Searching for a needle in a moving haystack…

Wattled Curassow (Crax globulosa) drawing by S. Bennett

Many years ago when I was but a Lad, I had become extremely interested in a Neotropical family of birds called Cracids.  In fact, I had spent a year studying the northern-most species, the Plain Chachalaca (Ortalis vetula), and spent a year studying one of the southern-most species, the Chaco Chachalaca (O. canicollis).  In 1993 an incredible opportunity had come about to leave my ‘day job’ at the Houston Zoo for a couple weeks to search for a much more elusive species in the Peruvian Amazon – the Wattled Curassow (Crax globulosa).  Basically, I could lead a natural history eco-tour emphasizing bird-watching to the region and stay down afterward to try and locate this little known and seldom-observed species.  Only a couple of people had seen this bird in the region I intended to visit, including the late Ted Parker.  I had met Ted once or twice during previous visits to the Museum Natural Science at LSU.  We were actually supposed to meet at LSU in late August 1994 with Dr. John O’Neill to discuss a possible new race of Bare-faced Curassow (Crax fasciolata), but due to most unfortunate circumstances, Ted died earlier that month in a plane crash while surveying some forest for a new reserve in South America. 

I was thoroughly exhilarated about the trip to Peru; little did I know at the time it would be the first of many.  The field of Neotropical Ornithology was much younger than it is today, but much older back then than it was before the original explorers who investigated a good swath of the area.  Leaders like Parker provided a spirit of elevated excitement about working in South America.  I for one was ecstatic, but what I thought I knew before I left for Peru was sadly naïve on my part.  I guess I just figured ‘searching for a Cracid is searching for a Cracid; if I can find some species without a problem, why wouldn’t I be able to find others?’

                                                                                                -DB, 12 November 2008

Searching for a needle in a moving haystack…

20 November – 4 December 1993
ACEER, Sucusari Tributary off the Napo River, Dept. Loreto, Peru

Map showing ACEER study site north of the Napo River, off the Sucusari TributaryWell, yesterday I had convinced myself that if only I looked more intensively I had to find some sign of the rare globulosa.  If I carried lunch with me in the field, I could spend 12 hours a day instead of just 3-4 hours post-sunrise and pre-sunset.  All I had turned up so far was a Razor-billed Curassow (Mitu tuberosa) – I got a mere glimpse of this massive and impressive bird as it heavily flew up into the mid-layer of the forest.  I was also able to account for Nocturnal Curassows (Nothocrax urumutum) calling from deep in the forest during night-time walks, but not so much as a trace of globulosa.  I interviewed some of the local Ribereños [folks living along the river who consume fish and wildlife in the area] to see if they could shed some light on what was going on.

Through the interviews I discovered that globulosa lives in a specialized seasonally inundated forest type called Varzea [actually a Portuguese word].  So I changed up my sampling protocol to cover inundated forest in a boat rather than terra-firme forest on foot.  By spending more and more time on the mighty Napo and Amazon Rivers, what I discovered boggled my mind.  The far off river bank was not a river bank at all, but a mere island within the vastly wide river.  Even more amazing than that, there would sometimes be two or three of these inundated forest islands in a row before you hit the opposite bank! 

One morning, my boat driver Gaspar and I set out before day break as usual in the standard 20’ metal john boat with outboard motor.  I asked him if we could go to the Yarina chain of inundated forest to search for globulosa there.  As we approached Yarina he slowed down quite a bit to nearly a complete halt, and quickly negotiated our path ahead.  I had no idea what he was looking at, so I asked him.  Then he pointed out a new sandbar ahead in the middle of the river that had not been there the week before.  I strained to see what he was talking about, then saw the shallow ripple of waves change their pattern as they glided across a bit of sand just up level with the water’s surface.  He paused for a bit to consider the best way around this obstacle.

During subsequent morning boat trips, I saw sandbars in various stages of plant community succession.  Some of the islands contained monotypic stands of the earlier colonizing species such as Cecropia, Gynerium and Heliconia, whereas other islands were quite massive, supporting a full array of Varzea forest.  Then I saw yet another amazing thing – frugivorous [fruit-eating] birds flying over the sandbars defecated, totally by coincidence of course, but they acted as the ‘Johnny Appleseeds” of these island forests.  By defecating the seeds of the fruits they were consuming onto the sandbars, they were actually planting the forests through seed dispersal!

I shared my amazing realization of sandbar and seed dispersal dynamics with other scientists at dinner that evening, and of course they informed me that I had observed something they (and others before them) had known a long time already.  They explained that the vast and fast-moving river was so dynamic in fact that by the time these sandbars supported a forest climax, they would often become destroyed or isolated as part of an oxbow lake.  Slowly the pieces of the puzzle began to unravel – aHA! so that is why these buggers are so hard to find!  Not only is globulosa restricted to this specialized Varzea forest, but the Varzea forest is constantly changing with the ebb and flow of the river’s seasonal water level.  It was all beginning to make sense now – finding this rare bird was like searching for a needle in a moving haystack…

Post-log (12 November 2008): As I learned more about the biology of globulosa, actually in collaboration with a former student, Claudia Garcia, one of the other things that made them difficult to locate in the field was the fact that their call was a high-pitched descending whistle (like a missile dropping on a Bugs Bunny cartoon), unlike other species of curassow that had a deep resonating ‘boom’ that could be heard for quite a distance, and consequently were a lot easier to find in nature.  My interest in Cracids became increasingly obsessive until I reached the peak of Cracidology, as Chair of the Cracid Specialist Group.  Of the decade’s worth of trips I took to the same region of Peru, I never found globulosa one single time.  I figured it was just me, so had others who I felt were more competent search for them as well, but they also came up empty handed.  What we now know of the species is it is just extremely patchily distributed, reflected by the dynamic and specialized habitat it thrives in – Varzea forest.  On a positive note, some great projects have since been established in Colombia (through the great work of Sarah Bennett and the local community she works with), Bolivia (through the hard work of Hugo Aranibar and Bennett Hennessey) and Brazil.  Even more work is taking place in these regions today to conserve the remnant populations of these rare and fascinating birds – the Wattled Curassow (Crax globulosa).