Answering the question -- on what page of Daphne Du Maurier's short story The Birds do the birds first attack -- is impractical, as it is dependent upon the student posing the question having the same edition or version of the story as that possessed or referenced by the individual answering the question. In responding to the question, this educator consulted the electronic version. A second difficulty in answering the question involves the definition of "attack." Is the question referring to the first seeming attack on humans described in the text, or is it referring to the first instance of a bird actually physically striking a human being? In the case of the first meaning of the word, the following passage is on page two of the version consulted:
“Yes,” said the farmer, “there are more birds about than usual; I’ve noticed it too. And daring, some of them, taking no notice of the tractor. One or two gulls came so close to my head this afternoon I thought they’d knock my cap off!
If the intent of the question is to inquire as to the first instance in the story in which blood is drawn, then the answer remains page two of the attached version of the story, and occurs when Nat, the story's main protagonist, responds to a tapping on his bedroom window and is pecked on the hand by a bird:
He opened it, and as he did so something brushed his hand, jabbing at his knuckles, grazing the skin.
The electronic version of the story probably corresponds fairly closely to other versions, and both of the above passages occur early in the story, but a question that asks for a specific page on which an ill-defined event takes place does not lend itself to a more specific answer.