::Regardless whether species names are proper nouns, I think the last sentence in Peter's previous comment is the best argument that could be made for maintaining capitalization of English species names in birds. Take the following very contrived sentences... "Many people do not realize that long-tailed tits are not long-tailed tits. Even though they are long-tailed, long-tailed tits are not tits because they are not in the tit family."" vs. "Many people do not realize that Long-tailed Tits are not long-tailed tits. Even though they are long-tailed, Long-tailed Tits are not tits because they are not in the tit family."