Explorations of an Ecologist: HWY 101 - Forest Birding Near Iguazú

Highway 101 is the main corridor that runs east-west along the top end of Misiones Province in Argentina. Though this road looks like a major artery on Google Maps, in practice it is nothing more than a clay track that receives very little traffic - mainly, just a few locals traveling between one of several small villages and the big city of Puerto Iguazu. By switching over to satellite view, it quickly becomes apparent why this road would hold great appeal for birders and other naturalist-types.

Highway 101, Misiones, Argentina

Lush forest surrounds the road for many kilometres. While most of this forest has been degraded from its original form, a number of large trees still stand and a wide variety of species utilize this area. And though no public trails have been cut into this forest, being limited to roadside exploring isn't a bad option. The minimal traffic is hardly a nuisance, and the opening created by the road allows most types of birding to be very productive (the exception being, of course, searching for those skulky understory species like antthrushes or antpittas).

Our visit to Iguazú Falls was enjoyable due to the surprisingly good 'naturalizing' we experienced in the busy park, but we were yearning for a bit of solitude. Just us and the forest. Plus, of course, a chance to connect with many species that can't be easily found in the national park. And so Laura and I spent the better part of two full days exploring Highway 101 east of Iguazú Falls.

Black Capuchin - Highway 101, Misiones, Argentina

February 5, 2023

The road conditions were a little treacherous on our first morning, as heavy rain the previous day had sodden the clay substrate and created a slick mess. I only drove a short ways down the road, nearly getting stuck in one area, before I found a safe pull-off. Luckily, the road dried out quickly in the tropical sunshine and a lack of further rain meant that the road was easy to navigate during all future visits.

Highway 101, Misiones, Argentina

The lifers came hot and heavy as we were exploring a new area for the first time. We heard our first Spot-winged Wood-Quails and Slaty-breasted Wood-Rails, while the first few mixed flocks contained Ochre-breasted and White-eyed Foliage-gleaners, Ochre-collared Piculet, Scale-throated Hermit and more.

Ochre-breasted Foliage-gleaner - Highway 101, Misiones, Argentina

It is hard to beat the anticipation that comes with birding an area for the first time. Probability dictates that lifers will be around nearly every bend.

White-eyed Foliage-gleaner - Highway 101, Misiones, Argentina

The haunting voices of Tufted Antshrikes rose up from the thick shrubbery. With a bit of effort we were soon face to face with this beautiful species; its sleek plumage matching the shadows where it resides. The Atlantic Forest has a number of really interesting antshrikes and we were keen to see them all, of course.

Tufted Antshrike - Highway 101, Misiones, Argentina

We spent an hour or so birding from an observation blind located beside the road which looks out over a small marsh and clearing. The blind is named after the late Daniel Pupi Somay, an influential birder from the area.

View from the Daniel Pupi Somay blind - Highway 101, Misiones, Argentina

We found a few more birds of interest here, including our first Three-striped Flycatcher and Sibilant Sirystes. The Three-striped Flycatcher was our fourth and final species in the genus Conopias that we have now seen, along with Lemon-browed, Yellow-throated and White-ringed Flycatchers. It was a little too far for anything more than just "record" shots, though.

Three-striped Flycatcher - Highway 101, Misiones, Argentina

But with the clock ticking and the sun rising higher in the sky, it was time to continue further down the road. I wanted to cover as much ground as possible during our few days along Highway 101 to increase our chances of finding a Creamy-bellied Gnatcatcher. This uncommon species has a small range in the Atlantic Forest, and the Iguazú area surely provided our best chance of crossing paths with one.

Luck was with us and I heard an interesting vocalization during the late morning hours. The gnatcatcher! The looks were brief as both birds were rather skulky. I mainly focused on obtaining good looks of them, but I squeezed out a few terrible photos as well.

Creamy-bellied Gnatcatcher - Highway 101, Misiones, Argentina

The butterflies along Highway 101 were incredible. Several dozen species were seen coming to puddles along the muddy, clay road and I made an effort to photograph as many of the species as I could.

Dynamine tithia - Highway 101, Misiones, Argentina

Adelpha thessalia - Highway 101, Misiones, Argentina

Lasaia agesilas - Highway 101, Misiones, Argentina

Coenus Sailor (Dynamine coenus) - Highway 101, Misiones, Argentina

Caria marsyas - Highway 101, Misiones, Argentina

Barbicornis basilis - Highway 101, Misiones, Argentina

Eventually, the direct angle of the midday sun was enough to send us back to town for a siesta. One benefit of our hotel was the friendly feline that we befriended during our stay. We enjoyed a midday nap together...

By the late afternoon we had renewed our energy stores to return to the road. Dusk is always a dynamic time to be in a tropical forest and I relish every opportunity we have to experience it.

Side road off of Highway 101, Misiones, Argentina

A short visit to the Daniel Pupi Somay blind produced a small flock of Chestnut-eared Aracaris whose antics were fun to observe.

Chestnut-eared Aracari - Highway 101, Misiones, Argentina

As night fell, the forest became alive with the hoots of Rufous-capped Motmots. This was a milestone species for us as it was our 14th and final species of motmot that we have seen and photographed! Laura was particularly excited as motmots are some of her favourite birds.

Rufous-capped Motmot - Highway 101, Misiones, Argentina

During the magical period where dusk turns to night, the forest came alive. A Short-tailed Nighthawk made several passes, just barely visible in the sky above us. Common Pauraques and a Ferruginous Pygmy-Owl sang, while a short walk down a side road produced a Black-capped Screech-Owl. Despite our best efforts, our only sighting of the owl was of a dark shape gliding overhead in the moonlight.

Common Pauraque - Highway 101, Misiones, Argentina

Our brief night-hike turned up the usual medley of insects, but herps remained absent.

Topana aguilari - Highway 101, Misiones, Argentina

Coptopteryx argentina - Highway 101, Misiones, Argentina

The next day, Laura and I visited Iguazú Falls (you can read about it in my previous post) but we revisited Highway 101 on February 7.

February 7, 2023

Despite our successful visit to Highway 101 a few days earlier, our second morning provided us with many new and exciting things. Bird-wise, the undisputed highlight was not a lifer, but a species we had heard on many previous occasions: a Barred Forest-Falcon. It flew right in and perched beside the road, letting us soak in the incredible views.

Barred Forest-Falcon - Highway 101, Misiones, Argentina

I rarely get a chance to observe these secretive raptors, and to have one at eye-level was just a bonus. What a bird!

Barred Forest-Falcon - Highway 101, Misiones, Argentina

Some of the "lifers" that we found this morning included Streak-capped Antwren, Greenish Tyrannulet and Rufous-crowned Greenlet. All of these are fairly common species in the Atlantic Forest that we would end up seeing many times in the subsequent months.

Rufous-crowned Greenlet - Highway 101, Misiones, Argentina

Iguazú Falls is one of the more reliable sites to watch Great Dusky Swifts in the region as hundreds nest and roost here. We had struck out with them during our only visit to the waterfall. Luckily, we were afforded redemption this morning, as a flock of around 150 individuals streamed over the road.

Great Dusky Swift - Highway 101, Misiones, Argentina

We continued eastwards down Highway 101, covering a much further distance than on February 5 due to the improved state of the road. We stopped for various birds - some singing White-shouldered Fire-eyes here, a Riverbank Warbler there - before reaching a bridge that can be a reliable site for the scarce White-bearded Antshrike.

White-shouldered Fire-eye - Highway 101, Misiones, Argentina

The antshrike was not cooperating and we heard just a single rendition of its song. The strong mid-morning sun had begun to shut down bird activity by this time, too. But that just meant that the butterfly action was really ramping up. The quickly drying puddles in the clay road were attracting them by the hundreds.

Below are some of my favourites. It was one of the better butterfly spectacles that I had ever witnessed.

Agathina Emperor (Doxocopa agathina) - Highway 101, Misiones, Argentina

Widespread Myscelus (Myscelus amystis) - Highway 101, Misiones, Argentina

Rusty-tipped Page (Siproeta epaphus) - Highway 101, Misiones, Argentina

Hydaspes Eighty-Eight (Callicore hydaspes) - Highway 101, Misiones, Argentina

Gulf Fritillary (Dione vanillae) - Highway 101, Misiones, Argentina

Unidentified hairstreak (tribe Eumaeini) - Highway 101, Misiones, Argentina

Ethemides Skipper (Thespieus ethemides) - Highway 101, Misiones, Argentina

Turquoise Emperor (Doxocopa laurentia) - Highway 101, Misiones, Argentina

This road-killed blind snake was an unfortunate discovery. I believe that it is called the Dark Blind Snake (Liotyphlops beui), a species which ranges from central Brazil south to northeastern Argentina and eastern Paraguay.

Dark Blind Snake (Liotyphlops beui) - Highway 101, Misiones, Argentina

Laura and I took a midday break, returning to the road for the late afternoon and evening. It had been a scorcher of a day and even at 5 PM the sun was vicious. Fortunately, the shadows were long by this hour. Birdlife was very quiet, though we heard a distant Red-breasted Toucan; our first.

We spent the evening spot-lighting for wildlife along Highway 101. Right around the time that the sun was setting, I noticed a dark shape roosting high in a tree. A closer inspection revealed that it was a Rusty-margined Guan.

Rusty-margined Guan - Highway 101, Misiones, Argentina

The dusk drive was really enjoyable, despite striking out with snakes (always our #1 target in the evening!). As night fell, we staked out the area near the White-bearded Antshrike bridge. Soon, our main target was singing - a Silky-tailed Nightjar - but it was too far off the road for us to attempt to spotlight it. We also heard our first of many Common Pauraques, a Ferruginous Pygmy-Owl, a Collared Forest-Falcon and a Tropical Screech-Owl here.

Common Pauraque - Highway 101, Misiones, Argentina

The owling was pretty good with five species tallied. Most of these were heard only, including the Atlantic Forest subspecies of Mottled Owl. Laura spotted a Tawny-browed Owl in flight, but it disappeared before proper looks could be had.

Below are some of the other creatures from our excursion. Another memorable evening...