We revisit the water penetration and repellency of feathers and these factors' relation to bird behavior and habitat in the light of information that has become available since 1985. We present the physical principles of water penetration and repellency of porous surfaces and their relevance to feathers. We show that the requirements for water repellency of feathers in air and those for resistance to water penetration under water are partly in conflict with each other. Both aspects can be presented and evaluated by the same parameter, expressed in terms of the width 2r and spacing 2d of the barbs, (r d)/r. This parameter is small for water birds, particularly for those that dive frequently and are concerned with water penetration. It is larger for terrestrial birds, which are concerned primarily with water repellency. In each family of water birds, with some exceptions, a balance between water repellency and resistance to penetration exists as an adaptation to their particular habitat and behavioral pattern. For example, we discuss the habit of cormorants and darters of spreading their wings after a period in the water in relation to the value of the parameter. We postulate that information on habitat and behavior and, indirectly, the family identity of water birds, including those of fossil taxa, can be inferred from this parameter.

The tamarisk beetle (Diorhabda spp.), a non-native biocontrol agent, has been introduced to eradicate tamarisk (Tamarix spp.), a genus of non-native tree that has become a dominant component of riparian woodlands in the southwestern United States. Tamarisk beetles have the potential to spread widely and defoliate large expanses of tamarisk habitat, but the effects of such a widespread loss of riparian vegetation on birds remains unknown. We reviewed literature on the effects of other defoliating insects on birds to investigate the potential for tamarisk beetles to affect birds positively or negatively by changing food abundance and vegetation structure. We then combined data on the temporal patterns of tamarisk defoliation by beetles with nest productivity of a well-studied riparian obligate, the Southwestern Willow Flycatcher (Empidonax traillii extimus), to simulate the potential demographic consequences of beetle defoliation on breeding riparian birds in both the short and long term. Our results highlight that the effects of tamarisk biocontrol on birds will likely vary by species and population, depending upon its sensitivity to seasonal defoliation by beetles and net loss of riparian habitat due to tamarisk mortality. Species with restricted distributions that include areas dominated by tamarisk may be negatively affected both in the short and long term. The rate of regeneration and/or restoration of native cottonwoods (Populus spp.) and willows (Salix spp.) relative to the rate of tamarisk loss will be critical in determining the long-term effect of this large-scale ecological experiment.

We present the first quantitative comparative study between current (2006–2008) distributions of landbird and those recorded prior to the massive planting of transgenic soy beans in the Pampas of central Argentina (Narosky and Di Giacomo 1993). We surveyed landbirds along transects covering 23 counties of Buenos Aires province. To allow a comparison between our observations and those of Narosky and Di Giacomo, we used the number of counties in which each species was recorded as an estimate of current and past distributions. We found grassland and wetland specialists in significantly fewer counties than did Narosky and Di Giacomo (P < 0.05), while habitat generalists and woodland specialists showed no significant change. The earlier study, however, covered a longer period of time, which could explain the reduction of wetland dwellers as a result of variation in the supply of temporary water bodies. The decreased area of occupancy of grassland specialists, on the other hand, may reflect the reduction of native grasslands due to increased agricultural cultivation, particularly in the Rolling Pampa, where agricultural expansion has left few remnant grasslands and we did not detect three formerly common grassland specialists, Hymenops perspicillatus, Embernagra platensis, and Pseudoleistes virescens. These findings emphasize the need for conservation actions to support populations of grassland bird in the Pampas.

Weather has a significant effect on avian migration, but whether the influence is similar across diverse geographic regions and across all species remains to be determined. We evaluated the effect of regional cold fronts and localized weather phenomena on the timing of autumn migration of multiple species of landbirds and raptors in southwest Idaho. The focus of the analysis was on total landbirds and the ten most common landbird species, along with total raptors and the eight most common raptor species. Using 13 years of data from the Idaho Bird Observatory in southwest Idaho (1997–2009), including standardized mist-net captures of landbirds and counts of raptors during autumn migration, we determined significant patterns that advance our understanding of the variables influencing avian migration in the West. Our data show a depression of numbers of most migratory species on the days immediately before, during, and after the passage of a cold front, with peak flights of most species occurring several days prior to or after cold fronts. This pattern was further substantiated by a detailed analysis of many weather variables illustrating that the majority of species choose to migrate during calmer winds, high pressure, and between cold fronts when the opportunity presents itself. In the Intermountain West, cold fronts are fewer in fall than in much of the rest of North America, so migrants may have greater choice of conditions under which to migrate and this behavior may be more common.

Large concentrations of migrating landbirds in cities have been well documented, but the refueling conditions urban stopover sites provide are almost entirely unknown. We compared plasma triglyceride (indicator of mass gain) and B-OH-butyrate (indicator of mass loss) concentrations in landbirds in three New York City forests to those of conspecifics in two less disturbed, non-urban forests outside the city to evaluate the quality of urban stopover habitats. We quantified diurnal mass gains with regressions of body mass and capture time and measured arthropod biomass in leaf litter to assess food abundance for ground-foraging insectivores. Metabolite concentrations in Ovenbirds (Seiurus aurocapilla) at urban and non-urban sites did not differ during spring or autumn. In autumn, triglyceride levels of Swainson's Thrushes (Catharus ustulatus) indicated significantly higher refueling rates at the urban sites. In the Yellow-rumped Warbler (Dendroica coronata), butyrate was lowest out-side the city, suggesting better refueling conditions there, but differences in triglyceride did not suggest a consistent difference between the habitats in refueling rates. Autumn triglyceride and butyrate levels of three additional species did not indicate different rates of refueling within and outside the city. In the city, significant mass-gain rates ranged from 1.0 to 2.5% of total body mass hr^-1. At no point during either season was there a consistent difference between habitat types in arthropod biomass. Our results suggest that although the availability of stopover habitats may be low in cities, migrating birds using these sites may refuel at rates comparable to those stopping in less disturbed areas.

We examined chronology and intensity of molt and their relationships to nutrient reserves (lipid and protein) of Lesser Scaup (Aythya affinis) to test predictions of two competing hypotheses. The “staggered cost” hypothesis states that contour-feather molt is nutritionally costly and should not occur during nutritionally costly periods of the annual cycle unless adequate nutrients are available. The “breeding plumage” hypothesis states that prealternate molt must be complete prior to nesting, regardless of nutrient availability. Males and females were completing prebasic molt during winter (Louisiana) and had similar molt intensities. Females underwent prealternate molt during spring migration (Illinois and Minnesota) and prebreeding (Manitoba) periods; 53% and 93% of females were in moderate to heavy molt in Minnesota and Manitoba, respectively, despite experiencing other substantial nutritional costs. Intensity of prealternate molt was not correlated with lipid reserves even though females, on average, were nutritionally stressed. Molt intensity was not negatively correlated with protein reserves at any location. Chronology and intensity of prealternate molt varied little and were not temporally staggered from other nutritionally costly events. Prealternate molt did not influence nutrient reserves, and nutrient reserves likely were not the ultimate factor influencing chronology or intensity of prealternate molt of females. We surmise that nutrients required for prealternate molt come from exogenous sources and that the “staggered cost” hypothesis does not explain chronology of prealternate molt in female Lesser Scaup; rather, it appears that molt must be complete prior to nesting, consistent with the “breeding plumage” hypothesis.

It is often assumed (explicitly or implicitly) that animals select habitat features to maximize fitness. However, there is often a mismatch between preferred habitats and indices of individual and population measures of performance. We examined the influence of fine-scale habitat selection on the overall population performance of the White-tailed Ptarmigan (Lagopus leucura), an alpine specialist, in two subdivided populations whose habitat patches are configured differently. The central region of Vancouver Island, Canada, has more continuous and larger habitat patches than the southern region. In 2003 and 2004, using paired logistic regression between used (n = 176) and available (n = 324) sites, we identified food availability, distance to standing water, and predator cover as preferred habitat components . We then quantified variation in population performance in the two regions in terms of sex ratio, age structure (n = 182 adults and yearlings), and reproductive success (n = 98 females) on the basis of 8 years of data (1995–1999, 2002–2004). Region strongly influenced females' breeding success, which, unsuccessful hens included, was consistently higher in the central region (n = 77 females) of the island than in the south (n = 21 females, P = 0.01). The central region also had a much higher proportion of successful hens (87%) than did the south (55%, P < 0.001). In light of our findings, we suggest that population performance is influenced by a combination of fine-scale habitat features and coarse-scale habitat configuration.

In many species of birds, periods of incubation of eggs within a clutch depend on the order in which the eggs were laid and determine whether the eggs hatch asynchronously or on the same day. Magellanic Penguins (Spheniscus magellanicus) lay two eggs 4 days apart that hatch 2 days apart; first eggs take 41 days to hatch, and second eggs take 39 days. We tested whether temperatures of the two eggs differ and whether delayed onset of incubation caused this pattern. First eggs were cooler than second eggs during their first few days (P < 0.001). First eggs averaged 23.4 ± 0.3 °C in the first 24–48 hours after they were laid. Second eggs averaged 27.9 ± 0.3 °C, warm enough for development. Egg temperature did not stabilize (33.9 °C) until eggs were about 18 days old. We swapped first and second eggs of different nests to determine if parental behavior caused the differences in temperatures and incubation periods. First eggs treated as second eggs developed as fast as control second eggs, and second eggs treated as first eggs developed nearly as slowly (40 days) as control first eggs. First eggs that were stored in a cooler until second eggs were laid took 2 days longer to hatch than control first eggs. Parental incubation behavior explained why the incubation period of second eggs was shorter than that of first eggs and controlled asynchrony of hatching, which affects chick growth and survival.

We compared the plumage, morphology, and the alarm call of two taxa of the Gray Hawk (Buteo nitidus) from north and south of a distributional gap in the species' range in Costa Rica. We found all age and sex classes completely distinguishable on the basis of several discrete plumage features. Three of four age and sex classes were diagnosably distinct by measurements of external morphology alone, and the two taxa had diagnosably different alarm calls. On the basis of the level and stability of morphological differentiation, and consistent with prior work suggesting substantial genetic differentiation between the two taxa, we recommend they be recognized as full species, B. nitidus, the Gray-lined Hawk, south of the distributional gap in Costa Rica, and B. plagiatus, the Gray Hawk, north of the gap.

We used satellite telemetry to investigate the migration patterns and wintering areas of Glaucous-winged Gulls (Larus glaucescens) from Middleton Island, Alaska, where this species' population increased tenfold from the 1970s to the 1990s. Fall migration spanned 11 weeks, including numerous stopovers en route, apparently for feeding. Spring migration from wintering sites to Middleton Island was shorter (4 weeks) and more direct. One juvenile spent several months in southern Prince William Sound. An adult spent several months near Craig, southeast Alaska, while three others overwintered in southern British Columbia. For all four wintering adults use of refuse-disposal sites was evident or strongly suggested. Commensalism with humans may have contributed to the increase on Middleton, but a strong case can also be made for a competing explanation-regional recruitment of gulls to high-quality nesting habitat in Alaska created after the earthquake of 1964. An analysis of band returns reveals broad overlap in the wintering grounds of gulls from different Alaska colonies and of gulls banded on the west coast from British Columbia to California. The seasonal movement of many gulls from Alaska is decidedly migratory, whereas gulls from British Columbia, Washington, and Oregon disperse locally in winter.

We examined the effects of the introduced gypsy moth (Lymantria dispar) on seven species of North American woodpeckers by matching spatially explicit data on gypsy moth outbreaks with data on breeding and wintering populations. In general, we detected modest effects during outbreaks: during the breeding season one species, the Red-headed Woodpecker (Melanerpes erythrocephalus), increased over pre-outbreak levels, while during the winter one species, the Yellow-bellied Sapsucker (Sphyrapicus varius), increased and one, the Downy Woodpecker (Picoides pubescens), decreased from pre-outbreak levels. Responses following outbreaks were similarly variable, and in general we were unsuccessful at predicting population responses to outbreaks from a priori knowledge of woodpecker ecology and behavior. We did, however, find evidence that the response of at least half of the species changed over the 34-year period covered by the study: except for the Northern Flicker (Colaptes auratus), whose response to outbreaks during the winter decreased, populations generally responded more positively to outbreaks with time. This temporal response suggests that North American woodpeckers may be taking greater advantage of the resource pulse and/or habitat changes caused by outbreaks of this exotic pest now than previously, so in the future the effects of gypsy moth outbreaks on these species may increase.

The endangered Red-cockaded Woodpecker (Picoides borealis) is a cavity-limited cooperative breeder that excavates cavities in living pines and maintains a resin barrier that repels rat snakes (Elaphe obsoleta and E. guttata), its principal predators. Heterospecific occupants of Red-cockaded Woodpecker cavities (cavity kleptoparasites) exacerbate the limitation of cavities. However, heterospecifics do not maintain the resin barrier, which deteriorates without upkeep. Thus, we predicted that heterospecific occupants of Red-cockaded Woodpecker cavities should suffer rates of nest predation higher than the Red-cockaded Woodpecker's. We compared the daily nest-survival rates of the Red-cockaded Woodpecker and two heterospecific occupants of its cavities, the Red-bellied Woodpecker (Melanerpes carolinus) and Great Crested Flycatcher (Myiarchus crinitus), in two forests in northern Florida. Results from both forests supported the differential-predation hypothesis. Although during incubation the three species' daily nest-survival rates were similar, the primary cause of failure was hatching failure for Red-cockaded Woodpeckers but predation for the two heterospecific occupants. During the nestling stage, daily nest success was significantly higher for Red-cockaded Woodpeckers than for Red-bellied Woodpeckers or Great Crested Flycatchers and similar for the latter two species (i.e., Red-cockaded Woodpecker » Red-bellied Woodpecker ≥ Great Crested Flycatcher); predators destroyed 3–6% of Red-cockaded Woodpecker nests and 21–37% of kleptoparasite nests. We hypothesize that rat snakes have an indirect positive effect on the Red-cockaded Woodpecker (increased cavity availability) by preying differentially on heterospecific occupants of its cavities.

We assessed interspecific ecological relationships between Say's (Sayornis saya) and Eastern (S. phoebe) phoebes at three scales by developing ecological niche models at two spatial extents and comparing the models' predictions with data from local-scale surveys. The two species' habitats differed in several environmental attributes, primarily precipitation, temperature, and vegetation indices, at both extents. Local-scale surveys between -97° and -101° longitude revealed a steep gradation in ratios of occurrences Say's to the Eastern Phoebe, increasing from east to west. Local-scale occurrences coincided with results of ecological niche models at the extent of both the continent and contact zone, except for Eastern Phoebe occurrences and vegetation indices at both extents. Say's Phoebes nested in open country with sparse or no surrounding woodland, whereas Eastern Phoebe nests were primarily along woodland streams but also at seven sites in more open country where Say's Phoebes had nested previously. At the contact-zone extent, the niche space of the Eastern Phoebe was embedded more into that of Say's Phoebe than the converse. Although niche models at the contact-zone extent indicated some potential for contact, competition between these two species for nest sites is probably less important in limiting distributions than are autoecological characteristics.

Using portions of three mitochondrial genes to resolve the uncertain systematic relationships, we constructed a phylogeny of the “gray shrikes” in the genus Lanius. We used the tree and estimates of the rate of evolution of passeriform mtDNA genes to project the nodes' ages and to assess the pattern and age of egg-rejection behavior in shrikes. Our results suggest that Lanius excubitor and L. m. meridionalis are sister taxa and that this clade is sister to L. ludovicianus, then L. sphenocercus is sister to this clade. Lanius excubitor from the Old World was considerably diverged from both New World species and part of a clade also containing four other subspecies of L. meridionalis. The paraphyly and sequence divergence between New World and Old World L. excubitor suggest that these populations represent distinct species. Mapping egg rejection onto the phylogeny suggests that rejection is deeply rooted in shrikes, as it is present as deep as two species, L. collurio and L. bucephalus, that are outgroups to the gray shrikes and in the derived L. ludovicianus. Rejection in L. ludovicianus may have been retained as long as 1.1–1.8 million years, since its clade split from the Old World L. sphenocercus, providing more evidence that once hosts evolve rejection they retain it for long periods of time. These results suggest hosts are becoming increasingly resistant to brood parasitism, which will force parasites to specialize on a few host species.

Chickadees and tits excel at identifying and exploiting novel food sources. One such food source in western North America is the larvae of Urophora gall flies (Diptera: Tephritidae), which were recently introduced to help control the spread of spotted knapweed (Centaurea maculosa). In winter, Black-capped Chickadees (Poecile atricapillus) of many western populations spend much of their time foraging exclusively on this new and rich food source. Because the number of gall flies within knapweed seedheads varies, I examined whether chickadees preferentially selected seedheads with high densities of prey. In large, semi-natural, outdoor aviaries, I presented bouquets of knapweed seedhead to chickadees and allowed them to forage until approximately half of the seedheads were removed. Seedheads rejected by chickadees had significantly fewer larvae than did seedheads not exposed to chickadee predation, indicating that chickadees had selected and removed seedheads with high densities of gall flies. Seedhead size was positively correlated with the number of insects housed within, and chickadees preferentially removed larger than average seedheads while foraging. These results indicate that size is one reliable cue that chickadees might use to select seedheads with high gall fly density. However, chickadees were more successful at selecting seedheads with higher larval density than expected if they used size alone, which suggests that these birds may also use other cues to further increase their foraging efficiency. This study demonstrates the types of subtle decisions chickadees and other birds make even when foraging on relatively novel food sources.

Habitat quality of a bird's breeding grounds has been typically evaluated by investigating patterns in nesting success, whereas events that follow fledging have been largely ignored. One especially overlooked aspect of breeding-habitat quality is how habitat affects the survival of young birds after they leave the nest, a period when mortality is notoriously high. We studied survival of fledglings of two mature-forest species, the Ovenbird (Seiurus aurocapilla) and Worm-eating Warbler (Helmitheros vermivorum), to identify intrinsic (e.g., age, condition) and extrinsic (e.g., habitat structure) factors that influence survival. From 2004 to 2007, we radio-tagged 51 Ovenbird and 60 Worm-eating Warbler fledglings in southeast Ohio. We recorded the birds' locations daily and compared vegetation structure at the fledglings' and paired random locations. Using known-fate models in program MARK, we calculated post-fledging survival to be 65% for the Ovenbirds (51 days after fledging) and 67% for the Worm-eating Warblers (31 days after fledging). Fledglings' condition at the time of radio tagging was positively related to survival after fledging, implying carryover effects from the nestling period. Fledglings of both species used dense vegetation with 40–60% more woody stems in the understory than at random locations. Moreover, use of dense vegetation actually promoted survival. Although riparian thickets and tree-fall gaps within some forests may provide abundant habitat for fledglings, other forests may lack the structural attributes that promote fledglings' survival. Our findings highlight the importance of both breeding and post-fledging requirements being considered in avian conservation plans.

We evaluated hypotheses that seek to explain breeding strategies of the Louisiana Waterthrush (Parkesia motacilla) that vary across a latitudinal gradient. On the basis of data from 418 nests of color-banded individuals in southwestern Pennsylvania and 700 km south in the Georgia Piedmont, we found that clutch size in replacement nests and probability of renesting were significantly greater in Pennsylvania (clutch size 4.4; renesting probability 0.66) than in Georgia (clutch size 3.8; renesting probability 0.54). Contrasts of the remaining measures of breeding were not statistically significant, and, in particular, mean daily nest survival in the two study areas was nearly identical (0.974 in Pennsylvania; 0.975 in Georgia). An individual-based model of fecundity (i.e., number of fledged young per adult female), predicted that approximately half of the females in both Pennsylvania and Georgia fledge at least one young, and mean values for fecundity in Pennsylvania and Georgia were 2.28 and 1.91, respectively. On the basis of greater support for the food-limitation hypothesis than for the season-length hypothesis, the trade-off between breeding in a region with more food but making a longer migration may be greater for waterthrushes breeding farther north than for those breeding farther south.

Invasive plants represent a serious threat to native biodiversity worldwide through direct competition with native species and indirect effects resulting in ecosystem-level changes. In the western U.S., the sagebrush ecosystem has been seriously altered by the invasion of cheatgrass (Bromus tectorum), an exotic annual, and other species including smooth brome (B. inermis), an exotic perennial. We monitored 112 Brewer's Sparrow (Spizella breweri) nests (2006 and 2007) in Grand Teton National Park, Wyoming, to assess the potential effects of a smooth brome vs. native understory on nest survival in sagebrush steppe. Brewer's Sparrows settled earlier and clutch size was larger in native habitat, but indices of nest success were higher in the exotic habitat. Rates of failure and nest predation were higher in the native habitat. Using the logistic-exposure method, we compared estimates of survival in the two habitats. The model with the greatest support, according to AIC_c model-selection criteria, consisted of year and percent cover of smooth brome. Daily survival was higher in the exotic habitat in both years combined and in 2007 alone. The hot, dry conditions of both years may have contributed indirectly to the year effect by influencing the abundance and distribution of predator and prey. The observed increase in daily nest survival with increasing cover of smooth brome suggests that in this situation, Brewer's Sparrows benefited from the presence of smooth brome. The denser smooth brome may serve as a refugium for insects during hot, dry summers. Smooth brome may also increase nest concealment.

More accurate estimates of survival after nestlings fledge are needed for population models to be parameterized and population dynamics to be understood during this vulnerable life stage. The period after fledging is the time when chicks learn to fly, forage, and hide from predators. We monitored postfledging survival, causespecific mortality, and movements of Grasshopper Sparrows (Ammodramus savannarum) in grassland managed with fire and grazing. In 2009, we attached radio transmitters to 50 nestlings from 50 different broods and modeled their survival in response to climatic, biological, and ecological variables. There was no effect of treatment on survival. The factor most influencing postfledging survival was age; no other variable was significant. The majority of chicks (74%) died within 3 days of radio-transmitter attachment. We attributed most mortality to mesopredators (48%) and exposure (28%). Fledglings' movements increased rapidly for the first 4 days after they left the nest and were relatively stable for the remaining 10 days we tracked them. On average, fledglings took flight for the first time 4 days after fledging and flew ≥10 m 9 days after fledging. Our data show that the Grasshopper Sparrow's survival rates may be less than most models relying on nest-success estimates predict, and we emphasize the importance of incorporating estimates of survival during the postfledging period in demographic models.

Tropical vertebrates are considered to have greater flexibility in the timing of life-history stages than are temperate-zone vertebrates. Yet the annual cycles of most resident tropical species are poorly understood, making latitudinal comparisons of phenology difficult. We investigated the reproductive seasonality and synchrony of a mid-elevation (∼2100 m), equatorial population of the Rufous-collared Sparrow (Zonotrichia capensis) and compared our data with data from three other populations of Zonotrichia across a range of latitudes and elevations (one equatorial high-elevation population of Z. capensis and two temperate-zone populations of Z. leucophrys, one at high elevation and one at sea level). We predicted that (1) the reproductive synchrony and seasonality of temperate-zone populations should be greater than those of the equatorial populations and (2) the reproductive synchrony and seasonality of populations breeding at high elevations should be greater than those of populations breeding at lower elevations. We found no seasonal pattern in the proportion of adults' life-history stages in the mid-elevation equatorial population of Z. capensis. Broader comparisons revealed that the reproductive synchrony and seasonality of temperate-zone populations were not always higher than those of the equatorial populations. Elevation of the breeding population had a strong effect on reproductive seasonality in both temperate-zone and equatorial populations. However, reproductive synchronies of temperate-zone populations were very different, while those of equatorial populations were similar. Thus elevation and climatic factors associated with latitude of breeding are important to reproductive seasonality and synchrony.

Knowing the extent to which the acoustic structure of songs is temporally stable is essential to understanding how cultural evolution affects song dialects in oscines. The acoustic structure of the most prevalent variant of the flight-whistle song recorded from male Brown-headed Cowbirds (Molothrus ater) in the Mammoth dialect (Mammoth Lakes, California) from 2005 to 2009 differed significantly and consistently from whistles recorded in 1989 and 1978–1985. The most common whistle variant in the 2005–2009 sample had structural features absent from whistles described in the earlier studies and overall was produced at a consistently lower acoustic frequency. Besides the emergence of this new variant sometime between 1989 and 2005, the prevalence of other variants of the whistle also changed from 1978 to 2009. Changes reported in other studies of cultural evolution in oscines have been based on lower-level structural elements (notes and syllables), whereas we found that entire songs appear to have evolved as cultural units or memes. We discuss possible mechanisms as to how these changes may have occurred. Despite these changes, the Mammoth whistle still retained the same basic three-syllable structure it had 31 years ago. This stability is notable because of the potential for extreme variation in whistle structure exemplified by the distinct whistles of nearby dialects in the region.

The decline of House Sparrow (Passer domesticus) populations in eastern North America has been proposed to be a consequence of competition between the House Sparrow and the House Finch (Carpodacus mexicanus), both introduced species. Previous research testing the hypothesis that House Sparrow declines are due to competition with House Finches focused on populations in the northeastern U.S., excluding other regions where the species coexist. We tested for effects of competition between these two species in the southeastern U.S. at two scales of analysis. First, we looked for evidence of competition at a local scale during the breeding season by examining patterns of co-occurrence of House Finches and House Sparrows at count points within a 28.3-km² study area centered on Auburn, Alabama. Second, we tested for the effects of competition at a regional scale across seven southeastern states by analyzing trends in Christmas Bird Count data. Using null-model analysis, we found no evidence for competitive exclusion in our assessment of local co-occurrence, suggesting that if there is competition between these species it is not important enough to affect their spatial distribution during the breeding season. At the regional scale, contrary to findings in the northeastern U.S., the decline of House Sparrow populations within the southeastern U.S. was not significantly correlated with House Finch abundance. Our results suggest that competition with House Finches is not a major cause of decline of the House Sparrow population in the southeastern U.S.