism in this (and other) avian species and suggests that sitespecific ecological conditions exert differing selective influences on the behavioral development of populations. The behavior adopted by individual vertebrate species may not, therefore, be rigidly fixed throughout their geographic range.

We studied the relationships among weather, reproductive success, and population density over 21 years (1980-2000) in a resident Song Sparrow (Melospiza melodia) population in coastal scrub habitat. Our goals were to test potential relationships between annual variation in weather and reproductive success, to evaluate whether reproductive success is density dependent, and to explore the effects of weather and population density on population dynamics. We analyzed the following components of reproductive success: clutch size, hatching success, fledging success, number of young fledged per successful nest, nestling weight, number of fledglings produced per female, number of broods per female, and probability of nest survival. During the study period, several very wet El Niño-Southern Oscillation (ENSO) events as well as an eight-year period of below-average rainfall occurred. Annual reproductive success and population density showed strong positive relationships to annual rainfall levels. Song Sparrow reproductive success increased with increasing rainfall and peaked at above-average rainfall levels. However, no component of reproductive success was related to an index of variation in the ENSO (i.e. Southern Oscillation Index). The components of reproductive success most strongly associated with rainfall were probability of nest survival and length of the breeding season. Nest predation rates were lower in wetter years. Song Sparrows nested over a longer period in years with higher rainfall and lower summer temperatures, and there was an increase in the number of successful broods per female in wetter, cooler years. Nestling weight was not associated with annual rainfall. Neither clutch size nor the onset of laying was associated with spring temperatures. Warmer summer temperatures were associated with a decrease in number of young fledged per successful nest. We found no evidence for decreased reproductive success in years of higher population density, which suggests that reproductive success was limited primarily by density-independent factors, such as weather. Changes in population density from one year to the next were positively related to rainfall-associated variation in reproductive success and negatively related to population density in the previous year. Rainfall in the previous year explained at least 49% of the annual variation in population density. Thus, population dynamics appeared to be driven both by density-independent and density-dependent factors.

We studied the songs of Wedge-tailed Sabrewings (Campylopterus curvipennis) in six localities from central Veracruz, Mexico, to document structure and variation within and between singing groups in the same geographic region. Wedgetailed Sabrewing songs were acoustically, structurally, and behaviorally complex, rivaling those of other taxa with complex signals. Songs of individual birds were composed of >45 well-differentiated and structurally complex syllables. We found 239 different syllable types across eight recorded singing groups of Wedge-tailed Sabrewings (∼20 syllable types per singing group), with the greatest versatility recorded in hummingbirds to date. The acoustic variation (15 variables) was summarized in three principal components (58% of acoustic variation), in which intragroup variability accounted for most of the observed variation. We found significant differences between and within groups in terms of syllable sharing (Jaccard’s similarity coefficient). Individuals generally shared >50% of syllable types within groups, whereas syllable sharing was <10% between individuals from different groups. The same microgeographic pattern was supported in a UPGMA (unweighted pair-group method with arithmetic mean) analysis where individual songs from each singing group clustered separately. However, songs recorded at the same location differed between seasons, which suggests that this species does not exhibit geographically distinct dialects that are consistent across time. The interplay among this species’ social system, distribution of its floral resources, and microgeographic and temporal variation of its song requires further research.

Within a population, the evolution of migratory behavior is accompanied by a suite of physiological, behavioral, and cognitive adaptations. Spatial memory is associated with the hippocampus in mammals and birds; in some cases, hippocampal neuroanatomy correlates with differences in behavior. In a recent study, a migratory subspecies of sparrow, the Dark-eyed Junco (Junco hyemalis hyemalis), performed better on room-scale spatial memory tests than did a nonmigratory conspecific. Migrants collected after migration also possessed greater hippocampal neuron density, which suggests a neurological basis for differences in spatial memory and a link between migratory behavior and enhanced spatial memory. It is likely that homing behavior, like migration, relies to some extent on spatial memory. In some instances, spatial memory performance has generalized across spatial scales, with pronounced differences at larger scales. We tested whether differences in spatial memory between migrants and nonmigrants, previously observed at a room scale, were detectable at a landscape scale; specifically, we investigated whether differences in homing ability could be detected after displacements of 1–40 km. We found no difference in number of returning individuals or in duration of return. Our results suggest that homing in this species may not rely on aspects of spatial memory that differed in aviary tests.

Some grassland passerine species are considered area-sensitive, but the mechanisms underlying that phenomenon are not understood, particularly on grazed grasslands. Area sensitivity may result from edge avoidance or higher nest predation near edges, both of which may be influenced by predator activity or cattle-induced vegetational differences between pasture edge and interior. We assessed the effect of distance to edge on nest density and predation Savannah Sparrows (Passerculus sandwichensis), Grasshopper Sparrows (Ammodramus savannarum), Bobolinks (Dolichonyx oryzivorus), and meadowlarks (Sturnella spp.) along wooded and nonwooded edges of Wisconsin pastures in 1998-2000 and the activity of potential mammalian nest predators along those edges in 2000-2001. We found a positive relationship between nest density and distance from edge for all edge types combined, but that was not the result of effects of wooded edges: we found no difference in density between nests located <50 or <100 m from wooded versus nonwooded (crop or grassland) edges. Models that included combinations of vegetation structure (e.g. concealment), initiation date, year, or edge variables (or all four) were poor predictors of the probability of nest predation. Placing nests away from edges, therefore, did not reduce the risk of nest predation. Eight species known to prey on grassland bird nests were documented along pasture edges, raccoon (Procyon lotor) being the most common. Frequency of raccoon and thirteen-lined ground squirrel (Spermophilus tridecemlineatus) visitation was higher along wooded edges and nonwooded edges, respectively. Cattle (Bos taurus) activity did not differentially affect vegetation height-density along edges compared with that in the pasture interior. Possible reasons for predation risk being similar in both pasture interiors and edges in a fragmented landscape include the ease with which predators can move within pastures, high percentage of resident grassland predators, and small size (median = 47.2 ha) of pastures.

Migratory birds are subject to the effects of various weather systems during the year. Fluctuations in population size may depend on survivorship of juveniles and adults at various stages of the annual cycle. Severe weather conditions can lower survival, especially in migrating passerines that feed on insects. We investigated the effects of climate and density dependence on survival in a population of Common House-Martins (Delichon urbicum), including variables of weather experienced both in their breeding areas and during autumn migration. Unfavorable weather conditions during autumn migration had a severe negative effect on adult apparent survival, irrespective of sex; whereas temperature in the breeding area and population size explained a significant proportion of variance in juvenile survival. Thus, weather conditions experienced in different areas can regulate various age classes in different ways, which suggests that climate change can have a significant but complex influence on demography in passerine populations.

The incidence of brood parasitism by Brown-headed Cowbirds (Molothrus ater; hereafter “cowbirds“) within host species typically reflects the continental pattern in cowbird abundance across North America, where parasitism is heaviest in the Great Plains. However, we found considerable variation in cowbird parasitism on Dickcissel (Spiza americana) nests within a subregion of the Great Plains (the Flint Hills), where the highest levels of cowbird parasitism on grassland bird nests had been previously reported. Local parasitism frequencies on Dickcissel nests varied latitudinally across the Flint Hills, ranging from 0% to 92% of nests parasitized. Interestingly, we found no obvious patterns in habitat or host attributes that were associated with this steep geographic gradient in brood parasitism. Cowbird parasitism on Dickcissel nests was not correlated with the vertical density of local prairie vegetation, mean nest distance to edge, proportion of forest to grassland habitat surrounding study sites (≤5 to 10 km), geographic variation in host abundance, or Dickcissel density or nest initiation dates. Parasitism frequencies and intensities (number of cowbird eggs per parasitized nest) on Dickissel nests were only significantly related to variation in local female cowbird density. Dickcissel clutch size and apparent fledging success were negatively correlated with local cowbird parasitism levels. Geographic patterns in cowbird abundance within and among regions should be considered when establishing conservation areas for grassland birds or other cowbird hosts of concern.

Understanding nest survival is critical to bird conservation and to studies of avian life history. Nest survival likely varies with nest age and date, but until recently researchers had only limited tools to efficiently address those sources of variability. Beginning with Mayfield (1961), many researchers have averaged survival rates within time-specific categories (e.g. egg and nestling stages; early and late nesting dates). However, Mayfield’s estimator assumes constant survival within categories, and violations of that assumption can lead to biased estimates. We used the logistic-exposure method to examine nest survival as a function of nest age and date in Clay-colored Sparrows (Spizella pallida) and Vesper Sparrows (Pooecetes gramineus) breeding in north-central North Dakota. Daily survival rates increased during egg laying, decreased during incubation to a low shortly after hatch, and then increased during brood rearing in both species. Variation in survival with nest age suggests that traditional categorical averaging using Mayfield’s or similar methods would have been inappropriate for this study; similar variation may bias results of other studies. Nest survival also varied with date. For both species, survival was high during the peak of nest initiations in late May and early June and declined throughout the remainder of the nesting season. On the basis of our results, we encourage researchers to consider models of nest survival that involve continuous time-specific explanatory variables (e.g. nest age or date). We also encourage researchers to document nest age as precisely as possible (e.g. by candling eggs) to facilitate age-specific analyses. Models of nest survival that incorporate time-specific information may provide insights that are unavailable from averaged data. Determining time-specific patterns in nest survival may improve our understanding of predator-prey interactions, evolution of avian life histories, and aspects of population dynamics that are critical to bird conservation.

Phylogenetic relationships among the antpitta genera were studied using DNA sequence data from the mitochondrial genome. The clade representing the traditional “antpitta” genera (Grallaria, Grallaricula, Hylopezus, Myrmothera, and Pittasoma) was found to be paraphyletic, owing to the sister relationship of Pittasoma and Conopophaga. In a previously unreported relationship, Pittasoma was strongly supported as the sister genus to Conopophaga (Conopophagidae). The remaining antpitta genera form a fully resolved and well-supported monophyletic lineage with two major subclades. The first clade consists of the genus Grallaria and supports the subgenera identified by Lowery and O'Neill (1969). The second antpitta clade has Hylopezus as the sister genus to Myrmothera, with Grallaricula as their sister genus. The results here allow for a new interpretation of the morphological characters used in previous studies.

After publication of the Larus phylogeny in Crochet et al. (2002), the taxonomic status of the “Larus thayeri“ and the “L. occidentalis“ specimens that were used in that study came into question. For each of those species, we sequenced the same mitochondrial DNA regions in new specimens of known identity. In addition, specimens of L. glaucescens were included. Results from using those specimens confirm that L. occidentalis was the first to diverge from the large white-headed gulls. Larus glaucescens, on the contrary, is part of the Arctic species clade, which also includes L. hyperboreus, L. glaucoides, L. thayeri, and L. schistisagus. The three new L. thayeri specimens differ substantially in mitochondrial DNA from the previously used sample of L. thayeri and share the same haplotype with L. glaucescens. The significance of this finding is unclear, because relationships within the “Arctic species“ clade are still unresolved; that is attributable to the unusually high incidence of lineage sharing and extremely low divergence of haplotypes in the group.

The following critiques express the opinions of the individual evaluators regarding the strengths, weaknesses, and value of the books they review. As such, the appraisals are subjective assessments and do not necessarily refl ect the opinions of the editors or any offi cial policy of the American Ornithologists' Union.