Green’s Dictionary of Slang

summer bird n.

[play on SE cuckoo, which appears in summer]

a cuckold.

[UK]E. More Schole house of Women Bii: And all to the ende, some other knaue Shall dubbe her husbande a sommer byrd.
Sack-full of Newes (1864) 171: The poore man was cruelly beaten, and made a Summers Bird.