A New Zealand subspecies of Black-backed Gull?

[Ian Southey]

This paper on Black-backed Gulls www.zoolstud.sinica.edu.tw/Journals/51.6/881.pdf gives New Zealand, the Chathams and the sub-Antarctic islands their own subspecies of Black-backed Gull antipodus.

I haven't read it carefully yet but it looks like I'm going to have to. By their criteria subspecies status means they can distinguish the right taxa 80% of the time using multivariate analysis. Even if you could carry out the analysis you can only really tell what you have by knowing where it came from as far as I can tell. Any vagrants would have to be identified from leg bands.

In their defense they do say, just once I think, that the NZ population may be a distinct subspecies but they use the name freely as if it was. The analysis is also restricted to plumage characteristics and measurements so it may be possible to find something distinctive in the colours of eyes or legs that works as an ID feature.

Their patterns apparently match some DNA results but at present I'm not sure that they shown much more than the kind of variation you might expect in a widely spread species inhabiting a broad climatic range. The conclusion may be correct but I'm not sure its proven.

Ian

[Michael Szabo]

Some authorities recognise a South African "Cape gull" as separate to southern black-backed gull. It is said to have an immaculate white tail and dark eye. Given the taxonomic changes made among large gull species in Eurasia it wouldn't be surprising to find that some relatively insulated southern populations of dominicanus are also distinct taxa.

Next time I'm down at the beach I'll have another look at them.

Michael

[Ian Southey]

This paper didn't distinguish the South African form from dominicanus but noted that the differences in the soft part colouration were sufficient to recognise the form. Maybe you will find something like that for the New Zealand birds when you look. Must have a try myself.

Ian

[Michael Szabo]

And plenty of plumage phases to sort through while looking!

Michael

[Peter Frost]

The correct link for this paper is http://zoolstud.sinica.edu.tw/Journals/51.6/881.pdf

Peter

[Ian Southey]

Peter

Thanks for fixing that. I thought I'd tested it out ... but it not my first problem with these things.

Ian