In many ways this column prefigures the Radio Nature League, not just in the kinds of concerns addressed (feed the birds, make bird houses) but in the way Burgess tries to create a personal connection with his audience.
Google News Archive offers access to these personal letters via its Milwaukee Journal collection. Not all of them are indexed, but I was able to browse through a few months worth to give you links to the first 25 or so of these columns.
You may remember that the Bedtime Story club concept was an invention of the Kansas City Star and was then picked up by other papers, most notably the New York Globe. The Milwaukee Journal first announced the club on May 20, 1915.
Children were instructed to clip a coupon from the following Sunday's paper to become a member (and receive a cool badge). It wasn't necessary to formally sign a pledge to be kind to animals; club membership was enough.
Here's the coupon
The club was advertised again the following week. Three thousand had signed up; the Journal wanted tens of thousands.
As far as I can tell, the club's main business for the first few months was a story contest. That changed, however, when Thornton W. Burgess himself became the effective club leader.
Burgess charges the membership to be "kind to Mother Nature's children" and "protect them from their enemies", adding that he wants to make the club a "tremendous power for good." He also invites readers to imagine that he has a personal relationship with each one of them.