Ruddock is a name for what bird?

It is the Robin red breast. Shakespeare refers to the Robin as the Rudduck in a beautiful passage in "Cymbeline".

"With fairest flowers

While summer lasts, and I live here, Fidele,

I'll sweeten thy sad grave: thou shalt not lack

The flower that like's thy face, pale primrose, nor

The azured harebell, like thy veins; no, nor

The leaf of Eglantine, whom not to slander

Out-sweeten'd not thy breath: the ruddock would,

With charitable bill,-o bill, sore shaming

Those rich-left heirs that let their fathers lie

Without a monument! bring thee all this;

Yea, and furr'd moss besides, when flowers are none,

To winter-ground thy corse."