Like the Alder Flycatcher, this is a bird of pioneer forests and shrubby vegetation.
When the new growth exceeds about 10 ft. in height the Willow Flycatchers lose interest and move to younger growth.
They build untidy nests in shrubs or low trees.
They are late to arrive in spring and it is usually late May or early June before they are heard: when they stop singing in August they are almost impossible to identify, so only those bird watchers active during the summer months will make their acquaintance.
Their “fitz-bew” song is the best means of separating this species from the Alder and Least Flycatchers.
Dr. J. Murray Speirs