The Swifts of Mexiquillo

The waterfall (cascada) in Parque Natural Mexiquillo, Durango, Mexico. Photo by Roberto González (CC-BY-2.0).

The waterfall (cascada) in Parque Natural Mexiquillo, Durango, Mexico. Photo by Roberto González (CC-BY-2.0).

We were excited to arrive at Parque Natural Mexiquillo before the break of dawn in June.  This underappreciated park is right on one of Mexico’s most celebrated birding routes, the Durango Highway — but it is an hour or two farther east than the Tufted Jay Preserve, and much less frequently visited.  The drier forests of Mexiquillo host a noticeably different avifauna than the wetter areas closer to the coast. Mexiquillo is more likely to produce birds typical of the dry “sky islands” of southern Arizona: Buff-breasted Flycatcher, Western Bluebird, Plumbeous Vireo, and even American Robin.  It’s much better habitat for the likes of “Type 6″ Red Crossbills (which we recorded) and Eared Quetzals (which we did not find). Of course, it also has Red Warblers, Elegant Euphonias, and Rufous-capped Brush-Finches.

And it has a waterfall.

This is particularly noteworthy because the mountains of west Mexico are high and dry — and not much water means not many waterfalls.  Which means not many places to look for waterfall-loving swifts.

We were very interested to see what kinds of swifts would be flying around the waterfall at daybreak. A report from 2013 had us wondering whether this would be a good place to record Black Swifts, and a tantalizing recording from Chihuahua had us wondering whether something super-rare might be lurking under the cascada (and under the radar), like the “avian unicorn” White-fronted Swift (Cypseloides storeri).

When we first arrived, before first light, all was quiet, except for the roaring water and the aerial singing of Violet-green Swallows. Off in the distance, a Spotted Owl hooted. No swifts. Soon a dawn-singing Pine Flycatcher became a serious distraction. By the time the sun was fully up, we were totally engaged in all the other wonderful birds in the park, and we had completely given up on the swifts.  Until suddenly, something dark swooped by overhead with a sound like the crackling of electrical wires.  Chestnut-collared Swift!

Then another group of swifts flew by, and I heard a sound familiar from the mountains of Colorado: Black Swift.

For the next hour, these two species swirled over our heads, sometimes swinging pretty low. The encounter was simultaneously a letdown and a thrill.  On the one hand, it woke us up from the pipe dream of documenting some ultra-rare Cypseloides vocalizations. On the other hand, it was a terrific opportunity to spend time with two species that it can be awfully hard to see and hear well. It cleared up a long-standing mystery about whether the Black Swifts of Mexico might sound different from the ones farther north (answer: they don’t). And it gave us the field experience necessary to help identify the Chihuahua mystery swift as the first Chestnut-collared documented in that state.  One key takeaway: Black and Chestnut-collared Swifts can look astonishingly similar, even when you get good, prolonged looks.  But by sound, they can be separated right away.

While I concentrated more on the audio recording, Andrew was able to get some decent flight shots of the Black Swifts:

We were hoping to figure out whether the Black Swifts of Mexiquillo belonged to the northern subspecies niger, which breeds in the United States and Canada, or the southern subspecies costaricensis, which breeds in — you guessed it — Costa Rica.  The birds in Mexico have been attributed to each of these subspecies by different authors. The Mexiquillo Black Swifts were surprisingly well marked, some with bright white foreheads, some with extensive white scalloping below. So we thought this might be a mark for costaricensis. But when Andrew reviewed and photographed Black Swift specimens in the Harvard collection earlier this week, he found it nearly impossible to separate the subspecies by coloration. The size difference is noticeable on the specimen table, but is subtle enough that it would be virtually useless in the field.

So, the subspecies of the Durango birds remains a bit of a mystery. Any comments or discussion would be appreciated!

Mexico’s Mystery Owl

It’s not every day that you photograph and audio record a bird that has never been photographed or audio recorded before. [Read more]

Do Bushtits Sing?

Of late, I’ve had occasion to question the conventional wisdom that Bushtits do not sing. [Read more]

The Toughest Birds to Record in North America

But ask a recordist about the toughest birds in the ABA area and you’ll get a very different list. Most of the species that I talk about below aren’t really “hard” birds to see. Some of them can be downright common in the right areas. But what makes a bird hard to record can be quite different than what makes it hard to find. [Read more]

Bohemian Rhapsody

Waxwings have some of the simplest repertoires of all passerines, with no true “song”, or at least none that has been documented. And even their calls are typically variations on the same trill. Or so I thought. [Read more]

More Than Just a Mudsucker

What was once a bird that made just a few simple, short chips or churrs suddenly has a large and varied repertoire that includes complicated aerial acrobatics and sounds as varied as low-pitched hooting to amazingly insect-like twittering. The first time I stood out on the tundra in Alaska I was blown away by everything I was seeing and hearing, and I’ve never looked at shorebirds the same way again. [Read more]

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]

Florida’s Online Sound Archive

The Florida Museum of Natural History has put its huge collection of bird sound recordings online in digital format for the first time. [Read more]

Describing Variation in Bird Sounds

Bird sounds vary on many levels. When talking about variation, it would be nice to be able to distinguish exactly which kind of variation we mean. [Read more]