Unusual Blackcollared Barbet behaviour

Whilst at Lower Sabie Rest Camp I witnessed some very unusual behaviour by a Blackcollared Barbet at a Masked Weavers nest. After speaking to numerous experts we still cannot come to any conclusions as to why the Barbet was doing this. They don't take over nests and hollow out a hole in a trunk as their nest, there was no eggs or youngsters in the nest and it did not remove anything from the nest. Needless to say the Weaver was close by and actually chased the Barbet away.

Blackcollared Barbet having an inspection

Just looking towards the nests owner that was sitting in a tree close by complaining

Another look inside

Shouting at the Weaver that just attacked the Barbet

A final inspection before being chased away

The Blackcollared Barbet after it was chased away