Phylogeography of the white-breasted nuthatch (Sitta carolinensis): diversification in North American pine and oak woodlands

Pine and oak woodlands are common North American floral communities with distinct regional species composition. The white-breasted nuthatch (Aves: Sitta carolinensis) is a common resident bird of North American pine and oak woodlands, and is distributed continentally across the highly disjunct distribution of these woodlands. We propose three historical hypotheses to explain the evolution of the white-breasted nuthatch in its principal habitat. (i) The species evolved in situ in the regional pine-oak communities and the isolation of populations in these regions is captured in cryptic genetic variation. (ii) Migration of individuals between regions is frequent enough to maintain the widespread distributions and prevent regional divergence. (iii) The species have recently expanded to occupy their current distributions and an insufficient amount of time has passed for divergence to occur. Phylogenetic analysis of mitochondrial DNA (ND2 gene) variation (N = 216) in the white-breasted nuthatch reveals four reciprocally monophyletic clades concordant with the distribution of the regional North American pine and oak woodlands, and supports hypothesis 1 of in situ evolution of populations in the regional pine and oak communities. Within-clade population structure and demographic history are also discussed.     

Variation in migratory behavior influences regional genetic diversity and structure among American Kestrel populations (Falco sparverius) in North America

Birds employ numerous strategies to cope with seasonal fluctuations in high-quality habitat availability. Long distance migration is a common tactic; however, partial migration is especially common among broadly distributed species. Under partial migration systems, a portion of a species migrates, whereas the remainder inhabits breeding grounds year round. In this study, we identified effects of migratory behavior variation on genetic structure and diversity of American Kestrels (Falco sparverius), a widespread partial migrant in North America. American Kestrels generally migrate; however, a resident group inhabits the southeastern United States year round. The southeastern group is designated as a separate subspecies (F. s. paulus) from the migratory group (F. s. sparverius). Using mitochondrial DNA and microsatellites from 183 and 211 individuals, respectively, we illustrate that genetic structure is stronger among nonmigratory populations, with differentiation measures ranging from 0.060 to 0.189 depending on genetic marker and analysis approach. In contrast, measures from western North American populations ranged from 0 to 0.032. These findings suggest that seasonal migratory behavior is also associated with natal and breeding dispersal tendencies. We likewise detected significantly lower genetic diversity within nonmigratory populations, reflecting the greater influence of genetic drift in small populations. We identified the signal of population expansion among nonmigratory populations, consistent with the recent establishment of higher latitude breeding locations following Pleistocene glacial retreat. Differentiation of F. s. paulus and F. s. sparverius reflected subtle differences in allele frequencies. Because migratory behavior can evolve quickly, our analyses suggest recent origins of migratory American Kestrel populations in North America.     

Demographic expansion of parasitic nematodes of livestock based on mitochondrial DNA regions that conflict with the infinite-sites model

Mitochondrial ND4 sequences of populations of four species of parasitic nematodes of livestock were subjected to demographic analyses. Deviation from selective neutrality was detectable using the frequency spectrum of segregating sites and highly negative neutrality statistics. However, the mitochondrial data sets do not comply with the infinite-sites model that underlies these tests, and as a consequence, it was not established whether these features are solely a result of population expansion, or whether aspects of the molecular evolution of these mitochondrial regions are also involved. Coalescent analyses based on Fu's Fs neutrality test, which incorporated estimates of rate heterogeneity, the transition-transversion ratio and nucleotide bias, as well as analyses that are fairly robust to deviations from the infinite-sites model supported population expansion. Also analyses that do not depend on the infinite-sites model suggested historical population expansion of these nematodes. The very similar time since expansion, the absence of signatures of positive selection in ND4 and the logical association with human demography imply that selective sweeps of mitochondrial variants are less probable, and that expansion is the most likely scenario for the parasitic nematodes of livestock. The methods used to characterize the expansion have different assumptions and emphasize different aspects of expansions. The resulting restrictions on the interpretation of expansions are outlined.     

Postglacial population expansion drives the evolution of long-distance migration in a songbird

The evolution of long-distance migratory behavior from sedentary populations is a central problem in studies of animal migration. Three crucial issues that remain unresolved are: (1) the biotic and abiotic factors promoting evolution of migratory behavior, (2) the geographic origin of ancestral sedentary populations, and (3) the time scale over which migration evolves. We test the role of postglacial population expansions during the Quaternary in driving the evolution of songbird migration against prevailing views favoring the role of intraspecific competition. In contrast to previous attempts to investigate these questions using interspecific phylogenies, we adopt an intraspecific approach and examine the phylogeography of a North American songbird, the chipping sparrow (Spizella passerina), which exhibits both long-distance migratory behavior in temperate North America and sedentary behavior in Mexico and Central America. We show that migratory populations descend from sedentary populations in southern Mexico and that migration has evolved as a result of a northward population expansion into temperate North America since the last glacial maximum 18,000 years ago. Migration appears to have evolved rapidly in some species as populations colonized areas of high seasonality in the temperate zone. The phylogeography of the yellow-eyed junco (Junco phaeonotus), a strictly sedentary species, provides a null model supporting the view that northward range expansions were driven solely by environmental factors and not by a predisposition to evolve migratory behavior. These results provide the strongest evidence to date that historical climate patterns can drive the rapid evolution of avian migration in natural populations, and they suggest a general mechanism for the repeated evolution of migration within and across bird lineages.     

Closing the gap: Avian lineage splits at a young,narrow seaway imply a protracted history of mixed population response

The evolutionary significance of spatial habitat gaps has been well recognized since Alfred Russel Wallace compared the faunas of Bali and Lombok. Gaps between islands influence population structuring of some species, and flightless birds are expected to show strong partitioning even where habitat gaps are narrow. We examined the population structure of the most numerous living flightless land bird in New Zealand, Weka (Gallirallus australis). We surveyed Weka and their feather lice in native and introduced populations using genetic data gathered from DNA sequences of mitochondrial genes and nuclear β‐fibrinogen and five microsatellite loci. We found low genetic diversity among extant Weka population samples. Two genetic clusters were evident in the mtDNA from Weka and their lice, but partitioning at nuclear loci was less abrupt. Many formerly recognized subspecies/species were not supported; instead, we infer one subspecies for each of the two main New Zealand islands. Although currently range restricted, North Island Weka have higher mtDNA diversity than the more wide‐ranging southern Weka. Mismatch and neutrality statistics indicate North Island Weka experienced rapid and recent population reduction, while South Island Weka display the signature of recent expansion. Similar haplotype data from a widespread flying relative of Weka and other New Zealand birds revealed instances of North Island—South Island partitioning associated with a narrow habitat gap (Cook Strait). However, contrasting patterns indicate priority effects and other ecological factors have a strong influence on spatial exchange at this scale.     

Does the migration programme constrain dispersal and range sizes of migratory birds?

Aim  It is generally believed that the migration programme constrains the dispersal and hence range sizes of migratory bird species. This conclusion is based on analyses of breeding ranges of migratory versus non-migratory (resident) terrestrial bird species, and rests on the assumption that there are no ecological or evolutionary constraints on extending the non-breeding range. To investigate this assumption, the abilities of migrant and resident terrestrial species to colonize new wintering areas were compared.
Location  Three major wintering regions of long-distance migrants: South America, sub-Saharan Africa and the Indian Subcontinent.
Methods  It was determined whether the relative numbers of residents and short- and long-distance migrants were the same in those species that have dispersed to a novel wintering region as in the source species pools.
Results  At the species level, long-distance migratory species are more likely to have non-breeding ranges that include more than one of the above regions than resident species. This indicates that the dispersal of migratory species is less constrained than that of resident species. The pattern holds irrespective of the inclusion or exclusion of species associated with coastal, freshwater and wetland habitats, and also holds for ecological groups such as aerial feeders. The pattern is most pronounced between the regions separated by the strongest dispersal barriers (South America and sub-Saharan Africa).
Main conclusions  It is unlikely that the migration programme per se constrains dispersal, but rather that difficulties in establishing new non-breeding areas prevent range expansions in migrant species.     

Relationships of bird community structure and species distributions to two environmental gradients in the northern boreal forest

Few studies have explicitly examined avian community structure in the North American northern boreal forest Herein we report upon the results of bird surveys in mature stands of boreal forest in the Great Clay Belt Ontario. Canada We related trends in avian community structure and individual bird species abundance to two environmental gradients described in a landbase classification scheme called the Forest Ecosystem Classification a moisture and a nutrient-richness gradient Variation in environmental characteristics is limited in the Ontario Clay Belt and this was reflected in short environmental gradient lengths However major trends in avian community structure were strongly associated with the nutrient-richness gradient axis summarized by this scheme Analyses of avian community composition indicated a continuum from moist coniferous habitats to drier aspen-dominated mixed woodlands with several bird species occurring in varying abundances across the width of both gradients 48 of the 58 species examined showed statistically significant associations with at least one of the two multivariate gradient axes A smaller proportion of short-distance migrant species were associated with these gradients than were species in either the neotropical migrant or resident categories We used a multivariate variable (habitat breadth) to compare degree of habitat specialization across different migratory groups A large proportion of neotropical migrants showed a high degree of habitat specialization m mature Clay Belt forests, and neotropical species with small habitat breadths were more commonly associated with habitats dominated by broad-leaved deciduous tree species than either short-distance or permanent resident species We discuss our findings in relation to the post-glacial history of the Clay Belt region     

Dispersal Pathways and Genetic Differentiation among Worldwide Populations of the Invasive Weed Centaurea solstitialis L. (Asteraceae)

The natural history of introduced species is often unclear due to a lack of historical records. Even when historical information is readily available, important factors of the invasions such as genetic bottlenecks, hybridization, historical relationships among populations and adaptive changes are left unknown. In this study, we developed a set of nuclear, simple sequence repeat markers and used these to characterize the genetic diversity and population structure among native (Eurasian) and non-native (North and South American) populations of Centaurea solstitialis L., (yellow starthistle). We used these data to test hypotheses about the invasion pathways of the species that were based on historical and geographical records, and we make inferences about historical relationships among populations and demographic processes following invasion. We confirm that the center of diversity and the native range of the species is likely the eastern Mediterranean region in the vicinity of Turkey. From this region, the species likely proceeded to colonize other parts of Europe and Asia via a slow, stepwise range expansion. Spanish populations were the primary source of seed to invade South America via human-mediated events, as was evident from historical records, but populations from the eastern Mediterranean region were also important. North American populations were largely derived from South America, but had secondary contributors. We suggest that the introduction history of non-native populations from disparate parts of the native range have allowed not just one, but multiple opportunities first in South America then again in North America for the creation of novel genotypes via intraspecific hybridization. We propose that multiple intraspecific hybridization events may have created especially potent conditions for the selection of a noxious invader, and may explain differences in genetic patterns among North and South America populations, inferred differences in demographic processes, as well as morphological differences previously reported from common garden experiments.     

Population fluctuations,power laws and mixtures of lognormal distributions

A number of investigators have invoked a cascading local interaction model to account for power‐law‐distributed fluctuations in ecological variables. Invoking such a model requires that species be tightly coupled, and that local interactions among species influence ecosystem dynamics over a broad range of scales. Here we reanalyse bird population data used by Keitt & Stanley (1998, Dynamics of North American breeding bird populations. Nature, 393, 257–260) to support a cascading local interaction model. We find that the power law they report can be attributed to mixing of lognormal distributions. More tentatively, we propose that mixing of distributions accounts for other empirical power laws reported in the ecological literature.     

Heterospecific attraction and food resources in migrants' breeding patch selection in northern boreal forest

We studied experimentally how heterospecific attraction may affect habitat selection of migrant passerine birds in Finnish Lapland. We manipulated the densities of resident tit species (Parus spp.). In four study plots residents were removed before the arrival of the migrants in the first study year, and in four other plots their densities were increased by releasing caught individuals. In the second year the treatments of the areas were reversed, allowing paired comparisons within each plot. We also investigated the relative abundance of arthropods in the study plots by the sweep-net method. This allowed us to estimate the effect of food resources on the abundance of birds. The heterospecific attraction hypothesis predicts that densities of migrant species (especially habitat generalists) would be higher during increased resident density. Results supported this prediction. Densities and number of the most abundant migrant species were significantly higher when resident density was increased than when they were removed. On the species level the redwing (Turdus iliacus) showed the strongest positive response to the increased abundance of tits. Migrant bird abundances seemed not to vary in parallel with relative arthropod abundance, with the exception of the pied flycatcher (Ficedula hypoleuca) which showed a strongly positive correlation with many arthropod groups. The results of the experiment indicate that migrants can use resident tit species as a cue to a profitable breeding patch. The relationship between the abundance of the birds and arthropods suggests that annual changes in food resources during the breeding season probably do not have a very important effect on bird populations in these areas. The results stress the importance of positive interspecific interactions in structuring northern breeding bird communities. Received: 1 September 1997 / Accepted: 22 January 1998     

Broad-scale latitudinal patterns of genetic diversity among native European and introduced house sparrow (Passer domesticus) populations

Introduced species offer unique opportunities to study evolution in new environments, and some provide opportunities for understanding the mechanisms underlying macroecological patterns. We sought to determine how introduction history impacted genetic diversity and differentiation of the house sparrow (Passer domesticus), one of the most broadly distributed bird species. We screened eight microsatellite loci in 316 individuals from 16 locations in the native and introduced ranges. Significant population structure occurred between native than introduced house sparrows. Introduced house sparrows were distinguished into one North American group and a highly differentiated Kenyan group. Genetic differentiation estimates identified a high magnitude of differentiation between Kenya and all other populations, but demonstrated that European and North American samples were differentiated too. Our results support previous claims that introduced North American populations likely had few source populations, and indicate house sparrows established populations after introduction. Genetic diversity also differed among native, introduced North American, and Kenyan populations with Kenyan birds being least diverse. In some cases, house sparrow populations appeared to maintain or recover genetic diversity relatively rapidly after range expansion (<50 years; Mexico and Panama), but in others (Kenya) the effect of introduction persisted over the same period. In both native and introduced populations, genetic diversity exhibited large-scale geographic patterns, increasing towards the equator. Such patterns of genetic diversity are concordant with two previously described models of genetic diversity, the latitudinal model and the species diversity model.     

Gene genealogy and properties of test statistics of neutrality under population growth

We consider the Wright-Fisher model with exponential population growth and investigate effects of population growth on the shape of genealogy and the distributions of several test statistics of neutrality. In the limiting case as the population grows rapidly, the rapid-growth-limit genealogy is characterized. We obtained approximate expressions for expectations and variances of test statistics in the rapid-growth-limit genealogy and star genealogy. The distributions in the star genealogy are narrower than those in the cases of the simulated and rapid-growth-limit genealogies. The expectations and variances of the test statistics are monotone decreasing functions of the time length of the expansion, and the higher power of R(2) against population growth is suggested to be due to their smaller variances rather than to change of the expectations. We also investigated by simulation how quickly the distributions of test statistics approach those of the rapid-growth-limit genealogy.     

Molecular genetic structure and evolution in native and colonized populations of the Chinese mitten crab, Eriocheir sinensis

Chinese mitten crab (Eriocheir sinensis), a native species in China, has populated Continental Europe and North America since 1912. In this paper, the nucleotide variation in the fragments of mitochondrial COII (693 bp), Cytb (766 bp), and nucleotide ITS (706 bp) was analyzed in native (Yantgze, Yellow, and Liaohe Rivers in China) and colonized (Elbe, Rhine, and Thames Rivers in Europe, and San Francisco Bay in North America) populations of the Chinese mitten crab. The major findings are as follows. First, the genetic variability in the native populations is higher than that in the colonized European and North American populations, with the exception of the Elbe River population, which possesses a similar level of variability with the native populations. Second, a remarkable loss of singletons has been associated with the colonization of Chinese mitten crabs. Third, the AMOVA and F _ST results demonstrate that there are no significant genetic differentiations among the populations from the three continents, but there is a significant differentiation between pairwise populations within and among continents. Fourth, it is found that expansion-drift and gene flow pattern are involved in the European populations. The neutrality test and R ₂ statistics suggest that a moderate founder population exists in the colonized populations, and only the Yangtze River population has undergone a recent population expansion. Finally, the results demonstrate that the European populations originate from multiple rivers in China on multiple occasions. The San Francisco population originates from both the native Chinese populations and the colonized European populations, most likely the Thames population.     

Biological relationship between Central and South American Chibchan speaking populations: evidence from mtDNA

We examined mitochondrial DNA (mtDNA) haplogroup and haplotype diversity in 188 individuals from three Chibchan (Kogi, Arsario, and Ijka) populations and one Arawak (Wayuú) group from northeast Colombia to determine the biological relationship between lower Central American and northern South American Chibchan speakers. mtDNA haplogroups were obtained for all individuals and mtDNA HVS-I sequence data were obtained for 110 samples. Resulting sequence data were compared to 16 other Caribbean, South, and Central American populations using diversity measures, neutrality test statistics, sudden and spatial mismatch models, intermatch distributions, phylogenetic networks, and a multidimensional scaling plot. Our results demonstrate the existence of a shared maternal genetic structure between Central American Chibchan, Mayan populations and northern South American Chibchan-speakers. Additionally, these results suggest an expansion of Chibchan-speakers into South America associated with a shift in subsistence strategies because of changing ecological conditions that occurred in the region between 10,000-14,000 years before present.     

Predicted range shifts in North American boreal forest birds and the effect of climate change on genetic diversity in blackpoll warblers (Setophaga striata)

As North American species’ ranges shift northward in response to climate change, populations isolated in high-elevation habitat “islands” at the southern edge of distributions are predicted to decrease in size or be extirpated. Levels of genetic structure and gene flow and the number of private alleles held within these peripheral populations can be used as a measure of the potential loss of genetic diversity due to climate change. We use GIS-based climate niche models to project geographic distributions of 15 boreal forest bird species for the year 2080 under two carbon emissions scenarios to predict the extent to which ranges will shift, leading to the extirpation of isolated populations at the southern periphery of the boreal forest. Breeding distributions of nearly all boreal bird species are predicted to expand as they shift northward, but will dramatically decrease or be completely lost from mountain populations in New York, Vermont, and New Hampshire by 2080. To examine the effect of these shifts on gene pools of migratory bird species we genotyped 178 blackpoll warblers (Setophaga striata) at nine microsatellite loci, sampling four imperiled high-elevation populations and four northern populations. In S. striata 10.4 % of microsatellite alleles were confined to populations expected to be lost due to climate change. However, these accounted for a nonsignificant percent of the genetic structure, and loss of these alleles would not significantly erode species heterozygosity or allelic richness. Our results indicate that isolated southern populations of S. striata, and possibly other migratory species with high gene flow, do not represent genetically isolated, independently evolving units. Efforts to mitigate the effect of climate change on boreal forest birds should focus on species in which peripheral populations harbor significant genetic diversity.     

Phylogeography at large spatial scales: incongruent patterns of population structure and demography of Pan‐American butterflies associated with weedy habitats

Aim Few studies of comparative phylogeography have been conducted at very large spatial scales, encompassing species that are distributed across multiple continents. Several Pan‐American butterfly species associated with weedy, human‐modified habitats were studied using comparative phylogeographic tools to test for the congruence of demographic histories across a range of spatial scales and to investigate the effects of human‐facilitated range expansion. Location North and South America, mainly the southern United States, Brazil and Argentina. Methods The mitochondrial DNA cytochrome c oxidase subunit II region (COII) was sequenced for Hylephila phyleus, Lerodea eufala, Erynnis funeralis and Agraulis vanillae across their North and South American ranges. Data from these conspecifics were compared with variation in COII sequences between allopatric congener pairs on both continents whose ranges approximate the conspecifics and also share similar weedy habitat associations: Ancyloxypha numitor versus Ancyloxypha nitedula, Vanessa annabella versus Vanessa carye, and Euptoieta claudia versus Euptoieta hortensia. We tested for similarities in demographic histories within and across continents for each species using pairwise distances, population genetic statistics, mismatch distributions and deviations from mutation‐drift equilibrium. Results Mean pairwise divergence across continents was lower for Lerodea eufala and Hylephila phyleus (with several shared Pan‐American haplotypes each) compared with Erynnis funeralis and Agraulis vanillae (both with no shared haplotypes). Differentiation between congeneric species pairs was generally significantly higher than conspecific divergence across continents, but North and South American populations of A. vanillae were more divergent than V. annabella and V. carye. We found deviations from mutation‐drift equilibrium in A. vanillae. Population‐level variation was greater than the variation across continents for H. phyleus and L. eufala. Main conclusions We find little congruence in phylogeographic patterns among these taxa across continents, although similar demographic patterns can be detected at smaller regional levels. Except for Californian populations of some species, the North American distributions of these weedy butterfly species appear to largely pre‐date the influences of human‐facilitated range expansion.     

Complete taxon sampling of the avian genus Pica (magpies) reveals ancient relictual populations and synchronous Late‐Pleistocene demographic expansion across the Northern Hemisphere

Previous studies have suggested that bird populations in east Asia were less affected by Pleistocene climatic fluctuations than those in Europe and North America. However, this is mainly based on comparisons among species. It would be more relevant to analyse geographical populations of widespread species or species complexes. We analyzed two mitochondrial genes and two nuclear introns for all taxa of Pica to investigate 1) which Earth history factors have shaped the lineage divergence, and 2) whether different geographical populations were differently affected by the Pleistocene climatic changes. Our mitochondrial tree recovered three widespread lineages, 1) in east Asia, 2) across north Eurasia, and 3) in North America, respectively, with three isolated lineages in northwest Africa, Arabia and the Qinghai‐Tibet Plateau, respectively. Divergences among lineages took place 1.4–3.1 million yr ago. The northwest African population was sister to the others, which formed two main clades. In one of these, Arabia was sister to Qinghai‐Tibet, and these formed the sister clade to the east Asia clade. The other main clade comprised the North American and north Eurasian clades. There was no or very slight structure within these six geographical clades, including a lack of differentiation between the two North American species black‐billed magpie P. hudsonia and yellow‐billed magpie P. nutalli. Demographic expansion was recorded in the three most widespread lineages after 0.06 Ma. Asymmetric gene flow was recorded in the north Eurasian clade from southwestern Europe eastward, whereas the east Asian clade was rooted in south central China. Our results indicate that the fragmentation of the six clades of Pica was related to climatic cooling and aridification during periods of the Pliocene–Pleistocene. Populations on both sides of the Eurasian continent were similarly influenced by the Pleistocene climate changes and expanded concomitantly with the expansion of steppes. Based on results we also propose a revised taxonomy recognising seven species of Pica.     

DNA‐based approaches for evaluating historical demography in terrestrial vertebrates

Contemporary DNA sequences can provide information about the historical demography of a species. However, different molecular markers are informative under different circumstances. In particular, mitochondrial (mt)DNA is uniparentally inherited and haploid in most vertebrates and thus has a smaller effective population size than diploid, biparentally inherited nuclear (n)DNA. Here, we review the characteristics of mtDNA and nDNA in the context of historical demography. In particular, we address how their contrasting rates of evolution and sex‐biased dispersal can lead to different demographic inferences. We do so in the context of an extensive review of the vertebrate literature that describes the use of mtDNA and nDNA sequence data in demographic reconstruction. We discuss the effects of coalescence, effective population size, substitution rates, and sex‐biased dispersal on informative timeframes and expected patterns of genetic differentiation. We argue that mtDNA variationin species with male‐biased dispersal can imply deviations from neutrality that do not reflect actual population expansion or selection. By contrast, mtDNA can be more informative when coalescence has occurred within the recent past, which appears to be the case with many vertebrates. We also compare the application and interpretation of demographic and neutrality test statistics in historical demography studies. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112 , 367–386.     

How consistent are trends in arrival (and departure) dates of migrant birds in the UK?

We examine the first arrival and last departure dates of migrant bird species from, respectively, six and three English area bird reports. Of all 145 bird series, 50% demonstrated significantly earlier arrival in recent years, with the average advance over all species being 0.25 days/year or 12 days earlier over 50 years. Thirty percent of 67 series demonstrated significantly later departure, with the average species delay being 0.16 days/year or eight days later over 50 years. There was greater consistency between species in trends in first arrival than in last departure, with species such as sand martin Riparia riparia significantly earlier at all six sites while, for example, spotted flycatcher Muscicapa striata showed no significant change in arrival at all sites. Significant negative correlations between arrival dates and English temperatures were found for 26% of all series, but temperature effects on departures were less clear. We provide some evidence that trends in arrival dates may be masked by population declines in birds. Since migrant bird populations are in decline generally, this may suggest that the real advance in arrival dates may be greater than that reported here.     

The Flight Apparatus of Migratory and Sedentary Individuals of a Partially Migratory Songbird Species

Variations in the geometry of the external flight apparatus of birds are beneficial for different behaviors. Long-distance flight is less costly with more pointed wings and shorter tails; however these traits decrease maneuverability at low speeds. Selection has led to interspecific differences in these and other flight apparatuses in relation to migration distance. If these principles are general, how are the external flight apparatus within a partially migratory bird species shaped in which individuals either migrate or stay at their breeding grounds? We resolved this question by comparing the wing pointedness and tail length (relative to wing length) of migrant and resident European blackbirds (Turdus merula) breeding in the same population. We predicted that migrant blackbirds would have more pointed wings and shorter tails than residents. Contrary to our predictions, there were no differences between migrants and residents in either measure. Our results indicate that morphological differences between migrants and residents in this partially migratory population may be constrained.