Abstract
When most of us think of skillfully constructed hanging nests, we envision one of the colorful members of the family Ploceidae (weavers and allies). A more temperate example would be that of the frequently encountered Baltimore oriole (Jcterus galbula) or, in the west, Bullock's oriole I. bulloceti), with their drooping nests often swaying in the wind from the branch of an old elm.
In the Central American tropics hanging nests are a commonly utilized nesting strategy. A number of small flycatchers construct elaborate pensile nests by matting together nest material instead of weaving it. The details of structure and location are specific to each type of flycatcher.
Without a doubt, the "maestro" of weaving must be the Montezuma oropendula Gyrnnostinops montezuma) with its clusters of 2 to 4 foot nests hanging from the tallest trees in the forest. Inhabiting southern Mexico south to the canal zone of Panama, it is predominately a Caribbean coastal species (although also encountered on the Pacific Coast where the continental divide is low in elevation such as in southern Mexico and northern Costa Rica).
The largest of the three species of oropendulas that inhabit Central America, the male Montezuma is about the size of the common crow. It derives its name from the Spanish words "oro" meaning gold and "pendulo" meaning hanging or pendulum. The first refers to the yellowish tail feathers and the latter to the drooping nature of its nests.
Except for its bright yellow tail feathers, its coloration has little to offer being mainly chestnut with a few spots of blue and reddish-orange on the fleshy cheek patches. Oropendulas are members of the Jcteridae family, It is a rather large family composed of oropendulas (12), orioles (27 including the troupiat), caciques (11), blackbirds (25), meadowlarks (5 ), grackles (11), cowbirds (7), marshbirds (2) and the bobolink.
Flying rather labored from tree to tree in search of fruit, it is not until it emits that rather liquid gurgle that it attracts one's attention. In a lone ceiba tree within the Chiquibul Forest Reserve a nesting colony has existed for over a decade. Although fond of the ceibas, in Belize, and in other portions of its range it has been known to nest even in clumps of tall palms, the main requirements being that the tree is tall, has drooping branches and is quite separate from the other trees in the forest. In Costa Rica, Skutch recalls one colony that contained 61 nests and another that had 88. The Belizean colony l observed contained only 47 active nests.
Nesting activity begins in January or February and spans the dry season. The colony is vacant from October to December when the hens go off to forage away from the nesting area. The midribs of banana leaves and shredded strips of palm fronds are the preferred nesting material. Although one's attention is generally drawn to the vocal males, they are greatly outnumbered by the females. Jn addition, they are rather insignificant in terms of the entire reproductive cycle as it is the females alone that lay, incubate and care for the nestlings (usually two eggs are laid). Pilfering of nest material is common among the hens. The famous tropical ornithologist A. Skurch theorizes that it results in more strongly built nests as loosely built ones are pilfered. The entire process requires several months after which the nests are rather tattered and torn looking. It is not uncommon to find several broken loose, in a mound at the base of the colony.
Despite the fortress-like appearance of the colony, not only are the oropendulas parasitized by the giant cowbird (Scapbidura oryzivora), but nestlings and eggs are frequently lost to several species of raptors, toucans and primates. The birds' habit of stripping banana leaves and piercing citrus fruit makes it unpopular with plantation owners. In addition, the felling of the large cieba trees (and other large trees) certainly must adversely affect the future stability of the colony.
Many newcomers to the tropics have visions of toucans, macaws and monkeys among the lush green vegetation. For many, the glimpses of these species are short and few. Most likely one leaves the forest with the liquid gurgle of the oropendulas. •