Willow Flycatcher Nesting within Narrowleaf Cottonwood in the Sierra Nevada

Abstract

in the Sierra Nevada the Willow Flycatcher (Empidonax traillii brewsteri) typically nests within wetlands in high-elevation meadows (Green et al. 2003), almost always in shrubby willows (Salix spp.) and alders (Alnus spp.) (Serena 1982, harris et al. 1987, Valentine 1987, Sanders and Flett 1989, Bombay et al. 2003) and rarely more than 3 m off the ground (Beedy and Pandolfino 2013). Occasionally, however, it nests in more complex multilayered riparian woodland comprising a shrub understory and an upper canopy featuring larger trees such as cottonwood and aspen (Populus spp.; Dietrich 2020), as elsewhere in the species’ range (Sogge et al. 2010). During surveys for nesting Willow Flycatchers in June 2021, i located a nest in a narrowleaf cottonwood (Populus angustifolia) tree along the Little Truckee river near Stampede reservoir in the Tahoe National Forest. The nest was 4.5 meters high, and the nest tree was surrounded by a mix of aspen and other cottonwood trees but also included an understory of shrubby willows (Figure 1). The cottonwood with the nest was approximately 8.5 meters tall, and other nearby cottonwood trees were similar in height. Nearby aspen trees were much taller (>10 m), and the willow shrubs of the understory were shorter (<3 m). The cup nest was located near the main trunk where two branches came together and appeared to be composed of grass and sedge-like vegetation (Figure 1). The area around the nest was dense with cottonwood branches and leaves that kept the nest well concealed and shaded. This group of riparian trees and shrubs were growing on a large sediment bar forming an island with channels on both sides near where the river flows into Stampede reservoir. Sogge et al. (2010) reported Southwestern Willow Flycatchers (E. t. extimus) nesting in smaller willow shrubs at high elevations in the Southwest but also in larger box elder (Acer negundo), coast live oak (Quercus agrifolia), russian olive (Elaeagnus angustifolia), and salt cedar (Tamarix spp.) trees. Whitfield et al. (1999) reported Southwestern Willow Flycatchers nesting in large willows and occasionally