Auswahl der wissenschaftlichen Literatur zum Thema „Circus hudsonius“

Feathers of an unknown bird of prey were collected on the coastal plain tundra near Meinypil’gyno (62°32′ N, 177°03′ E), SE Chukotka on June 5, 2021. An analysis of the mitochondrial cytochrome b gene and sex chromosome CHD1 gene fragments from DNA isolated from the feathers showed with full confidence that the feathers belonged to a male of the Nearctic Northern Harrier (Circus hudsonius (Linnaeus 1766)), formerly considered as being a subspecies of the Holarctic Hen Harrier (C. cyaneus (Linnaeus 1766)). No specimens of the American Harrier from the northern Far East of Russia are contained in the collections of the Zoological Museum of Moscow State University and the Zoological Institute of the Russian Academy of Sciences. Few other known visual observations of harriers in Chukotka are not properly documented for their correct species identification. The revealed vagrant American Harrier documents the first record of this species in Russia generally and in Chukotka in particular.

Abstract Nest depredation is one of the greatest threats posed to ground-nesting ducks. We employed cameras to monitor 164 duck nests (71 cinnamon teal, Spatula cyanoptera, 44 gadwall, Mareca strepera, 38 mallard, Anas platyrhynchos, and 11 nests of unknown species) in the wetlands surrounding Great Salt Lake, from 2015–2021. Of the 164 nests, 21% were successful, 73% were depredated and 7% were abandoned. We observed predators at 99 of the 119 depredated nests; predators at 20 nests went undetected. Raccoons (Procyon lotor, depredated nests) and striped skunks (Mephitis mephitis, ) were the most common of the 99 nest predators recorded. Other predators that depredated nests included long-tailed weasels (Mustela frenata), northern harriers (Circus hudsonius), California gulls (Larus californicus), Sandhill cranes (Antigone canadensis), common ravens (Corvus corax), coyotes (Canis latrans) and red foxes (Vulpes vulpes). Neither the number of eggs removed per depredation event nor the number of eggs remaining varied by predator species. Depredated nests were easier for predators to find than undisturbed, incubated nests, resulting in 68% of depredated nests being visited by multiple predators. All hens detected the approach of a predator and flushed before the predator reached the nest; no hens attempted to defend their nest or attack the predator. Only 21% of hens returned to their depredated nest, and those that did remained off their nest an average of 33 h and 23 h after their nest was depredated by a raccoon or skunk, respectively. Seventeen percent of hens resumed incubation of their depredated nest, but only 1 nest to which a hen returned successfully hatched an egg. Depredation events of raccoons and skunks were not distributed randomly during the 24-hour day, but rather occurred most often during the night and nautical twilight, and rarely during the day. Depredation events of avian predators occurred during the day, rarely during twilight, and none during the night. Depredation events during the night were more likely when the wind was calm but temperature, humidity, and actual moon illumination had no impact. Depredation events by skunks and raccoons occurred more often during the 1st and 4th phases of the moon (new moon) than in the 2nd or 3rd phase.

ABSTRACT Although there are a variety of methods available for trapping raptors, some species, such as Northern Harriers (Circus hudsonius), are not easily captured with standard methods. We tested several existing trapping methods and modified two of them based on Northern Harrier ecology and behavior across seasons in a study population in California. No previously successful methods described in the literature were effective for our study population. Two modified methods were most effective for trapping Northern Harriers: (1) placing two dho-gazas around the nest in a V-shape and flushing the adult female into the nets during the breeding season, and (2) using remote-triggered bow nets baited with waterbird carcasses in winter. Dho-gazas at the nest worked well during the early nestling-rearing stage, when nestlings were younger than 2 wk old and adult females were most attentive. This method was not suitable during the incubation stage because Northern Harriers are prone to nest abandonment. In the winter, Northern Harriers are known to scavenge, yet this aspect of their behavioral ecology has previously been rarely exploited for trapping purposes. These two methods allow for selective Northern Harrier trapping across seasons and provide modified options for research on this understudied and declining species in North America.