Why is there a puffin bird on guinness posters?

Although there is a slight similarity, it's not a puffin, it's a toucan pictured on the Guinness posters. The Toucan first appeared back in 1935 in an advertising campaign in which a toucan had 2 bottles of Guinness balanced on its beak with the caption:

• If he can say as you can
  "Guinness is good for you"
  How grand to be a Toucan
  Just think what Toucan do.

The ads were so recognizable that they used a toucan image in their ads for 45 years.