"Comparing Breeding Success:
 Snyder Excluders vs. Conley Excluders"
Ken Kostka
Purple Martin Preservation Alliance
Pittsburgh, PA


    Several years ago, Duke Snyder, a Purple Martin Landlord in Butler, PA, invented a revolutionary new starling-proof entrance hole called the Excluder (photo left). Prior to the development of this entrance hole, there were only starling-resistant holes, like the crescent or "ob-round" entrance holes.  
            I immediately began using the Excluder at one of the PMPA’s colony sites at Saxon Golf Course in Sarver, PA in 2002 & 2003: House#1 House#2.  Meanwhile, Willy Conley came up with a variation on the Excluder that some landlords said their martins preferred, claiming it was easier for martins to enter while still excluding starlings. This entrance hole was dubbed the WDC or Conley Excluder (photo right). In 2004, I decided to test for the martins' preference for the different Excluders, then to compare the breeding success in the two different types of entrance holes.

    The  site consists of two wooden T-14's, placed about 20 feet apart.  Conley Excluder entrance holes on every other compartment on both houses, so that there were a total of 14 entrance holes with Conley Excluders and 14 entrance holes with Snyder Excluders, equally distributed at all heights and facing all directions. The Conley Excluder entrance holes were 1/4" above the porch; whereas the Snyder Excluders were 1/2" above the porch. It is important to note that this difference is not a test variable, but rather a feature of the respective entrance holes. There was a piece of grit tape in front of each of all 28 entrance holes.


View Nest Check Data Sheets: House #1  House #2 (C = Conley Excluder Entrance; S = Snyder Excluder Entrance)

68 eggs were laid in the Snyder Excluders
69 eggs were laid in the Conley Excluders

59 nestlings fledged from Snyder Excluders
51 nestlings fledged from Conley Excluders
13.6% more martins fledged from the Snyder Excluders.

14 out of 14 pairs of martins bred successfully (fledged 1 or more young) in Snyder Excluder entrances (100%)
12 out of 14 pairs of martins bred successfully (fledged 1 or more young) in Conley Excluder entrances (85.7%)
14.3% more pairs bred successfully in Snyder Excluders.

According to a Mann-Whitney
test for ranked data there is no statistically significant difference between the outcomes.
Thanks to Dan Airola for conducting this statistical significance test.