Swanna, whose name in Japanese is the same (スワンナ), is most likely supposed to be a swan. The species

Swanna, whose name in Japanese is the same (スワンナ), is most likely supposed to be a swan. The species is ‘the white bird pokemon’ and in Japanese… 'swan’ is written as 白鳥 or literally 'White bird’. I am sure this is where it comes from.