Song Sparrows vs. cowbird brood parasites: Impacts of forest structure and nest-site selection
Song Sparrows vs. cowbird brood parasites: Impacts of forest structure and nest-site selection
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作者：
Larison, B;Laymon, SA;Smith, TB
我们研究了自然和恢复的河岸森林中的歌麻雀 (Melospiza melodia) 繁殖生态学，以评估栖息地结构和巢址选择对棕头牛鹂 (Molothrus ater) 寄生的影响。 Logistic回归显示，栖息地结构在两个尺度上影响寄生概率，即BROAD（距离巢穴11.3 m以内）和LOCAL（距离巢穴5 m以内）。高度 < 1 m (BROAD) 具有丰富侧向覆盖的巢穴不太可能被寄生，这表明地面侧向覆盖可以通过隐藏巢穴附近宿主的活动来减少寄生。相比之下，高度为 2-3 m 且树叶覆盖丰富的巢穴（局部）更有可能被寄生，这表明巢穴上方的树叶覆盖可能会增加寄生现象，因为它们为雌性牛鹂提供了可以观察寄主活动并寻找巢穴的栖息地。麻雀筑巢地点的选择因森林类型而异，但每种森林类型的巢穴的地面横向覆盖率和巢穴上方的树叶覆盖率相似。结果表明，进一步研究栖息地结构对巢穴选择和牛鹂寄生的影响可能会找到通过适当的栖息地管理和恢复工作来减少寄生的方法。
We studied Song Sparrow (Melospiza melodia) reproductive ecology in natural and restored riparian forest to evaluate the influence of habitat structure and nest-site selection on parasitism by Brown-headed Cowbirds (Molothrus ater). Logistic regression revealed that habitat structure affected the probability of parasitism at two scales, BROAD (within 11.3 m of the nest) and LOCAL (within 5 m of the nest). Nests with abundant lateral cover at a height of < 1 m (BROAD) were less likely to be parasitized, suggesting that lateral cover at ground level may reduce parasitism by concealing host movements in the vicinity of the nest. in contrast, nests with abundant foliage cover at a height of 2-3 m (LOCAL) were more likely to be parasitized, suggesting that foliage cover above the nest may increase parasitism by providing perches from which female cowbirds can watch host activities and find nests. Sparrow nest-site selection varied among forest types, but lateral cover at ground level and foliage cover above the nest were similar for nests in each forest type. Results suggest that further research on the effects of habitat structure on nest-site selection and cowbird parasitism could lead to methods of reducing parasitism through appropriate habitat management and restoration efforts.