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Integrated population models (IPMs) combine population counts with demographic data to improve the precision of estimates of population size and demographic rates. IPMs can also provide information on demographic parameters for which data are lacking (e.g., immigration) if other sufficient information is available. IPMs often use demographic data from one sex, usually females, implicitly assuming the chosen sex adequately represents the species' life history; for highly size‐dimorphic raptors, that assumption may not hold true. We developed a two‐sex IPM for a New Mexico population of the highly size‐dimorphic Cooper's hawk (Accipiter cooperii) from 2011 to 2020 and compared estimates of life history characteristics between sexes. Because we had data to directly estimate sex‐ and age‐specific probabilities of breeding, fecundity, survival, brood sex ratios, and emigration rates, we could indirectly estimate age‐specific immigration rates for both sexes. Our two‐sex IPM revealed that population growth was most strongly associated with increased immigration and decreased first‐year (FY) emigration in females and with after‐first‐year (AFY) survival in males. Most males that were recruited as new breeders in our study area were AFY residents, whereas most female recruits were AFY immigrants. All females that fledged in our study area and survived until their first breeding season bred in their first year, whereas only 3% of surviving FY males bred. We found evidence of density dependence in the survival of AFY males (r = −0.11, 95% credible interval = −0.36 to −0.03) and in AFY female immigration (r = −0.17, 95% credible interval = −0.27 to −0.12). Our findings reveal that male and female Cooper's hawks differ in their response to population density, and in how they contribute to population growth. Thus, sexual differences in vital rates can be an important consideration in raptor population models. [ABSTRACT FROM AUTHOR]

Abstract Integrated population models (IPMs) combine population counts with demographic data to improve the precision of estimates of population size and demographic rates. IPMs can also provide information on demographic parameters for which data are lacking (e.g., immigration) if other sufficient information is available. IPMs often use demographic data from one sex, usually females, implicitly assuming the chosen sex adequately represents the species' life history; for highly size‐dimorphic raptors, that assumption may not hold true. We developed a two‐sex IPM for a New Mexico population of the highly size‐dimorphic Cooper's hawk (Accipiter cooperii) from 2011 to 2020 and compared estimates of life history characteristics between sexes. Because we had data to directly estimate sex‐ and age‐specific probabilities of breeding, fecundity, survival, brood sex ratios, and emigration rates, we could indirectly estimate age‐specific immigration rates for both sexes. Our two‐sex IPM revealed that population growth was most strongly associated with increased immigration and decreased first‐year (FY) emigration in females and with after‐first‐year (AFY) survival in males. Most males that were recruited as new breeders in our study area were AFY residents, whereas most female recruits were AFY immigrants. All females that fledged in our study area and survived until their first breeding season bred in their first year, whereas only 3% of surviving FY males bred. We found evidence of density dependence in the survival of AFY males (r = −0.11, 95% credible interval = −0.36 to −0.03) and in AFY female immigration (r = −0.17, 95% credible interval = −0.27 to −0.12). Our findings reveal that male and female Cooper's hawks differ in their response to population density, and in how they contribute to population growth. Thus, sexual differences in vital rates can be an important consideration in raptor population models.

We explored nest site placement and re-use relative to ornamental tree usage and urbanization level in a diurnal raptor community in southern California (USA) during three discrete time periods spanning five decades (1971–2018). Re-use of prior years' nests varied among species, with Red-tailed Hawks (Buteo jamaicensis) and American Kestrels (Falco sparverius) showing moderate re-use rates (ca. 30%), and Red-shouldered Hawks (Buteo lineatus), and Cooper's Hawks (Accipiter cooperii) showing almost none. Nearly all nests were in native and naturally-occurring trees during the 1970s, yet by 2018, most Cooper's Hawk nests, and many Red-tailed Hawk nests, were located in ornamental vegetation such as pines (Pinus spp.) and eucalyptus (Eucalyptus spp.). The amount of urban cover around nest sites increased for Red-tailed, Red-shouldered, and Cooper's hawks during the study period, but not for American Kestrels, which were confined to the least-urban areas. Cooper's Hawks appear to now be selecting urban nest sites over wildland sites, based on the increase in surrounding urban cover, even as landscape urbanization has not substantially changed in the study area during the last two time periods. Our study illustrates the utility of long-term datasets in understanding how a species' urban tolerance can change over time, and highlights species (including three extirpated taxa) that may be failing to adapt to local urbanization. [ABSTRACT FROM AUTHOR]

The Cooper's Hawk (Accipiter cooperii) is often classified as a woodland species, but it exhibits marked plasticity by nesting successfully in what was previously thought to be atypical habitat such as urban areas and sparsely wooded grasslands, including the Little Missouri National Grassland in North Dakota. Forest expansion into North Dakota grasslands is likely due to the reduction of natural disturbances such as wildfires and grazing by bison (Bison bison). From the 1970s to 2001, forest cover increased in McKenzie County, North Dakota, by.1000%. From 1950 to 1972 there were two recorded instances of nesting Cooper's Hawks in McKenzie County. In 2001, we recorded 18 active nests, 13 of which were successful, four that failed, and one with unknown fate. Using the 2001 National Landcover Dataset (NLCD), we calculated that the mean proportion of forest cover in circular plots (18.1 km2) surrounding nests was 0.21. We found no relationship between nest fate and proportion of forest land cover. Additionally, we found no significant difference in proportion of forest cover between nest sites and randomly selected sites centered on forest land cover, indicating that Cooper's Hawks were using forest land cover in proportion to its availability. Understanding the relationship between the shifting landscape composition of North Dakota and its avifauna is important for monitoring and managing breeding Cooper's Hawks. [ABSTRACT FROM AUTHOR]

In recent decades Cooper's Hawks have successfully colonized urban landscapes, where there may be ample prey but also a greater prevalence of disease in their prey. We searched for nesting Cooper's Hawks in and around Berkeley, California, from 2002 to 2010, locating 95 nests, 89 of which successfully fledged at least one nestling. On average, each nest produced 3.6 fledglings. We evaluated the possible effects of the protozoan parasite Trichomonas gallinae on Cooper's Hawk reproduction from the proportion of potential prey items brought to Lindsay Wildlife Experience that tested positive for the parasitic disease. We did not find a correlation between T. gallinae in potential prey species and nest success (i.e., if the nest fledged any offspring) or reproductive success (i.e., number of fledglings produced). Similarly, we did not find a relationship between reproductive success and distance to parks or percent of impervious surface within 500 m of the nest. The high reported rates of reproduction and high densities of Cooper's Hawk in Berkeley and neighboring Albany suggest a robust population, and we did not find evidence that T. gallinae influences its reproductive success. [ABSTRACT FROM AUTHOR]

We used a two-step process to determine region of geographic origin for migratory Red-tailed Hawks (Buteo jamaicensis) and Cooper's Hawks (Accipiter cooperii). First, we used encounter data from the USGS Bird Banding Laboratory to estimate natal dispersal distances of Red-tailed Hawks and Cooper's Hawks. Then we used this information to assess whether hawks banded at migration stations and later encountered as breeding birds could be assigned to an approximate region of origin. Across the USA, the average apparent natal dispersal distance of Red-tailed Hawks was 137 ± 287 km (n = 127, median = 23 km) and of Cooper's Hawks was 40 ± 90 km (n = 70, median = 13.5 km). There were no differences in apparent natal dispersal as a function of latitude or longitude across the continent. From data on birds banded at migration stations and then encountered later as likely breeders, we inferred that these encounter locations will, on average, reflect these birds' region of origin. Because individuals of these two species tend to have short natal dispersal distances, we can infer regions of origin from breeding-season encounters of banded individuals originally trapped at migration sites across North America. As an example, we used data from migrating Red-tailed and Cooper's Hawks trapped in the Marin Headlands, California, that were later encountered as likely breeders to assign the region of origin of these individuals. Using this information, we inferred that early-migration-season Red-tailed Hawks originated in central California and that later-migration-season Red-tailed Hawks were a mix of individuals originating from central California and eastern Oregon. Cooper's Hawks captured during migration at Marin originated west of the Cascade and Sierra Nevada Mountains, including areas in northern California, Oregon, and British Columbia. Encounter data for hawks banded during migration then captured later during the breeding season may help migration researchers better understand origins of birds captured at migration sites and better link population trends at migration stations with population trends of breeding birds. [ABSTRACT FROM AUTHOR]

The article discusses the study of breeding of Cooper's Hawks in the city and state of Puebla and Mexico during winter season and record obtained during the breeding season by using ecological niche modeling techniques. It discusses the location record of Cooper's Hawk during breeding season and nests located in different greenspaces. It also discusses the impact of urbanization and landscape changes on the natural habitat of the species.

Abstract Numerous studies have demonstrated earlier timing of spring migration and egg‐laying in small passerines, but documentation of such responses to recent climate change in the life histories of higher trophic feeding birds such as raptors is relatively scarce. Raptors may be particularly susceptible to possible adverse effects of climate change due to their longer generation turnover times and lower reproductive capacity, which could lead to population declines because of an inability to match reproductive timing with optimal brood rearing conditions. Conversely adaptively favorable outcomes due to the influence of changing climate may occur. In general, birds that seasonally nest earlier typically have higher reproductive output compared to conspecifics that nest later in the season. Given the strong seasonal decline in reproductive output, and the heritability of nesting phenology, it is possible that nesting seasons would (adaptively) advance over time. Recent climate warming may release prior ecological constraints on birds that depend on food availability at the time of egg production, as do various raptors including Cooper's Hawks (Accipiter cooperii). Under this scenario, productivity, especially clutch size, might increase because it is likely that this reproductive demographic may be the most immediate response to the earlier seasonal presence of food resources. We demonstrated a statistically significant shift of about 4–5 days to an earlier timing of egg‐hatching in spring across 36 years during 1980–2015 for a partially migratory population of Cooper's Hawks in Wisconsin, United States, which is consistent with a recent study that showed that Cooper's Hawks had advanced their timing of spring migration during 1979–2012. Both studies occurred in the Great Lakes region, an area that compared to global averages is experiencing earlier and increased warming particularly in the spring in Wisconsin. The nesting period did not lengthen. We suggest that the gradual shift of six consecutive generations of hawks was likely in response to recent climate change or warming. We did not detect any long‐term temporal change in average clutch or brood sizes. However, such indices of reproduction are among the highest known for the species and thus may be at their physio‐ecological maximum for this population. Our study population appears to show resilience to and does not appear to be adversely influenced by the recent rate of changing climate at this time.

Serratospiculiasis is a parasitic disease caused by filariid nematodes of the genus Serratospiculum that parasitise the air sacs of various species of falcons, bald eagles and Cooper’s hawks around the world. An infection with Serratospiculum was recently confirmed in a nonspecific host, the great tit, in Slovakia. Parasitic material from this host was fixed for molecular analysis. Nematode found in the air sacs from a captive-bred gyrfalcon was also stored. Analysis of small subunit (18S) ribosomal DNA (18S rDNA) gene indicated that sequences from Serratospiculum sp. and Serratospiculoides amaculata were closely related to a reference sequence from Serratospiculum tendo, in agreement with morphology. This study is the first to generate molecular data and infer the phylogenetic position of S. amaculata as the first representative of the genus Serratospiculoides. [ABSTRACT FROM AUTHOR]

Cooper's Hawks (Accipiter cooperii) have been extending their breeding range into urban areas, prompting questions about the relative importance of cities to the demography and conservation of these raptors. A key unanswered question is how urban subpopulations interact with their precedent exurban subpopulations. Two general models have been proposed to describe relationships among subpopulations in a metapopulation: (1) source-sink, where immigrants from sources sustain sinks; and (2) balanced dispersal, where dispersal is proportionally equal among subpopulations. I evaluated whether either of these models predict metapopulation dynamics of urban and exurban Cooper's Hawks in central New Mexico using demographic data in a Bayesian integrated population model. All urban female Cooper's Hawks began breeding in their first year; 69% settled at nests in the urban subpopulation and 31% emigrated and settled in an exurban subpopulation. The high rate of female emigration was likely because of a shortage of breeding urban males, caused by a 1 yr delay in male age-at-first-breeding. Emigration exceeded immigration by nearly 30%, making a balanced-dispersal model implausible. Although the urban subpopulation was a source, the primary recipient subpopulation was not a sink; urban emigrants appeared to have a competitive advantage obtaining exurban nest sites. High urban winter prey abundance supported year-long residency among urban female Cooper's Hawks, whereas nearly all exurban females migrated. Resident urban females that emigrated settled on exurban nesting territories before migrants returned, and thus without direct competition from them. Previous metapopulation models do not incorporate the concept that differences in dispersal behavior between subpopulations can drive dispersal dynamics in a metapopulation. These findings provide further evidence that patch dynamics in a metapopulation can be complex, and may be governed by factors other than just demographic rates and connectivity. [ABSTRACT FROM AUTHOR]

The index includes references to general topics, common names, key words, and authors. Reference is also made to book reviews and letters. Taxa other than raptors are included where referenced by authors. [ABSTRACT FROM AUTHOR]

Cooper's Hawks ( Accipiter cooperii) from approximately the northern third of the species' breeding range are considered migratory, hawks in the central portion are either migratory or resident, and hawks farther south are believed to be nonmigratory. We compared long-distance movements (>100 km between natal nest and encounter location) of Cooper's Hawks banded as nestlings at two different ranges of latitudes (>35° and <35°N). Our goal was to determine whether long-distance movements indicate that Cooper's Hawks from southern latitudes (south of 35°N) are migratory and whether any migrate north, as do Bald Eagles ( Haliaeetus leucocephalus) from several locations in the southern U.S.A. and Red-tailed Hawks ( Buteo jamaicensis) from southern California. Long-distance movements by hawks banded as nestlings north of 35°N were strongly oriented to the south, with only 17% in a northerly direction. The only hawks encountered >100 km from nests south of 35°N were from southern Arizona and southern California. As opposed to the strong southward orientation of long-distance movements of hawks from north of 35°N, mean direction south of 35° was bipolar. Northward long-distance movements from nests in southern Arizona were relatively short (<200 km), while southward movements were substantially longer (1637 km in one case). Three Cooper's Hawks from southern Arizona were encountered in central Mexico, well south of the known breeding range, which suggests some individuals from southern Arizona are migratory. The pattern of long-distance movements from southern California was the reverse of that from southern Arizona. Most long-distance movements toward the south from southern California nests were comparatively short, whereas the three longest movements from that area (616-993 km) were to the north. Although tentative, we believe these longer movements are indicative of northward migration rather than natal or breeding dispersal. [ABSTRACT FROM AUTHOR]

La naturaleza carismática y la enigmática disminución poblacional de Falco sparverius ha provocado el interés y la preocupación tanto de científicos (ciudadanos y profesionales) como del público en general. Aunque se han propuesto diversas razones como causas de esta disminución, hay poca o nula evidencia empírica para la mayoría de las amenazas hipotetizadas y consecuentemente no existen recomendaciones de gestión apoyadas en evidencia empírica. Presentamos recomendaciones para investigaciones futuras sobre la causa de la disminución poblacional de F. sparverius. Además, sugerimos prioridades para monitorear e identificar los condicionantes de las tasas de supervivencia y reproducción a través de modelos demográficos. Investigaciones sobre la fenología, la conectividad migratoria y el uso de cavidades naturales como nidos mejorarían el seguimiento de F. sparverius y nuestra comprensión sobre los declives poblacionales, mientras que estudios demográficos durante el ciclo anual completo de F. sparverius van a ayudar a elucidar las causas del declive y las acciones potenciales de gestión.[Traducción del equipo editorial] [ABSTRACT FROM AUTHOR]

Raptors serve as the definitive host for several Sarcocystis species. The complete life cycles of only a few of these Sarcocystis species that use birds of prey as definitive hosts have been described. In the present study, Sarcocystis species sporocysts were obtained from the intestine of a Cooper's hawk ( Accipiter cooperii ) and were used to infect cell cultures of African green monkey kidney cells to isolate a continuous culture and describe asexual stages of the parasite. Two clones of the parasite were obtained by limiting dilution. Asexual stages were used to obtain DNA for molecular classification and identification. PCR amplification and sequencing were done at three nuclear ribosomal DNA loci; 18S rRNA, 28S rRNA, and ITS-1 , and the mitochondrial cytochrome c oxidase subunit 1 ( cox1 ) locus. Examination of clonal isolates of the parasite indicated a single species related to S. columbae (termed Sarcocystis sp. ex Accipiter cooperii ) was present in the Cooper's hawk. Our results document for the first time Sarcocystis sp. ex A. cooperii occurs naturally in an unknown intermediate host in North America and that Cooper's hawks ( A. cooperii ) are a natural definitive host. [ABSTRACT FROM AUTHOR]

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Among the stressors confronting urban wildlife, chemical contaminants pose a particular problem for high trophic feeding species. Previous data from fortuitous carcass collections revealed surprisingly high levels of persistent organic pollutants in raptor species, including the Cooper's hawk ( Accipiter cooperii), from urbanized areas of southwestern British Columbia, Canada. Thus, in 2012 and 2013, we followed up on that finding by measuring POPs in blood samples from 21 adult and 15 nestling Cooper's hawks in Vancouver, a large urban area in southwestern Canada. Reproductive success and circulating thyroid hormones were measured to assess possible toxicological effects. Model comparisons showed concentrations of polychlorinated biphenyls (ΣPCBs) were positively influenced by the level of urbanization. Total thyroxin (TT4) was negatively associated with increases in ΣPCBs. Total triiodothyronine (TT3) was negatively associated with ΣPCBs and polybrominated diphenyl ethers (ΣPBDEs). The legacy insecticide, dieldrin, appeared to have some negative influence on reproductive success. There is some evidence of biochemical perturbation by PBDEs and lingering impact of legacy POPs which have not been used for at least 40 years, but overall Cooper's hawks have successfully populated this urban environment. [ABSTRACT FROM AUTHOR]

Numerous studies have demonstrated earlier timing of spring migration and egg-laying in small passerines, but documentation of such responses to recent climate change in the life histories of higher trophic feeding birds such as raptors is relatively scarce. Raptors may be particularly susceptible to possible adverse effects of climate change due to their longer generation turnover times and lower reproductive capacity, which could lead to population declines because of an inability to match reproductive timing with optimal brood rearing conditions. Conversely adaptively favorable outcomes due to the influence of changing climate may occur. In general, birds that seasonally nest earlier typically have higher reproductive output compared to conspecifics that nest later in the season. Given the strong seasonal decline in reproductive output, and the heritability of nesting phenology, it is possible that nesting seasons would (adaptively) advance over time. Recent climate warming may release prior ecological constraints on birds that depend on food availability at the time of egg production, as do various raptors including Cooper's Hawks ( Accipiter cooperii). Under this scenario, productivity, especially clutch size, might increase because it is likely that this reproductive demographic may be the most immediate response to the earlier seasonal presence of food resources. We demonstrated a statistically significant shift of about 4-5 days to an earlier timing of egg-hatching in spring across 36 years during 1980-2015 for a partially migratory population of Cooper's Hawks in Wisconsin, United States, which is consistent with a recent study that showed that Cooper's Hawks had advanced their timing of spring migration during 1979-2012. Both studies occurred in the Great Lakes region, an area that compared to global averages is experiencing earlier and increased warming particularly in the spring in Wisconsin. The nesting period did not lengthen. We suggest that the gradual shift of six consecutive generations of hawks was likely in response to recent climate change or warming. We did not detect any long-term temporal change in average clutch or brood sizes. However, such indices of reproduction are among the highest known for the species and thus may be at their physio-ecological maximum for this population. Our study population appears to show resilience to and does not appear to be adversely influenced by the recent rate of changing climate at this time. [ABSTRACT FROM AUTHOR]

Capturamos, marcamos individualmente y pesamos 271 hembras reproductoras de segundo año de Accipiter cooperii durante la época de cría en dos áreas de estudio principales en Wisconsin durante el periodo comprendido entre 1980 y 2007. Luego recapturamos o volvimos a avistar a algunas de las aves utilizando prismáticos o telescopios y las identificamos a través del color de sus anillas. Para analizar la relación de la longevidad de la hembra con el tamaño, examinamos la masa corporal de adultos reproductores recapturados o avistados nuevamente por categoría de edad relativa durante el último año de detección. Encontramos que la masa corporal (o tamaño) en esta especie no estuvo relacionada con la longevidad ni con la dispersión reproductiva entre, o la fidelidad con, las áreas de nidificación en Wisconsin. Aunque previamente demostramos que la masa corporal tanto en machos como en hembras estuvo relacionada significativa y positivamente con la tasa reproductiva anual y con el número de reclutamientos (o la eficacia biológica), pero inversamente relacionada con el tiempo de la reproducción (i.e., las aves de mayor tamaño se reprodujeron antes en la temporada), parece que, para los machos, el tamaño corporal en A. cooperii está subordinado a otros factores no relacionados con el hábitat que influyen en la longevidad y la re-ocupación de las áreas de nidificación en Wisconsin. Los factores biológicos que influyen tanto sobre la dispersión interanual a un área de nidificación diferente por parte de una hembra experimentada, como sobre la fidelidad año tras año a un sitio se puede basar en comportamientos sociales complejos previos a la incubación en A. cooperii. Sugerimos que nuestro conocimiento de la dispersión reproductiva de aves rapaces mejoraría si se documentaran detalladamente las interacciones sociales entre individuos durante la adquisición de lugares de cría. [Traducción del equipo editorial] [ABSTRACT FROM AUTHOR]

The Northern Goshawk (Accipiter gentilis) is a large forest raptor with a Holarctic distribution and, in some portions of its range, a species of conservation concern. To augment previously reported genetic markers, 13 novel polymorphic microsatellite markers were developed to establish individual identification and familial relationships, to assess levels of genetic diversity, and to identify diagnostic markers. Of the 22 loci tested, 13 were polymorphic, seven were monomorphic, and two failed to amplify. This suite of microsatellite loci yielded a combined probability of parental exclusion of 98%; a single individual sampled from a North American population can be reliably identified using a combination of seven of the 13 polymorphic loci. Cross-species screening in Cooper's Hawks (A. cooperii) and Sharp-shinned Hawks (A. striatus) of the 20 loci that successfully amplified in Northern Goshawks identified 13 loci as polymorphic in each species. Six of these loci (Age1303, Age1308, Age1309, Age1312, and Age1314) appeared to be useful in distinguishing between Accipiter species. These markers will be useful to researchers investigating populations of North American accipiters. [ABSTRACT FROM AUTHOR]

Long-term monitoring programs that can detect a population change over time can be useful for managers interested in assessing population trends in response to forest management activities for a particular species. Such long-term monitoring programs have been designed for the Northern Goshawk ( Accipiter gentilis), but not for the more elusive Sharp-shinned ( A. striatus) and Cooper's hawks ( A. cooperii). The objectives of this study were to (1) determine if it was possible to survey for these two Accipiters at the same time successfully using a new survey technique, and (2) estimate occupancy rate and detection probabilities for both species. We used broadcast surveys (BSM) to determine presence/absence for nesting Sharp-shinned and Cooper's hawks at Mountain Home Demonstration State Forest located in the southern Sierra Nevada mountain range in California. We surveyed 34 sampling units that were defined as the average home-range size (1000 m2) of the smallest target species, the Sharp-shinned Hawk. The sampling units were surveyed twice in 2003 and 3-4 times in 2004 during the breeding season. We used program PRESENCE to estimate detection probabilities and model occupancy rates for Sharp-shinned and Cooper's hawks. Our results indicated that the BSM using both Accipiter vocalizations in sequence was valuable for surveying both Sharp-shinned and Cooper's hawks. Proportions of the study area occupied for Sharp-shinned and Cooper's hawks were 0.25 (SE = 0.079), and 0.40 (SE = 0.098), respectively. The probabilities of detecting Cooper's and Sharp-shinned hawks at any given site were 0.56 (SE = 0.098) and 0.47 (SE = 0.086), respectively. There were no published occupancy estimates or detection probabilities in the literature to directly compare to our study. Because these species are elusive and difficult to survey, it is imperative future studies that address occupancy estimation for Sharp-shinned and Cooper's hawk incorporate detection probabilities into their model. Incorporating other variables into an occupancy model, such as habitat type, timber harvest, forest health, and/or climatic variables will also improve occupancy estimates. [ABSTRACT FROM AUTHOR]

In some urban environments, human activities enhance resources for avian species, providing habitat that can support year-round occupancy. If both members of a mated pair stay on their breeding territories year-round, close proximity of pair members throughout the year may increase the potential for interactions outside the breeding season. Under these circumstances, avian species that would otherwise terminate their bonds following the breeding season may form perennial pair bonds. We examined behavior of mated pairs of adult Cooper's Hawks ( Accipiter cooperii) during the nonbreeding season in an urban environment to determine whether pairs retained their breeding territories outside the breeding season and if year-round maintenance of territories influenced the duration of pair bonds. Home ranges and core areas of pair members largely overlapped. Pair members remained close to the nest site they used during the previous breeding season, avoided neighboring conspecifics of the same sex, and selected areas within their home ranges that supported abundant avian prey and contained vertical vegetation structure. Pair members interacted throughout the nonbreeding season via acts of courtship and vocalizations, mainly in areas near the nest site. Perennial pair bonds in Cooper's Hawks in this urban environment are likely a response to high availability of prey throughout the year and facilitated largely by fidelity to and retention of all-purpose territories year-round. For Cooper's Hawks in this urban environment, maintaining pair bonds continuously may confer several advantages such as early initiation of breeding and higher reproductive success. [ABSTRACT FROM AUTHOR]

Documentamos dos tipos de plumajes melánicos aberrantes, pálido y oscuro, en tres individuos de Accipiter cooperii en estado silvestre. Capturamos y fotografiamos dos individuos de A. cooperii con plumaje pálido en Dakota del Norte y un individuo de la misma especie en Virginia. Este es el primer estudio de muda de un individuo de A. cooperii de un plumaje aberrante juvenil pálido a un segundo plumaje básico pálido. Además, una de las dos crías macho presenta un plumaje pálido como su madre, lo que sugiere que la aberración es heredable. También describimos el primer plumaje melánico oscuro para A. cooperii. [Traducción del equipo editorial] [ABSTRACT FROM AUTHOR]

Offspring sex ratios at the termination of parental care should theoretically be skewed toward the less expensive sex, which in most avian species would be females, the smaller gender. Among birds, however, raptors offer an unusual dynamic because they exhibit reversed size dimorphism with females being larger than males. And thus theory would predict a preponderance of male offspring. Results for raptors and birds in general have been varied although population-level estimates of sex ratios in avian offspring are generally at unity. Adaptive adjustment of sex ratios in avian offspring is difficult to predict perhaps in part due to a lack of life-history details and short-term investigations that cannot account for precision or repeatability of sex ratios across time. We conducted a novel comparative study of sex ratios in nestling Cooper's hawks ( Accipiter cooperii) in two study populations across breeding generations during 11 years in Wisconsin, 2001-2011. One breeding population recently colonized metropolitan Milwaukee and exhibited rapidly increasing population growth, while the ex-Milwaukee breeding population was stable. Following life-history trade-off theory and our prediction regarding this socially monogamous species in which reversed sexual size dimorphism is extreme, first-time breeding one-year-old, second-year females in both study populations produced a preponderance of the smaller and cheaper sex, males, whereas ASY (after-second-year), ≥2-year-old females in Milwaukee produced a nestling sex ratio near unity and predictably therefore a greater proportion of females compared to ASY females in ex-Milwaukee who produced a preponderance of males. Adjustment of sex ratios in both study populations occurred at conception. Life histories and selective pressures related to breeding population trajectory in two age cohorts of nesting female Cooper's hawk likely vary, and it is possible that these differences influenced the sex ratios we documented for two age cohorts of female Cooper's hawks in Wisconsin. [ABSTRACT FROM AUTHOR]

The article offers news brief related to avian biology as of 2015. Topics discussed include the parasite diversity that causes malaria in southeast African birds, the level of contaminants found in Cooper's hawk, and the migration of tiny songbirds over the Atlantic Ocean. Also mentioned the prediction of avian influenza outbreaks using a portable tool and the importance of birds' color in natural and sexual selection.

Copyright of Journal of Field Ornithology is the property of Resilience Alliance and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article focuses on the foraging behaviour of Northern Goshawks. It includes information on the diet of Goshawks, predation behaviour of Goshawks, and preying of ground squirrel. It also presents information on the raptor species for Goshawk's foraging including Cooper's Hawk, Ferruginous Hawks, and Harris's Hawks.

A Cooper’s hawk (Accipiter cooperii) was found dead in a ditch leading from a heap leach pad at a gold mine in Nevada. Observations at autopsy included an absence of external lesions, traces of subcutaneous and coronary fat, no food in the upper gastrointestinal tract, and no lesions in the viscera. Cyanide concentrations (µg/g ww) were 5.04 in blood, 3.88 in liver, and 1.79 in brain. No bacteria or viruses were isolated from tissues, and brain cholinesterase activity was within the normal range for a Cooper’s hawk. [ABSTRACT FROM AUTHOR]

The article discusses the undocumented behavior of Cooper's Hawks called prooning. Topics covered include the challenge faced by researchers to locate fledgling hawks as well as information on the capability of fledglings to fly in prone positions. Also mentioned is the observation of the breeding behavior of the hawks in Wisconsin.

During a pan-Canadian tickhost study, we detected the spirochetal bacterium, Borrelia burgdorferi sensu lato, which causes Lyme disease, in ticks collected from a raptor. Lyme disease is one of a number of zoonotic, tick-borne diseases causing morbidity and mortality worldwide. Larvae of the avian coastal tick, Ixodes auritulus, were collected by wildlife rehabilitators from a Cooper's hawk, Accipiter cooperii, on Vancouver Island, British Columbia. Using PCR amplification of the linear plasmid ospA gene of B. burgdorferi, 4 (18%) of 22 larvae were positive. Since these engorged I. auritulus larvae had not had a previous blood meal and B. burgdorferi is rarely transmitted from infected female ticks to their progeny, we propose that Cooper's hawks are reservoircompetent hosts of B. burgdorferi. Our tick-host discovery provides the first report of bird-feeding ticks on a Cooper's hawk, and exhibits the premiere record of B. burgdorferi-positive ticks on a raptor. Not only are passerine (perching) and gallinaceous (chicken-like) birds involved in the wide dispersal of Lyme disease vector ticks, raptors are now also implicated in the dissemination of B. burgdorferi-infected ticks. Although I. auritulus does not bite humans, this tick species plays an integral role in the 4-tick enzootic cycle of B. burgdorferi along the West Coast of North America. In essence, raptors and I. auritulus ticks may help to amplify this infectious agent in nature, and increase the likelihood of people contracting Lyme disease, especially in coastal areas. [ABSTRACT FROM AUTHOR]

We studied adult Cooper's hawks Accipiter cooperii on two study areas in north Florida from 1995 to 2001, an area dominated by large plantations managed for northern bobwhite Colinus virginianus and an area of mixed farmland and woods with no direct bobwhite management. We monitored 76 Cooper's hawk nesting attempts at 31 discrete nest areas, and radio-tagged 19 breeding males and 30 breeding females that we radio-tracked for up to 5 y. Nesting density (565 to 1,494 ha per occupied nest area) was comparable but productivity (1.8 and 2.8 young fledged per occupied and successful nest area, respectively) was lower than for the species elsewhere. Prey may have been more limiting than in other areas studied because chipmunks Tamias striatus, an important prey elsewhere, were absent. Annual Cooper's hawk survival averaged 84% for males and 81% for females, except in 1998 when survival was substantially lower. Average annual home-range size for male Cooper's hawks was 15.3 km² inclusive of one nesting area. Female annual ranges averaged 30.3 km², and included from three to nine nesting areas. Daily space use was similar between the sexes, but females had separate breeding and nonbreeding ranges whereas males were sedentary. Females used the same nonbreeding areas among years, but switched nesting areas 68%of the time compared with only 17% for males. Birds comprised 88% of the breeding and 98% of the nonbreeding season diet of Cooper's hawks by frequency. Important prey species all year were mourning doves Zenaida macroura, blue jays Cyanocitta cristata, and northern bobwhite; during summer, cattle egrets Bubulcus ibis, northern mockingbirds Mimus polyglottos and northern cardinals Cardinalis cardinalis were also important; and during autumn and winter, killdeer Charadrius vociferus, yellow-billed cuckoos Coccyzus americanus, and chickens were important. Female Cooper's hawks took larger prey than males; females were responsible for most cattle egret and chicken kills; whereas, males took most blue jays, killdeer, northern mockingbirds, and northern cardinals. Of avian prey brought to nests, 64% were nestling birds. Most adult male Cooper's hawks were adept at raiding bird nest boxes. Male Cooper's hawks captured 85% of the prey fed to nestlings. Female Cooper's hawks relied on males for food from early March until young were $12 d old, and 6 of 10 breeding females monitored intensively were never observed foraging for their broods. Most prey brought to nestling Cooper's hawks was captured within 2 km of nests, and foraging effort was consistent throughout the day. During the nonbreeding season, most prey captures occurred before 0900 hours or at dusk. Northern bobwhite made up 2% of male and 6%of female Cooper's hawk prey annually by frequency; this extrapolated to 18 bobwhite/year/adult Cooper's hawk on both study areas, 59%of which were captured between November and February. Outside the breeding season, male Cooper's hawks foraged evenly over their home range whereas females tended to focus on prey concentrations. Because female Cooper's hawks were so adept at finding and exploiting prey hotspots, perhaps the best strategy for reducing predation on bobwhite is habitat management that produces an even distribution of bobwhite across the landscape. [ABSTRACT FROM AUTHOR]

Life-history theory suggests that delayed maturation is beneficial to birds when costs of breeding early in life are high. We compared selected aspects of the biology of male Cooper's Hawks (Accipiter cooperii) that began breeding at 1 year of age (SY males) vs. males that began breeding ≥2 years of age (ASY males) in an effort to elucidate what renders breeding of SY males rare. Of the 732 males of known age whose breeding we studied over 32 years (1980-2011) 13 (2%) were SY and 719 (98%) were ASY. During this period, the incidence of breeding of SY males changed markedly, as 12 of the instances of breeding of SY males were recorded in the first half of our study, only 1 in the latter half. We suggest that SY males could acquire nest sites more readily in the first half of the study when the breeding population of ASY males was apparently lower. Males breeding in their second year were on average similar in size to ASY males but were molting more extensively than were ASY males. ASY males lived longer than males breeding in their second year, and maximum lifetime production of young was greater, so SY males may have sacrificed greater longevity for breeding early. A strategy of facultative breeding in response to the constraints of higher numbers of older breeding males and restraints of trade-offs in energy allocation may explain why SY male Cooper's Hawks rarely breed. [ABSTRACT FROM AUTHOR]

We used collection of prey remains, direct observations of hawks with prey, and video cameras at two nests to assess frequency of occurrence and biomass of prey species taken by breeding Cooper's Hawks (Accipiter cooperii) in Victoria, British Columbia, Canada during 1995-2010. Small (≤ 27 g) to medium-size (28-91 g) bird species contributed the majority (79-94%) of prey recorded from collection of 3,231 prey remains, 437 direct observations, and 783 video items at 87 nest sites. Avian prey contributed over half of prey biomass recorded in direct observations and video data (67% and 93%, respectively). One native and two introduced species provided most (> 85%) prey recorded in all samples in which birds were identified to species: American Robin (Turdus migratorius), European Starling (Sturnus wdgaris), and House Sparrow (Passer domesticus). Introduced species were an important component of the diet, contributing over half of items identified in all samples. There was a temporal shift in age of prey used: the early-season diet (Mar-Apr) was comprised of adult birds and subadult mammals, while avian young of the year dominated the diet from late May until the end of the breeding season (70-100% of identifiable items). Mammals were inconsequential in terms of frequency and biomass except at nests (6 of 87) on or near the University of Victoria campus where nearly all European rabbit (Oryctolagus cuniculus) prey was recorded. [ABSTRACT FROM AUTHOR]

The article presents a study to assess if nesting hooded warblers acoustically discriminate among predators and make short-term adjustments in their parental care according to the degree of perceived risk. It uses playback experiments in which nests of the hooded warbler are exposed to vocalizations of two nest predators such as blue jay and eastern chipmunk. Results suggest that nesting hooded warblers are discriminating the vocalizations of predators and adjust the time to return to nest.

This article presents a study which investigated the movement ecology of American Kestrel, Sharp-shinned Hawk and Cooper's Hawk, three raptors that are commonly banded in North America. Researchers examined banding encounter records from 1920 to 2006 for the three raptors. They determined the sex- and age-related differences in distances moved between summer and winter ranges, the regional differences in migration distances and wintering latitudes, as well the changes in migration distances and wintering latitudes over time.

This article presents a study which evaluated the extent of differential migration within five species of raptors in central coastal California. Researchers found that female Cooper's Hawks migrated earlier than males. Female Sharp-shinned Hawks, hatch-year American Kestrels, hatch-year Merlins, and half-year Red-shouldered Hawks also migrated earlier than their counterparts. Researchers also learned that their data on Cooper's Hawks, Sharp-shinned Hawks, American Kestrels, Merlins and Red-shouldered Hawks agreed with the patterns of migration seen elsewhere in Northern America.

In 2010, The Wildlife Center in New Mexico incubated four Cooper's hawk eggs. Two chicks survived and were hand-reared until release at 13 wk of age. Information is provided on incubation, diet, and growth rate of the birds as hatchlings, nestlings, and fledglings. Chicks were fed quail throughout the hand-rearing process, but were supplemented with nutritional products to assist in optimal health and development. Taurine, an amino acid important for normal brain, eye, and spatial skill development in some animals was incorporated into the hatchling diet. Thiamine and vitamin E were also provided in the diet from hatchling stage to release. Differential growth of two birds while consuming the same diet suggested one was male and the other female [ABSTRACT FROM AUTHOR]

To be considered for release, raptors undergoing rehabilitation must have recovered from their initial injury in addition to being clinically healthy. For that purpose, a good understanding of reference hematologic values is important in determining release criteria for raptors in a rehabilitation setting. In this study, retrospective data were tabulated from clinically normal birds within 10 days of release from a rehabilitation facility. Hematologic values were compiled from 71 red-tailed hawks (Buteo jamaicensis), 54 Eastern screech owls (Megascops oslo), 31 Cooper's hawks (Accipiter cooperii), 30 great-horned owls (Bubo virginianus), 28 barred owls (Strix varia), 16 bald eagles (Haliaeetus leucocephalus), and 12 broad-winged hawks (Buteo platypterus). Parameters collected included a white blood cell count and differential, hematocrit, and total protein concentration. Comparisons were made among species and among previously published reports of reference hematologic values in free-ranging birds or permanently captive birds. This is the first published report of reference values for Eastern screech owls, barred owls, and broad-winged hawks; and the first prerelease reference values for all species undergoing rehabilitation. These data can be used as a reference when developing release criteria for rehabilitated raptors. [ABSTRACT FROM AUTHOR]

Abstract: Urbanization is a leading cause of species endangerment in the United States; however, certain species thrive in urban habitats. The loss of key predators or the addition of new predators in urban areas could alter the structure of urban communities. A reduction in nest predation is hypothesized to explain the high density of urban birds, yet urban areas typically have increased populations of avian nest predators. The loss of important nest predators in urban habitats, prey switching of urban predators, or successful nest defense against avian nest predators could explain this urban nest predator paradox. To assess these hypotheses I compared nest predation rates of Northern mockingbirds (Mimus polyglottos) in parking lots and residential neighborhoods to populations in pastures and wildlife preserves during 2007–2009 in Florida, USA and placed video cameras on a subset of nests in 2008–2009. Data do not support the hypothesis that urban nest predation rates are consistently lower than non-urban nest predation rates. Of the 56 nest predation events recorded, cats were the dominant urban predator and Cooper’s hawks (Accipiter cooperii) were the dominant non-urban predator. There was no evidence for a loss of important nest predators in urban habitats; however, prey switching by Cooper’s hawks likely occurred. There was also indirect evidence for the importance of nest defense. Furthermore, some of the cats recorded as nest predators in residential neighborhoods were owned cats and all but one cat predation event occurred at night. To reduce nest predation rates, cat owners should keep their cats indoors at night. [Copyright &y& Elsevier]

The article discusses a study on the colonization of Cooper's Hawks or Accipiter cooperii in the Milwaukee, Wisconsin area in 1988-2008. It documents the natural colonization of the landscape by Cooper's Hawks population and its growth from 1993 to 2008. It notes that the population was possibly increasing at a rapid rate during the 1990s and continued to increase throughout the remainder of the study. An analysis of how reproduction of Cooper's Hawks varied with time and density is also offered.