Experimental Evidence for Phonemic Contrasts in a Nonhuman Vocal System
Fig 2
The aviary consisted of six compartments: the back comprised metal meshing (1 cm2), allowing the birds an outside view; the two sides were made of aluminium; and the front was specially designed perspex, allowing a one-way view from outside to inside. Occupied compartments contained natural perches, foraging substrate, a feeding station, babbler nest, and sleeping box, while unoccupied compartments contained the playback apparatus. Babbler nests are large (~45 x 30 cm), dome-shaped, with 6 cm diameter entrance hole, and robust. Babblers spent most of their time at mid-height; in all cases, relative to the speaker, birds had to look behind and up to look at the nest. Single birds used compartment 3 (n = 2), pairs of birds used compartments 1 and 3 (n = 1 pair) and trios used compartments 1, 3, and 6 (n = 4 trios) (S2 Text).