Seasonal and Interspecific Variation in Frugivory by a Mixed Resident-Migrant Overwintering Songbird Community
Many temperate passerine bird species switch from diets of mostly invertebrates in the spring and summer to diets that include fruit and seeds in the fall and winter. However, relatively few studies have quantified diet composition or the extent of seasonal shifts during the non-breeding period, par...
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MDPI AG
2021-07-01
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| Online Access: | https://www.mdpi.com/1424-2818/13/7/314 |
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| author | Wales A. Carter Scott F. Pearson Adam D. Smith Scott R. McWilliams Douglas J. Levey |
| author_facet | Wales A. Carter Scott F. Pearson Adam D. Smith Scott R. McWilliams Douglas J. Levey |
| author_sort | Wales A. Carter |
| collection | DOAJ |
| description | Many temperate passerine bird species switch from diets of mostly invertebrates in the spring and summer to diets that include fruit and seeds in the fall and winter. However, relatively few studies have quantified diet composition or the extent of seasonal shifts during the non-breeding period, particularly among species and across communities with both residents and migrants. We measured carbon and nitrogen stable isotope values in food items (fruits, C<sub>3</sub> and C<sub>4</sub> seeds, and insects from various trophic levels and plant communities) and in multiple tissues (feathers and plasma/whole blood) from 11 species of songbirds wintering in the southeastern U.S. We combined these diet and tissue values with empirically derived discrimination factors and used concentration-dependent mixing models to quantify seasonal diet shifts. We also validated mixing model results with data from fecal samples. Diets in this bird community, as delineated N and C isotopic space, diverged in the fall and winter relative to the summer as consumption of fruits and seeds increased. Across this songbird community, estimated contributions of fruit to plasma/whole blood increased from 16.2 ± 7.5% in the fall (mean ± SD; range: 4–26%) to 21.7 ± 10.3% (range: 9–37%) in the winter, while contributions of seeds increased from 29.4 ± 2.6% (range: 28–32%) in the fall to 36.6 ± 4.8% (range: 32–42%) in the winter. Fecal data showed qualitatively similar trends to mixing models, but consistently estimated higher contributions of fruit. Our work indicates that fruits and seeds constitute substantial sources of sustenance for non-breeding songbirds, there is considerable separation of resource use among species in the fall and winter, and fecal estimates of contributions to songbird tissues should be interpreted cautiously. |
| first_indexed | 2024-03-10T09:42:38Z |
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| language | English |
| last_indexed | 2024-03-10T09:42:38Z |
| publishDate | 2021-07-01 |
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| spelling | doaj.art-fa4541b0318a4e83b7e44ca8703734262023-11-22T03:36:09ZengMDPI AGDiversity1424-28182021-07-0113731410.3390/d13070314Seasonal and Interspecific Variation in Frugivory by a Mixed Resident-Migrant Overwintering Songbird CommunityWales A. Carter0Scott F. Pearson1Adam D. Smith2Scott R. McWilliams3Douglas J. Levey4Department of Natural Resources Science, University of Rhode Island, Kingston, RI 02881, USADepartment of Biology, University of Florida, Gainesville, FL 32611, USADepartment of Natural Resources Science, University of Rhode Island, Kingston, RI 02881, USADepartment of Natural Resources Science, University of Rhode Island, Kingston, RI 02881, USAPopulation and Community Ecology Cluster, Division of Environmental Biology, National Science Foundation, Alexandria, VA 22314, USAMany temperate passerine bird species switch from diets of mostly invertebrates in the spring and summer to diets that include fruit and seeds in the fall and winter. However, relatively few studies have quantified diet composition or the extent of seasonal shifts during the non-breeding period, particularly among species and across communities with both residents and migrants. We measured carbon and nitrogen stable isotope values in food items (fruits, C<sub>3</sub> and C<sub>4</sub> seeds, and insects from various trophic levels and plant communities) and in multiple tissues (feathers and plasma/whole blood) from 11 species of songbirds wintering in the southeastern U.S. We combined these diet and tissue values with empirically derived discrimination factors and used concentration-dependent mixing models to quantify seasonal diet shifts. We also validated mixing model results with data from fecal samples. Diets in this bird community, as delineated N and C isotopic space, diverged in the fall and winter relative to the summer as consumption of fruits and seeds increased. Across this songbird community, estimated contributions of fruit to plasma/whole blood increased from 16.2 ± 7.5% in the fall (mean ± SD; range: 4–26%) to 21.7 ± 10.3% (range: 9–37%) in the winter, while contributions of seeds increased from 29.4 ± 2.6% (range: 28–32%) in the fall to 36.6 ± 4.8% (range: 32–42%) in the winter. Fecal data showed qualitatively similar trends to mixing models, but consistently estimated higher contributions of fruit. Our work indicates that fruits and seeds constitute substantial sources of sustenance for non-breeding songbirds, there is considerable separation of resource use among species in the fall and winter, and fecal estimates of contributions to songbird tissues should be interpreted cautiously.https://www.mdpi.com/1424-2818/13/7/314diet shiftsdiet overlapfrugivorygranivoryisotopic nichemixing model |
| spellingShingle | Wales A. Carter Scott F. Pearson Adam D. Smith Scott R. McWilliams Douglas J. Levey Seasonal and Interspecific Variation in Frugivory by a Mixed Resident-Migrant Overwintering Songbird Community Diversity diet shifts diet overlap frugivory granivory isotopic niche mixing model |
| title | Seasonal and Interspecific Variation in Frugivory by a Mixed Resident-Migrant Overwintering Songbird Community |
| title_full | Seasonal and Interspecific Variation in Frugivory by a Mixed Resident-Migrant Overwintering Songbird Community |
| title_fullStr | Seasonal and Interspecific Variation in Frugivory by a Mixed Resident-Migrant Overwintering Songbird Community |
| title_full_unstemmed | Seasonal and Interspecific Variation in Frugivory by a Mixed Resident-Migrant Overwintering Songbird Community |
| title_short | Seasonal and Interspecific Variation in Frugivory by a Mixed Resident-Migrant Overwintering Songbird Community |
| title_sort | seasonal and interspecific variation in frugivory by a mixed resident migrant overwintering songbird community |
| topic | diet shifts diet overlap frugivory granivory isotopic niche mixing model |
| url | https://www.mdpi.com/1424-2818/13/7/314 |
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