(by Kent Justus)
Well, it seems that everyone here on the forum is learning that large gourds tend to be safer for martins from their number one predators: Great-horned and Barred owls. Yes, these two large owls are the NUMBER ONE predators of martins. Why?
Because
the martins all come in to roost in their gourds at night and are vulnerable to
the attacks of these huge, winged predators if the martins are nesting in
inadequate housing (6"x6" compartments in houses, and gourds smaller than 9" in
diameter). Now, the large gourds may be less desirable targets for the owls
than the Trio martin houses, but they are not immune to attack. The large owls
learn how to hunt martins in gourds. It is for this reason that even large
gourds need to be protected with an owl guard to prevent the owl from grabbing
the entrance hole with one claw, hang there beating its wings wildly, and then
grab martins as they flee from the gourd in terror. The key to protecting martins in gourds seems to be to prevent the owls from being able to get close enough to the gourd to grab it and hang there. The following photos demonstrate how I protect my martins from large owls. My dad lays linoleum floors and also installs laminate countertops for a living. He has a big stack of scrap aluminum trim for floors and countertops that I have access to. I formed the guards on my Chuck-Abare gourd rack from these materials. On the metal gourd racks (MPQ heavy duty poles with 1/2" steel conduit cross arms) I use a different approach. To protect the gourds facing out on the ends of the arms I have attached steel rods with wire coat hangers (the thick dark ones) bent into the oval shape. This presents a barrier that keeps the owl at claws length away from hovering close enough to grab onto the entrance holes. The martins seem to stay put in their gourd and freeze against the back wall of the gourd when under attack and will stay there as long as the owl doesn't physically grab and shake their gourd. I then string the #14 THHN wire between the arms forming sort of a "spider web" of wire to baffle the owls from gourds on the interior of the rack. Hopefully, this will give you some ideas to rig up your own guards.
Two
rods extending out over the entrance hole may be even more effective than just a
single rod by preventing an owl from coming in from one side of the rod.