This DoujinCG is a rare release from 2003 (Comic Revolution 34). It contains 640p,800p,1000p,1300p and omake pictures.
This version https://e-hentai.org/g/271212/96763fd216/ is an updated one released on late 2004 http://www.dlsite.com/maniax/work/=/product_id/RJ013295.html which has 飛べない鳥 and 飛べない鳥2 in one set. But lacks omake files and it also has different censorship.