HOSP TAKEOVER . . .
This page visually shows the house sparrow takeover of a regional park in La Mirada, California with standard 1-holed boxes (previous monitor logs 1999-2001). One starter box was placed in 1998 with no problems (the 1-box startup year is not included in chart). By 2001, the problems were so intense that the Audubon Society removed all boxes at season's end.
In 2002, Susan Bulger and I reopened the park using Mansions and revised monitoring techniques (see home page for links to detailed log notes). Bluebirds are making a comeback without any trapping or killing of house sparrows.
The chart segments are color-coded to the nearest 10 percent. Percentage of sites used by bluebirds are in blue, percent impacted by house sparrows (nest starts/takeovers) are shown in yellow.
1 9 9 9 2 0 0 0 2 0 0 1 March April May June July March April May June July April May June July 100% 100% 100% T D R I A S 67% I M L A 45%
50%
N 38% 38% 41% 40% T 33% L E D 1*0 9*0 10*0 8*4 4*5 1*2 6*6 5*8 5*8 5*7 2*3 ? ? ?
Bottom row shows number of sites controlled by Bluebirds vs. House Sparrows
2 0 0 2 2 0 0 3 Mar April May June July Mar April May June July 75% 57% 55% 57% 50% 50% 50% 54% 43% 14% 1*1 4*3 5*4 4*3 3*1 1*6 11*11 10*13 12*12 7*6 Bottom row shows number of sites controlled by Bluebirds vs. House Sparrows
2 0 0 4 2 0 0 5 Mar April May June July Mar April May June July 100% 0*11
House Sparrow Takeover Overview
1998 — One Starter Box
1-Holed Standard NABS Box New "starter" box, no HOSP problem
5 Western Bluebirds Fledged . . . HOSP seem to watch bluebirds use new boxes before they attempt a takeover
1999 — Approx 13 Sites 1-Holed Standard NABS Boxes Infrequent monitoring (HOSP nests advanced to young chicks) may create HOSP bond and set stage for greater problems during the following year(s). 58 WEBL Fledged . . . after first bluebird clutches, house sparrows begin takeover in June and control/impact 60% of the active sites by end of year.
2000 — Approx 13 Sites 1-Holed Standard NABS Boxes Infrequent monitoring. Major HOSP problems all year; young removed; boxes relocated, removed or paired with PVC (Gilbertson) tubes; HOSP allowed to sit on oiled eggs in paired boxes 43 WEBL Fledged . . . house sparrows control/impact approx. 60% of the active sites throughout season
2001 — Approx 7 Sites 1-Holed Standard NABS Boxes HOSP problems out of control; boxes removed; trail dismantled Only 13 WEBL Fledged from standard boxes . . . all boxes removed by local Audubon Society at end of 2001)
New Monitoring Techniques
2002 - 2004 Test Year Monitoring:
We did NOT follow the common advice to remove problem boxes: Many monitors will "solve" HOSP problems by removing boxes. However, Susan and I used all problem sites for experiments to thwart house sparrows. Nestbox removal is counterproductive since Bluebirds need boxes for nesting, house sparrows do not.
Training: Initial attempts to "train" house sparrows to avoid park boxes were made at this test park during 2002. Blue ribbons, decals were used to send messages to HOSP that these boxes are different from surrounding homeowner boxes where they have been allowed to nest.
We did NOT follow the common advice to keep house sparrows occupied: Many monitors will let house sparrows sit on oiled, boiled or pricked eggs. They feel this will keep house sparrows content so HOSP won't bother nearby bluebirds. I think this is poor advice and may actually reinforce the HOSP territory bond and create more problems for bluebirds during the next year(s). HOSP nests/eggs were promptly removed from these test boxes on a weekly basis and all HOSP eggs were still fresh with no visible chick formation when removed/destroyed.
House Sparrows did NOT go an retaliatory rampages when disturbed: Many monitors won't remove HOSP nests/eggs for fear of retaliatory rampages. See June 2002 discussion archives at: http://audubon-omaha.org/bbbox/bestofbbml/hosppassive9.htm. However, that does not occur on my trails and it did not happen at any of the test sites. Susan and I smashed eggs in or near the box, stabbed them with cocktail toothpicks and left them on bare nestbox floors, etc. where house sparrows could clearly and quickly see their nest attempts would fail. Very visual anti-HOSP "clues" were left repeatedly in and on HOSP problem test boxes (see logs) and there were no retaliatory house sparrow rampages.
Extra Boxes: Additional mansions were *temporarily* added to a few sites so bluebirds could nest while Susan and I continued with HOSP battles. Boxes were never added with the intent to keep HOSP "occupied/content."
Common advice to pair with PVC tubes may actually backfire: House sparrows are colonial nesters (multi-families in tight area). Previous monitor logs prove that house sparrows at the La Mirada, Calif. test site will end up occupying/controlling both the standard box AND the paired PVC tube.
PreSeason Checkups: Susan and I check our trails occasionally during the off season and twice during February when activity on our So. Calif. trails begin.
Weekly Monitoring: From the first week of March, Susan and I monitor on a weekly basis. This proved important when HOSP moved into a box immediately after a bluebird fledge—HOSP built the nest while the bluebirds were protecting new fledglings rather than the box. Quick removal of the HOSP nest enabled bluebirds to return to the box for their second (successful) clutch; see logs for the Pastrana box.
2002 — Approx 13 Sites Trail Re-opened as a HOSP Test Site All boxes left in place for active battles with HOSP; tried to leave very visual anti-HOSP clues, overt destruction of all HOSP nests/eggs on weekly basis (see logs); Bluebirds making comeback 38 WEBL Fledged . . . only one remaining HOSP battle during July.
2003 — Approx 30 Sites Second Test Year Row of "buffer/battle" boxes hung along street next to homeowner HOSP Boxes/Feeders (DeSparrowization Zone) 59 WEBL Fledged . . . fierce House Sparrow competition continues.
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