Isthmus Of Tehuantepec

November 22, 2021

The Isthmus of Tehuantepec represents the shortest distance between the Pacific and Atlantic in Mexico. Located in Veracruz and Oaxaca states, the width of the isthmus is only 200 km from ocean to ocean. While mountains are prominent geographical features in much of Mexico, they form a gap at the isthmus, breaking down into a broad plateau that is only 224 m at its highest elevation. These two factors - the narrowing of the continent, and the lack of prominent mountains - led to the importance of the Isthmus of Tehuantepec as an overland transport route prior to the construction of the Panama Canal. 

Aspidoscelis deppii - Isthmus de Tehuantepec, Oaxaca, Mexico

Generally speaking, unique geographic features often lead to corresponding biogeographic curiosities. With regards to the Isthmus of Tehuantepec, several unique species and forms have evolved here over millenia. The broad valley is surrounded by three separate mountain ranges; montane species in these corresponding ranges are separated from each other, while the valley itself is isolated. Several unique bird species can be found only in the isthmus including the Cinnamon-tailed Sparrow and Rose-bellied Bunting. The latter is absolutely gorgeous, a species that I have wanted to see for years.

Laura and I drove towards the Isthmus of Tehuantepec on our way to Chiapas state in the east. We overnighted in the city of Juchitán de Zaragosa and prepared for an early start in the morning. 

Isthmus de Tehuantepec, Oaxaca, Mexico

We began our morning at Ojo de Agua Tolistoque. A beautiful spring of water flows out of the limestone rocks next to a picturesque cave. At least, it would have been picturesque if humans hadn't spray-painted graffiti and strewn garbage about the place. We humans are a lovely species. At least it was possible to photograph the scene from a particular angle to avoid the graffiti and garbage. 

Ojo de Agua Tolistoque - Isthmus de Tehuantepec, Oaxaca, Mexico

We birded along the entrance road. Despite our early arrival, birdsong was almost nonexistent. The time of year did not help, nor did the very strong winds that seem to be a common theme in this region. We quickly observed the first Turquoise-browed Hummingbirds of the day along with a small mixed flock of warblers and vireos. 

Turquoise-browed Hummingbird - Isthmus de Tehuantepec, Oaxaca, Mexico

And then, there it was! A female Rose-bellied Bunting shot across the road and perched in view for a few seconds. 

Rose-bellied Bunting - Isthmus de Tehuantepec, Oaxaca, Mexico

And then, the magic happened. Our first male Rose-bellied, followed by several others! We counted around 20 individuals in this flock. Sensing an opportunity, I slowly walked up to several individuals while they fed happily on seeds from a type of aster. They tolerated my approach.

Rose-bellied Bunting - Isthmus de Tehuantepec, Oaxaca, Mexico

Rose-bellied Bunting photoshoot - Isthmus de Tehuantepec, Oaxaca, Mexico

The colours on a male Rose-bellied Bunting are absolutely ridiculous. I kept shooting in the soft morning light and managed a series of photos that I was thrilled to capture. 

Rose-bellied Bunting - Isthmus de Tehuantepec, Oaxaca, Mexico

This next photo is the money shot, as far as I am concerned. What an incredible experience. 

Rose-bellied Bunting - Isthmus de Tehuantepec, Oaxaca, Mexico

Female buntings in the genus Passerina often get no love. She was quite pretty, though, with a gorgeous blue tail that sadly is not visible in this photo.  

Rose-bellied Bunting - Isthmus de Tehuantepec, Oaxaca, Mexico

We continued to bird down the track. I refocused my attention on the Cinnamon-tailed Sparrow. While this species lacks the incredible plumage of a male Rose-bellied Bunting, it is also restricted to the Isthmus of Tehuantepec and I was quite keen to see it here. Unfortunately, the sparrow stayed quiet and out of sight. A small consolation was our first Green-fronted Hummingbird that landed for around 10 seconds, never to be seen afterwards. We felt fortunate that it chose to perch near us, at least. 

Green-fronted Hummingbird - Isthmus de Tehuantepec, Oaxaca, Mexico

Several other birds made appearances. A Ferruginous Pygmy-Owl called from somewhere up the hillside, as did a Citreoline Trogon. We noted our first Golden-fronted Woodpeckers and Scissor-tailed Flycatchers for Mexico, while a Red-tailed Hawk and Cooper's Hawk provided nice views. We even found another flock of Rose-bellied Buntings!

Red-tailed Hawk - Isthmus de Tehuantepec, Oaxaca, Mexico

We had only been here for 90 minutes but I made the decision to bail and drive to a different spot. The Cinnamon-tailed Sparrows had not cooperated, and the cool hours of the morning would only last so long. This other spot, sometimes referred to as Jabba's Canyon, also seemed like a good bet to find the Lesser Ground-Cuckoo (another potential lifer for both of us). 

Sphenarium histrio - Isthmus de Tehuantepec, Oaxaca, Mexico

My anxiety about missing the Cinnamon-tailed Sparrow was quickly put to rest. A pair of them happened to be some of the first birds we observed after getting out of the car!

Cinnamon-tailed Sparrows - Isthmus de Tehuantepec, Oaxaca, Mexico

The birds were incredibly confiding, providing "walk-away views", as they say. 

Cinnamon-tailed Sparrow - Isthmus de Tehuantepec, Oaxaca, Mexico

Cinnamon-tailed Sparrows - Isthmus de Tehuantepec, Oaxaca, Mexico

Cinnamon-tailed Sparrows - Isthmus de Tehuantepec, Oaxaca, Mexico

Cinnamon-tailed Sparrow - Isthmus de Tehuantepec, Oaxaca, Mexico

Jabba's Canyon happened to be a very productive location, even though the sun was beating down by this point in the morning. 

White-lored Gnatcatcher - Isthmus de Tehuantepec, Oaxaca, Mexico

Laura spotted a snake just off the trail - a Pacific Patchnose Snake. I managed a few poor photos before it slipped away. In the heat of the late morning, this one was certainly far too fast to be catchable!

Pacific Patchnose Snake (Salvadora lemniscata) - Isthmus de Tehuantepec, Oaxaca, Mexico

We heard the first Lesser Ground-Cuckoo from behind the small research building (it was locked up with no one around during our visit). We followed a path around behind the building into the dry scrub at the base of the hills. 

Isthmus de Tehuantepec, Oaxaca, Mexico

This was the domain of the Lesser Ground-Cuckoo. While we never managed the fully unobscured photos I had hoped for, we still enjoyed excellent views of two birds. A second pair was vocalizing nearby. 

Lesser Ground-Cuckoo - Isthmus de Tehuantepec, Oaxaca, Mexico

The Lesser Ground-Cuckoo isn't a "real" ground-cuckoo, as in, one of the five rare and elusive Neomorphus species found in the Neotropics. But it is a unique bird, the only member of the genus Morococcyx. The day could not get any better!

Lesser Ground-Cuckoo - Isthmus de Tehuantepec, Oaxaca, Mexico

Just for good measure, a few Rose-bellied Buntings were around including several sharp males. Even after the morning's experience, I could not resist snapping a few more photos. Who knows how long it will be until I see another bird of this beauty?

Rose-bellied Bunting - Isthmus de Tehuantepec, Oaxaca, Mexico

Rose-bellied Bunting - Isthmus de Tehuantepec, Oaxaca, Mexico

The wind in the isthmus is something to behold. From what I gather, it is nearly always windy here - not a surprise given the region's geography. This has become the number one area in Mexico for renewable energy projects. Turbines spin as far as the eye can see. Even for someone who spends a lot of time in southwestern Ontario, where turbines are more numerous than trees (I'm sadly not exaggerating by much), the sheer number of them in the isthmus was mind-boggling. 

Turbines - Isthmus de Tehuantepec, Oaxaca, Mexico

With all of our targets in the bag, Laura and I backtracked the half an hour to our hotel to pack our bags and continue east. So far in Mexico, we have used an abundance of caution to reduce the potential of break-ins to our vehicle. A friend of ours had his truck broken into at Ojo de Agua Tolistoque several weeks earlier and we did not want to take any risks. While this meant that we had to waste an extra hour driving, it gave us the peace of mind that none of our valuables were unattended in the vehicle while we explored. As it turned out we only saw one other vehicle during the entire morning, making it a moot point. But, better safe than sorry! Knock-on-wood, but we have never had any item stolen during all of our travels, and we would like to keep it that way. 

Rose-bellied Bunting - Isthmus de Tehuantepec, Oaxaca, Mexico

We drove for several hours eastward, leaving the isthmus and its wind behind, and entered Chiapas state.  We checked into our hotel in Tonalá and began a search for the Giant Wren. Stay tuned...