we're marked

our house must be marked. all day for the last three days (since we got about 7" of snow!) we've had non-stop birds at our bird feeder. we no longer have a huge tree in our backyard, so we were kinda surprised to see just as many, if not more, birds come this year than normal. the birds must have some sort of marking device, like they do for the hobos and the underground railroad, so they know that "see that house over there? it has food. go get it all"