In their book The Pottery of Acoma Pueblo (University of New Mexico Press, 2014),pages 317-318,  Dwight Lanmon and Francis Harlow discuss Historic Acoma pots of birds with two heads. Lanmon and Harlow state:

Birds that have two heads "one open at the top or between the beaks; the other closed ), were also collected at Acoma and Laguna in the 1870s and early 1880s. We do not know what these double-headed figures are intended to convey or represent. Many of the closed heads contain loose material that rattles" (page 317).

This double-headed vessel is clearly of the same type that Lanmon and Harlow were discussing. Interestingly, it also has some loose material that rattles. 

The birds themselves are charming and the pot has survived the years in excellent condition. There is no evidence of any breaks or repairs.