….will probably reign for ever more unless the bird is trapped. Could it even be Acadian? Information from the USA’s Cornell Lab of Ornithology states:
Alder Flycatcher is difficult to distinguish from the Willow Flycatcher by any feature other than voice.
Song is the only definitive way to tell them apart. However, measurements of crown color with a colorimeter, together with other measures of wing shape, bill and tail, may be able to distinguish birds in the hand that are not calling.
Willow and Alder flycatchers do not respond to playback of recordings of each other’s songs, even where their ranges overlap.
Willow Flycatcher has a thin white eyering which may be lacking. (The Nanjizal bird has a very obvious one)
The distribution/migration maps show Alder Flycatcher to migrate only on the eastern side of America to its wintering quarters in Nothern south America, whereas Willow, migrates south across the whole of central America to winter in central and southern America.
The photos below all show WILLOW Flycatcher. I have trawled through 100’s of photos of Willow and cant find many that show (a) as bold, bright wingbars as the Nanjizal bird and (b) as prominant an eyering as the Nanjizal bird? On the other hand all the literature states they can only be seperated on call.
Paul Freestone (c) Cornwall Birding 2008.