- 期刊
Reproductive Ecology of Three Tibetan Waterbird Species, with Special Reference to Life-History Alterations along Elevational Gradients
並列摘要
Life-history theory predicts that birds nesting at higher elevations will have lower reproductive output due to ecological constraints. Higher-elevation birds should allocate more energy into individual offspring through producing fewer and larger eggs to allow their offspring to better survive the harsh environments. To test the prediction, I collected reproductive data on 3 waterbirds, the Mallard Anas platyrhynchos, Common Moorhen Gallinula chlorpus and Eurasian Coot Fulica atra, at Lhalu Wetland (3650 m in elevation), the largest marshland with macrophytes on the Tibetan Plateau. These birds became regular nesters after prohibition of yak grazing and reed harvesting in the wetland since 2003. Mallards laid eggs from mid-Apr. to mid-June, moorhens from early May to mid-June, and coots from mid-May to late June. Clutch size and egg size of these high-elevation waterbirds were smaller or intermediate compared to those of their lowland counterparts, partially supporting the prediction. The pattern might be associated with a balance between environmental harshness and allocation of body reserves in terms of the number of clutches produced annually, and the number and size of eggs within a clutch across elevational gradients. The high-elevation mallards and moorhens primarily used reeds Phragmites australis as nesting habitat (with 92% and 68% of nests located there, respectively), whereas coots preferred rushes Juncus effusus (77%). Predation by mammals and flooding contributed to about 1/2 of the failed mallard and moorhen nests, whereas predation was responsible for the majority of coot nest loss. My data also suggest the importance of wetland management based on species-specific habitat requirements for conserving this breeding waterbird assemblage.