Christine Boran of Woolwine, Virginia agreed to test a 2-holed box at a problem House Sparrow site over a period of three years (2010 to 2012) per the Keys to Success. It proved successful.
Test Site Conditions:
Test boxes are placed only at sites with active HOSP/bluebird competition because the purpose of test boxes is to document HOSP/bluebird competition in boxes with an escape hole.
Monitors at test sites cannot trap HOSP, nor install any add-ons (spookers, halo) nor interfere with HOSP/bluebird competition other than to remove HOSP nests/eggs.
Christine's test box is at an in-town location where there was a history of active House Sparrow/bluebird competition in a 1-holed box prior to the installation of the 2-holed test box. The rest of her trail is rural with no HOSP problems.
No other box design (to my knowledge) has undergone rigorous tests such as these where the nestbox is placed in areas with intense HOSP/Bluebird competition to document whether bluebirds can successfully defend the test nestbox with no trapping of House Sparrows and no deterrents (Magic Halos and Spookers).
Here are 2-Holed Box Plans and the Keys to Success
Photo taken by Christine during the beginning of the 3-year test. There is what appears to be a seed feeder in the background hanging from the nearby tree; but it is my understanding that no seed was actually offered at the test site during the active nesting seasons.
An active seed feeder was relocated further away from the test box as of mid-February 2012 (just prior to the last test year).
2-HOLED Box (First Test Year)
|Monitor Action||2-Holer installed for 2010 season|
|3/10/10||Partial HOSP nest||Removed Partial HOSP Nest|
|3/17/10||Partial HOSP nest & pair seen||Removed Partial HOSP Nest|
|3/24/10||Partial HOSP nest||Removed Partial HOSP Nest|
|4/1/10||Partial HOSP nest||Removed Partial HOSP Nest|
|4/8/10||Partial nest (ID not certain)||Left nest for positive ID|
|4/11/10||HOSP nest (fem flew out), no eggs||Removed HOSP Nest|
|4/15/10||Partial HOSP nest (no eggs)||Removed HOSP Nest|
|4/22/10||Partial HOSP nest (no eggs)||Removed HOSP Nest|
|4/27/10||Partial HOSP (huge w/trash, no eggs)||Removed HOSP Nest|
|4/28/10||Partial HOSP nest (fem flew out)||Removed HOSP Nest|
|5/6/10||HOSP nest & 2 eggs||Removed HOSP Nest & Eggs|
|5/14/10||HOSP nest & 1 egg (egg under nest)||Removed HOSP Nest & Egg|
|5/21/10||Partial HOSP nest (no eggs)||Removed|
|5/29/10||HOSP nest & 3 eggs (egg under nest nest)||Removed HOSP Nest & Eggs|
|6/3/10||-0- Homeowner reported EABL & "brown" bird were on nestbox roof multiple times||-0-|
|6/12/10||Partial HOSP nest (no eggs)||Removed|
|6/19/10||Appears to be completed EABL nest||-0-|
|6/22/10||3 EABL eggs (fem foraging nearby)||-0-|
|6/24/10||4 EABL eggs (fem foraging nearby)||-0-|
|6/29/10||4 EABL eggs (fem flew out)||Treated for blowflies w/DE|
|7/5/10||4 EABL eggs (fem flew out)||-0-|
|7/6/10||1 Hatchling & 3 EABL eggs||-0-|
|7/11/10||3 Hatchlings & 1 EABL egg||-0-|
|7/13/10||3 Nestlings (looking weak) Fem feeding||-0-|
|7/15/10||3 Nestlings (looking OK)||-0-|
|7/20/10||3 Nestlings (about 14 days old)||-0-|
2-Holed Box (3rd Test Year)
THIRD TEST YEAR
|An active seed feeder was relocated away from the 2-holed test box as of mid-February, 2012|
|3/16/12||Soft grasses, not ID'd||-0-|
|3/21/12||Completed EABL nest||-0-|
|3/26/12||Same EABL nest, male EABL flew from box upon approach||-0-|
|3/29/12||3 EABL eggs, female flew from box||-0-|
|4/2/12||5 EABL eggs||-0-|
|4/7/12||5 EABL eggs, fem flew out on approach||-0-|
|4/10/12||5 EABL eggs, fem flew out on approach||-0-|
|4/12/12||No count, fem stayed on nest||-0-|
|4/16/12||5 EABL young (est. hatch = 4/14)||-0-|
|4/19/12||5 EABL young @ 5 days old||-0-|
|4/24/12||5 EABL young @ 10 days old||-0-|
|4/30/12||ALL JUST FLEDGED (fresh fecal droppings in nestcup); Adult defense of nestbox during cleanout||Cleaned out nestbox|
|5/2 - 5/5||-0-||Stovepipe guard replaced|
|5/12/12||Few grasses dropped in nestbox, not positively I.D'd yet||-0-|
|5/17/12||More grasses added, no positive I.D.||-0-|
3 EABL eggs (2nd clutch of season)
Homeowner found feathers from a dead male bluebird under shrubbery. Indicative of a cat attack.
|5/28/12||4 EABL eggs||-0-|
|6/2/12||4 EABL eggs, heard 1 bluebird in trees||-0-|
|6/8/12||4 EABL eggs, fem flew off nest||-0-|
|6/9/12||2 EABL hatched, heard 2 EABL in trees; no gender ID||-0-|
|6/10/12||4 EABL hatchlings||-0-|
|6/15/12||4 EABL @7 days, two bluebirds heard in trees, not sure if pair (or female & fledgling)||-0-|
|6/16/12||4 EABL @8 days, adult female and a male bluebird vocalizing in tree during check||-0-|
|6/23/12||4 EABL @15 days, adult female and a male||-0-|
|6/26/12||All Fledged (6/25 or 6/26) @ 18 days,||Very clean nest, pair jumping around in trees, could not see fledglings.|
|7/7/12||New nesting materials dropped inside box; appears to be EABL. Heard EABL singing in trees||-0-|
|7/9/12||Add'l nest material. Heard EABL in trees||-0-|
|7/11/12||EABL nest completed; heard EABL singing loudly in trees||-0-|
|7/16/12||4 EABL eggs, heard EABLs in trees||-0-|
|7/16/12||4 EABL eggs, heard EABLs in trees||-0-|
|7/20/12||4 EABL eggs, parents in trees||
Puffed Diatomaceious Earth inside nest to deter/prevent blowfly larvae. Winds picked up so more to be added at next check.
|7/27/12||4 EABL eggs, parents in trees, calm||Puffed Diatomaceious Earth inside nest to deter/prevent blowfly larvae.|
|7/28/12||2 EABL just hatched & 2 eggs. Parents active, watching, chattering|
|8/1/12||3 EABL nestlings. 1 unhatched egg. Could not remove unviable eggs. Looked small for 5 days age. Parents in trees.||Added DE|
3 EABL nestlings. Nestlings had some growth. Parents chattering in trees nearby.
|Removed unhatched egg.|
|8/6/12||3 EABL nestlings about 10 days old. Both parents in the area.|
2010 (1st Test Year) = Transition year; usually the most difficult year as Bluebirds learn they can safely escape from the box during HOSP battles and compete with HOSP outside the box.
2011 (2nd Test Year) = Bluebirds usually defend the 2-holers with more confidence and success.
2012 (3rd Test Year) = By the third year using 2-holers, there usually are no further HOSP problems if there is just one Bluebird box (a 2-holer) on two acres of forage and other Keys to Success are followed (don't put out food for House Sparrows).
Here is the Construction link showing how to build these boxes.
As of June 15, 2012