Suet

I had an old wire bird feeder that I used to fill often with a square slab of suet.

Source: tatoeba (4603783)

Spotted dick is a British pudding made with suet and dried fruit.

Source: tatoeba (6772038)

[T]he ſevvet of oxen […] is alſo good againſt the inflammation of the eares, the ſtupidity and dulneſſe of the teeth, the running of the eyes, the vlcers and rimes of the mouth, and ſtiffneſſe of the neck.

Source: wiktionary

Many seed-eating birds also need animal fat and protein which they obtain from insects, animal carcasses, and suet.

Source: wiktionary