They agreed to a trapping / shooting plan and we went to work! The next year (2008), I only had 3-4 HOSP show up, in 2009 I had 2-3 show up (1 of which managed to inflict lethal damage on 5 baby TRES http://i524.photobucket.com/albums/cc33 ... kTRES2.jpg, and last year, I only had 2 show up. However, last year, I was very involved in mentoring more landlords and didn't push my neighbors as hard to eliminate their breeding HOSP. One of my neighbors let them go entirely and I believe he fledged more than 3 broods of HOSP. I was at his house yesterday and saw a flock of at least 25-30 HOSP.
Now I will have to deal with these when my housing goes up this year. My aunt refuses to eliminate HOSP and I stopped counting at 45 at her house yesterday . In 2010, I noticed that she had 3 pair of breeding HOSP in one of her Trio houses and 2 pair of purple martins which had had 8 pair of purple martins in 2009. Overall her PM population was down 20% last year. Her next door neighbor - who had managed to finally draw in a breeding pair of PM's in 2009, didn't have any martins in 2010, but he had 3 breeding pairs of HOSP.
I found this study conducted by the USDA in 1993 that shows the dispersal of HOSP and thought I would post it here. It seems that if the HOSP are not dealt with in your area, there will be a population explosion (Cornell link states they can have up to 4 broods per year). And since the max dispersal range they found was only 4 miles, it will be a huge, concentrated population of HOSP.
I know it's entirely unrealistic to be able to remove all HOSP from your area, but I would encourage everyone to help out your neighbors with trapping HOSP. Educate them on the problems with HOSP, help them build a trap (and if needed, help them dispose of the trapped HOSP), etc. In the end, your colony will benefit also. See the link above to see the damage that just ONE HOSP (unprovoked) can inflict on your cavity-nesting birds.
From Cornell: http://www.birds.cornell.edu/nestinginf ... accts/hosp
USDA study: http://digitalcommons.unl.edu/cgi/viewc ... aarsfacpub
Previous studies have shown that during winter house sparrows rarely travel more than 6 km (3.6 mi.) to reach food sources (Weaver 1939), and most house sparrows will spend their lives within 4 km (2.5 mi.) of their natal sites. None of the legflagged birds were observed beyond 6.5-km (4 mi.) from the trap site, which supports the earlier results of Weaver (1939) showing that house sparrows have a limited range.
A concerted effort based on trapping could reduce house sparrow damage on the small, experimental plots of cereal grains and sunflower grown at the station.