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Habitat use and productivity of Sharp-shinned Hawks nesting in an urban area
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We measured productivity and vegetation parameters of habitat quality at 16 Sharp-shinned Hawk (Accipiter striatus) nests in and near the greater Montreal area in order to evaluate nesting habitat use and its possible relationship to reproductive success in an urban setting. Mean clutch size was 4.4 and hatching success was 3.8 eggs per nest. At least one egg hatched in 11 of 16 nests (68.8%), 10 (62.5%) pairs raised young to a bandable age (≥10 days old), and 8 (50%) pairs successfully produced at least one fledgling. Immature individuals comprised 33.3% of male and 38.5% of female breeders. Mean values in the habitat assessment included nest tree height, 14.0 m; tree density, 955/ha; total canopy cover, 88.1%; coniferous cover, 39.7%; mean dbh, 17.6 cm; and distance to the nearest forest opening, 19.7 m. Sharp-shinned Hawks nested in a range of forest types, from mature conifer plantations to young, almost purely deciduous stands, and this population exhibited considerable flexibility with respect to most of the habitat features that we measured. Their use of older stands with more deciduous cover than those used by conspecifics elsewhere may reflect regional differences in habitat availability as well as in the abundance of competitor species. Breeding in an urbanized area does not seem to be detrimental to Sharp-shinned Hawks, as evidenced by this population’s relatively large proportion of immature breeders and normal productivity, which appeared to be independent of all the assessed parameters of habitat quality.
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... I found seven studies that identified the nest habitat characteristics of Sharp-shinned Hawks (Clarke 1984, Coleman 2002, Garner 1999, Rankin 2010, Reynolds 1982, Trexel 1999, Wiggers 1991 In total these studies describe 81 nests in seven states and Quebec, Canada. The exact habitat characterizes identified for the nest sites were slightly different from study to study, but all were based on a set of characteristics recommended by James (1970). ...
... A typical set of measurements recorded at the nest site is listed in Table 1. Table 1 Habitat characteristics for Sharp-shinned Hawk nests in the Montreal area of Quebec (Coleman 2002). This list of characteristics is typical of the seven studies I examined. ...
... The smaller the coefficient of variation for a characteristic the less variability and the more useful the characteristic is in a habitat quality index. Table 1 shows the coefficient of variation for all the Sharpie nesting habitat characteristics in the Coleman (2002) study. The two least variable habitat characteristics of Sharp-shinned nest sites are "total canopy cover" (percent of forest covered overhead by tree needles, leaves, and branches) and "canopy height" (average tree height). ...
I developed a habitat index based on average tree height and canopy cover to score the quality of pine stands as nesting habitat for Sharp-shinned hawks. Sixty pine stands averaging about 20 acres in size were scored in 2009. Ten of the stands (17%) had a habitat index score of the highest possible 6. When these stands were searched for nests 69% contained old nests and 23% were found to contain an active nest. According to the breeding bird survey produced by the U.S. Geological Survey (Figure 1) Sharp-shinned Hawks nest in nearly every one of the continental United States. But their distribution tends to be spotty, localized to areas with the dense pine or spruce stands of medium height that Sharpies need for nesting (Bent 1937).
... However, some other raptors respond well to urban environment because of the large biomass of suitable prey items such as small birds or squirrels. Cases of urbanized raptors include Cooper's Hawks Accipiter cooperii, Sharp-shinned Hawks A. striatus, Merlins Falco columbarius, and Tawny Owls Strix aluco (Warkentin et al. 1992, Coleman et al. 2002, Stout et al. 2007, Solonen & af Ursin 2008. In some of the cases, availability of prey items might be the major reason for their colonization of towns and cities (Warkentin et al. 1992, Solonen & af Ursin 2008, Kumar et al. 2014. ...
... We define fledgling as the nestling reaching 48 days old, when the young typically leave and stand outside the nest (Lin et al. 2008). A nest with at least one fledgling was defined as a nesting success (Coleman et al. 2002, Steenhof & Newton 2007). ...
Capsule A Crested Goshawk population recently colonizing an urban area of Taiwan is characterized by earlier egg-laying dates, a higher ratio of mixed-age pairs and higher nesting success.Aims To compare breeding time, productivity and pairing pattern of Crested Goshawk populations between urban and rural areas.Methods A total of 117 nests, comprising 49 rural and 68 urban ones, were monitored in Taichung, central Taiwan over six years. Age of parents, egg-laying date, clutch size and number of fledglings were recorded from each nest.Results The urban Crested Goshawk bred 34 days earlier on average than the rural population with a significantly higher nesting success. Mixed-age pairs occurred in a higher frequency in urban (30.9%) than in rural (14.3%) areas. Predation (55.6%) and inclement weather (27.8%) were the two main factors causing nesting failures in rural areas, whereas neither occurred in the urban area.Conclusion We conclude that the urban Crested Goshawk population benefits from high food supply and low predation risk. The year-round abundance of prey might increase the breeding success of young adults and advance their breeding schedule, which coincidently shifts the brooding period away from the heavy rainy season.
... To our knowledge, the investigation of Sharpshinned Hawks breeding in and near Montreal, Quebec, Canada, is the only publication of urban nesting Sharp-shinned Hawks (Coleman et al. 2002). This apparent sole publication may suggest that Sharp-shinned Hawks are uncommon to rare urban breeders, and thus that Sharp-shinned Hawks impart relatively little predation pressure continentally on urban House Sparrows compared to Cooper's Hawks. ...
We discuss select imprecise and untenable natural history information about migration, urban habitat use, and diet presented in the technical literature about Accipiter hawks in North America. We focus primarily on challenging the claim that Sharp-shinned Hawks (Accipiter striatus) are more frequent predators of House Sparrows (Passer domesticus) than are Cooper's Hawks (A. cooperii). We urge scientists to be cognizant of the ever-changing dynamics of the predatory behavior, nesting, and migration ecology of Sharp-shinned and Cooper's hawks due to anthropogenic factors, features that are in constant flux and may not be well tracked long term or apply to the entire distributional ranges of these 2 species.
... Nests almost exclusively in coniferous forests, seldom in mixedwood stands ; preferred forests are very dense, with 80% or more canopy cover, are even-aged, and typically 25 to 50 years old (Apfelbaum and Seelbach 1983;Moore and Henny 1983;Reynolds et al. 1982); plantations are frequently used (Wiggers and Kritz 1991); it nests in upland and lowland stands, but appears to prefer wetlands or areas near lakes or watercourses ; nests are usually at the edges of forest ; forests 20 to 30 ha in size or larger appear to be preferred , but it appears to be adapting to fragmented habitat and nests in urban areas in Montreal (Coleman et al. 2002); usually nests in spruce, hemlock, cedar, or pine ; most nests are 6 to 10.5 m from the ground, usually at the trunk a few metres from the top of the tree ; selects trees with particularly dense crowns in areas of high tree density (Apfelbaum and Seelbach 1983;Flood and Bortolotti 1984;Reynolds et al. 1982); usually builds a new nest every year, but almost always within 100 m of the previous year's nest, even if another Upland Sandpiper Nests in old fields, hayfields, pastures, and at airports ; may have originally been associated with short-grass prairie, also occurs on alvars; appears to require about 25 to 40 ha of open habitat, or even as much as 100 to 200 ha (Bollinger 1995;Jones and Vickery 1995;Vickery et al. 1994;Walk and Warner 1999); prefers uniform grass cover 15 to 30 cm in height, avoids areas where grass height exceeds 60 cm (Kantrud and Higgins 1992); presence of residual vegetation from previous years is important (Kirsch and Higgins 1976); needs perches for displaying such as fenceposts (White 1983). ...
... These have affected raptor populations with some species using sub-urban areas. Raptors have proven their ability to thrive in urban areas, such as the Red-tailed hawk [122], Sharp-shinned Hawk [123], as well as more recent urban colonists, such as the Northern goshawk [120], emphasizing their suitable role as sentinels. ...
Reported human cases of West Nile virus (WNV) in Europe increased dramatically in 2018. Lineage 1 strains had been circulating in Euro-Mediterranean countries since the early 1990s. The subsequent introduction of WNV lineage 2 has been responsible for the remarkable upsurge of European WNV outbreaks since 2004, including the dramatic increase in human cases observed since 2018. The virus exists in a natural cycle between mosquitoes and wild birds, with humans and horses acting as dead-end hosts. As the key vertebrate hosts in the transmission cycle of WNV, avian species have been the focus of surveillance across many countries. Raptors appear particularly susceptible to WNV infection, resulting in higher prevalence, and in some cases exhibiting neurological signs that lead to the death of the animal. In addition, birds of prey are known to play an important role as WNV reservoir and potentially amplifying hosts of infection. Importantly, raptor higher susceptibility/prevalence may indicate infection through predation of infected prey. Consequently, they are considered important target species when designing cost-effective surveillance for monitoring both seasonal WNV circulation in endemic countries and its emergence into new areas, where migrating raptors may play a critical role in virus introduction. This review summarizes the different aspects of the current knowledge of WNV infection in birds of prey and evaluates their role in the evolution of the epizootic that is spreading throughout Europe.
... Nests of urban sharp-shinned hawks (Accipiter striatus) in Quebec were situated in conifers within mixed deciduous-conifer stands that had high canopy closure, and were located on average 20 m from an opening that in many cases constituted considerable human activity; researchers noted that the large variability in most measurements suggested significant flexibility in nest-site requirements. 40 Swainson's hawks (Buteo swainsoni) in California nested in conifers in residential neighborhoods that were more than 20 years old and preferred neighborhoods older than 45 years old, which provided suitably mature trees for nesting; in the middle-aged neighborhoods (20-45 years old), hawks selected larger-than-average trees. 29 Urban eastern screech-owls more often used, and had higher reproductive rates in, nest boxes that were situated closer to the nearest house, possibly because such sites harbored fewer predators. ...
Raptors are an unusual success story of wildness thriving in the heart of our cities—they have developed substantial populations around the world in recent decades. But there are deeper issues around how these birds make their urban homes. New research provides insight into the role of raptors as vital members of the urban ecosystem and future opportunities for protection, management, and environmental education.
A cutting-edge synthesis of over two decades of scientific research, Urban Raptors is the first book to offer a complete overview of urban ecosystems in the context of bird-of-prey ecology and conservation. This comprehensive volume examines urban environments, explains why some species adapt to urban areas but others do not, and introduces modern research tools to help in the study of urban raptors. It also delves into climate change adaptation, human-wildlife conflict, and the unique risks birds of prey face in urban areas before concluding with real-world wildlife management case studies and suggestions for future research and conservation efforts.
Boal and Dykstra have compiled the go-to single source of information on urban birds of prey. Among researchers, urban green space planners, wildlife management agencies, birders, and informed citizens alike, Urban Raptors will foster a greater understanding of birds of prey and an increased willingness to accommodate them as important members, not intruders, of our cities.
... Nests of urban sharp-shinned hawks (Accipiter striatus) in Quebec were situated in conifers within mixed deciduous-conifer stands that had high canopy closure, and were located on average 20 m from an opening that in many cases constituted considerable human activity; researchers noted that the large variability in most measurements suggested significant flexibility in nest-site requirements. 40 Swainson's hawks (Buteo swainsoni) in California nested in conifers in residential neighborhoods that were more than 20 years old and preferred neighborhoods older than 45 years old, which provided suitably mature trees for nesting; in the middle-aged neighborhoods (20-45 years old), hawks selected larger-than-average trees. 29 Urban eastern screech-owls more often used, and had higher reproductive rates in, nest boxes that were situated closer to the nearest house, possibly because such sites harbored fewer predators. ...
If there is a single unifying characteristic of urban/suburban wildlife species, it is likely adaptability. Species that can occupy urban areas are behaviorally flexible,1,2 and this flexibility drives changes in the way they use urban space and cohabit with people. Raptors too exhibit behavioral changes when they move from rural to urban environs.³ Inherent plasticity allows some raptors to adjust their behavior to survive in circumstances that may differ greatly from those of more typical, rural, or natural areas. For example, they may move into urban environments that are suitable for them,4,5 or they may persist by tolerating human activity in a natural area that has been overwhelmed by suburbia. They may perceive human-made objects such as rooftops, utility towers, billboards, and bridges as potential nest sites,3,6,7,8 especially in areas where nest sites in traditional, natural locations are limited. Additionally, they may take advantage of a different prey type that is present, such as rats (Rattus spp.),9,10 or a typical prey type that is more abundant or available (e.g., birds at feeders).5,11
... Altwegg et al. 2013). The degree of urbanization may have a strong influence on species home range sizes, which may be smaller in urban environments compared to rural areas for raptors specialized in avian prey (Sodhi & Oliphant 1992, Parker 1996, Mannan & Boal 2000, Dykstra et al. 2001, Coleman et al. 2002, Rutz 2006, Morrison et al. 2016, that benefit from an accumulation of prey-sized birds in the city (Sorace & Gustin 2009). On the other hand, unlike passerines, raptors have the capacity to extend their home range sizes beyond urban boundaries (Tella et al. 1996, Riegert et al. 2007a, 2007b and therefore do not need to meet all their ecological requirements within innercity districts. ...
Capsule: Urban black sparrowhawk males hunt mostly within 2.27 km from their nest during the breeding season (‘home range’ of 16.15 km2) and increased the distance slightly to 2.43 km outside of the breeding season (18.56 km2). We found incredibly high individual variation within and between 6 GPS tagged males breeding, but no significant seasonal differences in the urban environment of Cape Town.
... Raptors vary in their tolerance of urbanization, however (Berry et al. 1998, Schmidt andBock 2004), and individuals living in urban environments often differ from conspecifics living in rural environments in home range size, survival, reproductive success, habitat use, and responses to human activity. Individuals of some species experience similar or higher reproductive success, nest at higher densities, and have smaller home ranges in urban environments (Parker 1996, Coleman et al. 2002, Dykstra et al. 2000. These findings suggest that urban landscapes can provide high quality habitat perhaps due to a variety of potential nesting substrates, high density of prey items, and the absence of persecution by humans (Sodhi et al. 1992, Bloom et al. 1993, Boal and Mannan 1998. ...
Raptors increasingly live and nest successfully in urban areas. In the urban landscape of Hartford, CT, red-tailed hawks established home ranges in large green spaces such as parks, golf courses, and cemeteries but also nested successfully in the commercial district of downtown and in densely built urban and suburban neighborhoods. Data collected from 11 radio-tagged breeding adult hawks indicated that year-round home ranges averaged 107.7 ha, much smaller than home ranges reported for hawks inhabiting rural areas. Most hawk home ranges had multiple core areas that were usually associated with favored perches or larger patches of ‘usable’ green space, defined as patches ≥0.25 ha in size, and home range size was positively associated with larger usable green space patches in core areas. Most nests were located in the largest core area and were within a larger patch of green space within the largest core area. Rather than just the amount or size of green space patches, the value of urban green spaces for these hawks likely also varies with the number and proximity of suitable perches such as buildings or tall trees, types and density of prey, and amount of human activity in and adjacent to these spaces. Territoriality and intraspecific competition may also influence home range size and dispersion of red-tailed hawks nesting in Hartford. In this urban area, mortality due to ingestion of rodenticides and collisions with vehicles affected hawk reproductive success.
... This could also apply to recent colonizations of urban habitats by other small-bird specialist species, which have coincided with declines in sparrow populations. These include the Merlin (Falco columbarius) and Sharp-shinned Hawk (Accipiter striatus) in North America (Sohdi et al. 1992, Coleman et al. 2002, and the Collared Sparrowhawk (A. cirrhocephalus) in Australia (Veerman 2003). Both of these regions have much in common with Europe in their history of human activities affecting birds of prey, including the severe effects of organochlorine pesticides on populations that recovered and ultimately colonized urban habitats after the chemicals were withdrawn (Bednarz et al. 1990, Olsen 1995. ...
We compared the pronounced geographic pattern in the recolonization of Britain by the Eurasian Sparrowhawk (Accipiter nisus) from 1970 onward with the spatiotemporal pattern among House Sparrow (Passer domesticus) populations over the same period, using data on the occurrence of both species at garden feeding stations. Using a simulation of House Sparrow population trends based on a logistic model that incorporated a predation index derived from Eurasian Sparrowhawk incidence functions, we generated a close approximation to the unique trajectories among House Sparrow populations in rural and urban sites in different regions of Britain. We carried out further comparisons using two contrasting methods that focused solely on temporal patterns. We used estimates of the varying date of Eurasian Sparrowhawk recolonization at different sites to derive time variables in relation to recolonization date. One such relative time variable proved to be a better predictor of House Sparrow numbers than chronological time; it indicated that House Sparrow numbers were generally stable or increasing prior to recolonization by Eurasian Sparrowhawks but declined continuously afterward. We also detected a significantly greater decrease in House Sparrow numbers when Eurasian Sparrowhawks were present using a method that compared annual changes in the abundance of prey species in the presence or absence of a predator. On the basis of these results, we argue that predation by Eurasian Sparrowhawks may be a sufficient explanation for the decline in House Sparrows in Britain. We also argue that urban House Sparrow populations' long-term release from predator pressure made them especially vulnerable when urban habitats were colonized by Eurasian Sparrowhawks. Received 3 April 2009, accepted 31 October 2009.
As part of a study of long-term population changes and their possible causes, about 100 Osprey nests in six areas in southern and central Sweden were investigated twice annually during the period 1971-73. This paper reports on population status and reproductive success and discusses some factors influencing the breeding of the Osprey. Over the census period there was no significant change in the size of the population. The mean clutch size was about 2.88, the mean number of young hatched was calculated as 1.80, and the mean number of young surviving to the age of 4-5 weeks was 1.48. (This figure is used to express the reproductive success in the active nests.) A comparison with figures on brood sizes selected from bird-ringing data indicates a decrease in reproductive success since 1947.