Abstract
Before you read the article or finish reading this caption, see if you can find the bird in the photo. This is an extraordinary example of natural camouflage to protect a bird from predators. You haven't found ityet?Okay, cbeck tbe end of tbe stump. On it, an extension of the stump, if you will, is a common potoo (Nyctibius griseus) which in reality is not a very common bird at all.
After two years of almost constantly searching for the common potoo, Nyetib i us griseus, in the Panamanian jungles, I finally stumbled, quite by accident, onto the elusive bird on the Caribbean slope of the Republic. The sight of this bird made me feel the wonderful sense of accomplishment that one finds only after enduring numerous hardships.
I had searched for this bird at night using a powerful spotlight and during daylight hours, all to no avail.
I was thrilled to learn of a birdwatching trip that was scheduled for the sixteenth of June to the Caribbean side of the Republic by the Panama Audubon Society. I had never birded this area so I was really looking forward to it, for there are many species of birds that are found only in this area. We set
out at 5:00 a.rn -, so we would meet with the rest of the group by 6:30 a.m.
We finally set out to bird an area known as "Black Tank Road'.' After walking a couple of miles and seeing many new species of birds, from black crested jays to green honeycreepers, I still had the potoo in the back of my mind. Many Amazon parrots filled the air with their constant chatter as they flew overhead, and this, mixed with the morning mist that had collected on the fronds of many plants, gave one the sense of delight that can only be experienced while communing with nature.
Once we were deep in the trail I separated from the group, for I believe that the presence of too many people usually tends to scare birds away. I had walked the equivalent of a city block when, still with the thought of potoos in the back of my mind, I came to a small clearing on the side of the road. Here I happened to look to my left and noticed a vertical log reaching about fifteen feet into the air. To my surprise, on the summit of this log lay a beautiful common potoo. The surprise and excitement I felt is indescribable by any literary means.
I immediately ran back to gather the rest of the group and inform them of my discovery. I had this awful feeling that the bird could have picked another branch to sleep on while I gathered the people to show him off. Fortunately the creature didn't think people were worth interrupting his sleep although he knew he was being closely watched. After several photographs and about fifteen minutes of observation, the group moved on leaving me behind to admire the beauty of the bird.
But now let me describe the potoo.
Besides the fact that the bird is nearly impossible to detect during the daytime it really fits no accurate description, other than it resembles the continuation of a dead tree trunk. It is colored in buffs, browns, and blacks. It doesn't seem to have a definite pattern other than all members of this species have a creamy-white throat patch. The tail, which is barred with black, has an intricate weaving of subtle brownish colors as do the back and abdomen. It also sports a necklace of uneven black spots on its upper breast. It measures fifteen inches in length. The potoo relies on its cryptic coloration to protect it from predators.
When humans sight the bird they always find it with its head directed straight up in the air and the rest of its body in a stiff branch-like posture. Potoos only take this position when they sense the presence of predators, for otherwise they assume a slumped, resting position on the branch. When any unexplained movement has been noticed, the bird very slowly assumes the erect position, trying to sit undetected. During the day the potoo maintains its eyes closed to a slit, but I noticed, while looking at it with my binoculars, that it had its eyelids partly open trying to inspect the surroundings.
Inasmuch as the potoo is nocturnal in its habits, at the coming of dusk it leaves its perch to hunt for insects, the mainstay of its diet. Its behavior is rather "flycatcher-like" as it leaves its perch, grabs an insect in flight and returns to the same spot. The bird's eyes glow orange when sighted with a spotlight. Its call is one of the most mournful of all tropical birds. He is known as "poor-me-all-alone" in South America. Its call begins with a high note and, slowly descending in scale, finishes with the lowest one.
The potoo usually nests high up in the tree canopy, using the depression left by a broken-off branch for its nest site. It lays one egg in this depression and in-
cubates it for approximately a month.
Alexander Skutch (Birds of Tropical America, 1983) says about the incubation, "The potoos always incubated facing the supporting branch with the long axis of the body vertical, the base of the abdomen covering the single egg, and the long tail touching the branch below." Skutch goes on to say that the egg, being white splotched with grey and lilac, seems to be glued in place and that the parents never rotate it.
Skutch also mentions, "If we count from the hatching of the egg to the first time the young potoo was seen anywhere but on the nest or the branch beside it, the nestling period was fortyseven days (Jan. 4-Feb. 20). If we count from hatching to its departure from the nest tree on Feb. 24, the nestling period was fifty-one days. Add to that at least thirty-three days for incubation, and we have at least eighty-four days for the total occupancy of the nest tree'.' He also mentions that it is a long time for any bird to reach fledgling age while being perched in such a precarious location.
Common potoos have been kept in captivity by only one person that I am aware of. NathanB. Gale, D.V.M., kept a pair in an aviary for nearly a year. He mentions that in the time he kept them they never made their call. He fed them a diet of 8-10 pinkie mice per night. They simply opened their two-inch gapes and he would drop them in. This was enough food per night. He also went on to say that you couldn't possibly give them the insect supply that they would need in one night while in captivity.
The following measurements were given by Alexander Wetmore in the second volume of his book The Birds of the Republic of Panama:
"Males - ( 15 from Panama and Colombia), wing 264-282 (271.3), tail 174-196 (182), cul.men from base 24.2-29.8 (26.2), tarsus 12.0-14.8 (13.3) mm.
Females - (3 from Panama and Colombia), wing 268-282 (275), tail 178-196 (185), culmen from base 25.5-27.6 (26.4), tarsus 13.0-13.5 (13.2) mm"
Wetmore calls this bird the lesser potoo.
The potoos are found exclusively in the neotropics, from Mexico to northern Argentina. Panama has two of the five species that comprise the Nyetibiidae family. The other Panamanian relative is the rare and much looked for great potoo.