A Birder’s Paradise: The Atlantic and Pacific Slopes of Oaxaca, Mexico
By Dessi Sieburth
The Rosita's Bunting is endemic to southwestern Mexico.
I visited the Mexican state of Oaxaca for a birding trip from January 11th to January 17th, 2019. Oaxaca is located southeast of Mexico City, and is the 5th largest Mexican state. It is bisected by the Sierra Madre Mountain range, which creates a continental divide between the Atlantic slope to the north and the Pacific Slope to the south. The two slopes vary greatly in habitat; the Pacific Slope is mostly dry, with coniferous forest and dry scrub, whereas the Atlantic slope has high rainfall and is largely covered by rainforest. Consequently, the two slopes are home to different bird species; the Atlantic Slope harbors iconic rainforest species like toucans, oropendolas, and antpittas; the Pacific Slope is home to many endemic species and migrants from North America like buntings, warblers, and wrens. The slopes are separated by a large gorge through the Sierra Madre Occidental known as the Continental Divide, but birds seem reluctant to cross it. I had the privilege of visiting both slopes, and I especially enjoyed seeing the endemic birds of the Pacific Slope.
Boucard's Wren, an Oaxacan endemic, abounds in the desert-like habitat.
We began our birding adventure near Oaxaca’s capital, Oaxaca City. Oaxaca City is located at an elevation of 5,000 feet, in an isolated valley that has many species of birds not found elsewhere in the world. We searched the dry desert-like habitat for endemics around Yagul, the hometown of our very knowledgeable guide, Eric Martinez. The first of these endemic species we saw was a Boucard’s Wren that resembles our Cactus Wren. Like Cactus Wrens, they build their nests deep in a cactus to protect their young from predators. Other endemic species we saw and heard were Gray-breasted Woodpeckers eating fruit on the cacti, White-throated Towhees, and female Beautiful Hummingbirds, which spent most of their time flying low near the ground.
Long-tailed Wood-Partridge
The Sumichrast's Scrub-Jay, an endemic subspecies, differs from our California Scrub-Jay by lacking a breast band and a white eyebrow.
We continued to the Pacific Slope at the dry pine-oak woodland at the northern end of the valley, where it borders the Sierra Madre Mountains. After hearing the bizarre call of a Long-tailed Wood-Partridge, another Mexican endemic, we were lucky to see it and got some recordings. In fact, our guide had seen the species only twice before! To hear the bird’s call that I recorded, visit https://macaulaylibrary.org/asset/136662941. After that, we observed the common endemic “Sumichrast’s” Scrub-Jay, currently considered a subspecies of Woodhouse’s Scrub-Jay found in the Great Basin of North America. However, it looks and sounds quite different from Woodhouse’s, so it is possible that it may have its own species status one day. The incredibly beautiful endemic Red Warbler was common as well. In these woodlands, birds often form large multi-species flocks, often led by endemic Gray-barred Wrens. After hearing the call of the Gray-barred Wren, we were soon surrounded by a flock of 15 wrens, along with specialties such as the endemic Dwarf Jay, Elegant Euphonia, and Collared Towhee.
The Montezuma Oropendola is a common rainforest species from eastern Mexico to Panama.
The following morning, we drove due north from Oaxaca City over the continental divide to the rainforests of the Atlantic Slope. Once in the rainforest, we observed species like the Keel-billed Toucan, Crimson-collared Tanager, and Montezuma Oropendola. This habitat also houses a few endemic species, the most notable being the Sumichrast’s Wren, which inhabits caves in limestone outcrops, as well as the beautiful Azure-crowned Hummingbird which perched and foraged from the understory of the forest canopy. On the Atlantic Slope we saw migrants from eastern North America, such as Magnolia, Hooded, and Blue-winged Warblers, whereas on the Pacific Slope, with its the dry scrub, we found western North American migrants, such as Nashville, Black-throated Gray, and Townsend’s Warblers.
This West Mexican Wood Owl is an endemic subspecies of the Mottled Owl.
The following day we went back to the Pacific Slope to search for endemics along the coast. We obtained excellent looks at Rosita’s Bunting, which Francis Sumichrast (of Sumichrast’s Wren fame) discovered and named after his wife. While watching the Rosita’s, an equally beautiful bird, the Orange-bellied Bunting, popped up right next to it. Both buntings are endemic to western Mexico. That evening, we did some owling and were rewarded with looks at a roosting endemic Pacific Screech-Owl, a cavity nester that eats insects and small rodents, and several Mottled Owls, which were making distinctive deep, popping hoot calls. One of my favorite sightings were several Buff-collared Nightjars resting on the cliffs. They are nocturnal, and because of their weak legs, they can not perch in trees. Usually, this species is incredibly secretive and often heard rather than seen, but we got within 20 feet of nearly a dozen on the cliffs!
The exquisite Orange-breasted Bunting was seen on the Pacific Coast.
The Rosita's Bunting has subtle shades of blue and pink.
This Buff-collared Nightjar, normally difficult to see, provided excellent looks.
On our final day, we spent the morning in the mountains on the Pacific coast before driving back to Oaxaca City. We saw the endemic Blue-capped Hummingbird and Wagler’s Toucanet. While eating our final lunch at an outdoor restaurant at a shaded coffee plantation, Eric suddenly paused and yelled “Black Hawk-Eagle!” He had heard the bird despite being in a noisy restaurant, and surely enough, when we looked up, a Black Hawk-Eagle was soaring over with some Black Vultures.
My Oaxaca birding trip was spectacular. My favorite part was seeing the endemic birds as well as the beautiful rainforest. The state of Oaxaca with its Pacific and Atlantic slopes is one of the most important areas for high biodiversity in Mexico, which makes it an extraordinary birding location. Unlike other parts of the Neotropics, Oaxacan forests remain largely intact and one reason for this is that local communities have ownership rights over their forests. They manage many of their forest areas and they collaborate with conservation agencies to practice sustainable and conservation-oriented land use. One example of this are shade-grown coffee plantations, where coffee plants are planted under a native tree canopy, which provides habitat for migratory and endemic birds. Treeless sun-grown coffee plantations often produce higher coffee yields, but they contribute to deforestation and offer little habitat for birds. The Smithsonian Migratory Bird Center certifies shaded coffee plantations with a high biodiversity as “bird friendly.” We can help migratory and endemic birds in the tropics by buying certified bird-friendly early-bird Allegro coffee at Whole Foods.
The endemic Collared Towhee was a common inhabitant of the highlands of the Pacific Slope
Thanks to Eric Martinez, our bird guide (mirmidons_1987@yahoo.com), biologist John Sterling, as well as Lance Benner and Kathi Ellsworth.