Hoatzins!!!

Ok this bird is cool.  And with travel restrictions making the planet feel bigger as international ares become inaccessible it feels a little bit surreal that I've recently seen them.  They're really like nothing else, enough that I was motivated to pull up some papers on SORA to learn more.

It turns out that they're giant cuckoos.  They're bizarre enough though that they were originally put in the cracid family (turkeys/guans/etc), then moved to rails (!), before egg white protein studies carried out by the elder Sibley showed them to be cuckoos.  Sibley speculated that their foot structure (3 toes forward, 1 back) probably played a big role in their original assignments (cuckoos typically have 2 forward and 2 back).

They eat leaves.  Lots of leaves.  And take a completely different approach than any other bird.  Geese eat grass, and the grass, well, passes through the goose in proverbial fashion.  Since there isn't a ton of nutrition in leaves geese pass them through the digestive track quickly to get what they can, move it along, and eat more, ignoring the energy that is stored in the hard-to-break-down plant cell walls. 

Hoatzins take the opposite approach and ferment the leaves in a crop that's so big that it takes the place of some of the breastbone and pectoral muscles, leaving the hoatzin a very weak flier.  The crop is big enough that it makes the bird front heavy when full and the birds develop calluses on the skin atop the base of their breastbone from leaning against branches.  And that process takes time.  Some grad students (not sure how you'd pitch this study to someone ... hey!  want to join our lab?  We do Hoatzin Poop Studies!) fed captive hoatzins some undigestable tiny plastic pellets in their feed ... and then counted how long it took the pellets to end up on the floor of the cage.  It took 4-5 days to pass them all (maybe we have a replacement for watching paint dry?), a rate that's much more analogous to some of the herbivorous cud-chewing mammals than to a bird.

A likely offshoot of trying to raise young on a diet of fermented leaves is that hoatzins often will have helpers at their nest since the younger adults may not be able to produce enough leaf malt on their own to raise young and may help their parents in raising the next year's brood.  Young at nests with helpers grew faster and fledged at higher rates than those without

and this doesn't even touch on the babies having wing claws that are useful to clamber about the foliage when young (I forgot to ask Fito or Jason when the young Hoatzins are about).  I guess I'll just have to go back...

References
Grahal et al.  Structure and Function of the Digestive Tract of the Hoatzin:  a Folivorous Bird with Foregut Fermentation.  Auk 112(1): 20-28. 1995.

Grahal et al.  Passage Rate of Digestive Markers in the Gut of the Hoatzin, a Folivorous Bird with Foregut Fermentation.  Condor 94(3): 675-83. 1995.

Sibley and Ahlquist.  The Relationships of the Hoatzin.  Auk 90(1): 1-13. 1973.

Vanderwelf et al.  Effects of Unit Size and Territory Defense on Communal Nest Care in the Hoatzin.  Auk 107(3): 626-28.  1990.

On to Sani

After 3 or 4 days at Shiripuno we moved one river north and arrived at Sani Lodge.  After working our way down the Napo our guides canoed us down backwater channels that I don't think actually connected to the river.

And there were birds, Great Potoo (again!), and a little flock we couldn't really catch up to, though an Olivaceous Woodcreeper bailed out somewhat dramatically.

 Lineated Woodpecker put on a show

Jason recognized the call of an Orange-crowned Manakin.  I cautioned the group that it wouldn't look like a manakin ... and then still didn't believe when the bird popped out that it was one until it flashed the crown a couple times.

Shortly after this pic was taken Guillermo (paddling in the front of the kayak in the top pic) attempted to re-position the canoe while standing ... and tipped himself right out of the boat!  The other guides and lodge personnel were giving him grief for the rest of the trip.

These White-winged Swallows paid no attention though.

This was another place where I should have taken more scenery pics...

Crane Hawk!

Our final morning at Shiripuno was spent ... leaving Shiripuno.  It was a 3-4 hour boat trip back upstream (and given we had about that in trucks and then about that in a boat down the next river to the next spot) we left before the sun was up.  It was a little unnerving to be going upstream basically in the dark, but the sun rose quickly.

I really should have taken more scenery shots on this trip.

The early morning light was perfect for getting a decent exposure for a black and white bird like the Wattled Piping-guans. 

I saw a perched hawk and was having trouble shoe-horning it into something I knew.  Fortunately it flew behind some trees before appearing directly overhead.

Crane Hawk is a bird that's been theoretically possible on most trips I've taken that reached lowlands in the tropics (heck there's at least one record for S Texas), and the contrasting white underwing comma is pretty unique (though I was once fooled by a Yellow-headed Caracara), so it's a bird that's been on the wish list so long that they kind of felt like a myth.  But the myth appeared overhead (and a second one did about 20 minutes later as it turned out) so I was pretty happy.

Blue-and-yellow Macaw also generally makes me pretty happy.

We had more flyover Red-bellied's as well.

Sunbittern on the other hand I've had a lot better luck with.  This is my 3rd country with a sunbittern (though I'm still missing Sungrebe everywhere).

A pic of a Squirrel Monkey

Finally the last lifer of the boat trip, Greater Yellow-headed Vulture.  I've got a bunch of pics that are almost pretty good, but all have some combo of a wingtip cut off, or the eye shadowed, or a weird angle, but ah well.

The orange head was a really neat contrast to the TV's we're used to.

trip emblem?

The larger forest floor birds were some of the more interesting ones we encountered at Shiripuno (though admittedly we often saw them atop trees).  Guans, Piping-guans, Chacalacas, (vocalizing) Tinamous, and Curassows were much better represented at this location than any I've been to.  Probably fewer birders have seen Nocturnal Curassow than any other bird I've seen.  We'd heard Salvin's a few times, but it's always nice to see the birds.  So when a Salvin's Curassow walked out to drink along river's edge as we boated back to the lodge on our final evening at Shiripuno we were pretty excited

Striated Heron (Green's close cousin) on the other hand, is a lot more common along the rivers.

Red-throated Caracara's range just barely starts in the Panamanian Darien, at it was nice to see (and hear!) this bird again.

I've seen Laughing Falcons a few times in the tropics but this was the first time on one of the group tours I've arranged

Finally another treetop bird we'll be searching for in a month or so, Olive-sided Flycatcher!