But is that a reason for planting yews rather than any other trees?

On a pedantic note, yews don't produce berries. They are conifers, and berries are found in flowering plants only. If you look closely you'll see that the red fleshy part (the aril) forms a cup-like structure around the seed but doesn't enclose it completely. Some animals eat the fleshy part and pass the seed through the gut without digesting it. I wouldn't recommend experimentation in this regard.