Ecology of Willow Flycatchers (Empidonax traillii) in the Sierra Nevada, California: Effects of Meadow Characteristics and Weather on Demographics

Abstract Population declines in songbirds are often attributed to regional habitat loss and fragmentation caused by land-use practices, which might be further aggravated by climate change. These concerns are particularly evident in the Intermountain West, where riparian areas are considered a priority for conservation because of predicted reductions in winter precipitation and increases in spring temperatures. These climatic changes might increase the susceptibility of species reliant on riparian areas to regional extirpation from loss of habitat. The Willow Flycatcher (Empidonax traillii) is a California species of concern because of precipitous population declines in the past three decades. In 1997, we established a long-term research program to determine population demographics and the effects of weather events and regional-scale meadow distribution and vegetative structure on nesting success of Willow Flycatchers. We monitored territory establishment and reproductive success of 786 territories and 850...