Humans have drastically altered the population of willow flycatchers through means of land development as well as land manipulation. Most habitats of the willow flycatcher have been destroyed as a result of the human construction of dams as a means of river management for flood control. Moreover, agricultural development and the development of developmental and urban development has also resulted in the loss of habitat for these endangered birds. Urban development next to or in willow flycatcher habitat greatly affects their population as residential areas usually have a demand for fresh water and thus the construction of more dams. Moreover, human recreation has also affected the population of the willow flycatchers as recreational areas are often built in riparian habitats. Riparian areas are popular for recreational purposes because of the shade, water, fishing, boating, and swimming opportunities they provide. However, there are many consequences to making these areas open to recreational use as it is home to many species who live there. This includes a reduction in vegetation, bank erosion, and increased the incidence of fire. With little to eat and a destroyed habitat, willow flycatcher populations drastically decrease numbers.
Livestock and wild ungulate grazing also contribute to the depletion of the Willow Flycatcher population.Over time, willow flycatchers have evolved with herbivores. Overgrazing as well as over-utilization of soil and plants in riparian areas by animals such as deer and elk have reduced the amount of vegetation available for willow flycatchers. This overgrazing has occurred as a result of the introduction of non-native species such as wild horses and burros by humans and a reduction of beavers who were previously native to riparian habitats. As a result of vegetation depletion, alter riparian habitats and can increase flood flows. This, however, is not the only example of how the human introduction of non-native species to riparian areas have contributed to the decline of willow flycatcher population. The introduction of the brown-headed cowbird by Europeans has also drastically affected willow flycatcher population numbers. With an increase in the development of suburban and agricultural areas, the number of cowbirds in riparian areas has similarly increased. These birds act as a parasite to willow flycatchers as they lay their eggs in the nest of other species. Once hatched, cowbirds often grow quicker than host eggs and out compete baby willow flycatchers for parental care. They also remove willow flycatcher eggs form the nest, displacing and predating on the Willow Flycatcher population.
Lastly, fire ecology and management is another way humans have impacted the habitat of willow flycatchers. Riparian vegetation is not fire adapted nor is it able to regenerate after fire. However, the lack of regulated flood events in river controlled areas (such as dams) can result in an increased amount of fuels and flammable tamarisk and arrowweed. This has resulted in an increase in fires as well as their size in willow flycatcher habitats.
The following table shows the impact recreation has on riparian areas in the Southwestern region of the US where the Willow Flycatcher resides.
“Recreation impacts in riparian habitat in the southwestern United States.”Recreation impacts in riparian habitat in the southwestern United States. Adapted from Cole and Landres (1995).”
willow flycatcher 