Mixed-species Foraging Flock - in The Old World Tropics

In The Old World Tropics

The flocks in the Old World are often much more loosely bonded than in the Neotropics, many being only casual associations lasting the time the flock of core species spends in the attendants' territory. The more stable flocks are observed in tropical Asia, and especially Sri Lanka. Flocks there may number several hundred birds spending the entire day together, and an observer in the rain forest may see virtually no birds except when encountering a flock. For example, as a flock approaches in the Sinharaja Forest Reserve in Sri Lanka, the typical daytime quiet of the jungle is broken by the noisy calls of the Orange-billed Babbler (Turdoides rufescens) and Greater Racket-tailed Drongo (Dicrurus paradiseus), joined by species such as the Ashy-headed Laughingthrush (Garrulax cinereifrons), Kashmir Flycatcher (Ficedula subrubra) and Velvet-fronted Nuthatch (Sitta frontalis).

A mixed flock in the Cordillera Central of Luzon in the Philippines was mainly composed of Bar-bellied Cuckoo-shrikes (Coracina striata: Campephagidae), Philippine Fairy-bluebirds (Irena cyanogaster: Irenidae) and Violaceous Crows (Corvus (enca) violaceus: Corvidae). Luzon Tarictic Hornbills (Penelopides manillae: Bucerotidae) were also recorded as present. With the crows only joining later and the large hornbills probably only opportunistic attendants rather than core species, it is likely that this flock was started by one of the former species – probably the bold and vocal cuckoo-shrikes rather than the more retiring fairy-bluebirds, which are known to seek out such opportunities to forage.

African rainforests also hold mixed-species flocks, the core species including Pycnonotidae (bulbuls) and Nectarinidae (sunbirds), and attendants being as diverse as the Red-billed Dwarf Hornbill (Tockus camurus) and the Tit-hylia (Pholidornis rushiae), the smallest bird of Africa. Dicruridae (drongos) and Monarchidae (paradise-flycatchers) are sometimes described as the sentinels of the flock, but they are also known to steal prey from other flock members. Acanthizidae are typical core members in New Guinea (Gerygone) and Australia (Acanthiza); in Australia, fairy-wrens (Malurus) are also significant. The core species are joined by birds of other families such as minivets (Pericrocotus).