Irrigated pastures and postponed cattle grazing: Strategies for augmenting wetland avian production.

摘要

I experimentally tested the effects of grazing postponement on bird use of irrigated cattle pastures in close proximity to an established wetland. Pastures with early (May-initiated) and late (July-initiated) grazing were compared. Furthermore non-irrigated, salt-desert scrub habitat was examined. Grazing postponement did not result in greater use of irrigated pastures by foraging waterfowl, shorebirds and various passerine species. Use of irrigated pastures by nesting waterfowl was greater when grazing was postponed, yet this result was dependent on vegetation height of pastures as well as the availability of alternate nesting habitat throughout the wetland. High rates of nest predation resulted in low nest success within irrigated cattle pastures regardless of grazing regime. Postponed grazing of irrigated pastures has the potential to augment wetland bird production through the provisioning of tall and dense vegetation for nesting. Yet, high rates of nest predation may limit the realization of this potential.