You might try attaching some anti-roosting bird spikes over the down spout. We finally resorted to them along the ledges of our front porch overhang. The barn swallows, in about three years, went from being utterly adorable to NOT WELCOME!

We just put the spike strips up a couple of weeks ago, and no sign of swallows yet, but it might still be too early. They start building their nests a bit later than other birds.

The attached link shows you what ours look like. The strips are made up of a polycarbonate plastic. We bought enough to use along window ledges, too, as the robins seemed interested in nesting there last year. It took a LOT of convincing to get her to move elsewhere.

Sorry, I forgot to attach it.

Here is a link that might be useful: {{gwi:1345034}}