While Adams, Franklin, and Jefferson did serve on a committee in '76 to begin designing a seal for the country, the decision was delayed for several years, at which point a new committee included the eagle as a representative. Franklin made his opinion of the choice of bird known in a letter to his daughter, Sarah Bache, in 1784:
Old Military and Civil Records LICON, Textual Archives Services Division (NWCTB), National Archives [ARC Identifier 299956]
Postscript: As I was writing this post with the TV on in the background, The Real Story of Thanksgiving appeared on the History Channel. There was a nice feature on Plimoth Plantation in the last few minutes. It's always nice to see living history sites and interpreters getting some positive publicity!