Help! Birds pecking out pointing on sandstone house

Hello

I have lived in my house 3 years and every spring/summer small birds peck the pointing out from around the sandstone. The house has normal pointing in it not lime based if that means anything to any one!!

They only seem to peck the bottom metre of the wall. Our house is directly next to a b road with a path of about a metre between the house and the road.

We are going to have it re pointed for the third time and dont want to have to do it again! How can me stop them.

please help!

thanks Abi