Birds
Alder Flycatcher
Empidonax alnorum · also called alder flycatchers
For decades, ornithologists lumped the alder flycatcher together with its near-identical relative, until a careful look at song patterns revealed two genuinely separate species hiding behind one very confusing shared appearance.
Overview
The alder flycatcher, Empidonax alnorum, is a small, insect-hunting bird native to boggy alder thicket and wetland edge habitat across Canada and the northern United States. Its recent taxonomic split from the nearly identical willow flycatcher, reliance on song for identification, and long migration to South America make it one of the more scientifically interesting flycatchers in North America.
A species defined by sound, not sight
Where appearance fails to separate the alder flycatcher from its closest relative, its distinctive burry song succeeds completely, giving researchers and birders alike the one dependable tool for telling the two apart.
Status
Least Concern — widespread and stable across suitable boggy shrub and wetland habitat throughout Canada and the northern United States.
Alder Flycatcher: common questions
Why were the alder flycatcher and willow flycatcher once considered the same species?
The two look almost indistinguishable by sight, so they were treated as a single species until the 1970s, when researchers confirmed that their songs, the alder flycatcher's burry "free-beer" and the willow flycatcher's sharper "fitz-bew," never overlap, providing solid evidence to justify splitting them into two separate species.
How can you tell an alder flycatcher from a willow flycatcher?
Song is the most reliable method, since the alder flycatcher produces a burry, two-noted call often rendered as "free-beer," distinctly different from the willow flycatcher's sharper "fitz-bew," while the two species look nearly identical in the field.
Where does the alder flycatcher prefer to breed?
This species generally breeds farther north than the willow flycatcher, favouring boggy, wet thickets of alder and other shrubs across the boreal and northern temperate zones of Canada and the northern United States.
How far does the alder flycatcher migrate?
It undertakes a long-distance migration each year, travelling from its northern breeding grounds in Canada and the northern United States all the way to South America to spend the winter, one of the more extensive journeys among North American flycatchers.