{"title":"Are Northern Harriers (Circus hudsonius) Facultative Specialists on Arvicoline Rodents in Midwestern Agroecosystems?","authors":"M. Zagorski, R. Swihart","doi":"10.1637/0003-0031-184.2.188","DOIUrl":null,"url":null,"abstract":"Abstract. We assessed geographic and temporal variation in diets of wintering Northern Harriers (Circus hudsonius) in western Indiana, U.S.A., using multivariate regression on counts of prey from pellets collected at communal roosts. Because there is no uniform method for determining the minimum number of individuals (MNI) contained in a pellet, we also assessed whether application of four different counting methods influenced our conclusions. We collected 821 Northern Harrier pellets from four roosts in 2018 and 2019. Pellet contents differed between years, months, and roost sites. Voles (Microtus spp.) were the most commonly occurring prey group at all roosts and in both years (range: 45–73%), but were encountered 35% less frequently than reported on average by other studies in the midwestern U.S.A. Accordingly, other small mammal prey groups became more important dietary components than reported by most other midwestern studies, including mice (Peromyscus; 5–16%), western harvest mice (Reithrodontomys megalotis; 4–14%), and northern short-tailed shrews (Blarina brevicauda; 8–18%). The four methods of counting MNI produced no discernible effects on our conclusions concerning pellet contents between months or roosts. Northern Harriers in western Indiana exhibited great diet flexibility, which likely reflects local prey populations and constraints of life in intensive agroecosystems.","PeriodicalId":50802,"journal":{"name":"American Midland Naturalist","volume":"184 1","pages":"188 - 204"},"PeriodicalIF":0.6000,"publicationDate":"2020-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"2","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"American Midland Naturalist","FirstCategoryId":"93","ListUrlMain":"https://doi.org/10.1637/0003-0031-184.2.188","RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"Agricultural and Biological Sciences","Score":null,"Total":0}
引用次数: 2
Abstract
Abstract. We assessed geographic and temporal variation in diets of wintering Northern Harriers (Circus hudsonius) in western Indiana, U.S.A., using multivariate regression on counts of prey from pellets collected at communal roosts. Because there is no uniform method for determining the minimum number of individuals (MNI) contained in a pellet, we also assessed whether application of four different counting methods influenced our conclusions. We collected 821 Northern Harrier pellets from four roosts in 2018 and 2019. Pellet contents differed between years, months, and roost sites. Voles (Microtus spp.) were the most commonly occurring prey group at all roosts and in both years (range: 45–73%), but were encountered 35% less frequently than reported on average by other studies in the midwestern U.S.A. Accordingly, other small mammal prey groups became more important dietary components than reported by most other midwestern studies, including mice (Peromyscus; 5–16%), western harvest mice (Reithrodontomys megalotis; 4–14%), and northern short-tailed shrews (Blarina brevicauda; 8–18%). The four methods of counting MNI produced no discernible effects on our conclusions concerning pellet contents between months or roosts. Northern Harriers in western Indiana exhibited great diet flexibility, which likely reflects local prey populations and constraints of life in intensive agroecosystems.
期刊介绍:
The American Midland Naturalist has been published for 90 years by the University of Notre Dame. The connotations of Midland and Naturalist have broadened and its geographic coverage now includes North America with occasional articles from other continents. The old image of naturalist has changed and the journal publishes what Charles Elton aptly termed "scientific natural history" including field and experimental biology. Its significance and breadth of coverage are evident in that the American Midland Naturalist is among the most frequently cited journals in publications on ecology, mammalogy, herpetology, ornithology, ichthyology, parasitology, aquatic and invertebrate biology and other biological disciplines.