Slifkin, Rabbi Nosson (29 March 2005). "The Circle of Life". Current Issues: Science & Medical. Aish. Retrieved 2009-02-04.; see, e.g., the source citations in Rabbi Nosson Scherman, Perek Shirah: The Song of the Universe (2005, Brooklyn, Mesorah Publications), and in Rabbi Natan Slifkin, Perek Shirah: Nature's Song (2nd ed., 2009, Zoo Torah). The dove's second verse, the frog's verse, and the verse of the wild beasts of the field, are from the Talmud. The rooster's first verse is from the Zohar. A very few verses (such as the mouse's) cannot be identified.
jewishencyclopedia.com
Macy Nulman, The Encyclopedia of Jewish Prayer (1993, NJ: Jason Aronson) page 266; Bacher, Wilhelm; Judah David Eisenstein. "SHIRAH, PEREK (PIRKE)". Jewish Encyclopedia. S. Retrieved 3 February 2009.; Malichi Beit-Arie, PEREK SHIRAH, Encyclopedia Judaica (2nd ed. 2007) vol. 15, page 760.
Bacher, Wilhelm; Judah David Eisenstein. "SHIRAH, PEREK (PIRKE)". Jewish Encyclopedia. S. Retrieved 3 February 2009.
mechon-mamre.org
A particular example is a winged creature called the retzifi, whose song is the verse of Isaiah 40:1; the word does not appear in the Bible or Talmud. Slifkin's first edition (2001) identified this (as had many previous commentators) as the bat (although the Hebrew Bible uses the word atalayf _for the bat), and was followed in this by Scherman, but in his 2009 second edition, Slifkin had revised this to the laughing dove.
