נשמת כל חי תברך את שמך
The language implies all living creatures (and not just humans) bless HaShem. This corresponds with the expressions about the Flood which is כל אשר נשמת רוח חיים באפו מתו which refers to all living creatures.
This prayer referring to the blessings of all living creatures is easy to understand in the context of Perek Shira, which tells of the praises of the various animals in the Creation. We do not know who authored this work, however, the Gemara often mentions from there the praises involving animals and birds.
One place is Chulin 64b, where one Chacham learns the prohibition of eggs from a tameh bird from the item listed in Parshas Shemini "בת היענה" which indicates an egg of a certain type of bird. But the Gemara asks from the verse "תכבדני חית השדה תנים ובנות יענה" (ישעיה מד, כ) which implies that the young of this bird honors HaShem. How is it possible for something inside the egg to offer praises (to HaShem for providing water in the desert for this young bird)? Thus, the item listed in Shemini cannot be referring to an egg but to the young of that species.
Nevertheless, the indication is clear that the Gemara states that birds (and animals) praise HaShem, which is the intention of this prayer that animals in addition to humans praise HaShem.
