The song appears in an issue of _The Crisis_ (NAACP publication), vol. 29, 1924. (The piece it occurs in seems to have been republished (?) in a 1969 issue, too.)

I am only able to view a snippet of it on Google Books. (However, I may get access to it, soon.)

What I can see is this (pg 183):

[...] mate stopped them. One of their favorite songs was "What Did the Blackbird Sing?"

What did the blackbird sing to the Crow?
Mah'nd how you swing yo' tail.
If we don't get sunshine, we're sure to get snow
Mah'nd how you swing yo' tail.
Hilo...Hilo

This is followed by a reference to a statement by Stanton H. King (Official Chanteyman of US Merchant Marine).

Chanties containing both "hilo" and blackbirds singing to crows have turned up elsewhere. (Terry's "Hilo Somebody" and Bullen's "Hilo Come Down Below", in addition to Hugill's "Hilo Boys Hilo").