E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Birds of a feather flock together. Persons associate with those of a similar taste and station as themselves. Qui se ressemble sassemble. Cicero says, Similes similibus gaudent, pares cum paribus facillime congregantur. Ne nous associons quavec nos égaux (La Fontaine).
To kill two birds with one stone. To effect two objects with one outlay of trouble.