This

![American_black_bear][1]

this

![Grizzly bear][2]

and this

![Polar bear][3]

are all "bears".

This is a European robin

![European robin][4]

and this is an American one

![American robin][5]

There is not a unique English word for every animal in the world.

And (as with "robin") it was common for English-speaking Americans to assign existing animal names to new, unfamiliar animals that they encountered in the New World, rather than invent new names.  There in nothing at all strange about this behavior

(It needs to be understood that "New England" was colonized mainly by religious and economic refugees from the British Isles and adjacent coastal Europe.  While these were not uneducated people, few would have spent any time in Italy or otherwise been exposed to Italian cuisine and Italian seafood.  And, when they arrived in the New World, their first priority was survival, not a careful cataloging of the fauna.  A community that settled on the shore first and foremost needed to know that this strange crustacean was edible, and how to catch it.  Settling on a community-accepted name for the beast as soon as possible facilitated this.  They didn't have time to look it up on the Internet.)

Bear images: http://en.wikipedia.org/wiki/American_black_bear, http://www.dailymail.co.uk/news/article-2194244/Denali-National-Park-Hiker-Richard-White-close-grizzly-bear-attack.html, http://en.wikipedia.org/wiki/Polar_bear

European robin: http://commons.wikimedia.org/wiki/File:European_Robin,_London.jpg

American robin: http://www.southriverfederation.net/index.php/news/blog/robins-return-to-the-south-river.html

  [1]: https://i.sstatic.net/Chlow.jpg
  [2]: https://i.sstatic.net/lOqS8.jpg
  [3]: https://i.sstatic.net/Iao9J.jpg
  [4]: https://i.sstatic.net/12k9b.jpg
  [5]: https://i.sstatic.net/WBeLe.jpg