Back in the dugout at 6am, our first excursion today was to the new canopy tower constructed on the far side of Challuacocha. According to Domingo, the old tower, whose wooden stairs are dangerously decrepit, offers significantly better birding as it provides clearer access to the canopy and is somehow more consistently in the path of moving mixed flocks. Given all the recent rain, though, he insisted that we visit the new tower, which is constructed mostly out of steel and should prove more durable and less harmful to the ceiba tree it incorporates. The ride across the lake was typically dreamy with the Capped Heron and Slender-Billed Kite both crossing our path overhead in the gray dawn. 
Given the circumstances, which could keep any birder up all night in expectation, I felt pretty relaxed on the short walk to the base of the tower, stopping to admire a male Black-Faced Antbird singing just in front of us. At this point, I've spent enough time in canopy towers in the eastern lowlands to be familiar with most birds, and the handful of species that I'm missing don't require much more than vigilance and a lot of luck to see. Mostly, I was just excited to take some good photographs with my new telephoto lens, and I was also hoping that my father would have a fulfilling experience, especially having promised him some good raptors to observe.
Already in the canopy of the ceiba tree itself were a number of decent birds, including the Yellow-Browed Tody-Flycatcher, White-Browed Purpletuft, Cobalt-Winged Parakeet, Gray-Crowned Flatbill, Masked Tityra, and White-Lored Euphonia. Unfortunately that was about the peak of bird activity in the tree this morning, and the rest of the time we scrambled to located perched birds in the far distance, which was difficult given the density of the crown we were standing in. Stationing ourselves in different corners of the tower, we managed to add a few good birds to our list before it started to rain again, including Spangled Cotinga, Common Piping Guan, Red-Stained Woodpecker, and Masked Tanager. There's nothing worse than having the prime birding hours in the day being rained out, and we stood around grimly for an hour until the weather cleared.
As the sun came out, bird activity sprang to life again, and a variety of raptors were spotted perching on exposed tree branches to dry out. In the scope we line up the Double-Toothed Kite, Crane Hawk, and Slate-Colored Hawk in succession, and then I found a pair of stunning Blue-and-Yellow Macaws preening in a dead tree. Although no tanager flocks passed within sight, we enjoyed watching a group of Yellow-Tufted Woodpeckers scare off a Buff-Throated Woodcreeper from a hollow in a cecropia tree. My father was absorbed in a group of calling White-Throated Toucans for a while, as Domingo and I looked at each other and raised our eyebrows in lamenting the general lack of uncommon birds this morning. Hopefully, we would have better luck as we returned to the dugout and passed deeper into the varzea at the western end of Challuacocha.
My jaw dropped when I learned that the target bird of our next excursion was one of Ecuador's few endemic bird species, the Cocha Antshrike; in fact, Domingo claimed it was certain that we'd find it as long as we had playback available (guides rarely make this claim because it doesn't offer their clients much of anything except for the occasional extreme disappointment). He took us in the dugout canoe directly to the spot, where after a few minutes of tape, we had a female Cocha Antshrike out in the open several meters away. The male stayed deep within cover but hung around long enough for me to take my camera out and rip off a few shots. Both sexes of this recently discovered antshrike look remarkably similar to the rather common White-Shouldered Antbird, with only voice being dramatically different. Domingo explained that his uncle was part of the original group that found the bird, although he didn't receive any credit for it. Happily, the bird is one of the few South American species to incorporate a Quechua word in its English common name (cocha is a versatile word generally meaning body of water, I believe).
Returning to the lodge for lunch under a blazing sun, we stumbled upon some terrific birds, including the Cocoi Heron, Anhinga, and Least Bittern. We flushed the latter while discussing the breeding Agami Herons that Domingo had seen on the Yasuni River; last winter a boatman had taken him to a small tributary in which thousands of Agami Herons were nesting out in the open. No doubt it was my exclamation that startled the bittern, but instead of flushing away out of site, it remained in the grass on the edge of the lake, raising its head querulously on its long neck until we passed by. Although the Cocha Antshrike was certainly the best bird of the morning, this encounter was the most memorable.
Later that afternoon, we set off into the forest behind the lodge, exploring a confusing network of overgrown trails that had us all feeling lost and overwhelmed, except for Domingo. The birding was typically slow but spectacular, as we started out with the Golden-Headed Manakin, moved onto a Screaming Piha lek, happened upon two Golden-Collared Toucanets passing through the forest, and found the resident juvenile Ornate Hawk-Eagle perched on a branch beside its nest. Despite its young age, the hawk-eagle peered down at us impressively from above, one of its already massive yellow talons visible from below. Domingo told us that the bird had just left the nest recently and would remain in this territory for another year and a half before leaving to establish its own, as adult eagles reproduce only once every two years. At mid-morning on the following day we would hear one of the adults calling insistently and eventually find it perched in the distance before it took flight for the rest of the day.
Pushing deeper into the forest, Domingo heard some obligate antswarm followers calling up ahead. This was the moment I had been waiting for, and I turned excitedly to my father and Adrien, the young Frenchman who accompanied us, to explain what was happening. Plunging into the undergrowth in pursuit of Domingo, I barely caught site of a Bicolored Antbird before the monospecific flock moved on in search of an antswarm, I guess, as there were no ants present. This rather unfulfilling experience was quickly followed by one of those mysterious sightings that make birding so wonderful and addictive. Domingo asked me to play the call of the Brownish Twistwing again in the growing darkness, but the bird that responded and darted about overhead was noticeably slighter and slightly different in behavior from what he expected. Was it the ultra-rare Amazonian Royal-Flycatcher, which has a similar call and habitat? It was too dark to tell, and the bird moved off quickly before we could investigate it further. (For the record, Domingo has seen the Amazonian Royal-Flycatcher only twice before, and I'm familiar with the western slope version, the Pacific Royal-Flycatcher). Notable birds seen: Anhinga, Least Bittern, Cocoi Heron, Capped Heron, Swallow-Tailed Kite, Slender-Billed Kite, Double-Toothed Kite, Crane Hawk, Slate-Colored Hawk, Ornate Hawk-Eagle, Speckled Chachalaca, Common Piping-Guan, White-Tipped Dove, Blue-and-Yellow Macaw, Chestnut-Fronted Macaw, Great Potoo, Common Potoo, American Pygmy Kingfisher, White-Eared Jacamar, White-Chinned Jacamar, White-Fronted Nunbird, Golden-Collared Toucanet, Red-Stained Woodpecker, Chestnut-Winged Hookbill, Cocha Antshrike, Black-Faced Antbird, Bicolored Antbird, Black-Faced Antthrush, Yellow-Browed Tody-Flycatcher, Gray-Crowned Flatbill, Cinnamon Atilla, Dusky-Capped Flycatcher, Crowned Slaty Flycatcher, Masked Tityra, White-Browed Purpletuft, Screaming Piha, Spangled Cotinga, Bare-Necked Fruitcrow, Purple-Throated Fruitcrow, Golden-Headed Manakin, Masked Tanager, Red-Capped Cardinal.