Spatial segregation between Gray-cheeked Thrush and an introduced nest predator in a managed forest landscape
Introduced species are known for inducing changes in ecosystems and for their impacts on endemic island species. North American red squirrels ( Tamiasciurus hudsonicus ) were introduced to Newfoundland, Canada, during the 1960s and have been hypothesized as a cause of the precipitous decline of the...
| Main Authors: | , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Resilience Alliance
2023-12-01
|
| Series: | Avian Conservation and Ecology |
| Subjects: | |
| Online Access: | https://www.ace-eco.org/vol18/iss2/art5 |
| _version_ | 1797372305622433792 |
|---|---|
| author | Jenna P. B. McDermott Darroch M. Whitaker Ian G. Warkentin |
| author_facet | Jenna P. B. McDermott Darroch M. Whitaker Ian G. Warkentin |
| author_sort | Jenna P. B. McDermott |
| collection | DOAJ |
| description | Introduced species are known for inducing changes in ecosystems and for their impacts on endemic island species. North American red squirrels ( Tamiasciurus hudsonicus ) were introduced to Newfoundland, Canada, during the 1960s and have been hypothesized as a cause of the precipitous decline of the Newfoundland Gray-cheeked Thrush ( Catharus minimus minimus ). To test the prediction that the impacts of squirrels led to range contraction by thrushes, we completed 1960 point count surveys for squirrel and thrush over two years (2016 and 2017) in western Newfoundland. Thrushes and squirrels were strongly segregated by elevation, with thrushes now being commonly detected at only high elevation, squirrels being detected most frequently at low elevation, and both species being rare and inversely likely to be present at intermediate elevations. We evaluated local (5.5 ha) and landscape (490.8 ha) scale habitat affiliations of thrushes using landcover data from a provincial forest resource inventory to assess the potential for synergistic impacts on thrush of squirrel invasion and forest management. Gray-cheeked Thrushes were associated with regenerating (10–30 years post-harvest) clear-cuts, conifer forest, and tall scrub at the local scale, but avoided tall scrub, regenerating stands, and second growth forest at the landscape scale. Regenerating clear-cuts and modified strip cuts were selected by thrushes at a local scale. Breeding Bird Survey data show that Gray-cheeked Thrushes were abundant at lower elevations prior to the expansion of squirrels across Newfoundland, so our finding of strong elevational segregation adds to the growing body of evidence suggesting that the introduction of squirrels played an important role in the sudden decline and range contraction of this insular songbird subspecies. Management for squirrels should include efforts to prevent spread upslope and to nearshore islands while more study is done on this and other hypotheses regarding the cause of Gray-cheeked Thrush decline, as well as on relevant aspects of the ecology of this little-studied thrush. |
| first_indexed | 2024-03-08T18:33:50Z |
| format | Article |
| id | doaj.art-939bcc4b4e2249968e504d6872208d34 |
| institution | Directory Open Access Journal |
| issn | 1712-6568 |
| language | English |
| last_indexed | 2024-03-08T18:33:50Z |
| publishDate | 2023-12-01 |
| publisher | Resilience Alliance |
| record_format | Article |
| series | Avian Conservation and Ecology |
| spelling | doaj.art-939bcc4b4e2249968e504d6872208d342023-12-29T17:00:10ZengResilience AllianceAvian Conservation and Ecology1712-65682023-12-01182510.5751/ACE-02472-1802052472Spatial segregation between Gray-cheeked Thrush and an introduced nest predator in a managed forest landscapeJenna P. B. McDermott0Darroch M. Whitaker1Ian G. Warkentin2Cognitive and Behavioural Ecology, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, CanadaParks Canada, Rocky Harbour, Newfoundland and Labrador, CanadaEnvironmental Science, Memorial University of Newfoundland, Corner Brook, Newfoundland and Labrador, CanadaIntroduced species are known for inducing changes in ecosystems and for their impacts on endemic island species. North American red squirrels ( Tamiasciurus hudsonicus ) were introduced to Newfoundland, Canada, during the 1960s and have been hypothesized as a cause of the precipitous decline of the Newfoundland Gray-cheeked Thrush ( Catharus minimus minimus ). To test the prediction that the impacts of squirrels led to range contraction by thrushes, we completed 1960 point count surveys for squirrel and thrush over two years (2016 and 2017) in western Newfoundland. Thrushes and squirrels were strongly segregated by elevation, with thrushes now being commonly detected at only high elevation, squirrels being detected most frequently at low elevation, and both species being rare and inversely likely to be present at intermediate elevations. We evaluated local (5.5 ha) and landscape (490.8 ha) scale habitat affiliations of thrushes using landcover data from a provincial forest resource inventory to assess the potential for synergistic impacts on thrush of squirrel invasion and forest management. Gray-cheeked Thrushes were associated with regenerating (10–30 years post-harvest) clear-cuts, conifer forest, and tall scrub at the local scale, but avoided tall scrub, regenerating stands, and second growth forest at the landscape scale. Regenerating clear-cuts and modified strip cuts were selected by thrushes at a local scale. Breeding Bird Survey data show that Gray-cheeked Thrushes were abundant at lower elevations prior to the expansion of squirrels across Newfoundland, so our finding of strong elevational segregation adds to the growing body of evidence suggesting that the introduction of squirrels played an important role in the sudden decline and range contraction of this insular songbird subspecies. Management for squirrels should include efforts to prevent spread upslope and to nearshore islands while more study is done on this and other hypotheses regarding the cause of Gray-cheeked Thrush decline, as well as on relevant aspects of the ecology of this little-studied thrush.https://www.ace-eco.org/vol18/iss2/art5elevationforest managementhabitatintroduced speciesnorth american red squirrel |
| spellingShingle | Jenna P. B. McDermott Darroch M. Whitaker Ian G. Warkentin Spatial segregation between Gray-cheeked Thrush and an introduced nest predator in a managed forest landscape Avian Conservation and Ecology elevation forest management habitat introduced species north american red squirrel |
| title | Spatial segregation between Gray-cheeked Thrush and an introduced nest predator in a managed forest landscape |
| title_full | Spatial segregation between Gray-cheeked Thrush and an introduced nest predator in a managed forest landscape |
| title_fullStr | Spatial segregation between Gray-cheeked Thrush and an introduced nest predator in a managed forest landscape |
| title_full_unstemmed | Spatial segregation between Gray-cheeked Thrush and an introduced nest predator in a managed forest landscape |
| title_short | Spatial segregation between Gray-cheeked Thrush and an introduced nest predator in a managed forest landscape |
| title_sort | spatial segregation between gray cheeked thrush and an introduced nest predator in a managed forest landscape |
| topic | elevation forest management habitat introduced species north american red squirrel |
| url | https://www.ace-eco.org/vol18/iss2/art5 |
| work_keys_str_mv | AT jennapbmcdermott spatialsegregationbetweengraycheekedthrushandanintroducednestpredatorinamanagedforestlandscape AT darrochmwhitaker spatialsegregationbetweengraycheekedthrushandanintroducednestpredatorinamanagedforestlandscape AT iangwarkentin spatialsegregationbetweengraycheekedthrushandanintroducednestpredatorinamanagedforestlandscape |