I use a bunch of Troyer Horizontal and Vertical Gourds in my current purple martin colony. These gourds have been well accepted by the martins and their shape provides significant horizontal depth to give more protection from avian predators like owls.
For the 2012 martin season I have 54 Troyer Verticals with tunnels/porches; 65 Troyer Horizontals with cling plates; and 108 Troyer Horizontals with tunnels/porches. I have these spread out on a variety of gourd racks and some are even attached to my four house systems.
Here are some photos showing martins using Troyer Gourds:
Three martins at a Troyer Horizontal with a cling plate

Female martin on porch of Troyer Vertical

Martins gathered around Troyer Horizontals with tunnels/porches at a 24 gourd Deluxe type system

Pair of martins on porch of Troyer Horizontal with tunnel/porch

Martins gathered around Troyer Horizontals with cling plates at a 24 gourd Super System

Martins gathered around Troyer Horizontals with cling plates at PMCA Deluxe rack

Martins gathered around Bob’s (my neighbor) 24 gourd Super System. Notice that Bob inverted the gourd crossbar mounting method so that the flat section faces downward. In this way, the martins have a much easier time perching on the rim rather than the flat slick top section. Bob did this several years ago when he first erected this system.

Steve
