While researchers have made great progress investigating the molt of temperate-zone birds, few studies have examined the molt of tropical birds. We carried out this study in 2009 and 2010 in the cerrado biome, Distrito Federal, Brazil. On the basis of 334 birds captured with mist nets, we describe the timing, duration, and intensity of the flight-feather molt in eight species. Molt scores indicated the direction of replacement and points where molt series started and ended. The innermost primary usually was the first flight feather to drop, and primaries were replaced proximal to distal. Secondaries were replaced in two series, and S6 or S5 typically was the last remex to complete growth. Rectrices were replaced in a single series on each side, from R1 (central) to R6 (lateral). All species replaced their primaries according to the rules followed by most passerines. The White-eared Puffbird (Nystalus chacuru: Galbuliformes) was an exception; it replaced primaries in two molt series and possibly does not molt its secondaries completely every year. In comparison to similar temperate-zone birds, whose molts take 42–105 days tropical birds seem to have a slower metabolism, with molt having an average duration of 122 days and intensity of 3.1 feathers growing simultaneously. Larger species required more time to molt. In four species we found overlap of molt and breeding.

Food availability and acquisition are critical components of a stopover site's suitability, but we know relatively little about how changes in food availability affect the stopover ecology of migrating landbirds. We examined fruit and arthropod availability in three habitats, studied foraging behavior and diet, and investigated use versus availability for passerines migrating through southwestern Idaho in autumn. Hemiptera dominated foliage-dwelling arthropod communities in all three habitats, whereas Hymenoptera were most numerous among ground-dwelling arthropods. Mountain shrubland had relatively high biomass of both ground-dwelling and foliage-dwelling arthropods, whereas conifer forest had high biomass of foliage-dwelling arthropods only and shrubsteppe had high biomass of ground-dwelling arthropods only. Species' foraging behavior varied, but most species foraged in mountain shrubland more often than expected by chance. Diets of most species included a high proportion of certain Hemiptera and Hymenoptera with smaller proportions of Coleoptera, Diptera, and Heteroptera; Coleoptera and some Hemiptera were consistently preferred by most species. Importantly, all 19 bird species examined consumed some fruit, and this is the first documentation of frugivory for two warbler species. These data point to the importance of several arthropod taxa, especially the Hemiptera and Hymenoptera, and fruits to landbirds migrating in mountain shrubland in autumn. Finally, we found no effect of annual variation of fruit or arthropod abundance on migrants' energetic condition, suggesting that food was sufficient for mass gain in all years of this study and/or that foraging behavior may be plastic enough to allow birds to gain mass despite annual differences in food availability.

By searching for carcasses weekly year round, we estimated rates of avian fatality from collision with ten 50-m and eight 60-m temporary meteorological towers supported by guy wires near wind turbines at the Altamont Pass (n = 3) and Collinsville Montezuma Hills (n = 15) wind resource areas in central California. All towers were searched out to 55 m, beyond the farthest guy-wire anchors. Estimates for the total number of fatalities were based on searchers‘ efficiency and scavengers’ removal rates determined empirically at one of the wind farms. In 1632 searches (90.7 ± 5.4 per tower; 136.0 ± 2.8 per month), we found 85 carcasses of 19 species, for an average of 2.8 carcasses per tower per year. When adjusted for searchers‘ efficiency and scavenging, fatalities per tower per year were 6.8 ± 1.1 for all birds. Icterids, the Horned Lark (Eremophila alpestris), pipits, and sparrows accounted for 60% of carcasses, whereas night-migrating songbirds accounted for only 7% of carcasses. This level of mortality likely did not result in population effects because fatalities were spread among many, mostly common species and the towers were temporary structures. Because the towers we studied were similar in structure to guyed communication towers of the same height, our findings are likely applicable to those structures in California. There is currently no other empirical information available on fatality from towers of these heights and support systems, even though they are one of the most common types of such towers in California and elsewhere.

One technique for monitoring population trends of many species of migratory songbirds is to assess changes in population indices at constant-effort mist-netting stations located at sites of migration stopover. However, few studies have attempted to validate this approach. We compared long-term (1969–2001) population trends based on annual variation in capture rates at two banding stations located 30 km apart in southern Rhode Island, with one on the mainland, the other on an offshore island. Of 24 species with sufficient sample sizes, 21 species exhibited a significant linear decline at one or both stations. There was a high degree of conformity in trend-slope directions observed at each station. Annual fluctuations and trend magnitude conformed less well, although there was more concordance for nine transient species that do not breed in southern New England. At both stations trends were similar to those at a migration-monitoring station ∼95 km away in coastal Massachusetts. The trends at this network of three migration-monitoring stations were more negative than those of Breeding Bird Surveys in northern New England and southeastern Canada. Our results demonstrate that constant-effort mist-netting stations could be used to monitor population trends of many species of migratory songbirds, although it is not clear which breeding populations are being monitored. This suggests that banding stations could be used to supplement existing large-scale monitoring programs.

Information regarding microhabitat, here defined as small-scale vegetation structure, is often useful in predicting use of habitat by birds. Quantifying microhabitat, however, is expensive and labor intensive compared to assessment of habitat at a larger scale, possibly from remotely sensed imagery. To assess the importance of microhabitat information in constructing predictive models of habitat occupancy, we compared occupancy models built on the basis of macro- and microhabitat together and separately. We based our models on counts of wintering migratory bird species and vegetation surveys within Tuskegee National Forest, Alabama, completed during winter 2009. Models built from macrohabitat data only outperformed models built from microhabitat data only for five of the six species analyzed. However, the best model for every focal species included both macro- and microhabitat covariates. Pine forests—excluding plantation—were the only land-cover classification important to our focal species, and measures of density of vegetation were important in predicting occupancy. Our results suggest that migrants wintering at our study site select habitat at multiple scales—specializing in certain types of cover and then preferring specific structural aspects of vegetation within them. We conclude that microhabitat information is important for inference into use of habitat by wintering migratory birds.

Ratios of stable isotopes in feathers have great potential for identifying the connectivity of bird migrations and the origin of harvested individuals of game species. In particular, the relationship between the hydrogen ratio due to latitudinal variation in precipitation (δD_p) and that in feathers (δD_f) is often used to determine unknown individuals' latitude of origin. We assessed this relationship between Canada Geese nesting in the temperate zone (Branta canadensis maxima) and the subarctic (B. c. interior). For this game species, the origin of harvested birds is important for developing management that maintains a desirable level of harvest while ensuring continued viability of all subspecies and breeding populations. We collected freshly grown primaries from three populations of interior and five of maxima and analyzed them for δD, δ¹³C, and δ¹⁵N. Multivariate analysis suggested no overall differences in isotopic composition between subspecies. A univariate assessment indicated a significant difference in δ¹⁵N_f, despite substantial overlap between subspecies, and no difference in δD_f or δ¹³C_f. Of particular interest is the lack of difference in δD_f, despite the large latitudinal differences in δD_p and between the subspecies' breeding ranges. Values of δD_f averaged -131.85‰ ± 1.36 for interior, -131.63‰ ± 0.71 for maxima, and we found no overall relationship between δD_f and δD_p. Overall, our results suggest that δD, δ¹³C, and δ¹⁵N alone have limited ability to discriminate between subspecies interior and maxima and hence have limited applicability for estimating the origin of harvested birds and/or identifying molt migrants of maxima.

Directionality is a key feature of vocalizations in birds and can provide insight into vocalizations° function and propagation. Despite recent interest in birds' production of nonvocal acoustic signals, little is known about the directionality of these sounds. Here, we examine the directionality of the drumming display of male Ruffed Grouse (Bonasa umbellus), a nonvocal acoustic signal used in mate attraction and territorial defense. We recorded drumming males with a low-frequency microphone and measured sound-pressure levels with a sound-level meter from three orientations: front (0°), behind (180°), and side (90°). The sound-pressure level was significantly higher in front of and behind a drumming male than on the sides, indicating that the drumming sound radiates primarily along the displaying bird's longitudinal axis. Spectral analyses of the recordings did not, however, yield consistent differences in frequency among the three orientations. The acoustic radiation pattern of the drumming display differs from that of vocalizations in that the sound-pressure levels are just as high behind the bird as they are in front of it. This directionality likely affects estimation of distance by predators and intended receivers as well as potentially limiting the number of receivers able to perceive the signal.

Bryan's Shearwater (Puffinus bryani) was described in 2011 on the basis of a specimen collected on the Midway Atoll in 1963. This specimen and another recorded on Midway in the early 1990s are the sole reliable records to date. Since 1997, we have found six specimens of a remarkably small Puffinus shearwater morphologically similar to Bryan's Shearwater on the Bonin Islands, northwestern Pacific. In this study, we examined the Bonin samples genetically and confirm that they are of Bryan's Shearwater. A morphological analysis suggests that the small body size and relatively long tail are characteristics of this species. Because the most recent individual was found on an islet to the north of Chichijima Island in 2011, the species has evidently survived in the Bonin Islands, where it may breed, although the exact location remains unclear. Three of the individuals found on an islet off Chichijima Island were carcasses preyed upon by black rats (Rattus rattus). Attempts were made to eradicate rats from this island in 2008, and rats may pose a problem on other islands where the shearwaters may breed. Regardless, Bryan's Shearwater appears to be very rare and threatened on the Bonin Islands. To conserve this species effectively, its breeding sites must be identified and the infesting rats eradicated.

In some conservation situations, there is a need for estimates of numbers of seabirds migrating past a specific site, such as sites of proposed offshore wind farms. Migration counts from points strategically located on the coast can be a reliable and effective method of reaching this goal. We propose a consistent and statistically robust method for estimating such numbers by generalized additive modeling of the numbers passing during periods when counts are interrupted. This procedure has the advantage of accounting for the effects of covariates, such as wind, on the counts in a flexible manner, potentially increasing accuracy and precision. We develop a reliable method of estimating precision, based on a parametric bootstrap, and applied a sensitivity analysis to our models to test their accuracy. We demonstrate the method with three species of seabirds migrating through the Strait of Gibraltar. Estimated numbers of the Northern Gannet (Morus bassanus) are similar to the estimated Atlantic population that winters in the western Mediterranean Sea, while for both Cory's (Calonectris diomedea) and Balearic (Puffinus mauretanicus) Shearwaters they are greater than the current population estimates. These results have important implications in conservation and highlight the necessity for reestimation of the latter two species' global population. Potential sources of biases include the constraint on detectability due to distance and the possibility of double counting due to local movements. To avoid overestimates, we suggest that values imputed for the gaps in counts be conservative.

Because of the high, albeit seasonal, availability of carcasses, the Mara-Serengeti ecosystem, Kenya, has a high diversity of scavengers, leading to considerable competition between species. From patterns of occurrence of vultures at 163 carcasses over an 8-year period in the Masai Mara National Reserve, we were able to identify some mechanisms that may reduce competition. Species are associated on the basis of similar dietary needs and beak morphology, and they are highly interdependent, showing little evidence of disassociation. Social vultures (genus Gyps) dominated the vulture scene at the reserve; they were more abundant at carcasses when migratory ungulates were present in the dry season, when more carcasses are likely to be available, than when migratory ungulates were absent. In addition, regardless of the predator's identity, presence of a predator reduced the number of vultures, suggesting that vultures prefer carrion not killed by predators where available. Comparisons between past and current counts of carcasses suggest a substantial shift in Gyps vultures with an increase in the relative abundance of Rüppell's Vulture (G. rueppellii) with respect to that of the White-backed Vulture (G. africanus). In addition, our findings suggest that as changing land use in the Mara-Serengeti ecosystem leads to reductions of large ungulates, social vultures will be the most adversely affected.

The Northern Goshawk (Accipiter gentilis) is the largest of the three North American species of Accipiter and is more closely associated with older forests than are the other species. Its reliance on older forests has resulted in concerns about its status, extensive research into its habitat relationships, and litigation. Our objective was to model the spatial patterns of goshawk territories in the Black Hills, South Dakota, to make inferences about the underlying processes. We used a modification of Ripley's K function that accounts for inhomogeneous intensity to determine whether territoriality or habitat determined the spacing of goshawks in the Black Hills, finding that habitat conditions rather than territoriality were the determining factor. A spatial model incorporating basal area of trees in a stand of forest, canopy cover, age of trees >23 cm in diameter, number of trees per hectare, and geographic coordinates provided good fit to the spatial patterns of territories. There was no indication of repulsion at close distances that would imply spacing was determined by territoriality. These findings contrast with those for the Kaibab Plateau, Arizona, where territoriality is an important limiting factor. Forest stands where the goshawk nested historically are now younger and have trees of smaller diameter, probably having been modified by logging, fire, and insects. These results have important implications for the goshawk's ecology in the Black Hills with respect to mortality, competition, forest fragmentation, and nest-territory protection.

The Rock Sandpiper (Calidris ptilocnemis) is endemic to the Bering Sea region and unique among shorebirds in the North Pacific for wintering at high latitudes. The nominate subspecies, the Pribilof Rock Sandpiper (C. p. ptilocnemis), breeds on four isolated islands in the Bering Sea and appears to spend the winter primarily in Cook Inlet, Alaska. We used a stratified systematic sampling design and line-transect method to survey the entire breeding range of this population during springs 2001–2003. Densities were up to four times higher on the uninhabited and more northerly St. Matthew and Hall islands than on St. Paul and St. George islands, which both have small human settlements and introduced reindeer herds. Differences in density, however, appeared to be more related to differences in vegetation than to anthropogenic factors, raising some concern for prospective effects of climate change. We estimated the total population at 19 832 birds (95% CI 17 853–21 930), ranking it among the smallest of North American shorebird populations. To determine the vulnerability of C. p. ptilocnemis to anthropogenic and stochastic environmental threats, future studies should focus on determining the amount of gene flow among island subpopulations, the full extent of the subspecies' winter range, and the current trajectory of this small population.

We examined daily activity patterns, flock-size variations, use of vertical space, and small-scale habitat selection of the New Caledonian Parakeet (Cyanoramphus saisseti), Horned Parakeet (Eunymphicus cornutus), and New Caledonian Rainbow Lorikeet (Trichoglossus haematodus deplanchii) on mainland New Caledonia. All three species had bimodal patterns of activity, with most encounters occurring in the morning and a second smaller peak of encounters in the late afternoon. The parakeets were usually seen singly or in twos, and most flocks contained fewer than four individuals. Parakeet flocks remained relatively consistent in size through the day and through the year. Most Rainbow Lorikeet flocks contained only a few individuals, though some reached up to 40 birds. Rainbow Lorikeets were encountered mainly in small flocks during the breeding season from September to January, and their average flock size was higher and more variable for the rest of the year. Rainbow Lorikeets selected valley forest and urban areas, where they were most common in parks and gardens. New Caledonian Parakeets favored slope forest over valley forest, and they foraged low, either at the edge of forest, in slope forest, or in maquis (shrubland). Horned Parakeets generally fed at greater heights than did New Caledonian Parakeets, preferred valley forest to slope forest, and avoided maquis. We suggest that the observed difference in habitat use between the New Caledonian Parakeet and Horned Parakeet is the result of spatial resource partitioning, which allows these closely related species to coexist.

In temperate regions of the Southern Hemisphere, avian parental care is understudied, in particular for the neotropical family Furnariidae. We measured rates of nest building, mud carrying, incubation, brooding, feeding, and nest-sanitation behaviors of molecularly sexed Rufous Horneros (Furnarius rufus) nesting in the humid pampas of Argentina. We also evaluated the coordination of all these behaviors between the partners, and compared the frequency of uncoordinated behaviors of each sex. Males and females worked equitably throughout the nesting cycle with few exceptions: (1) both sexes built the nest, but males supplied somewhat less mud at the beginning of nest construction, (2) though highly involved in incubating the eggs males did so slightly less often than females during early incubation, (3) even if males also brooded the nestlings, they brooded less often and for slightly briefer periods than did females, and (4) young nestlings were fed less often by males than by females. We found no differences in nest-sanitation rates. The proportion of behaviors coordinated between partners performing different parental tasks was very high through the entire nesting cycle. Analysis of the frequency of uncoordinated behaviors revealed females were more prone than males to skip turns only at the onset of nest building and the beginning of the nestling period. The sexes' similar and coordinated effort is probably essential for the building of the Rufous Hornero's remarkable nest and reaching the high rate of nest success that characterizes the species.

The geographic range of the Long-tailed Antbird (Drymophila caudata) extends from the Paria Mountains of Venezuela south through the Andes to northern Bolivia, a geographic and elevational distribution unique in the antbirds (Thamnophilidae). Plumage variation among most populations is not obvious, and although eight subspecies have been described, half have been synonymized. We took a multidimensional approach to reexamining the taxonomy of the complex. We identified lineages by evaluating divergence in mtDNA, and defined study groups within them to take into account previously described plumage differences. We then assessed the taxonomic status of principal lineages and study groups by comparing vocal differences among them to established taxonomic “yardsticks” for thamnophilid antbirds. Finally, we related taxa to the ecology of the regions in which they occur. The outcomes revealed substantial diversification, sufficient for recognition of four species, three restricted to the north and one widespread along the main body of the Andes extending from northwestern Colombia south to Bolivia. Speciation in Andean Drymophila antbirds is partially associated with elevational and environmental divergence. The results provide valuable inputs to mapping and understanding avian evolution in the Andes and demonstrate the value of a multifaceted approach in solving taxonomic problems.

Group differences in avian space use relate to group differences in resource use and demographic parameters. However, studies that consider year-round, intraspecific variation in the space use of noncooperatively breeding species are relatively rare. A greater understanding of factors relating to intraspecific variation in space use is especially important for managing human-subsidized predators, such as the Common Raven (Corvus corax). We hypothesized that sex, sociality, and the distribution of bonanzas of food should influence year-round space use by breeding and nonbreeding Common Ravens on the Olympic Peninsula of Washington State. We detected differences in space use between breeders and nonbreeders but not between the sexes. Breeders shared little space with their neighbors and displayed strong site fidelity, except in the fall and winter or after the death of a mate, when some breeding ravens moved extensively. Nonbreeders moved widely, were more gregarious, and their home ranges intersected a greater proportion of communal food resources than did those of breeders. Breeders shared little space with their adult neighbors, but they shared more space with nonbreeders when communal food resources fell within their territories. Pair bonds were broken only by the death of a partner, which in some cases was followed by extensive movements by the surviving adult prior to pairing with a new mate or settling in a new breeding territory. This study is the first to consider the space use of both nonbreeding and breeding Common Ravens in the same population simultaneously.

In species that defend all-purpose breeding territories, territory size is usually inversely related to food abundance, but it is unclear whether this relationship results from reduced need to defend a large territory if food is abundant or from greater competitive pressure from conspecifics. Although studies of both breeding and winter territories suggest that competitive pressure is the proximate determinant of territory size, with food abundance acting indirectly by increasing the density of competitors, results are often equivocal because competitor density and food abundance tend to be positively correlated. In the Tree Swallow (Tachycineta bicolor), an aerial insectivore that defends only nest sites, defense of a food supply is not a determinant of territory size. I describe two series of experiments involving manipulation of nest-box spacing and measurements of insect abundance at four sites at and near Long Point, Ontario, Canada. Rates of occupancy of nest boxes spaced 24 m apart (beyond the normal range of territorial defense) were high at all sites (75–100%) and positively correlated with insect abundance. Occupancy of nest boxes placed 3 m apart (within the range Tree Swallows defend) was 28% to 100%, and the effect of close spacing on occupancy (attributable to territorial behavior) was also positively correlated with insect abundance. I conclude that the latter relationship must result from variation in competitive pressure because the food resource is not defended. Food abundance acts indirectly on occupancy and territory size by influencing the level of competitive pressure for nest boxes.

Microorganisms are known to play an important role in shaping the life histories of animals. Recent studies have proposed that the coloration of birds' plumage could reflect individual quality through associations with feather-degrading bacteria. However, few studies have explored such relationships. We studied breeding female Great Tits (Parus major) during nest building and chick rearing to explore associations between bacteria inhabiting their yellow chest feathers and feather coloration. Specifically, we used flow cytometry and ribosomal intergenic spacer analysis (RISA), respectively, to study the densities of all free-living and attached bacteria and the phylotypic richness of feather-degrading bacterial assemblages. We used chroma (color saturation) as a measure of feather coloration. During chick rearing but not during nest building, the female's chroma was negatively related to the phylotypic richness of feather-degrading bacteria. Also, a seasonal change in the density of attached bacteria associating with individual birds was negatively associated with change in chroma over the same period. These findings suggest that conspicuous coloration of female Great Tits may reflect the numbers and character of bacteria inhabiting feathers.

The rate at which parent birds deliver food to their young may depend on several factors, both intrinsic (e.g., brood demand) and extrinsic (e.g., time of day). Using PIT tags, we determined patterns of nestling provisioning in the Blue Tit (Cyanistes caeruleus) and the proximate factors affecting them. Over 3 years, we monitored the rates of provisioning by Blue Tits in two types of forest (evergreen and deciduous) in Cabañeros National Park (Spain). Pairs breeding in the deciduous forest visited the nest at rates higher than did those in the evergreen forest. Contrary to expectation, males fed their offspring more than females did, and the rates of feeding were positively related to those of the social partner. Sex roles in provisioning were consistent through the day, suggesting that parents did not work in concert. Provisioning rates also tended to decline through the day and were negatively correlated with ambient temperature. In females, but not in males, the adult's body condition was negatively related to provisioning effort. There was no relationship between nestlings' condition and parental provisioning rates. We found a strong correlation between hourly feeding rates and the total number of feedings registered over a 24-hr period, which indicates that short-term samples are representative of what occurs over a longer time. Overall, our study represents a significant contribution to the understanding of proximate factors influencing parental provisioning strategies in altricial birds with biparental care.

The Brown-headed Nuthatch (Sitta pusilla) is listed as a species of conservation concern throughout most of its range. Forest conditions that support the imperiled Red-cockaded Woodpecker (Picoides borealis) are thought to provide excellent habitat for the nuthatch, but ambiguity exists because the nuthatch has disappeared from some areas where the woodpecker persists. We studied Brown-headed Nuthatches in two forest types that spanned an environmental gradient in central Florida and also differed in terms of forest structure and the presence of woodpeckers. Sandhill forests had mature timber that supported a large woodpecker population (∼70 territories); flatwood forests were dominated by younger pines and supported no Red-cockaded Woodpeckers. We used repeated surveys incorporating broadcast vocalizations and patch-occupancy analysis to assess variation in nuthatch occupancy and detection in relation to forest type, four structural covariates (snag density, basal area of pines and hardwoods, and pine diameter), and proximity to Red-cockaded Woodpecker territories. In our best model, occupancy and detection varied in relation to forest type and pine basal area. Occupancy and detection probabilities were higher in the younger flatwood forests and averaged 0.96 and 0.75 as compared to 0.56 and 0.37, respectively, in older sandhill forests. Occupancy and detection were not influenced by proximity to Red-cockaded Woodpecker territories. The higher encounter rates recorded in younger flatwood forests likely stemmed from differences in habitat quality, while variation attributable to forest structure and woodpecker distribution warrants further study.

In the House Wren (Troglodytes aedon), polygyny is characterized by males' partial desertion, males providing little or no help in feeding the nestlings of one of their mates. We evaluated whether contributions to feeding nestlings and patterns of provisioning by partially deserted females can explain geographic variation in the species' rate of polygyny. From 2003 to 2007, we studied two populations differing in polygyny rate (U.S., 40%; Argentina, 2%). We induced polygyny in the monogamous population by removing males from their territories before the onset of egg laying. We predicted that if patterns of parental care are related to variation in the social mating system, monogamous males should contribute more in the monogamous population than in the polygynous population, in the monogamous population partially deserted females should not compensate for the lack of help by feeding at rates higher than do aided females, and partial desertion should be more costly in the monogamous population. Monogamous males of the two populations did not differ significantly in their contribution to provisioning. Females' pattern of provisioning was also similar; partially deserted females fed nestlings at a rate higher than did aided females but did not fully compensate for the lack of help. Furthermore, the cost of male desertion seems greater in the polygynous population, as the breeding and fledging success of poorly aided females were lower. We suggest that the male's contributions to parental care and the patterns of unaided females' feeding cannot explain the geographic variation in the House Wren's mating systems.

In continuous forests, roads may function as barriers to dispersal by forest wildlife. By testing responses to recorded calls, we compared bird movement over a paved road with movement within forest-interior plots in Cuc Phuong National Park, northern Vietnam, in summer 2007. We focused on two mid-story species, the Striped Tit-Babbler (Macronus gularis) and Rufous-throated Fulvetta (Fulvetta danisi), and two ground-feeding species, the Puff-throated Babbler (Pellorneum ruficeps) and Buff-breasted Babbler (P. tickelli). The probabilities of mid-story species' approaching the recording at the road sites were similar to those at the forest-interior sites. The probabilities of the terrestrial species' approaching the recording were lower at the road sites than in the forest interior. For all species, the delay in response was slightly longer at the road sites than at forest-interior sites. Our results indicate that narrow forest roads may inhibit dispersal by understory birds but are less important barriers for mid-story species.

Traits under strong directional or stabilizing selection can nonetheless vary considerably if the selective forces impinging on them vary in strength or direction. Although such variation is commonly manifested between unrelated individuals, some of the largest differences occur between siblings because of differences in their developmental experience. This is exemplified by the broods of altricial birds, in which asynchronous hatching produces a competitive hierarchy that influences an individual's developmental rate and fitness. Using Lincoln's Sparrow (Melospiza lincolnii), I examined whether the order of hatching or the seasonal timing of development (another factor that influences offspring fitness and estimated as the date of initiation of the clutch from which an individual hatched) predicted variation in bill shape, a trait often under strong natural and sexual selection. I measured individuals as nestlings and as adults for a metric of bill shape (height/width) that is associated with an adult male Lincoln's Sparrow's song performance. I found that an individual's bill shape during the nestling stage positively correlated with its bill shape during the adult stage. Nestling bill shape declined (became wider and flatter in cross-section) with hatching order, and the bill shape of both nestlings and adults declined with the individual's seasonal timing of development. These findings raise the possibility of a trade-off between life stages in the optimization of songbird bill morphology and may explain the persistence of suboptimal bill shapes among adult songbirds in the presence of strong stabilizing or directional selection.

The poorly known Pseudochloris mendozae Sharpe, 1888, has usually been considered a subspecies of the widespread Greenish Yellow-Finch (Sicalis olivascens) of the Andes of Peru, Bolivia, northern Chile, and northwest Argentina. In this work, we present data on morphology, vocalizations, ecology, and distribution supporting the recognition of the Monte Yellow-Finch (Sicalis mendozae) (Sharpe 1888) as a full species. S. mendozae is 10% smaller in size (with no overlap in wing or bill measurements), and its average weight is 80% that of S. olivascens. In comparison with S. olivascens, breeding males of S. mendozae are considerably brighter, lack any olive tinge on the throat and breast, lack any dorsal mottling or streaking, and have a brighter olive rump. In fresh plumage nonbreeding males are similar to four other Sicalis species, differing subtly. Female S. mendozae is closest in appearance to the allopatric Patagonian Yellow-Finch (S. lebruni), differing chiefly by its olive rump. The song, complex song, and calls of S. mendozae are diagnostic, though it also imitates some other birds. S. mendozae is endemic to the arid Monte Desert of western Argentina from western Tucumán south to Mendoza, and is parapatric with S. olivascens of high Andean steppes. Contrary to literature reports, S. mendozae is nonmigratory but may move altitudinally, descending to lower altitudes during winter. We propose the recognition of the Monte Desert as a new Endemic Bird Area, based on the overlap of the geographic ranges of several bird species.