Dramatic Declines of Evening Grosbeak Numbers at a Spring Migration Stop-Over Site
Evening Grosbeak (<i>Coccothraustes vespertinus</i>) populations have been hypothesized to be in steep decline across North America. Data characterizing long-term changes are needed to quantify the magnitude of the declines. We surveyed grosbeaks at a spring migratory stop-over site in C...
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MDPI AG
2022-06-01
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| Series: | Diversity |
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| Online Access: | https://www.mdpi.com/1424-2818/14/6/496 |
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| author | W. Douglas Robinson Jessica Greer Juliana Masseloux Tyler A. Hallman Jenna R. Curtis |
| author_facet | W. Douglas Robinson Jessica Greer Juliana Masseloux Tyler A. Hallman Jenna R. Curtis |
| author_sort | W. Douglas Robinson |
| collection | DOAJ |
| description | Evening Grosbeak (<i>Coccothraustes vespertinus</i>) populations have been hypothesized to be in steep decline across North America. Data characterizing long-term changes are needed to quantify the magnitude of the declines. We surveyed grosbeaks at a spring migratory stop-over site in Corvallis, Oregon, USA, where birds gather annually during April and May to feast on elm (<i>Ulmus</i> spp.) seeds before departing to breeding sites. An estimate produced by a statistics professor in the 1970s indicated peak numbers were 150,000 to 250,000 birds. Our surveys in 2013–2015 found annually variable numbers, from a few hundred grosbeaks in the lowest year to less than five thousand birds in the highest year. If the original estimate is approximately true, Evening Grosbeak numbers have experienced dramatic declines, averaging −2.6%/year, over the last four decades. Our local observation of declines during spring aligns with declines documented in winter across North America by bird feeder studies and in summer by the Breeding Bird Survey. We explore potential explanations for the changes in population size, such as influences of spruce budworm outbreaks, disease, and decreased structural diversity of forests owing to harvest practices. We also consider the challenges of interpreting changes in abundance of species with exceptionally variable populations, especially if population fluctuations or cycles may have long periodicities. Finally, we call for additional planned surveys to track the numbers of this enigmatic and charismatic species. |
| first_indexed | 2024-03-09T23:58:11Z |
| format | Article |
| id | doaj.art-35e9dcea3baf44e18b74de7368a85a7e |
| institution | Directory Open Access Journal |
| issn | 1424-2818 |
| language | English |
| last_indexed | 2024-03-09T23:58:11Z |
| publishDate | 2022-06-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Diversity |
| spelling | doaj.art-35e9dcea3baf44e18b74de7368a85a7e2023-11-23T16:21:02ZengMDPI AGDiversity1424-28182022-06-0114649610.3390/d14060496Dramatic Declines of Evening Grosbeak Numbers at a Spring Migration Stop-Over SiteW. Douglas Robinson0Jessica Greer1Juliana Masseloux2Tyler A. Hallman3Jenna R. Curtis4Oak Creek Lab of Biology, Department of Fisheries, Wildlife, and Conservation Sciences, Oregon State University, Corvallis, OR 97331, USAOak Creek Lab of Biology, Department of Fisheries, Wildlife, and Conservation Sciences, Oregon State University, Corvallis, OR 97331, USAOak Creek Lab of Biology, Department of Fisheries, Wildlife, and Conservation Sciences, Oregon State University, Corvallis, OR 97331, USAOak Creek Lab of Biology, Department of Fisheries, Wildlife, and Conservation Sciences, Oregon State University, Corvallis, OR 97331, USAOak Creek Lab of Biology, Department of Fisheries, Wildlife, and Conservation Sciences, Oregon State University, Corvallis, OR 97331, USAEvening Grosbeak (<i>Coccothraustes vespertinus</i>) populations have been hypothesized to be in steep decline across North America. Data characterizing long-term changes are needed to quantify the magnitude of the declines. We surveyed grosbeaks at a spring migratory stop-over site in Corvallis, Oregon, USA, where birds gather annually during April and May to feast on elm (<i>Ulmus</i> spp.) seeds before departing to breeding sites. An estimate produced by a statistics professor in the 1970s indicated peak numbers were 150,000 to 250,000 birds. Our surveys in 2013–2015 found annually variable numbers, from a few hundred grosbeaks in the lowest year to less than five thousand birds in the highest year. If the original estimate is approximately true, Evening Grosbeak numbers have experienced dramatic declines, averaging −2.6%/year, over the last four decades. Our local observation of declines during spring aligns with declines documented in winter across North America by bird feeder studies and in summer by the Breeding Bird Survey. We explore potential explanations for the changes in population size, such as influences of spruce budworm outbreaks, disease, and decreased structural diversity of forests owing to harvest practices. We also consider the challenges of interpreting changes in abundance of species with exceptionally variable populations, especially if population fluctuations or cycles may have long periodicities. Finally, we call for additional planned surveys to track the numbers of this enigmatic and charismatic species.https://www.mdpi.com/1424-2818/14/6/496biodiversity benchmarks<i>Coccothraustes vespertinus</i>Evening GrosbeakAmerican elmDutch elm diseasemigratory stopover |
| spellingShingle | W. Douglas Robinson Jessica Greer Juliana Masseloux Tyler A. Hallman Jenna R. Curtis Dramatic Declines of Evening Grosbeak Numbers at a Spring Migration Stop-Over Site Diversity biodiversity benchmarks <i>Coccothraustes vespertinus</i> Evening Grosbeak American elm Dutch elm disease migratory stopover |
| title | Dramatic Declines of Evening Grosbeak Numbers at a Spring Migration Stop-Over Site |
| title_full | Dramatic Declines of Evening Grosbeak Numbers at a Spring Migration Stop-Over Site |
| title_fullStr | Dramatic Declines of Evening Grosbeak Numbers at a Spring Migration Stop-Over Site |
| title_full_unstemmed | Dramatic Declines of Evening Grosbeak Numbers at a Spring Migration Stop-Over Site |
| title_short | Dramatic Declines of Evening Grosbeak Numbers at a Spring Migration Stop-Over Site |
| title_sort | dramatic declines of evening grosbeak numbers at a spring migration stop over site |
| topic | biodiversity benchmarks <i>Coccothraustes vespertinus</i> Evening Grosbeak American elm Dutch elm disease migratory stopover |
| url | https://www.mdpi.com/1424-2818/14/6/496 |
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