How to Identify a Timberline Sparrow

On the field marks and audio cues that separate nominate Brewer’s Sparrows from the “Timberline” subspecies. [Read more]

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]

Common and Hoary Redpolls

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

Splitting the Golden-fronted Woodpecker

At least one call in the Golden-fronted Woodpecker’s repertoire varies geographically, corresponding to the geographic boundaries between two major subspecies groups that probably deserve species rank. [Read more]

North by Northwest

There are few species in North America as ambiguous as Northwestern Crow (Corvus caurinus). Even in a group of birds that are exceedingly similar the differences between American Crow (Corvus brachyrhynchos) and Northwestern Crow are minuscule at best. The only “surefire” way to tell them apart is by range; however a number of sources also cite vocal differences as a distinguishing characteristic. [Read more]

Rufous Antpitta Feature

Antpittas are one of those quintessential groups of tropical birds. They may not be colorful, like tanagers, coatings, or manakins, nor are they large and noisy birds that are out in the open and in your face, like toucans or parrots. But there’s just something about them and their weird, nearly tailless bodies on top of stilt like legs, and their way of moving through the dense growth in bounding leaps that makes them irresistible. [Read more]

Identifying Eastern and Western Warbling Vireos

Eastern (gilvus group) and western (swainsonii group) Warbling Vireos may represent two species, and if they are ever split, song would be the best way to identify them. [Read more]

Eastern and Western Blue-gray Gnatcatchers

The Blue-gray Gnatcatcher sounds different in the West than it does in the East. However, the differences in song are not well understood by most birders, nor particularly well described in most field guides. [Read more]

Fox Sparrow, Part 2: Alarm & Contact Calls

In my last post I promised a discussion of Fox Sparrow alarm and contact calls, and it’s time to deliver on that promise. [Read more]