Shoot, I hate when that happens! The birds here scatter so much seed around that the sunflowers sprout up everywhere; usually I'll just dig up a few of the sprouts and put them where I want them. I had some really cool branching ones last summer, with lots of flowers on each plant. Maybe try winter sowing some seeds... get a milk jug or something similar (I use kitty litter jugs because I have lots of them), make some drainage holes in the bottom, cut it so the bottom part is 3-4" deep, add some potting soil, plant and water your seeds, tape the jug back together with some duct tape, leave the cap off, and put it outside in the shade somewhere to do its own thing. Check it every now and then and you should get plenty of sunflower seedlings to grow!
