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Cheryl R. Dykstra

Cheryl R. Dykstra
Raptor Environmental

Ph.D.

About

76
Publications
7,728
Reads
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796
Citations
Education
August 1988 - December 1994
University of Wisconsin–Madison
Field of study
  • Wildlife Ecology

Publications

Publications (76)
Article
Full-text available
Urban and suburban raptors live in close proximity to humans, and some species defend their nests and young vigorously, even diving at or striking humans walking on the ground. Such raptors may be more defensive of their nests than rural birds. We investigated (1) whether Red-shouldered Hawk (Buteo lineatus) nest defense behavior differs between su...
Article
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Black-capped chickadees (Poecile atricapillus) and other species that feed at bird feeders balance the benefit of easy foraging with the added risk of predation. Individual birds respond differently to risky situations, and these differences have been attributed to the birds’ personalities, which researchers commonly assess with an “open-field” beh...
Article
Full-text available
In many raptor species, hatching asynchrony results in a size hierarchy among nestlings, which may facilitate brood reduction by means of sibling aggression-induced mortality, especially in times of low food resources. However, few researchers have investigated the relationships among hatching asynchrony, sibling aggression, and nestling feeding ra...
Article
Full-text available
The south Florida subspecies of the Red-shouldered Hawk (Buteo lineatus extimus) is distinctly paler and smaller than other subspecies, reproduces at a lower rate, and can occupy very different habitats such as open marshes and grasslands with only scattered trees. We evaluated population differentiation between the south Florida population of Red-...
Article
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We report on egg-laying and hatching dates (n = 656), and morphological characteristics (n = 642) of nestling Bald Eagles (Haliaeetus leucocephalus) from six study areas in Minnesota and Wisconsin, USA, from 2006 to 2011, 2014, and 2015. Nestling age was estimated from length of the eighth primary feather using sex-specific equations from the liter...
Article
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Birds that forage at feeders must balance the risk of predation with the benefit of food acquisition. We color-banded black-capped chickadees (Poecile atricapillus) in a wild population and investigated their responses to a predator (Cooper's hawk, Accipiter cooperii) model placed 1 m or 5 m from a feeding platform. Over 40 trials, we recorded a to...
Article
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Global climate change has advanced the breeding phenology of many avian species. However, raptors’ breeding phenologies may not respond in the same way to the factors that influence passerine breeding dates. We studied reproduction of suburban and rural Red-shouldered Hawks (Buteo lineatus) in southern Ohio, United States, from 1997 to 2020. Mean h...
Article
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Research is underway around the world to examine how a wide range of animal species have responded to reduced levels of human activity during the COVID-19 pandemic. In this perspective article, we argue that raptors are particularly well-suited for investigating potential ‘anthropause’ effects, and that the resulting insights will provide much-need...
Article
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We measured concentrations of up to 17 polybrominated diphenyl ethers (PBDEs) in plasma of 492 bald eagle (Haliaeetus leucocephalus) nestlings between 1995 and 2017 from 12 study areas in Wisconsin and Minnesota, USA. Geometric mean concentrations of the sum of 9 PBDE congeners (∑PBDE) measured across all years ranged from 2.88 to 10.8 µg/L, and ne...
Article
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Like many raptors, Red-shouldered Hawks (Buteo lineatus) exhibit asynchronous hatching, which is thought to be a parental strategy for rearing the maximum number of offspring under conditions of unpredictable prey availability. Current knowledge of incubation patterns and the associated behavioral mechanisms by which asynchronous hatching occurs in...
Article
Both habitat and weather can strongly influence reproductive rates of birds. We measured reproductive rates of suburban and rural Red‐shouldered Hawks Buteo lineatus in southern Ohio, USA, from 1997 to 2016, and then tested how weather conditions and habitat in the areas surrounding the nest‐sites were related to two measures of reproductive rate....
Article
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We analyzed concentrations and trends of perfluoroalkyl substances (PFAS) in blood plasma samples of bald eagle (Haliaeetus leucocephalus) nestlings at 6 study areas in the upper Midwest of the United States, 2006 to 2015, and long‐term trends at 2 Lake Superior sites, 1995 to 2015. Nestling blood plasma concentrations of the sum of 15 PFAS analyte...
Article
Full-text available
We used banding data to investigate dispersal and survival of Red-shouldered Hawks (Buteo lineatus) in two study areas in southern Ohio from 1996 to 2018. Of the 2448 nestlings we banded, 167 (6.8%) were encountered (dead or alive) some time after banding. Mean distance from the natal nest at the time of encounter was 31.6 ± 6.2 km (median = 10.0,...
Article
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We analyzed concentrations and trends of DDE, total PCBs, and mercury in bald eagle (Haliaeetus leucocephalus) nestlings at six study areas in the upper Midwest, 2006–2015, and long-term trends at two Lake Superior sites, 1989–2015. Eaglet plasma from the Apostle Islands in Lake Superior had the highest concentrations of DDE (geometric mean [GM] =...
Chapter
With its beautiful black-and-white wings and tail contrasting with a richly rusty body and its insistent “kee-kee-kee” calls, the red-shouldered hawk (Buteo lineatus) is a welcome neighbor for many suburban residents—a little bit of wilderness that inserts itself into everyday life. That it eats mainly rodents, snakes, and other species perceived a...
Chapter
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....
Book
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 oppo...
Article
Full-text available
There have been no detailed studies of predator or non-predator causes of mortality and failure at nests of the Red-shouldered Hawk (Buteo lineatus), and identification of such causes has been largely speculative. There is ample information about rates of nest success, defined as the fledging of ≥1 nestling from a nest, but this measure of reproduc...
Article
Full-text available
We report on patterns and trends in polybrominated diphenyl ethers (PBDEs) in plasma of 284 bald eagle nestlings sampled between 1995 and 2011 at six study areas in the upper Midwestern United States. Geometric mean concentrations of total PBDEs (Ʃ of nine congeners) ranged from 1.78 ng/mL in the upper St. Croix River watershed to 12.0 ng/mL on the...
Article
Full-text available
Nestling growth may be used to estimate age of nestling raptors, which is valuable for investigating hatch order dynamics and nestling behavior, as well as assessing reproductive rate and back-calculating hatching date. To estimate nestling age, the most valuable parameter to measure growth is one that does not vary greatly with environmental facto...
Article
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We examined nestling Red-shouldered Hawks (Buteo lineatus) in 56 nests (147 nestlings) in suburban southwestern Ohio and in 25 nests (67 nestlings) in rural forested Hocking Hills in southcentral Ohio, ∼80 km east of southwestern Ohio. Fifteen of 25 nests in Hocking Hills had Protocalliphora avium larvae on one or more nestlings and/or pupae in the...
Article
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Sexing of raptors is important for understanding their ecology and demography. Males and females of monomorphic species such as Red-shouldered Hawks (Buteo lineatus) may be distinguished using molecular and morphometric techniques. We collected blood samples and morphometric measurements from adult and nestling Red-shouldered Hawks in southern Ohio...
Article
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Little is known about the habitat and ecology of suburban Barred Owls (Strix varia), a species sometimes considered the nocturnal equivalent of Red-shouldered Hawks (Buteo lineatus). We compared nesting habitat of Barred Owls to that of Red-shouldered Hawks nesting in suburban and urban areas, in and near the city of Cincinnati, Ohio, to determine...
Article
Full-text available
We measured concentrations of DDE, total PCBs, and mercury in bald eagle (Haliaeetus leucocephalus) nestlings at three locations in the upper Midwest: Lake Superior, the upper Mississippi River, and the St. Croix River, 2006–2008. We also analyzed trends in concentrations of these contaminants for eagles on the southern shore of Lake Superior, from...
Article
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We measured the reproductive rate of Red-shouldered Hawks (Buteo lineatus) nesting in suburban southwestern Ohio and in a rural forested region in Hocking Hills, southeastern Ohio, from 1997 to 2005. In the suburban region, the reproductive rate varied greatly from nest to nest, less so from year to year, indicating that some nest areas consistentl...
Article
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Red-shouldered Hawks (Buteo lineatus) typically line their nests with fresh branches of coniferous and deciduous trees. We recorded all species of green material present in 63 nests from 2003 to 2005 in suburban Cincinnati in southwestern Ohio, and in 35 nests in Hocking Hills in southeastern Ohio, United States. We identified all trees within 0.08...
Article
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 ea...
Article
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We investigated the trend in contaminant concentrations in Lake Superior bald eagles (Haliaeetus leucocephalus) from 1989–2001, and examined the relationship of contaminant concentrations to eagle reproductive rate during that time. Concentrations of dichloro-diphenyl-dichloroethylene (DDE) and total polychlorinated biphenyls (PCBs) in nestling blo...
Article
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We banded nestling Red-shouldered Hawks (Buteo lineatus) in southwestern Ohio and north- ern Kentucky (SW OHIO, hereafter) to examine movements and determine causes of mortality in this suburban population. For comparison, we examined band recovery records for nestling Red-shouldered Hawks banded in rural northern Ohio. Of 899 nestlings banded in S...
Article
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We used direct observations to quantify prey types, prey delivery rate, and adult and nestling behavior at nests of Red-shouldered Hawks (Buteo lineams) in suburban southwestern Ohio. Twenty-one nests were observed for 256 hr in 1997-2001. Small mammals made up the largest percentage of the identified prey (31.5%), followed by reptiles (22.7%), inv...
Article
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We used a remote video recording system and direct observation to quantify provisioning rate and adult and nestling behavior at Bald Eagle (Haliaeetus leucocephalus) nests in north-central Wis- consin in 1992 (N = 5) and 1993 (N = 8). Eagles nesting in this region have a high reproductive rate (-->1.3 young/occupied territory), and the number of oc...
Article
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Bald eagles (Haliaeetus leucocephalus) nesting on the shores of Green Bay, Lake Michigan, had reproductive rates significantly lower than those of neighboring eagles nesting in inland Wisconsin (0.55 vs. 1.1 young per occupied territory). This study investigated effects of two factors which have depressed eagle reproductive rates at other locations...
Article
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We measured an index of Red-shouldered Hawk (Buteo lineatus) abundance along streams in southern Ohio and related differences in abundance in- dex to landscape-scale habitat characteristics within the surveyed areas. Fifteen study sites, each a 5.8-km reach of a permanent stream, were surveyed four times using broadcasts of Red-shouldered Hawk call...
Article
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We measured the home ranges and habitat use of 11 Red-shouldered Hawks (Buteo lineatus) during the breeding season and 9 during the nonbreeding season in suburban Ohio, using standard telemetry techniques. Mean home ranges, calculated using the adaptive kernel method (95% isopleth), were 90 ha ;pm 11 SE during the breeding season, 189 ha ;pm 33 SE...
Article
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We measured field metabolic rate of nestling Bald Eagles (Haliaeetus leucocephalus) in northern Wisconsin, using doubly-labeled water. In inland northern Wisconsin and along the Wisconsin Lake Superior shore, eaglets aged 39–60 days, weighing 3.08–4.85 kg, expended an average of 2,427 ± 100 kJ day−1. Nestling field metabolic rate was weakly correla...
Article
Full-text available
We measured nest site selection and productivity of suburban-nesting Red-shouldered Hawks (Buteo lineatus) in southwestern Ohio and rural-nesting Red-shouldered Hawks in south-central Ohio. At both the suburban and the rural locations, nest sites had greater canopy height and overall tree basal area than paired random plots, and were located closer...
Article
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Reproductive rate (productivity) of bald eagles (Haliaeetus leucocephalus) nesting on the shores of Lake Superior was significantly less than that of neighboring eagles nesting in inland Wisconsin (1.0 vs. 1.3 young per breeding attempt, 1989–1993), and at other inland lake/riverine habitats in the Great Lakes Basin. It is possible that the current...
Article
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We validated the doubly labeled water (DLW) technique for measurement of energy expenditure in bald eagles (Haliaeetus leucocephalus) in captivity by simultaneously measuring metabolizable energy intake in a feeding trial. We calculated CO2 production using two equations, one typically used by animal ecologists (the "one-pool" equation) and the oth...
Article
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We tested the hypothesis that brood size in House Wrens (Troglodytes aedon), which have a mean mass of 10.6 g, is confined by digestive limits to maximal rate of energy flow in parents feeding nestlings. Using doubly-labeled water (DLW), we measured field metabolic rate during feeding of nestlings ( ${\rm FMR}_{{\rm r}}$ ), tested whether it increa...
Article
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We compared digestive tract structure and function in house wrens (Troglodytes aedon) feeding on crickets at two intake levels (5. 18 g/d and 2.42 g/d). We increased the birds' intake through a combination of lowered air temperature and forced exercise. Apparent metabolizable energy coefcient (1-(energy excreted/energy ingested)) was. 771 in high-i...

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