A Scientific Test: Preference for 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. The martins bred very successfully in them but occasionally a martin seemed to experience difficulty entering or exiting. 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). I decided test the martins' preference for this new variation of the Excluder entrance hole versus the original Snyder Excluder entrance hole in 2004.

    The test site consists of two wooden T-14's, placed about 20 feet apart.  I put 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.

    The site ended up with 100% occupancy (28 nesting pairs), so clutch initiation date (the date when the first egg is laid) was used as an indicator of which compartments were chosen first, and presumably preferred. The nest with the earliest clutch initiation date is the "first nest", the nest with the second earliest clutch initiation date is the "second nest", and so on.


10 of the first 14 nests (71%) were in Conley Excluders;10 of the last 14 nests (71%) were in Snyder Excluders; The actual order was: C/C C C S C S S/C C/C S/C C S/S/S/C S/S/S S/S/S S C C C  (X/X/X = same day clutch initiation date)
View Nest Check Data Sheets: House #1  House #2 (C = Conley Excluder Entrance; S = Snyder Excluder Entrance)

Interestingly, the last 3 nests were in Conley Excluders, as were the first 3 nests. The only 2 nests that failed to to fledge at least one nestling were both in Conley Excluders.

PLEASE NOTE: It should be noted that martins bred very successfully in cavities with BOTH types of entrance holes: The number of eggs laid and martins fledged from each type was about equal. 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. Therefore breeding success was not correlated with preference for entrance hole type. See an article comparing breeding success.