Yoreh Deah Siman 19 Seif 6

 

ו הַמְבָרֵךְ עַל דַּעַת לִשְׁחֹט חַיָּה אַחַת, וְאַחַר כָּךְ הֵבִיאוּ לוֹ יוֹתֵר, יְכַסֶה דַּם הָרִאשׁוֹן וִיבָרֵךְ עָלָיו, וִיבָרֵךְ עַל הַשְּׁחִיטָה הַשְׁנִיָּה וְלֹא עַל הַכִּסוּי; וְהָנֵי מִלֵּי כְּשֶׁהֱבִיאוּם לוֹ קֹדֶם שֶׁבֵּרַךְ עַל כִּסוּי הָרִאשׁוֹנָה

 

Seif 6

If one had in mind to slaughter one wild animal when he recited the blessing, and afterwards they brought him more animals, he should cover the blood of the first then recite the blessing over it, and afterwards bless over the slaughter of the second one but not over the covered blood.  The same would be if the next animal were brought before blessing for the first animal  for the blood being covered.