How testing works
Currently the two broadly accepted approaches are tunnel testing and field testing. While each has its advantages and disadvantages, both methods are used to advance the quality and efficacy of bird-friendly glazing systems.
Tunnel testing
In 2004, the Biologische Station Hohenau-Ringelsdorf debuted an outdoor protocol to compare effectiveness of different patterns on glass for preventing bird collisions. The Hohenau-Ringelsdorf tunnel is a binomial choice protocol. Birds, protected by a net, have the option to “exit” by flying either towards a test sample or unmarked control glass, seen at the far end of a dark, enclosed space. The tunnel was constructed (and is still operating) at Hohenau, a bird banding station, where netting migratory birds makes it possible to test large numbers of samples in a relatively short period.
The ABC adopted a similar protocol; PARC is a permanent banding station led by scientist, Dr. Christine Shepard. In a typical year, more than 11,000 birds of 100 species are netted, banded, measured, visually sexed, and weighed. Most are migratory birds netted during spring and fall migrations. In a relatively short period, this provides large sample sizes of species which are typically victims of collisions.
The PARC tunnel is 8 m (27 ft) long with a cross section of 1 m2 (10.9 sf) at the sample end, tapering to 0.2 m2 (2.2 sf). The tunnel is open at the sample end. A mounting apparatus holds two 1 x 0.5 m (3.3 x 1.65 ft) panels separated by a 100-mm (3.04-in.), 6-mm (0.24-in.) clear window glass control (supplemental materials A) and a test sample.
A net prevents birds from hitting the glass. At the operator end, a lightproof sleeve permits birds to be released in a dark interior, with brightly lit “exits” viewed at the far end. A video camera is mounted to record flights, and control glass permits direct comparison of samples in the same trial.
The tunnel is mounted on a pivot and is moved every one to five minutes to keep a constant orientation, with the sun directly behind the operator. Timing depends on visual assessment of shadows before each trial. Mirrors at the sides of the tunnel reflect light onto the front surfaces of the glass, and natural light falls on the back surface. Test materials are presented in random order and in equal frequency on the left and right sides. At the start of the testing season, trials using two clear panes are run as a control. Equal numbers of flights to the sides indicate the tunnel itself is not influencing the choice made by the birds. A tunnel score of 50 (±5) means a test glass product does not influence flight direction.
