The Harpy Eagle is the most magnificent bird of prey in the neotropics and perhaps the world. Every time I'm in the eastern or western lowlands I always ask guides and other birders whether they know of a recent sighting, and I have heard the most outrageous stories in return. The easiest way to see a Harpy Eagle is to visit a known nest, of course, but it's also spotted on occasion from canopy towers in the eastern lowlands; in fact, a group of biology students from my school was visiting Tiputini Research Station in Yasuni National Park a few years ago and they saw one for a few minutes from the tower there. I missed a great opportunity to see the Harpy Eagle myself, when I failed to visit Gareno Lodge outside Tena where a nest was active a few years ago; the tree it was located in recently fell to the ground. 
The Orange-Throated Tanager is a large, spectacular arboreal tanager that lives in the remote Cordillera del Condor in extreme southeastern Ecuador and northeastern Peru. While touring the Zamora region a few summers ago, we decided to drive way out to Cabanas Yankuam for a few nights to visit the Shuar territory up the Nangaritza River and have a try for the bird. Sadly, the forest around Shaime is heavily degraded and we trekked for many hours along a deep, muddy trail in pouring rain before arriving at the site where the birds are normally seen. Our Shuar guide wasn't very attuned to our search and spent most of the time talking about which birds in the field guide were good to eat, but he did locate a group of Orange-Throated Tanagers briefly way overhead. I never lined them up properly in my binoculars, though, and the birds dispersed in the dense, towering canopy not to be located again.Update: Returning to Cabanas Yankuam over Semana Santa, Aimee and I observed two different groups of Orange-Throated Tanagers with relative ease.
The Agami Heron is rare and inconspicuous along varzea streams and oxbow lakes in the eastern lowlands. It is extremely elegant with a long, narrow bill, and it hunts solitary and motionless in dense vegetation. Every time we visit a lodge in the eastern lowlands, we travel through what I imagine is perfect Agami Heron habitat by dugout canoe while I peer expectantly into the darkness hoping to pick out this richly-colored heron perched on an exposed branch. I've never seen it, though. To make matters worse, our guide at Sani Lodge this summer, Domingo, told me about an acquaintance of his who found a colony of thousands of nesting Agami Herons on a little-visited tributary of the Tiputini River; the guy explained that there were birds everywhere out in the open as far as you could see.
Update: I finally observed this species during my last trip to Amazonia, once before dawn with Oscar Tepuy at a regular site at Sacha Lodge, and another time with Domingo at Sani Lodge. The latter occasion was at such close range, I didn't need binoculars.
The Golden-Chested Tanager is found in the far northwestern lower foothills. It's a plain navy blue bird with a gold patch on its chest, but it's been driving me crazy as I've visited a well-known site twice now and barely missed it both times. To have a chance for the tanager, you must drive six hours from Quito to Jocotoco Foundation's Rio Canande Reserve, where expensive reservations are required, and then walk four hours up a steep ridge, where it's sometimes found rather high in the dense, bromelia-laden canopy with mixed flocks. I spent hours looking for it on my last visit right after my iPod stopped working due to the humidity (supposedly the bird responds well to recordings of its buzzy call). While pouring over a monospecific flock of Tawny-Crested Tanagers, I heard our guide Galo come up behind me and spot it before it moved down the ridge. There simply must be an easier site for this bird.The Rufous-Crowned Antpitta is so rare and difficult that I actually didn't mind just missing it on our last visit to the Jocotoco Foundation's Rio Canande Reserve in the northwestern lowlands. Aimee, Galo, and I were just getting started on a long day's journey up to the Black-Tipped Cotinga Viewpoint when we heard the mythical antpitta calling in the undergrowth near the Red-Capped Manakin Trail turnoff. Despite calling quite close by, the two birds could have been anywhere around us due to the acoustical affect of being on a ridge. I knew as soon as we heard them that we didn't have a chance of seeing one, but we gave it an honest effort for fifteen minutes until the pair stopped calling and went their separate ways on either side of the ridge. Considering no one ever sees this bird, I felt pretty good about our near miss until Dusan Brinkhuizen from Aves Ecuador let me know what a shame it was that we let it get away.
Update: Amazingly, I saw the Rufous-Crowned Antpitta in January at Mangaloma Reserve, obtaining decent photographs as well.
The Gray-Headed Antbird is an attractive, rather long-tailed antbird like the Blackish Antbird but much more elegantly patterned. It's highly localized, though, and if you're interested in seeing it in Ecuador, then you'll need to travel all the way down south to the Jocotoco Foundation's Utuana Reserve. Actually the bird is found most regularly in some bamboo stands along the road from Sozoronga as you approach the reserve, but you get the idea. If you're traveling down here, it's most likely you're a birder, and as you want to see as many species as possible on your trip, then this bird is important to you, much more important than if it were widespread. Birds like the Gray-Headed Antbird take us to remote, forgotten places that wouldn't interest anyone else; they are what make us unique as travelers, so missing them erodes our identity and sense of purpose.
The Black-Spotted Bare-Eye is a gorgeously patterned antbird found in varzea forest in the eastern lowlands. While it generally attends antswarms, the bird is occasionally found on its own, always extremely shy. Amazingly a colleague of mine saw one at an antswarm at Sani Lodge a few years ago and even photographed it despite not being a birder himself. This isn't a bird I ever expected to see myself, but on my last visit to Sani we heard one calling not far from Domingo's reliable White-Lored Antpitta site. At the same time, though, we heard the rare and local Rufous-Headed Woodpecker calling from above. At this point, Domingo had to make a decision as a guide: do we chase an obscure and skiddish antbird that's difficult to see with playback, or do we try to locate one of the most prized woodpeckers in the neotropics? Although I had seen the woodpecker before, I agreed with his decision to abandon the Black-Spotted Bare-Eye. Update: Another long-desired bird that I finally tracked down on my last trip to Amazonia. We heard small groups of them every day, but had to be very patient and persistent to line them up properly in our binoculars.
The Spectacled Owl is a large, almost comical-looking owl that is widely distributed in Central and Southern America. Missing this owl in Ecuador isn't going to kill me, but the manner in which I've missed it will. Nothing is worse than taking a lot of time to visit a bird's roosting site and have it not be where it's supposed to be. On my most recent visit to Sani Lodge, our guide Domingo took us an hour by boat up the Napo and half an hour on foot onto his father's property to see a pair of roosting Spectacled Owls. Just like the Crested Owls we had missed the same morning, they were nowhere to be found. Who knows what other birds we were missing somewhere nearby while we were purposefully pursuing this one? (As it turns out we missed a Yellow-Fronted Nunbird calling near the riverbank.) Update: Domingo and I finally found the pair of owls at their roosting site, just as we had planned last year.
The Yellow-Throated Spadebill is the type of bird that I miss because I don't spend a lot of time birding with guides, in part because the services of a very good one are expensive. The spadebill is rare and local in subtropical forest on the eastern slope, but there's a particular trail at Wild Sumaco Lodge where the bird is found somewhat regularly. After much research and study of its call I tried for it early one morning while staying at the lodge, which is a big investment of money in itself. While checking out a territorial male Chestnut-Crowned Gnateater, I recognized the call of the spadebill coming from down the trail. Scrambling to set up my iPod and keep up with the birds, which were speeding down the trail for some reason, I couldn't seem to located them as they moved from perch to perch presumably right in front of me. Another set of eyes surely would have helped, but how many other difficult birds have I missed because I didn't know their call?
The Black-Breasted Puffleg is a very rare and endangered hummingbird that I should have seen by now. Seriously, I've been to its habitat on the northwestern slope of Pichincha at least ten times during the months of April to August when it annually appears, missing it each time while plenty of other birders have seen it visiting the feeders at Yanacocha Reserve, for example. Although this site is less than an hour's drive from Quito, I admit that it's difficult to find a rare and obscure hummingbird, considering that you're basically forced to wait at the hummingbird feeders until one shows up. Still, the bird has appeared briefly but regularly at other sites downslope, including Verdecocha Reserve, and it's my own fault that I didn't go after it when I heard the news. I have one more season left to see this Ecuadorian endemic, though, and I'm really going to go for it.Honorable mention: Collared Puffbird, Black-Necked Red Cotinga, Elegant Crescentchest, Beautiful Jay, Golden-Eyed Flowerpiercer, Sharp-Tailed Streamcreeper.