This is an interesting question as this is just may be the particular attribute that Mute Swans have as the coloring around the knob surrounds the eyes and ends near the bill.

There are many species of birds and mammals that differ within their taxon of family members and their attributes may or may not have anything to do with the habitat. It is just the way that the species is put together, serves as a mate attractant, etc.

Some paleontologists believe that Mute Swans are native to North America and also have taxonomical attributes of the southern hemisphere swans such as the Australian Black Swan. So, any of the above could be the reason or none of the above. We may never know. Thanks for an interesting question. The Regal Swan
« Hide