Wiley, R. H.   1980.   Multispecies antbird societies in lowland forests of Surinam and Ecuador: stable membership and foraging differences.   Journal of Zoology, London, 191:   127-145.


Flocks of insectivorous birds in the understory of lowland wet forest in Surinam and eastern Ecuador regularly included two species of antshrikes in the genus Thamnomanes (ardesiacus and caesius ) and four species of antwrens in the genus Myrmotherula (in Surinam, axillaris, menetriesii, longipennis and gutturalis; in Ecuador, the first two plus hauxwelli and ornata ) (Formicariidae), as well as a number of other species particularly in the families Furnariidae and Dendrocolaptidae.

Each flock included only a pair or occasionally a small group of each species. Although the individuals in a flock often spread over an area 30 m in diameter, the Myrmortherula, Thamnomanes and several other species moved cohesively through the forest. Each flock persisted throughout a day and, over periods of a least a week, recurred within the same largely exclusive range in the forest.

The two Thamnomanes species had distinctive vocalizations that provided the primary signals for flock cohesion and alarm calls.

Although most of the species of Myrmotherula had loud vocalizations, these were uttered too infrequently to contribute to flock cohesion and played no role in reactions to predators.

In Central America, on the other hand, where Thamnomanes does not occur, M. fulviventris produces loud vocalizations, that resemble those of Thamnomanes, during disturbances to a flock.

The species of Myrmotherula in each locality segregated ecologically in two dimensions, height of foraging above ground and preference for foraging in live or dead foliage. A shift in the foraging height of axillaris depending on the presence of absence of longipennis in the same flock suggested that competition for food has favored ecological segregation of foraging height by these species.

Thamnomanes-Myrmotherula flocks attain an unusual degree of cohesiveness and integration of foraging specialties in comparison with other mixed aggregations of animals.

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