Common vs. Chihuahuan Ravens

I’m starting to think that voice is actually a very good character — maybe the best field character — for separating these two species. [Read more]

A Bicknell’s Thrush Critique

In 1995, in the 40th Supplement to their checklist, the American Ornithologists’ Union recognized Bicknell’s Thrush (Catharus bicknelli) as a full species, splitting it from the Gray-cheeked Thrush (Catharus minimus) on the basis of “differences in morphology, vocalizations, habitat preferences, and migration patterns.” In this post, I reassess the evidence for a consistent difference in flight calls between Bicknell’s and Gray-cheeked Thrushes. [Read more]

Long Calls of Gulls

Most people don’t listen to gulls much. But as I’ve paid more attention to them over the past year, I’ve realized that many species can indeed be identified by sound alone, and this fact has greatly improved my birding skills. [Read more]

Common and Hoary Redpolls

Some have argued that Common and Hoary Redpolls differ in vocalizations. I set out to verify this claim. [Read more]

Empid Mystery Solved!

Remember the mysterious two-part call of the unidentified Empid? Nacho Areta has filled in the missing piece of the puzzle. [Read more]

“Russet-backed” vs. “Olive-backed” Swainson’s Thrushes

Over the past decade, the work of Kristen Ruegg and her colleagues has shown that the two forms of Swainson’s Thrush not only look different, but migrate on different schedules to markedly different wintering grounds. They hybridize in a contact zone in British Columbia, but that contact zone is quite narrow, prompting occasional rumors and rumblings of a potential future species split. One of the proposed lines of evidence concerns differences in vocalizations. [Read more]

More on the Mystery Empid Call

A few months ago I wrote about a mysterious new “whit-beert” call that I took to be a previously undescribed sound of Yellow-bellied Flycatcher. Now, new information has come to light that calls my earlier conclusions into question. [Read more]

Greater vs. Lesser Yellowlegs

Can you tell Greater and Lesser Yellowlegs apart by voice? Can anybody? [Read more]

The “Tink” Call

Many species of warbler and sparrow give high, sharp “tink” notes that seem worth of their own category, separate from the “call” and the “flight call.” [Read more]

Learning Laplands

In trying to catalog Lapland Longspur calls, I ended up making a map of variation. [Read more]