Chapter 3: Threats

The continued survival of the southwestern willow flycatcher (Empidonax traillii extimus) is threatened indirectly by the loss, modification, and fragmentation of riparian habitat, and directly by factors that impact the survival and reproductive success of flycatchers. Because the impact of habitat loss on small populations can be particularly severe, we first discuss some of the population-level effects that may be influencing flycatcher population dynamics. We then review some contemporary cases of habitat loss and discuss other factors potentially impacting the flycatcher. The effects of brown-headed cowbird (Molothrus ater) parasitism on the southwestern willow flycatcher are discussed in detail in Chapter 8. For additional information on site-specific threats to the southwestern willow flycatcher readers should consult Greenwald (1998).