I have a Holly tree in the back yard. The last two years have been mild winters with little snow. This year with snow on the ground the food pickings are harder for the birds. The Robins seem to be the only birds with a throat big enough to swallow the Holly berries whole. Other birds try to get scraps left by the Robins. This has happened each year that there is snow on the ground. There are a lot of Holly starts from their leavings.