some points about your posting:
the quotation is incorrect. the three witches are talking of the battle to come, and of the fact that it will take place in a field:
first witch: I come, Graymalkin
second witch: Paddock calls
third witch: anon!

the witch is basically saying: "the field (of battle) calls"

which is why the witches then depart

Paddock is in LEO already: Dictionary: paddock

not supported

Langenscheidt (Der Kleine Muret-Sanders E-D, 2000)

Ohne über das Shakespeare-Zitat und die Schlegelsche Übersetzung streiten zu wollen: "paddock" heißt auch "Kröte"

paddock (toad) - a toad mentioned by the witches in the first act of William Shakespeare's play MacBeth. Paddock is an archaic English word for "toad."

http://www.answers.com/topic/paddock

Ein Blick ins OED zeigt, dass huxley recht hat (paddock: 1.frog; 2. toad).

Auch The Concise Scots Dictionary führt paddock/puddock als "frog; toad" auf.

Supported!

I retract my posting from above - I had no idea of the alternative meaning of the word. I hope not to have caused too much confusion.
:o(