Search

Raptors around the world have experienced marked declines from a variety of reasons in recent decades. We continued an effort that began in the 1940s to monitor an entire raptor community in a protected landscape in northwest Wyoming. Our goals were to describe basic information on nesting raptor ecology such as nesting substrate use, nest re-use, nest switching, and nest persistence, and to track changes in the raptor community over time. We searched a 31.1-km2 area intensively for all nesting raptors and surveyed a 841.1-km2 study area primarily for Red-tailed Hawks (Buteo jamaicensis) and Common Ravens (Corvus corax), but recorded other nesting raptors and corvids when observed. In 2001–2002 and 2014–2015, we located and monitored 182 nesting attempts during intensive monitoring in the smaller study area. Between 1992 and 2015, we located and monitored an additional 984 nesting attempts in the larger study area. Nests were used by 14 raptor species and 2 corvid species. Nests built in trees accounted for 92.5% of all located nests. Most nests, 75.3%, were used only 1 y, although nest re-use varied from 1 to 13 y. When a nest was reused, it was most commonly used by the same species. From the 1940s through 2015, very little change occurred in the raptor community with the exception of a slight decrease in Red-tailed Hawks and a slight increase in Common Ravens. Our results inform a basic understanding of nesting raptor needs and support the idea that protected landscapes may be effective tools for conserving species like raptors. [ABSTRACT FROM AUTHOR]

We investigated nesting behavior, food habits, and interspecific interactions of Short-eared Owls (Asio flammeus) within an arctic tundra raptor community on Herschel Island and Komakuk Beach, northern Yukon, Canada. Short-eared Owls were the least common nesting raptor. We found only three nests, all on Herschel Island. All nests were on relatively elevated sites with fairly substantial vegetative cover. All nests failed in the egg stage, from a combination of human disturbance and possible prédation by Arctic Fox (Vulpes lagopus) or Red Fox (Vulpes vulpes). Short-eared Owls nested only in years when small rodent densities were at least 4 to 5 individuals per hectare in the spring. Short-eared Owls ate Northern Collared Lemmings (Dicrostonyx groenlandicus), Brown Lemmings (Lemmus trimucronatus), and Tundra Voles (Microtus oeconomus) almost exclusively, without clear selectivity. Peregrine Falcons (Falco peregrinus) killed two adult Short-eared Owls. In northern Yukon, the Short-eared Owl remains an uncommon summer resident and uses the region as a migration route. Spring rodent densities and interspecific prédation are prominent limiting factors, and human disturbance also limits nesting success. We recommend restricting access to most tundra areas during periods when the birds are mating, initiating nesting, and incubat-ing eggs. We recommend that human infrastructure be designed so that it cannot support novel nesting (and therefore local range expansion) by other nesting raptors that compete with and prey on Short-earned Owls. [ABSTRACT FROM AUTHOR]

Scavenging raptors have been postulated to be declining at a rate far higher than predatory raptors. To test this hypothesis we reviewed the historical and present status of the seven raptor species—three scavengers (two kites and a vulture), one partial scavenger (a buzzard) and three species (osprey and two falcons) that take live prey—that breed on the Cape Verde islands. Scavenging raptors have experienced steeper declines and more local extinctions than non-scavengers in Cape Verde, with the partial scavenger midway between the two groups. Causes of scavenger decline include incidental poisoning, direct persecution and declines in the availability of carcasses and other detritus. These findings, which highlight the conservation importance of the island of Santo Antão, indicate the priority that needs to be accorded to scavengers, particularly in Europe where many insular populations are reaching unsustainable levels. [ABSTRACT FROM PUBLISHER]

Abstract: For a total of 9years, we examined the patterns of a nesting raptor community that utilized European Magpie (Pica pica) nests in the Zuojia Natural Reserve, northeast China. Eight raptor species and two other bird species were recorded nesting in magpie nests. The reuse rate of abandoned magpie nests was 51.6%, and the number of reused nests was positively correlated with their availability. Raptors utilized 83.3% of the reused abandoned magpie nests. Nests followed for more than 1year were reused by raptors an average of 1.13 times. Interspecific nest usurpation was common, with 17.3% of new magpie nests being usurped by raptors, and four cases of usurpation occurred among different raptor species. At the community level, 8 of 11 raptor species took over magpie nests to breed in the study area, and 91.9% of their nests came from magpie nests. European Magpies represent the core species in the nest web of the local raptor community that utilizes magpie nests. At the forest stand level, closer proximity to forest edges and greater distances from occupied raptor nests were the best predictors of nest reuse. At the nest-site level, arbor density and canopy coverage were the best predictors of nest reuse. [Copyright &y& Elsevier]