RESEARCH ARTICLE


Evidence for a Relationship Between the Movements of the Common Redpoll (Acanthis flammea) and the American Goldfinch (Spinus tristis)



Paul J. Dougherty*, W. Herbert Wilson, Jr.
Department of Biology, Colby College, 5739 Mayflower Hill Drive, Waterville, ME 04901, USA


Article Metrics

CrossRef Citations:
0
Total Statistics:

Full-Text HTML Views: 1816
Abstract HTML Views: 1382
PDF Downloads: 923
ePub Downloads: 819
Total Views/Downloads: 4940
Unique Statistics:

Full-Text HTML Views: 835
Abstract HTML Views: 618
PDF Downloads: 340
ePub Downloads: 251
Total Views/Downloads: 2044



© 2018 Dougherty and Wilson.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: (https://creativecommons.org/licenses/by/4.0/legalcode). This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Department of Biology, Colby College, 5739 Mayflower Hill Drive, Waterville, ME 04901, USA; Tel: 508-479-1910; E-mails: pdoughel@uwyo.edu, whwilson@colby.edu


Abstract

Background:

Many bird species that breed at high latitudes exhibit irregular southward incursions in response to spatial and temporal variation in winter food availability.

Methods:

We analyzed Christmas Bird Count records to compare the migratory behavior of the Common Redpoll (Acanthis flammea), an Arctic breeder known to invade southern latitudes every other winter, with that of the American Goldfinch (Spinus tristis), a closely related finch species that breeds broadly in temperate latitudes in North America.

Results and Discussion:

Historic data indicate that east of the Rocky Mountains, both species overwinter in relatively even numbers across latitudes. In contrast, we found few significant positive correlations between the winter records of each species in different areas along the same longitude. We attribute these patterns to the fact that resource levels and environmental conditions tend to be similar across latitudes. While previous studies of historic data have identified a biennial pattern in the migration of the Common Redpoll, we found evidence that populations of American Goldfinches breeding in the northern parts of the species’ range similarly display significant southward movements every other year. Because these two species breed at different latitudes and show large-scale southward movements during the same years, areas across southern Canada and the northern United States alternate between having high winter abundances of Common Redpolls and American Goldfinches. We propose that these alternations are caused by a shared response to cyclical seed crop failure across the northern regions of North America.

Keywords: Irruption, Facultative migration, Finch, Christmas bird count, Masting cycles, Redpoll, Goldfinch.