Mishnayos Chullin Perek 6 Mishnah 5

In a case of the blood of an undomesticated animal or bird that was mixed with water, if there is in the mixture the appearance of blood one is obligated to cover it. If the blood was mixed with wine one views the wine as though it is water, and if a mixture with that amount of water would have the appearance of blood one is obligated to cover it. Likewise, if the blood of an undomesticated animal or a bird was mixed with the blood of a domesticated animal, which one does not have to cover, or with blood of the undomesticated animal that did not flow from the neck and does not require covering, one views the blood as though it is water. Rabbi Yehuda says: Blood does not nullify blood. Therefore, even if the undomesticated animal’s blood, which one must cover, is not recognizable in this mixture, he is obligated to cover the mixture nevertheless.