Use of alternate upland nesting habitat reduces brood parasitism in an endangered bird
The Least Bell’s Vireo ( Vireo bellii pusillus ) is a federally endangered songbird restricted to Southern California, USA, and Baja California, Mexico. Historically abundant, it suffered a catastrophic population decline during the twentieth century due to widespread habitat destruction and the arr...
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| Language: | English |
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Resilience Alliance
2025-06-01
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| Series: | Avian Conservation and Ecology |
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| Online Access: | https://www.ace-eco.org/vol20/iss1/art7 |
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| author | Kevin B Clark Kimberly Ferree |
| author_facet | Kevin B Clark Kimberly Ferree |
| author_sort | Kevin B Clark |
| collection | DOAJ |
| description | The Least Bell’s Vireo ( Vireo bellii pusillus ) is a federally endangered songbird restricted to Southern California, USA, and Baja California, Mexico. Historically abundant, it suffered a catastrophic population decline during the twentieth century due to widespread habitat destruction and the arrival of Brown-headed Cowbirds ( Molothrus ater ) within its breeding range. We monitored Least Bell’s Vireo nests and conducted cowbird removals for over 13 years in a protected natural area along the Otay River in San Diego County, California. We evaluated the effects of lay date (day of the first egg laid in each nest), nest habitat (river channel versus adjacent upland terrace), and cowbird removals on Least Bell’s Vireo brood parasitism rates and nest success. Least Bell’s Vireos nested in 11 different host plant species, but over half of vireo nests were found in the upland shrub laurel sumac ( Malosma laurina ). We located and monitored 177 Least Bell’s Vireo nests, of which 20% were parasitized. The rate of parasitized nests was strongly associated with whether cowbird removals had occurred that season (9%) or had not (35%), despite the low number of female cowbirds removed annually (1–4 females per year). We also found that nests located in the upland terrace had a lower parasitism rate compared to the river channel (12% vs. 29%), with this difference more pronounced in years without cowbird removals. These differences in parasitism rates also drove differences in nest success; only 29% of channel nests were successful versus 48% of nests on the terrace. The best model predicting cowbird brood parasitism included lay date, cowbird removals, and nest habitat (river channel versus upland terrace). Thus, recovering populations of Least Bell’s Vireos may benefit by nesting outside of riparian habitats in adjacent upland habitat due to reduced cowbird parasitism rates. Conservation and restoration of upland habitats adjacent to riparian areas may provide refugia from cowbird parasitism, allowing for continued population increases in areas with limited funding for cowbird management. Conservation of upland habitats will also increase habitat available to Least Bell’s Vireos under future drier climate scenarios. |
| format | Article |
| id | doaj-art-f4e672d87b1945cfbde4e999b5a81a51 |
| institution | Kabale University |
| issn | 1712-6568 |
| language | English |
| publishDate | 2025-06-01 |
| publisher | Resilience Alliance |
| record_format | Article |
| series | Avian Conservation and Ecology |
| spelling | doaj-art-f4e672d87b1945cfbde4e999b5a81a512025-08-20T03:30:03ZengResilience AllianceAvian Conservation and Ecology1712-65682025-06-01201710.5751/ACE-02807-2001072807Use of alternate upland nesting habitat reduces brood parasitism in an endangered birdKevin B Clark0Kimberly Ferree1San Diego Natural History MuseumSan Diego Natural History MuseumThe Least Bell’s Vireo ( Vireo bellii pusillus ) is a federally endangered songbird restricted to Southern California, USA, and Baja California, Mexico. Historically abundant, it suffered a catastrophic population decline during the twentieth century due to widespread habitat destruction and the arrival of Brown-headed Cowbirds ( Molothrus ater ) within its breeding range. We monitored Least Bell’s Vireo nests and conducted cowbird removals for over 13 years in a protected natural area along the Otay River in San Diego County, California. We evaluated the effects of lay date (day of the first egg laid in each nest), nest habitat (river channel versus adjacent upland terrace), and cowbird removals on Least Bell’s Vireo brood parasitism rates and nest success. Least Bell’s Vireos nested in 11 different host plant species, but over half of vireo nests were found in the upland shrub laurel sumac ( Malosma laurina ). We located and monitored 177 Least Bell’s Vireo nests, of which 20% were parasitized. The rate of parasitized nests was strongly associated with whether cowbird removals had occurred that season (9%) or had not (35%), despite the low number of female cowbirds removed annually (1–4 females per year). We also found that nests located in the upland terrace had a lower parasitism rate compared to the river channel (12% vs. 29%), with this difference more pronounced in years without cowbird removals. These differences in parasitism rates also drove differences in nest success; only 29% of channel nests were successful versus 48% of nests on the terrace. The best model predicting cowbird brood parasitism included lay date, cowbird removals, and nest habitat (river channel versus upland terrace). Thus, recovering populations of Least Bell’s Vireos may benefit by nesting outside of riparian habitats in adjacent upland habitat due to reduced cowbird parasitism rates. Conservation and restoration of upland habitats adjacent to riparian areas may provide refugia from cowbird parasitism, allowing for continued population increases in areas with limited funding for cowbird management. Conservation of upland habitats will also increase habitat available to Least Bell’s Vireos under future drier climate scenarios.https://www.ace-eco.org/vol20/iss1/art7brood parasitismbrown-headed cowbirdconservationhabitatleast bell's vireoproductivityriparian |
| spellingShingle | Kevin B Clark Kimberly Ferree Use of alternate upland nesting habitat reduces brood parasitism in an endangered bird Avian Conservation and Ecology brood parasitism brown-headed cowbird conservation habitat least bell's vireo productivity riparian |
| title | Use of alternate upland nesting habitat reduces brood parasitism in an endangered bird |
| title_full | Use of alternate upland nesting habitat reduces brood parasitism in an endangered bird |
| title_fullStr | Use of alternate upland nesting habitat reduces brood parasitism in an endangered bird |
| title_full_unstemmed | Use of alternate upland nesting habitat reduces brood parasitism in an endangered bird |
| title_short | Use of alternate upland nesting habitat reduces brood parasitism in an endangered bird |
| title_sort | use of alternate upland nesting habitat reduces brood parasitism in an endangered bird |
| topic | brood parasitism brown-headed cowbird conservation habitat least bell's vireo productivity riparian |
| url | https://www.ace-eco.org/vol20/iss1/art7 |
| work_keys_str_mv | AT kevinbclark useofalternateuplandnestinghabitatreducesbroodparasitisminanendangeredbird AT kimberlyferree useofalternateuplandnestinghabitatreducesbroodparasitisminanendangeredbird |