A ‘bird wave’, or a ‘mixed-species feeding flock’, is made up of different bird species, usually insectivores, that move together while foraging. The variety of lookouts in such a flock confers some safety from predators. It also improves feeding efficiency as insects flee one predator, only to be caught by another. For instance, a tree-creeper disturbs a moth from a trunk that is then snapped up mid-air by a fantail.
On a dull winter’s day, you hear twittering by thornbills approaching through the canopy. Moments later the swooping flight of a tree-creeper catches your eye, then you are diverted by the chime of a shrike-thrush's call, and then by the fire-engine chest of a Scarlet Robin. Suddenly your senses struggle to keep up with the feathery crossings and re-crossings of sittellas, honeyeaters, shrike-tits, pardalotes and fantails. Within a few minutes the flock moves on, leaving you momentarily bereft, a pedestrian passed in the street by an airy parade.
The bird wave phenomenon can only happen where a healthy woodland supports a diversity of resident and migratory species. One day on the Merri you may enjoy being a bystander to an avian cavalcade.