Starling Resistant Entrance Holes are also Screech Owl Proof Entrance Holes
From: Ken Kostka, PMCA, Edinboro, PA
Date: 11/12/99
Even at sites where starlings are strictly controlled, it’s a good idea to have SREH's (Starling Resistant Entrance Holes) since they will also exclude Screech Owls. Screech Owls are one of the lesser-known and admittedly less common predators of martins, but one that is capable of inflicting significant losses on a colony site just like their bigger cousins, the Great Horned and Barred Owls. Screech Owls can enter a 2" round hole, and occasionally roost in martin housing. Consider this passage from the writings of J. Warren Jacobs of Waynesburg, PA from 1909:
During the past summer a carpenter from this town was repairing a house in the country, the yard of which contained a well-filled martin house. He said he became much interested in the birds, and while watching them in the evenings he observed a Screech Owl go to the box but did not enter. Later he heard a martin struggle as an owl flew from the bird house. Upon closer observation, he discovered that the owl clung to the entrance perch, thrust a claw through the entrance and drew out a young bird, then almost fully fledged. After witnessing a repetition of this performance several times on consecutive evenings, he procured a gun, and, to his surprise, dropped screech owls to the number of five from the cupola of the bird house as they came at different intervals during one evening." J. Warren Jacobs, Gleanings. 1909
Please note: Today, all birds of prey are strictly protected by state and federal laws and may not be harmed.
In 1909, 6" x 6" compartments were the standard. Today, we know that martins are much better off in 10-12 inch deep compartments that don’t allow predators landing on the porch (owls, hawks, crows, gulls, etc") to reach to the back of the cavity and extract young. However, even with deep compartments, a Screech Owl could enter a 2" entrance hole, which makes using SREH’s a great idea. Blue Jays are also known to prey on martin nestlings (rarely), and SREH’s would also exclude Blue Jays.
Additionally, if everyone used SREH’s, I think it's reasonable to assume that martins would be more likely to use them at new, unestablished sites, where having only SREH’s is sometimes considered a disadvantage since investigating martins often prefer a 2" round hole. Martins that fledge from SREH’s will be familiar with how to negotiate them, and therefore less likely to be discouraged from using them at new sites. (An article about a Screech Owl nesting in an active martin house appears in Purple Martin Update Vol 8(3) pp.11-13)
