Moisture as a determinant of habitat quality for a nonbreeding Neotropical migratory songbird
Identifying the determinants of habitat quality for a species is essential for understanding how populations are limited and regulated. Spatiotemporal variation in moisture and its influence on food availability may drive patterns of habitat occupancy and demographic outcomes. Nonbreeding migratory...
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Published in | Ecology (Durham) Vol. 91; no. 10; pp. 2874 - 2882 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
United States
Ecological Society of America
01.10.2010
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Subjects | |
Online Access | Get more information |
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Summary: | Identifying the determinants of habitat quality for a species is essential for understanding how populations are limited and regulated. Spatiotemporal variation in moisture and its influence on food availability may drive patterns of habitat occupancy and demographic outcomes. Nonbreeding migratory birds in the neotropics occupy a range of habitat types that vary with respect to moisture. Using carbon isotopes and a satelliteâderived measure of habitat moisture, we identified a moisture gradient across home ranges of radioâtracked Northern Waterthrush (Seiurus noveboracensis). We used this gradient to classify habitat types and to examine whether habitat moisture correlates with overwinter mass change and spring departure schedules of Northern Waterthrush over the lateâwinter dry season in the tropics. The two independent indicators of moisture revealed similar gradients that were directly proportional to body mass change as the dry season progressed. Birds occupying drier habitats declined in body mass over the study period, while those occupying wetter habitats increased in body mass. Regardless of habitat, birds lost an average of 7.6% of their mass at night, and mass recovery during the day trended lower in dry compared with wet habitats. This suggests that daily incremental shortfalls in mass recovery can lead to considerable seasonâlong declines in body mass. These patterns resulted in consequences for the premigratory period, with birds occupying drier habitats having a delayed rate of fat deposition compared with those in wet habitats. Taken together with the finding that males, which are significantly larger than females, are also in better condition than females regardless of habitat suggests that highâquality habitats may be limited and that there may be competition for them. The habitatâlinked variation in performance we observed suggests that habitat limitation could impact individual and populationâlevel processes both during and in subsequent periods of the annual cycle. The linkage between moisture and habitat quality for a migratory bird indicates that the availability of highâquality habitats is dynamic due to variation in precipitation among seasons and years. Understanding this link is critical for ascertaining the impact of future climate change, particularly in the Caribbean basin, where a much drier future is predicted. |
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Bibliography: | http://dx.doi.org/10.1890/09-2212.1 |
ISSN: | 0012-9658 1939-9170 |
DOI: | 10.1890/09-2212.1 |