Austin Roberts Bird Sanctuary animals. The natural veld type of the sanctuary is mixed bushveld. Upwards of 170 native bird species have been recorded, but the presence or breeding of some have been transient, due to urbanization and other factors. Resident or visiting passerine birds include thick-billed weaver, southern red bishop, African reed-warbler, little rush-warbler and lesser swamp-warbler. Various heron species visit the reserve, including black-crowned night-heron, little bittern, green-backed heron, purple heron, black and little egret. Other regular water birds are red-knobbed coot, fulvous duck, Egyptian goose, white-faced duck, Cape teal and southern pochard. Pinioned crowned cranes and blue cranes have been released
Bird vocalization and prevent an energetically costly fight . In birds with song repertoires, individuals may share the same song type and use these song types for more complex communication. Some birds will respond to a shared song type with a song-type match (i.e. with the same song type). This may be an aggressive signal, however results are mixed. Birds may also interact using repertoire-matches, wherein a bird responds with a song type that is in its rival's repertoire but is not the song that it is currently singing. This may be a less aggressive act than song-type matching. Communication through bird