Harmony and Conflict in the Living World - Alexander F. Skutch [39]
Colonial nesting has a different aspect when several or many nests are contained in a single massive structure built by the occupants themselves. Among the conspicuous features of Hispaniola are the nests of Palm-Chats, distant relatives of waxwings, nearly always situated in the crown of one of the stately Royal Palms so abundant on that large Caribbean island. One such nest was a mass of interlaced twigs that I estimated to be ten feet high by four in diameter (3 by 1.2 meters). At a much smaller nest, I counted about twenty-five of the starling-sized brown birds with streaked
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white breasts flying back and forth, bringing more sticks. These great nests are avian apartment houses, containing many chambers that do not connect internally. Each chamber appears to be occupied by a single breeding pair; the birds domestic activities remain to be thoroughly studied. The same palm that upholds the Palm-Chats' massive structure may contain in its columnar trunk numerous holes of the Hispaniolan Woodpecker, one of the few members of this great family that nests colonially In one trunk with twenty-four holes, I found four pairs of woodpeckers nesting simultaneously, and others seemed to be preparing to do so.
Nests of similar size are made by the Monk Parakeet, or Cotorra, of Argentina, one of the few parrots that builds instead of nesting in a cavity in tree or cliff Strongly constructed of interlaced thorny twigs, the nests may hang from outer branches of trees or even from a large palm frond. They may attain a height of seven feet (2.1 meters), weigh a quarter of a ton, and provide separate, unconnected chambers for up to a dozen pairs of the parakeets, each of which lays four to eight dull white eggs in an unlined compartment that is approached through a porch or vestibule from a downwardly directed entrance (Conway 1965).
Of quite different construction, and even more ponderous, are the apartment houses of the Sociable Weaver. In one of the scattered trees in arid Namibia (formerly Southwest Africa), Herbert Friedmann (1930) found an edifice that measured about twenty-five by fifteen feet at the base by five in height (7.6 by 4.6 by 1.5 meters). To start such a construction, the whole flock of sparrow-sized birds, working together, builds a spreading roof by interlacing coarse dry grasses and small twigs. Beneath this general covering each pair attaches its own nest made of similar materials, until the lower surface of the mass is perforated by small, circular openingsnearly a hundred in the very large structure found by Friedmann. Each year the birds attach new nests below the old ones, until finally the overladen branch breaks beneath the weight of the huge edifice. Like the PalmChats and the Monk Parakeets, the weaver birds sleep in their nests even when they are not breeding, thereby saving much energy on chilly desert nights and decreasing their need of food.
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Sociable Weavers, Philetairus socius,
at their many-chambered nest
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Still closer cooperation in breeding is practiced by the lanky black anis we have already had occasion to mention. Although a pair will often nest alone, frequently two, three, or even more pairs join forces to build a simple, open nest of coarse sticks, which they line with green leaves that are brought daily until the young hatch. In this broad, open bowl the females lay their chalky white eggs in a common heap. All the participating anis of both sexes take turns incubating, one at a time, and later all feed the nestlings, making no distinction between their own offspring and those of their coworkers. Each night a single male takes charge of the eggs or nestlings. Bold in the defense of their families, Groove-billed Anis have often buffeted the back of my head while I looked into their nest (Skutch 1983).
Although Palm-Chats,