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Condor, &1:320@ The CooperOrnithologicalSociety1979

FIRST NEST DESCRIPTIONTHE GENUS MICRASTUR(FOREST FALCONS)WILLIAM

FORJ. MADER

The genus Micrustur is a distinct group of six speciesof small to large falcons with long tails and short wings
that inhabit forests from southern Mexico to Central
Argentina. Little information exists on the natural habits of its members; indeed even nidification remains
unknown (Brown and Amadon, Eagles, hawks and falcons of the world, McGraw-Hill
Book Co., 1968;
Schwartz, Condor 74:399415,1972). To my knowledge, the following is the first description of a nest forthis genus.
I discovered a nest of the Collared Forest Falcon (M.
semitorquatus)
in a canopied forest (estimated to be20-40 m high) in southwestern Guarico state, Venezuela. The nest was 12 m from the ground in the cavity
of a 38-m tree (determined from a clinometer). TheCuarico River was 200-300 m east of the nest. I foundthe nest around IO:00 h on 20 August 1978 and returned four hours later with three companions and tree
climbing gear. I discovered one nearly fledged chickinside the nest cavity. I estimated the cavity to beabout 0.50 m deep and 0.60 m wide. There were two
openings into the hollow, both well sheltered from therain and on opposite sides of the tree trunk. One wasround, about 20-30 cm in diameter and at the top of
the cavity. The hole appeared to be the place wherea limb had broken off and since rotted. I first locatedthe nest by hearing the chick calling and then seeing
it peering out through this hole; it was probably theentrance used by the adults. The second entrance tothe cavity was a vertical slit about 30 x 20 cm. Looking
into the cavity from this opening, I could see no evidence of nesting material on the floor of the cavity sopresumably this species of falcon, like most others, lays

its eggs in a bare scrape. The floor of the cavity hadvines growing across it while the sides of the cavity
were white-washed from falcon droppings. Although
I could not see any prey remains, the nest smelledheavily of decaying animal matter. When I tried to grab
the chick to obtain measurements and photographs it
jumped to the round entrance hole and clumsily flew
about 30 m to a tree. After climbing down I looked at
the chick through 10 x 50 binoculars. The primaries
and rectrices were noticeably
short and not fullygrown. I believe that this chick was the only one because I did not hear any others calling.
I first found this pair of falcons on 16 July. Although
I saw an adult, presumably the female (with an obvious
brood patch) I failed to find the nest. This bird walked
along horizontal tree limbs and called at me. On subsequent visits I saw little of the adults but often heard
them. They uttered two calls. The first appeared to be
an alarm call aimed at me and sounded like “ho, ho,ho.” The second call sounded like a single long “ho.”At times an adult gave this call and the chick returned
it, but at a different pitch. On other occasions the adults
gave this call back and forth to one another.
The fact that the falcons nested roughly between
June and August suggests that breeding may usuallyoccur in the wet season (April-Novemberin Guarico).
Other forest hawks such as the Roadside Hawk (ButeoCrane Hawk (Gerunospiza
caerulesmugnirostris),tens), and Bicolored Hawk (Accipiter bicolor) also
breed in the wet season (pers. observ.).
I thank Kerry and Carla Rabenold and Linda Robinson for their help when I climbed to the nest. Thiswork was incidental to a study of the Savanna Hawk(Heterospizius meridionalis) which was funded by theFrank M. Chapman Memorial Fund of The American
Museum of Natural History, and The National Geographic Society. I also thank Tomas Blohm, whose generous support made my field work possible.
Departmentof Zoology, Brigham Young Uniuersity,
Prouo, Utuh 84602. Accepted for publication 31 March
1979.

Condor,81:320321
0 The CooperOrnithologicalSociety1979

THEGREATDONALD

POT00

IN COSTA

RICA

R. PERRY

Little is known about the life history and behavior of
the Great Potoo (Nyctibius grandis), probably because
this species generally roosts in very tall trees in tropical forests and because its coloration-whitewithbrown mottling-matchesclosely that of the limbs on
which it rests (Wetmore 1968). The hunting as well as
the roosting habits of N. grandis have been reported
by Haverschmidt (1948).
I report here on observations made above the canopyof a primary lowland wet forest at Finca La Selva (aresearch station of the Organization for Tropical Studies), near Puerto Viejo, Heredia Province, on the Caribbean coast of Costa Rica.
I first saw a Great Potoo on 11 July 1978 from a platform I had built 33 m up in a Monkey-pot tree (Lecythiscostaricensis). It sat on a limb of a leafless, 46 m tallHymenolobium
sp. (Leguminosae) tree some 80 maway, within unbroken forest in the south corner ofWashington Plot I (a permanent research site at La Selva). The bird was very difficult to distinguish, for it
closely resembled the stump of a branch. This was thefirst time a Great Potoo had been seen in the area. Thespecies has not been previously reported with certainty from Costa Rica (Slud 1964), although expected, forit was known to occur in regions to the north and south.
The very few records from the north have come from
Nicaragua (Wetmore1968), Guatemala(Land andSchultz 1963) and a sighting, but no specimens, from
Honduras (Monroe 1968).
On the afternoon of 13 July I climbed 40 m up into
the Hymenolobium(Perry 1978). I saw the bird
perched on the same limb as before (Fig. 1) at my level.
It stood within a small area of bare bark, devoid of theusual encrusting lichens, suggesting that this was aregular perch site. Over the next two months I visitedthe tree at varying intervals and nearly always foundthe bird there. I photcggraphed it repeatedly, confirming the identification, and noted some of its behavior.
When the potoo was not disturbed, it sat upright,

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FIGURE 1. Great Potoo at Finca La Selva, near Puerto Viejo, Costa Rica.

facing forward, eyes closed, and with its head feathers
erect so that it had an owl-like appearance. My presence several meters away did not seem to disturb thebird. When I made abrupt moves that shook the tree
or when I called out, the potoo apparently became
alarmed and immediately raised its head until it faced
vertically,
with eyes closed and head feathers depressed. In this position it resembled
even moreclosely a part of the branch. Often, in either position,
the mouth was held partially open. The bird was probably panting as it always sat in full sun. The mouthlining was a dull red.
Occasionally, for no apparent reason, the potoo shifted its body to a horizontal orientation; its head however, remained facing out, never down. At other times
it stretched its wings or turned its head and looked
around.
The bird perched on lateral limbs of the tree crownthat ranged in diameter from about 15 cm to about 35
cm. It stayed within regions from one-halfto two-thirds

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321of the distance from the trunk to the periphery of thecrown.
During the period of my observations the Hymenolobium tree was in its reproductive phase. By the last
two weeks of August, the fruit had become attractive
to other birds, especially the Red-lored Parrot (Amazona uutumnulis). These parrots came to the tree ingroups of up to twenty and foraged noisily. On 23 August, after several days of this activity, I searched forthe potoo but it was not in the Hymenolobium.
On 1
September the potoo was in the tree again. At around
16:OO several Red-lored Parrots flew into the tree andbegan walking about the limbs looking for fruit. One
parrot came to within a meter of the potoo, and thelatter appeared to become agitated. It looked repeatedly toward the parrots as it made uncharacteristicallyquick movements and finally assumed its vertical alarm
posture. The bird was not in the tree the next day andit still had not returned by 15 September, when I left
La Selva.
The coloration of the potoo matches closely that of
the lichen-covered
limbs of Hymenolobium
sp., andthese trees, along with others that have similarly colored limbs, could be preferred perches. The species isprobably more numerous than is generally realized but
its cryptic coloring and habits make it difficult to find.
Further inspection of canopy tree crowns may corroborate these conclusions.
My work was supported by Mr. and Mrs. Ft. E. Collins and S. E. Merschel, and is a by-product of N.S.F.
Grant DEB 77-75558 (PrincipalInvestigator,K. S.
Bawa). I thank Mike Grayum, Buck Sanford and Tom
Sherry for their field assistance. Thanks also go to F.
Gary Stiles and Thomas R. Howell, who identified thebird from a description and photographs, respectively.
I especially thank T. Howell for his helpful comments
and critical reading of the manuscript.

LITERATURE

CITEDHAVERSCHMJDT, F. 1948. Observations on Nyctibiusgrundis in Surinam. Auk 65:30-32.
LAND, H. C., AND W. L. SCHULTZ. 1963. A proposed
subspecies of the Great Potoo, Nyctibius grundis(Gmelin). Auk 80:195-196.
MONROE, B. L. 1968. A distributional survey of thebirds of Honduras. Omithol. Monagr. No. 7
PERRY, D. R. 1978. A method nfaccess into the crnwnsof emergent and canopy trees. Biotropica 10: 155157.
SLUD, P. 1964. The birds of Costa Rica: distributionand ecology. Bull. Am. Mus. Nat. Hist. 128.
WETMORE, A. 1968. The birds of the Republic of Panama. Smithson. Misc. Collect. 150, part 2.
University of California
at Los Angeles, Depurtmentof Biology, Los Angeles, California 90024. Acceptedfor publication 14 February 1979.