More info on the "Magic Halo" and such deterrents can be found here:
http://www.sialis.org/halo.htm
And yes, I should have used the term "monofilliment" not fishing line. If done properly it will not harm any birds, just deter the House Sparrows.
If concerned then do as is says on sialis : "tie the line/wire to ground stakes or a second ring on the ground; or tie the line to springs attached to a stake or nail in the ground. If hobby wire lines are hanging free, use something heavy (a metal nut or fishing weight) to weight them down"
Edit: back on topic, my yard birds are fairly few right now. Few days ago I had D E ??Junkos, the cardinal pair, Chickadees and a Blue Jay (a rarity for in my yard...)
