Walter H Piper, Jason Grear, Brian Hoover, Elaina Lomery, Linda M Grenzer
{"title":"Plunging floater survival causes cryptic population decline in the Common Loon.","authors":"Walter H Piper, Jason Grear, Brian Hoover, Elaina Lomery, Linda M Grenzer","doi":"10.1093/condor/duaa044","DOIUrl":null,"url":null,"abstract":"<p><p>Populations of many vertebrates are declining and geographic ranges contracting, largely as a consequence of anthropogenic threats. Many reports of such decline, however, lack the breadth and detail to narrow down its causes. Here we describe population decline in the Common Loon (<i>Gavia immer</i>), a charismatic aquatic bird, based on systematic resighting and measurement of a marked population. During our 27-year investigation, age-adjusted chick mass has fallen by 11%, mortality among young and old chicks has increased by 31% and 82%, respectively, and fledging success has declined by 26%. Meanwhile, the return rate of marked nonbreeders (\"floaters\") has plunged by 53%, and the adult population overall has declined by 22%. Consistent with the thinning ranks of floaters, the rate of territory eviction has decreased by 52% during the study. Despite the decline in floaters, territory occupancy remains unchanged. However, a matrix model, updated with recent estimates for breeding success, juvenile survival, and senescence, yields a recalculated deterministic population growth rate (λ) of 0.94 for our study population, which suggests that declines in vital rates could lead to a loss of 52% of the current population and a decline of 37% in territory occupancy by 2031. Lack of data on floaters in other upper Midwest and New England loon populations leaves their status in doubt.</p>","PeriodicalId":50624,"journal":{"name":"Condor","volume":null,"pages":null},"PeriodicalIF":2.6000,"publicationDate":"2020-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11363150/pdf/","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Condor","FirstCategoryId":"99","ListUrlMain":"https://doi.org/10.1093/condor/duaa044","RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ORNITHOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
Populations of many vertebrates are declining and geographic ranges contracting, largely as a consequence of anthropogenic threats. Many reports of such decline, however, lack the breadth and detail to narrow down its causes. Here we describe population decline in the Common Loon (Gavia immer), a charismatic aquatic bird, based on systematic resighting and measurement of a marked population. During our 27-year investigation, age-adjusted chick mass has fallen by 11%, mortality among young and old chicks has increased by 31% and 82%, respectively, and fledging success has declined by 26%. Meanwhile, the return rate of marked nonbreeders ("floaters") has plunged by 53%, and the adult population overall has declined by 22%. Consistent with the thinning ranks of floaters, the rate of territory eviction has decreased by 52% during the study. Despite the decline in floaters, territory occupancy remains unchanged. However, a matrix model, updated with recent estimates for breeding success, juvenile survival, and senescence, yields a recalculated deterministic population growth rate (λ) of 0.94 for our study population, which suggests that declines in vital rates could lead to a loss of 52% of the current population and a decline of 37% in territory occupancy by 2031. Lack of data on floaters in other upper Midwest and New England loon populations leaves their status in doubt.
期刊介绍:
The Condor is the official publication of the Cooper Ornithological Society, a non-profit organization of over 2,000 professional and amateur ornithologists and one of the largest ornithological societies in the world. A quarterly international journal that publishes original research from all fields of avian biology, The Condor has been a highly respected forum in ornithology for more than 100 years. The journal is one of the top ranked ornithology publications. Types of paper published include feature articles (longer manuscripts) Short Communications (generally shorter papers or papers that deal with one primary finding), Commentaries (brief papers that comment on articles published previously in The Condor), and Book Reviews.