There are many synonyms for the phrase "be as happy as a bird on the tree". Some common ones include "beaming with joy", "delighted", "ecstatic", "overjoyed", "thrilled", "elated", "radiant", "exhilarated", "blissful", and "content". All of these synonyms convey a feeling of extreme happiness, just like a bird perched on a tree during a beautiful day. It is important to remember that happiness comes in many forms and can be found in various situations. Whether it be watching a sunset, spending time with loved ones, or simply enjoying a peaceful moment, finding joy in life is essential for overall well-being.