The pukekos always give an alarm when they have a pooklet and any kind of gull flies over.

The gulls on the roof are Black Backed Gulls, a very large variety which is bigger than the pukekos.

They seem instinctively programmed to attack these gulls if they land in or near the stream when there is a pukeko chick anywhere nearby.

I have seen them do this & they all attacked as a group. The gull could not fight them all off & played dead for an hour until it was sure the coast was clear to get away.