Saturday, April 17, 2010

Splits, Splits, Splits

Winter Wren / Photo by ~Shanth

Yesterday David Sibley posted a list of the bird species that he thought were most likely to be split into multiple species. You can read his comments for each of the splits at his site, but here are the ten:
  1. Willet
  2. Whippoorwill
  3. Winter Wren
  4. Xantus's Murrelet
  5. Yellow-rumped Warbler
  6. White-breasted Nuthatch
  7. Marsh Wren
  8. Fox Sparrow
  9. Spruce Grouse
  10. Western Scrub-Jay

As far as I know, most of these are still being researched and debated, so the AOU may not take action on them for some time. 

The only one of these potential splits that would give me an armchair life bird is the split of Winter Wren into its western and eastern populations (currently Troglodytes troglodytes pacificus and Troglodytes troglodytes hiemalis). I still remember listening to the western subspecies when I was in Washington a few years ago. Their songs and those of Hermit Thrushes form part of my memory of the Cascades.

According to Nathan Pipelow, the AOU's Checklist Committee has already voted on the split of Eastern and Western Winter Wrens, and it will become official with the publication of the next supplement to the AOU Checklist in the summer. The only remaining question is whether to split the hiemalis subspecies from the Eurasian populations. If you would like to read more about the reasons for splitting, I would suggest this post by Nick Sly. Winter Wren (Troglodytes troglodytes) has a Holarctic distribution; however, it has up to 44 subspecies, some of which may be species in their own right. The North American populations are being split because ornithologists found a contact zone where the eastern and western subspecies did not interbreed. In addition, these populations have subtle differences in appearance and sing different songs, and genetic studies found scant evidence of hybridization.

In addition to Nick's post, I would recommend Nathan's posts on differentiating eastern and western Winter Wrens by call and by song.

Western Willets are often reported along the New Jersey coast in the winter, so I could probably add that pretty easily if I took the time to separate the subspecies. Among the others, I still have not seen the western populations. In some cases, such as Whippoorwill, I have yet to encounter the species at all.

So what armchair life birds would you get out of this list? Are there any that would be easy for you to add?