Avian Guards

Avian guards provide protection from eagles, while creating a sturdy vertical structure that allows for the addition of a chickenwire mammalian guard. Various heights were tested, averaging 24-26”, which LPC uses as their standard height. Observations were focussed on striking a balance between shade, air circulation, and natural v. manmade materials.

Shade 

Because the birds tend to pant when on nest on hot days, we provided a source of shade for all rafts placed in direct sunlight. In the past we have used camouflage cloth or evergreen boughs. In the 2021 field tests, we used a combination of the two, first laying camouflage cloth across the top of the avian guard, and then holding it down with hemlock boughs and zip ties. Two violent windstorms in June led to earlier than expected loss of hemlock needles, although ample shade was then provided by the camouflage cloth (see photos of raft at the beginning and end of season below). Stripped of their needles, the hemlock branches provided scaffolding against wind for the camouflage cloth and at least some natural camouflage, but next year cedar boughs will be tested to see if they provide longer lasting coverage. 

Two grades of camouflage material were tested. The standard camouflage cloth (top photos) and a more expensive version of the same with a net backing and hemmed edges (directly above). While the higher quality material showed promise at first, maintaining the hemmed edges required using the piece in it is entirety, which provided more coverage than necessary, with the possible downside of less air circulation. While the netting layer attached to the bottom of the cammouflage cloth provides additional structure, we found that the addition of evergreen boughs secured with zip ties overtop of the camouflage cloth (top photos) provided a better structure. Therefore, the added expense of the higher quality cloth did not seem worthwhile.

We are currently looking for a natural plant material that can be woven into the trap wire replacing the need for camouflage cloth altogether. Because cattails, which would otherwise work well, can harbor mold that triggers aspergillosis, we are searching for a material that could be woven into the avian guard that would be safe for the birds. 

Open Top Rafts

While we have used avian guards on all of our traditional rafts, the success of the Virginia Lake raft has led us to wonder if some of our unused traditional rafts located in shaded sites, might be more attractive to those particular pairs of birds if we swapped out the traditional rafts for open top Robinson rafts. We currently plan to do this in at least one location. Tall saplings/sticks will be planted/secured in the side boxes, to ward off Kezar’s ever-present eagles.