Ecology of the

Cock-of-the-Rock

Note: This online review is updated and revised continuously, as soon as results of new scientific research become available.  It therefore presents state-of-the-art information on the topic it covers.

The Cock-of-the Rock is one of the world's most spectacular birds.  Its fantastic plumage and colorful courtship display equal those of any bird of paradise.  Two species are recognized:  (1) the Andean Cock-of-the Rock (Rupicola peruviana), and (2) the Guianan Cock-of-the Rock (Rupicola rupicola).

Both species are restricted to mountainous areas of northern South America.  The Andean Cock-of-the-Rock is distributed in the Andes from Venezuela south to Bolivia, while the Guianan Cock-of-the Rock is found in the more ancient, and highly eroded mountains that lie east of the Andes and north of the Amazon River (i.e. in the Guianas and adjacent areas of Venezuela, Brazil and Colombia).

The diet of both species is mainly fruit, and their nests are built on the rock faces of cliffs, large boulders, caves or steep gorges.  The female Cock-of-the-Rock builds the nest and raises the young without assistance from the male.  The normal clutch size is 2 eggs.

Adult Cock-of-the-Rock males spend much of their time at communal courtship sites called leks, where they defend ground display courts and/or nearby perches from other males.  Here they display to Cock-of-the-Rock females visiting the lek.  The females then select which males to mate with (Snow 1982).

Courtship and nesting behavior of the Cock-of-the-Rock increases local plant diversity

When the Cock-of-the-Rock eats fruit, it swallows many of the seeds whole and most of these are not damaged when they pass through its digestive system.  Thus, many seeds remain capable of germinating when the Cock-of-the-Rock defecates or regurgitates them at considerable distances from the parent trees.  In this way, the Cock-of-the-Rock plays an important role in dispersing seeds of many different species of forest trees. 

Since the adult male Cock-of-the-Rock concentrates his time and activities around the lek, and the adult female concentrates her time and activities around cliff nest sites (where several females may build nests in close proximity to each other), seeds are deposited more frequently at leks and at nest sites.

For example, at a lek of the Guianan Cock-of-the-Rock in French Guiana, Thery and Larpin (1993) found seeds of 21 species of plants under the perches of males.  All were believed to have been defecated or regurgitated by the males.   Likewise, Erard et al. (1989) collected droppings under a nest of the Guianan Cock-of-the-Rock in French Guiana, and found in them the seeds of 52 plant species.  In an earlier study, Benalcazar and Benalcazar (1984) collected droppings under 7 nests of the Andean Cock-of-the-Rock at a site west of Cali, Colombia, and in them found the seeds of at least 35 plant species.

When high densities of seeds are deposited in this way at Cock-of-the-Rock leks or nest sites, and when environmental conditions are favorable for their germination and growth, the abundance and diversity of plant species growing from these seeds can be greatly increased at leks and nests, making the plant communities at these sites different from that of the surrounding forest.

For example, at the lek of the Guianan Cock-of-the-Rock in French Guiana mentioned above, where Thery and Larpin (1993) found seeds of 21 species of plants under the perches of males, they also found evidence that the Cock-of-the-Rock males had altered the diversity and abundance of plants at the lek by seed dispersal.  The lek was located on the ridge of a steep granite hill, and its vegetation differed markedly from that of the surrounding forest and nearby ridge tops.  While most of the flora at these other sites was fairly homogeneous, the vegetation at the Cock-of-the-Rock lek was a mosaic of plant species typical of many different communities.  After analyzing the lek vegetation more thoroughly, Thery and Larpin concluded that the greater part of it resulted from long-term seed dispersal by Cock-of-the-Rock males.

In a tropical forest in British Guiana, Gilliard (1962) found a number of papaya (Carica papaya) trees growing at the base of a huge rock upon which several Guianan Cock-of-the-Rock females were nesting.  Because he saw no other papaya trees in the forest, he speculated that the Cock-of-the-Rock females had fed on papaya fruit in native gardens a long distance away, and then later regurgitated the seeds at their nests, which then fell to the ground below and germinated.

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Photograph at top of page:  A male Guianan Cock-of-the-Rock in Amazonas Province, Brazil, by Hugo Viana (Brazil).