white-throated sparrow

white-throated sparrow

Wednesday, July 23, 2014

Who Says What? Vocalizations of the Cordilleran Flycatcher

Vocalizations are an important, and sometimes critical, aspect of identifying flycatchers of the genus Empidonax.  Alder and Willow Flycatchers, for instance, are so similar morphologically that many individuals cannot even be separated in the hand, but their vocalizations are diagnostic.   Mostly it is the song that birders learn, but oftentimes the call notes are equally important to learn - and in the case of Dusky vs. Hammond's Flycatchers, the call notes are more easily distinguished than the songs.

But Empidonax flycatchers have more vocalizations than are typically described in a field guide, and the line between what is a "song" and what are "calls" is unclear in this genus.  In most Empidonax species, and in fact many other flycatchers (e.g. pewees and phoebes), the male sings a "dawn song", given only at first light, that is a longer and more complicated version of its daytime vocalizations.  Sometimes a vocalization that is referred to as a song (e.g. the "FITZ-bew" of the Willow Flycatcher) may actually be analogous to another species' "position note" (e.g. the two-note call of the Cordilleran Flycatcher): in both cases, these are calls uttered throughout the day, typically by males.  However, males and females are identical in all Empidonax flycatchers, so  exceptions to these rules go unnoticed unless one is studying a group of color-banded birds, whose sexes have been determined in-hand.  Below, I will use my experience with a color-banded breeding population of Cordilleran Flycatchers in Colorado to describe each vocalization, its context, and which sex uses it and when.

1. Dawn Song or Primary Song

Play Recording

The Cordilleran Flycatcher has a three-part song, used only by the male during the breeding season.  Early in the season this may be sung during the daytime, presumably by males that have not yet attracted a mate.  Later in the season, mated males sing it only for a few minutes at dawn.

2. "Male Position Note"

Play Recording

This is the common call heard throughout the day in summer, and during migration and winter, is the only way to distinguish the Cordilleran Flycatcher from its closely-related look-alike Pacific Slope Flycatcher.  In the literature, this two-note call is referred to as the "male position note".  I use quotes here, because although I have found that the male uses this call consistently, I have also observed females using it.  Sometimes the female utters a higher-pitched, slurred version; other times it is identical to the male's call.  The most frequent context seems to be territorial advertisement - saying "I'm here and this is my territory".  The male utters this call non-stop throughout the day early in the season, when territorial boundaries are being established.  He then goes quiet much of the time while the female is incubating and while he and his female are feeding nestlings.  Later in the season though, I've noticed that the male resumes his near-constant use of this call throughout the day; this coincides with two things: 1) fledging, which leads to a breakdown in established territories as the fledglings wander around; and 2) arrival of early migrant Cordilleran Flycatchers, most likely failed breeders from nearby who, with no time left for a second nesting attempt, have abandoned their territories and begun pre-migratory wandering.  These forces put pressure on the pair to defend their territory, and it is during this time that I have seen the most frequent use of the "male position note" by females. 

Nothing yet is known about the Cordilleran Flycatcher's behavior on the wintering grounds, but stay tuned - I have received some funding to work on this species in Mexico, and I bet you anything that both males and females defend winter territories using this call.  We'll see!

3. "Female Position Note"

Play Recording
Again with the quotes, because while the female uses this vocalization far more frequently, I've seen males use it on occasion.  This is a single, high-pitched call, and although I suspect it is used in multiple contexts including communication with the male, most often it seems to be given in alarm.  Anytime I approach a nest or fledglings, the female gives this call repeatedly, accompanied by nervous tail-flicking.  Her fledglings know what it means, too - they go quiet and still when they hear this call. 

After two seasons of close observation, I've noticed slight variations in this call, even within individual females - sometimes the note is flatter, sometimes sharper, and I strongly suspect this variation is related to context.  I'd love to get some high-quality recording equipment and study this.

4. "Gurgle Call" or "Interaction Calls"

Play Recording
This is a call I've never seen mentioned in any field guides.  It's a soft series of rolling or gurgling notes, used by Cordilleran Flycatchers when in close proximity to each other.  Pairs use it when approaching each other, such as passing one another while feeding nestlings, and strangers use it while chasing each other.  Thus is it often used in aggressive contexts (both among strangers/neighbors and within the pair), but might also have a non-aggressive context within the pair.  It is used by both males and females.

5. "Soft Interaction Calls"

Play Recording
This is another type of vocalization used in close interaction between individuals.  It is soft, lower-pitched than the position notes but not as low and growling as the aggressive "gurgle call".  Both males and females use this, and the most frequent context I've noted is around fledglings, especially when the parents are trying to gather up a scattered brood.

It's a joy to be able to study a species intensively, to learn the context of its various vocalizations and to come to know calls that are not described in most field guides.  I want to acknowledge Xeno-Canto (www.xeno-canto.org) as the source of the vocalizations used in this post - this is a fantastic repository for bird vocalizations.  Someday I hope to purchase some nice recording equipment and contribute my own recordings to this site.

Thursday, May 1, 2014

Colorado River Migration Spectacular

I stand and watch as waves of songbirds appear in a nearby mesquite, pause briefly for a snack, and then flit on northward.  A Blue Grosbeak perches high in a branch, brilliant blue in the early morning light, its metallic “chink” call and delightful mellow warbling song reminding me of dense willows along rivers coursing through hot deserts.  Now there is a handsome male Black-throated Gray Warbler, heading north to grace montane oak forests with its cheery buzzing song.  A Townsend’s Warbler appears next, a stunning orange and black gem that will soon adorn the magnificent Douglas fir trees in the Pacific Northwest.  Spritely Wilson’s Warblers, drab greenish Orange-crowned Warblers, Nashville Warblers, Pacific-slope Flycatchers, Western Tanagers, Black-headed Grosbeaks; all passing by on their way to various points in western North America.  Above, an endless river of swallows, swifts, and blackbirds cruise by, and shorebirds forage furiously in pools of water, fueling up for their journey to the tundra.  Four species of rails skulk amongst the marsh vegetation, their presence revealed only by their strange and evocative calls: Yuma Clapper Rail, Virginia Rail, Sora, and Black Rail.

This is El Doctór, and this is the most amazing migration spectacle I have ever seen.

El Doctór is a nature reserve that protects 1850 acres of wetland within the Colorado River Delta in Mexico, providing critical habitat for marshbirds (including the threatened Yuma Clapper Rail) and stopover habitat for migrating shorebirds and songbirds.  It is an oasis within the vast Sonoran Desert, and one of the last remnants of what was once a vast network of wetlands within the Colorado River Delta.  I visited this area as part of a larger team effort to investigate the effects of a large water release (“pulse flow”) into the Colorado River channel.  Scientists from both Mexico and the US were out in force, measuring water flow, seed dispersal, and seedling sprouting - I was there to observe the foraging behavior of birds.  While it is too soon to speculate on how well the birds are responding to the pulse flow, I can share my experiences with the area's birds.

Birding the Lower Colorado River

Most of the study areas were public lands that could be visited by anybody, although they were generally not well-signed (except Cienega Santa Clara) and interested birders should contact a local guide for directions or assistance getting to the sites (see http://mexicobirdingtrail.org/plan-a-trip/colorado-river-delta/).  I had no trouble getting around in my car; then again, I've taken my Saturn on some crazy roads before and know how to drive it through the myriad sand patches that characterize the dirt roads in this region.  There are hotels in the border town of San Luis Rio Colorado, and all sites can be reached within an hour and a half.  Gas and delicious tacos are available in the small town of Luis B. Sanchez.  I can’t attest to any of lodging options - I was hosted by Juan Butrón at his house in a tiny community near Cienega de Santa Clara.

El Doctór

El Doctór is a wetland is one of the first places with trees and water that northbound migrants encounter after crossing the Sea of Cortez or large stretches of surrounding Sonoran Desert- and as you can see from the map, the desert around here is VERY sparse and dry, quite unlike the relatively lush saguaro-palo verde-mesquite desert scrub around Tucson.  Hence I saw the largest concentrations of migrants during my visits to this site.  Of course my brief visit provided only a snapshot of migration - for instance, it was too early for many Empidonax flycatchers other than Pacific-slope - but this spot had the highest diversity of migrant warblers (10 species) and was the one place at which I heard all four rail species.  Year-round residents included Crissal Thrasher, Verdin, Northern Mockingbird, and Abert’s Towhee.

Cienega de Santa Clara

This is an even larger area of wetland a bit north of El Doctór - 14,000 acres of cattail marsh, critically important for the Yuma Clapper Rail.  Another literal oasis in the desert, the last few kilometers of the road to the cienega pass through bare sand completely devoid of vegetation, bringing to mind the Sahara or another planet entirely!  Juan treated me and a trio of Canadian journalists to a long boat ride through the cienega on my first full evening in Mexico.  American Coots bobbed on the water throughout and handsome male Cinnamon Teal caught the evening sunlight.  After an hour of gliding quietly through the dense cattails, we reached a shallow area on which hundreds of shorebirds had gathered.  Black-necked Stilts, American Avocets, and Long-billed Dowitchers dominated the scene, and the sound of a hundred American Coots running on the water’s surface as they fled our boat sounded like a thunderous ocean wave.  During a second visit to the cienega another evening, I explored the shoreline, mostly short pickleweed and a few scraggly tamarisks.  Migrant warblers were using this area, especially Yellow-rumped Warblers (Audubon’s race), many of which were sallying and tumbling after invisible flying insects.  A large flight of Tree Swallows came by, a stream of them that lasted a good forty minutes.  Song Sparrows sang from the edge of the pools, and a few shorebirds stopped by now and then, a Least Sandpiper obligingly foraging in the late evening sunlight mere meters from me.  I tried to make a third visit the next week, but I unwisely chose a windy day, and the blowing dust was so thick as I approached the cienega that visibility abruptly reduced to ten feet and soft sand was piling up on the road - I decided to turn around!

Rio Colorado Restoration Sites

I made numerous visits to many places along the Rio Colorado, but Pronatura Noroeste has some nice restoration areas along the river not far outside Luis B. Sanchez.  Workers have removed large stands of invasive tamarisk and have replaced them with native mesquite, cottonwood, and willow.  The plots are in various stages of development - there are bare fields with Horned Larks singing their tinkling songs from the sky, plots with cottonwoods no taller than me, and dense thickets with mature willow and mesquite (these were favored by the warblers).  The sound of Ring-necked Pheasants from the surrounding wheat fields brought incongruous memories of a summer working in Iowa - apparently this species is expected here, but it had not been on my radar!  The larger trees and open spaces provided habitat for Bullock’s Orioles and many flycatchers - Vermillion Flycatchers, brilliant red balls of fluff performing their fluttering flight songs; pugnacious Western Kingbirds; Ash-throated Flycatchers investigating nest holes.  Lesser Nighthawks coursed by in broad daylight, and Burrowing Owls frequently flushed from the dirt levees.  Remaining areas of tamarisk housed rasping families of Black-tailed Gnatcatchers, skulking Crissal Thrashers, and Greater Roadrunners.  The river itself held plenty of slow-moving water and dense marsh vegetation, with rails, Marsh Wrens, Caspian Terns, and Pied-billed Grebes.

It was a very successful trip, the sheer number of migrants provided me with a wealth of foraging data, and the sight of cottonwood seedlings sprouting provided new hope for the region.  I was impressed by the dedication to nature shown by many of the Mexicans I met, and with seven more years of pulse flows planned, perhaps some of this amazing riparian habitat can expand across the salt flat currently separating the river from the Sea of Cortez and revitalize the farthest reaches of the delta.

Wednesday, February 26, 2014

Driving to Mexico

I’ve been meaning to update for quite a while.  I’ve taken two birding trips to Mexico since my last post and had fully intended to write detailed trip reports after each once.  I’ll blame my failure to do so on grant writing season.  Or perhaps my lack of motivation to sit in front of my computer in the evening after a day of... sitting in front of a computer.  But here it I go; first up, a bit of info on driving in Mexico.  


What you need to know if you plan to drive to Mexico

For a recent trip to southern Sonora for Christmas Bird Counts, I decided to drive and take several other participants- here I will share what I learned about driving one’s own vehicle in Mexico, many of the details specific to crossing in and out via Nogales.

To drive in Mexico you MUST have Mexican insurance - from what I read, you could GO TO JAIL if something happens and you are uninsured (most US companies will not cover you outside the US).  This was fairly straightforward to obtain online, there are also places in Tucson and other border towns where you can walk in and purchase insurance.  The rate was roughly $45 for a 7-day plan.  Another necessity, which was less straightforward, was obtaining a car permit for Mexico.  I believe you can go a certain distance into Mexico without one, and there is apparently a separate Sonora-only permit and a federal Mexico permit (although they cost the same).  In my confusion I got a federal permit (even though I wasn’t going beyond Sonora) issued at the same location as the tourist visas, 21 km beyond the border from Nogales. As of late 2012 this now requires a $300 !! deposit (plus the $50 permit fee), of which I was unaware before arriving. I kept an eye on my credit card balance and this transaction was indeed cancelled about a week after leaving the country- when heading back into Nogales, watch for the rather unofficial-looking booths immediately across from the tourist visa facility, you have to pull off the road and go through this booth to get your permit removed and deposit refunded.  

What was it like?

I dare say that driving in Mexico is easier than in many places within the US, as there seemed to be far fewer distracted drivers.  Larger towns are a bit more hectic but nothing I haven't negotiated before.  The main thing to watch for are slow trucks, pedestrians, and physical obstacles.  The main toll highway south from Nogales is currently under construction, and many of the older sections are potholed.  Watch for speedbumps that may or may not be well-marked while passing through towns. 

Of course, there were exceptions that lent a sense of adventure to driving my own car into Mexico. There is currently some dispute over water rights (I don't know the full details), and in demonstration one group is stopping all commercial truck traffic at the tiny village of Vicam between Guaymas and Cuidad Obregon; apparently they let the trucks pass at 5 pm daily. They let passenger cars go by, but this is no easy task when hundreds of semis are occupying both lanes for kilometers in either direction. The solution? Just drive over the median and drive against traffic on the other side. If the median happens to be a ditch where you need to cross, well, tough luck. I've taken my Saturn on some pretty crazy roads before, so I knew what it was capable of and managed to get across said ditch with no more than an uncomfortable scraping sound and proceeded to drive against traffic into Vicam- but lots of other cars were doing that, so no big deal, right?  We encountered a similar situation right before crossing back into the US - I'm not even sure what was going on, I guess the truck line was really slow so they were just waving passenger cars into the oncoming lane.

I leave you with this drawing of the "welcome sign" you see as you cross into Mexico... I drew it in paint because I was driving and did not have my camera handy.  But's pretty realistic ;-)