Friday, April 08, 2005

Effect of Flash Photography on Owl Retinas

5/8/05-- Many people have worried about the effects of flash photography [the flashes necessary to produce all those wonderful pictures] on the Central Park screech family.

I will post a paper presenting the other side of the story soon -- someone has promised to send it to me. In the meanwhile, here is something Rebekah Creshkoff has brought to my attention. She is the founder of New York City Audubon's Project Safe Flight that strives to prevent bird collisions with reflective glass. The project's volunteers also take care of birds that have, alas, already collided.

From -- This is by Graham R.Martin, a scientist who's written on light and bird collisions. This is excerpted from a passage he wrote:

"[I]t seems reasonable always to err on the side of caution in these matters. The scotopic spectral sensitivity and rate of dark adaptation of avian retinas are very similar to those of mammals, including ourselves. Thus if our own dark adapted vision is disrupted by the flash used then it is wise to presume that the bird's dark adaptation will be equally affected. If we are temporally "blinded" by the flash then so also will be the bird for a similar length of time. For example, if you knock out a fully dark adapted retina assume it will take up to 30min for full
sensitivity to be recovered.

"Remember also that disruption of dark adaptation is never likely to occur in nature. Ambient light levels change through dusk and dawn at a relatively slow rate. Even at the equator, where dusk light levels change most rapidly, the rate of change is more or less in step with the rate of dark adaptation, and so under natural conditions a bird will always be well adapted to the ambient. With the exception of entry from a dark roosting site into full day light, there are few, if any, natural situations where marked light level changes are experienced and hence dark adaptation