As I noted the last time we took a look at a song from Walt Disney's Enchanted Tiki Room, Imagineers did not operate in a cultural bubble. They were very attuned to the popular music and trends of their times, especially those they grew up with. To the exception of The Tiki, Tiki, Tiki, Tiki, Tiki Room, written by the incomparable Sherman Brothers, most of the music sung by the birdies were actually popular Big Band Era hits.
Let's All Sing Like the Birdies Sing was first written in 1932, by the team of songwriter Tolchard Evans and lyricists Stanley Damerell and Robert Hargreaves, along with Harry Tilsley. The first recording of the song was by Henry Hall, the English Big Band leader most famous for The Teddy Bears' Picnic.
Like many songs of the time, the Max Fleischer Studio made Let's All Sing Like the Birdies Sing into the focal point of an animated short. Released in 1934 as part of their Screen Songs series, it was directed by Dave Fleischer and starred Artie Dunn and Les Reis performing the title song. Screen Songs were a continuation of the Fleischers' Song Car-Tune series, which included the first animated films with synchronized sound, released in May of 1924 (predating Steamboat Willie by four years). Each of the Car-Tunes and Screen Songs featured a sing-along sequence inviting the crowd to join by following the bouncing ball. The tradition continues with the invitation to sing like the birdies, at least at the Disneyland USA version of the attraction.