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In North America, the population genetic structure of many raptor species has been shaped by patterns of post‐glacial population expansion and anthropogenic forces, such as the widespread use of the organochlorine pesticide dichlorodiphenyltrichloroethane (DDT) during the mid‐20th century. While common themes of post‐glacial avian population expansion have emerged, little is known about the genetic impacts of DDT on raptor species that experienced a population bottleneck but were not the focus of conservation efforts. We investigated how the combination of post‐Pleistocene environmental change and the DDT‐era population bottleneck have influenced the contemporary population structure of Merlins Falco columbarius in North America. We genotyped migrating Merlins across North America (n = 272) at 23 polymorphic microsatellite loci and generated sequence data for a 569‐base‐pair segment of the mitochondrial control region. We used hierarchical analysis of molecular variance, pairwise FST/ϕST comparisons and Bayesian clustering analyses to assess genetic differentiation between individuals from eastern and western North America, distinct migratory flyways, and three recognized North American subspecies. Across all analyses, we found low or no population differentiation, suggesting that North American Merlins largely comprise one panmictic population showing evidence of a post‐glacial population expansion with little genetic differentiation detected between regions. Furthermore, we did not detect a contemporary signal of a genetic bottleneck that could have resulted from the DDT‐era population decline with the markers used in this study. Consistent with other avian species, we found a correlation between allele length variation at a microsatellite isolated from the 3′ untranslated region of the ADCYAP1 gene and migratory versus sedentary characteristics in Merlin subspecies. We detected two common mitochondrial control region haplotypes in the geographical regions sampled, a unique pattern among other widespread North American raptor species. This study furthers our understanding of the genetic and demographic history of Merlins in North America and can inform future genomic studies of this species. [ABSTRACT FROM AUTHOR]

During autumn migration, bird‐eating raptors are thought to rely on flocks of migrant songbirds (Passeriformes) as a critical resource to fuel the energetic demands of long‐distance migration. However, this hypothesis has been challenging to investigate, and the foraging ecology during migration of most migrant raptors remains unexplored. To address these knowledge gaps, our objective was to document the diet of a bird‐eating falcon on active migration. We swabbed visible and trace prey residues from the exterior surface of beaks and talons of migrant juvenile Merlins Falco columbarius in the autumn of 2015 and 2016 at a raptor migration monitoring station positioned on the Pacific Coast of western North America. We used a DNA metabarcoding approach and detected the presence of 40 distinct prey species derived from 210 individual prey species detections on 63 of the 72 (87.5%) migrant juvenile Merlins sampled. We detected an average of 3.3 ± 1.6 prey species on individual Merlins. We found that juvenile males selected smaller prey on average compared with juvenile females. Of the prey species detected, over 80% were migratory songbird species within the Pacific Flyway. In 2015, we detected a greater proportion of irruptive migrants in juvenile Merlin diet compared with 2016. In 2016, we found that the proportion of annual migrants consumed by Merlins corresponded to the timing of peak annual songbird migration in the Pacific Flyway. This study represents one of the first detailed descriptions of songbird prey species consumed by a migrating raptor and supports the hypothesis that migrating juvenile Merlins rely on migrant songbirds to support the energetic demands of migration. [ABSTRACT FROM AUTHOR]

The large-scale patterns of movement for the Sharp-shinned Hawk (Accipiter striatus), a small forest hawk found throughout western North America, are largely unknown. However, based on field observations we set out to test the hypothesis that juvenile migratory A. striatus caught along two distinct migration routes on opposite sides of the Sierra Nevada Mountains of North America (Pacific Coast and Intermountain Migratory Flyways) come from geographically different natal populations. We applied stable isotope analysis of hydrogen (H) and oxygen (O) of feathers, and large scale models of spatial isotopic variation (isoscapes) to formulate spatially explicit predictions of the origin of the migrant birds. Novel relationships were assessed between the measured hydrogen and oxygen isotope values of feathers from A. striatus museum specimens of known origin and the isoscape modeled hydrogen and oxygen isotope values of precipitation at those known locations. We used these relationships to predict the origin regions for birds migrating along the two flyways from the measured isotope values of migrant's feathers and the associated hydrogen and oxygen isotopic composition of precipitation where these feathers were formed. The birds from the two migration routes had overlap in their natal/breeding origins and did not differentiate into fully separate migratory populations, with birds from the Pacific Coast Migratory Flyway showing broader natal geographic origins than those from the Intermountain Flyway. The methodology based on oxygen isotopes had, in general, less predictive power than the one based on hydrogen. There was broad agreement between the two isotope approaches in the geographic assignment of the origins of birds migrating along the Pacific Coast Flyway, but not for those migrating along the Intermountain Migratory Flyway. These results are discussed in terms of their implications for conservation efforts of A. striatus in western North America, and the use of combined hydrogen and oxygen stable isotope analysis to track the movement of birds of prey on continental scales. [ABSTRACT FROM AUTHOR]

The article presents a study which investigates the extent of the West Nile Virus (WNV) infection which causes the high levels of mortality of hawks and owls in North America. It recalls the beginning of the WNV and highlights the objective of the study which is to test the immunological exposure of the species to WNV. It outlines the result of the study which reveals that the species tested were not infected with antibodies to WNV and suggests that level of its infection was so low.

We report three cases of hybridization between wild Swainson's Hawks (Buteo swainsoni) and Red-tailed Hawks (B. jamaicensis) identified by using nuclear and mitochondrial DNA markers. The hybrid individuals were field-identified as Swainson's Hawks and sampled from Alberta. Canada (n = 2) and Utah, USA (n = 1). Nineteen nuclear microsatellite loci were used in a factorial correspondence analysis to create genotypic clusters of 468 Red-tailed and 357 Swainson's hawks. Three suspected hybrids were identified by an intermediate genetic position between the genotypic clusters of the two species, indicating a hybridogenetic composition. We examined mitochondrial control region sequence data to identify the maternal background of the putative hybrids: two of the hybrid specimens had Red-tailed Hawk mtDNA haplotypes and the third a Swainson's Hawk haplotype. These results suggest that hybridization between these two species may occur in their shared breeding range and can result in reciprocal hybrid offspring, barring any social, behavioral, or biological isolating mechanisms. [ABSTRACT FROM AUTHOR]

Merlins, Falco columbarius, breed throughout temperate and high latitude habitats in Asia, Europe, and North America. Like peregrine falcons, F. peregrinus, merlins underwent population declines during the mid-to-late twentieth century, due to organochlorine-based contamination, and have subsequently recovered, at least in North American populations. To better understand levels of genetic diversity and population structuring in contemporary populations and to assess the impact of the twentieth century decline, we used genomic data archived in public databases and constructed genomic libraries to isolate and characterize a suite of 17 microsatellite markers for use in merlins. We also conducted cross-amplification experiments to determine the markers' utility in peregrine falcons and gyrfalcons, F. rusticolus. These markers provide a valuable addition to marker suites that can be used to determine individual identity and conduct genetic analyses on merlins and congeners.

In an evolutionary context, parasites tend to be morphologically conservative relative to their hosts. However, the rate of neutral molecular evolution across many parasite lineages is faster than in their hosts. Although this relationship is apparent at the macroevolutionary scale, insight into the processes underpinning it may be gained through investigations at the microevolutionary scale. Birds and their ectoparasitic lice have served as important natural experiments in co-evolution. Here, we compared mitochondrial and morphological divergence in 2 recently diverged avian host lineages and their parasites. Gálapagos hawks (Buteo galapagoensis) are phenotypically divergent from their closest mainland relatives, the Swainson's hawk (Buteo swainsoni). Both species are host to a feather louse species of Craspedorrhynchus (Insecta: Phthiraptera: Ischnocera, Philopteridae). We sequenced the 5′ end of the mitochondrial gene cytochrome oxidase c subunit I (COI) from a set of hawks and lice. Although this fragment allowed unambiguous identification of host and parasite lineages on the islands and the mainland, only a single variable site was present in the 2 hosts, but 2 major Craspedorrhynchus clades divergent by ~10% were recovered that sorted perfectly with host species. We found significant population genetic structure within the Galápagos Craspedorrhynchus lineage. While the host species are highly differentiated phenotypically, the 2 Craspedorrhynchus louse lineages are phenotypically overlapping, although subtle but significant morphological differences exist.

Traditional subspecies classifications may suggest phylogenetic relationships that are discordant with evolutionary history and mislead evolutionary inference. To more accurately describe evolutionary relationships and inform conservation efforts, we investigated the genetic relationships and demographic histories of Buteo lineatus subspecies in eastern and western North America using 21 nuclear microsatellite loci and 375-base pairs of mitochondrial control region sequence. Frequency based analyses of mitochondrial sequence data support significant population distinction between eastern (B. l. lineatus/alleni/texanus) and western (B. l.elegans) subspecies of B. lineatus. This distinction was further supported by frequency and Bayesian analyses of the microsatellite data. We found evidence of differing demographic histories between regions; among eastern sites, mitochondrial data suggested that rapid population expansion occurred following the end of the last glacial maximum, with B. l. texanus population expansion preceding that of B. l. lineatus/alleni. No evidence of post-glacial population expansion was detected among western samples (B. l.elegans). Rather, microsatellite data suggest that the western population has experienced a recent bottleneck, presumably associated with extensive anthropogenic habitat loss during the 19th and 20th centuries. Our data indicate that eastern and western populations of B. lineatus are genetically distinct lineages, have experienced very different demographic histories, and suggest management as separate conservation units may be warranted.

Landscape-scale population genetic structure in vagile vertebrates was commonly considered to be a contradiction in terms whereas recent studies have demonstrated behaviour and habitat associated structure in several such species. We investigate whether landscape features influence morphological and genetic differentiation in a widespread, mobile raptor. To accurately describe genetic differentiation associated with regional landscape factors, we first investigated subspecies relationships at a continental scale. We used 17 microsatellite loci and five morphological measurements to investigate differentiation between eastern and western subspecies of red-tailed hawks (Buteo jamaicensis) and to identify patterns between differentiation and habitat within western North America. Bayesian and frequency-based analyses of microsatellite data revealed clear distinctions between B. j. borealis (eastern) and B. j. calurus (western) samples. Furthermore, hawks sampled in Texas were stouter than those collected from the Rocky Mountains and farther west. Among western samples, birds from the Great Basin, Rocky Mountains, and Washington were significantly different in morphology than those from Oregon and California. We identified a pattern of isolation by distance among western breeding sites around the Sierra Nevada. Given the long-range dispersal capabilities of raptors, this pattern suggests that population-specific habitat preferences, corresponding with habitat breaks between eastern and western slopes of the Sierra Nevada, and/or regionally variable population densities limit migration between the Mediterranean habitat of central California and the xeric habitats of southern California and interior west. We suggest habitat preferences and regionally disparate population densities may play a role in shaping genetic structure in vagile avian taxa.

DNA sequences of the mitochondrial control region were analysed from 298 individual sharp-shinned hawks (Accipiter striatus velox) sampled at 12 different migration study sites across North America. The control region proved to be an appropriate genetic marker for identification of continental-scale population genetic structure and for determining the historical demography of population units. These data suggest that sharp-shinned hawks sampled at migration sites in North America are divided into distinct eastern and western groups. The eastern group appears to have recently expanded in response to the retreat of glacial ice at the end of the last glacial maximum. The western group appears to have been strongly effected by the Holocene Hypsithermal dry period, with molecular evidence indicating the most recent expansion following this mid-Holocene climatic event 7000-5000 years before present.