chough/currawong relationships

["Philip Veerman" <>]

Hi Marg,

 

A tendency for our black & white birds to nest near to each other is long known. I think as far back as A.H. Chisholm. The chapter of his 1934 book Bird Wonders of Australia "A study in black & white" I think goes into this (I won't read it all whilst replying to you.) It can be regarded as an example of Muellerian mimicry (various species that share some similar attribute - of vigorous nest defence - coming to share similar signalling function - pied plumage so that all may gain some benefit from association with some common signal). This is functionally different from Batesian mimicry and of course totally different from most bird vocal mimicry. However beyond that, the Currawong is a nest predator, so it will be cheating as well as getting the better part of the relationship. Choughs being social nesters and similar size to a currawong are probably mostly able to defend against nes predation from a Currawong. As it takes a lot of work for them to build a nest, they probably wouldn't be keen to abandon it, if Currawongs later come to nest nearby.

 

Philip