What happens to the number of owls if amount grass increase?

The relationship between the amount of grass and the number of owls is an indirect one. Grass is food for mice and other small rodents. Owls prey on these rodents for food. So, if the amount of grass increases, it provides more food for the rodents, which in turn increases their population size. This increase in the rodent population provides more prey for owls, allowing their population size to increase as well. Therefore, if the amount of grass increases, the number of owls will likely also increase.