By "amateur birding community" I take it you mean competitive listers among whom keeping ticks straight is a high priority? A "little tern" isn't necessarily "countable" after all while a "Little Tern" most certainly is. Bird watchers/lovers in general I should think would have no more interest in capitalization and standardized names than such other large and passionate hobbyist groups as anglers or gardeners. The question then becomes why a comparatively small number of twitchers should have gotten their way to the extent that they have. ??
I think your example of little gull shows why initial capitals are a good idea. In speech we can use word stress and intonation to distinguish between a little gull and a Little Gull or a yellow warbler and a Yellow Warbler. In writing, all we have are caps.
Jeff


