The Duck Conundrum
I was spending time with my ducks in the Dunedin Botanical Garden the other afternoon (along with some hungry pigeons, red-billed gulls, and chaffinches), and I finally decided to answer the question that has been plaguing me for some time. Where are these blue billed ducks coming from?
While I have not come up with a definite answer, here are my findings.
The mallard duck, as we know them, are an introduced species to NZ. Males and females are very different in appearance. As seen in the top left picture above, males (drakes) are quite colorful with a greenish head and white/black bodies while females (hens, lower left) are muddled brown. Both sexes have orange/yellow bill, orange feet, and a blue speculum lined with white (feathers on the wing).
The endemic and endangered grey duck, however, looks very much like a female mallard (hen). To be honest, I am not entirely sure the sexes of the grey ducks in the right picture, although for easier explanation I am calling the top one male because it has a speculum of green lined with black, distinct from the mallards. Both females and males have dark, stripped heads, olive/grey legs, and a grey bill.
But what about those blue billed ducks? Well here is my hypothesis. It is well known that grey ducks and mallards hybridize quite frequently. Actually, it is thought that true grey ducks are almost extinct in the wild. These new hybrid birds (perhaps even a new species) are everywhere and can be said to be more grey duck like or more mallard like most of the time. Anyways, when these hybridizations occur, I think color morphs are born. So, the top picture could be a mallard-looking hybrid with a blue bill. This is not definite and just a theory, but it is what I think. If anyone knows the true, proven answer, please let me know!
Now there was also this huge duck that looked both female and male mallard with a bit of paradise duck mixed in, but he/she is another story….