“Why do turkeys always go ‘Gobble! Gobble!’?”/“Because they never learned good table manners.”

A popular Thanksgiving turkey riddle is:
 
Q: Why do turkeys always go “Gobble! Gobble!”?
A: Because they never learned good table manners.

 
The “gobble” joke has been cited in print since at least 1996.
 
 
Google Groups: schl.sig.lmnet
Thanksgiving riddles
Madelynne Johnson
11/16/96
LMNETters,
1. Why do turkeys always go “gobble, gobble”?  They never learned good table manners
     
28 November 1996, St. Petersburg (FL) Times, “Talkin’ Turkey” by Janet K, Keeler, pg. 1D:
The World Wide Web is awash with Thanksgiving sites. The kids might get a kick out of some of the activities at http://www.night. net/thanksgiving/ including games, trivia and jokes (Why do turkeys gobble? Because they never learn good table manners).
 
Google Groups: ott.singles
Turkey Humour! (side note: alcohol is involved)
Amanda
12/2/98
(...)
Why do turkeys always go, “Gobble, gobble?”
Because they never learned good table manners!
     
22 November 1999, Atlanta (GA) Constitution, “Check It Out, pg. C8:
Why do turkeys go gobble gobble? Because they never learned good table manners! (Hee hee!)
   
Google Books
Bulletin Board Power:
Bridges to Lifelong Learning

By Karen Hawthorne and Jane E. Gibson
Greenwood Village, CO: Libraries Unlimited
2002
Pg. 21:
Q: Why do turkeys always go “Gobble, gobble”?
A: Because they never learned good table manners!
 
Twitter
Micki
‏@MickiNelson
Why do turkeys always go ‘gobble! gobble!’? Because they never learned good table manners! Happy holiday y’all!
3:07 PM - 21 Nov 2007
 
Google Books
The Everything Big Book of Jokes:
Hundreds of the Shortest, Longest, Silliest, Smartest, Most Hilarious Jokes You’ve Never Heard!

By Evan C. Thomas
Avon, MA: Adams Media
2014
Pg. 196:
WHY DO TURKEYS GOBBLE?
BECAUSE they never learned table manners.
 
Google Books
The Super, Epic, Mega Joke Book for Kids
By Whee Winn
Grand Rapids, MI: Zonderkidz
2016
Pg. ?:
Why do turkeys gobble?
Because they never learned their table manners.