Early Estrus Cow Call - Moose Calling 101 During the months of September to November: (The Start of the Cycle) Exactly how I said it on camera — this is how a cow sounds at the beginning of her estrus. This call usually starts showing up in early September when the first rut begins, but it can happen again later in the season if a cow wasn’t bred. Even in mid-October or November, a cow entering her second or third estrus will make the same moaning call — the timing changes, not the sound. This i