Spotlighting effect on birds' eyes

I recall at a slide night once, where flash photos had been taken of an owl 
and at quite close range, that I asked about the effect of the flash on the 
bird and/or its eyes.

The response was that, as the bird showed no visible signs (eg going into a 
fit, falling off its perch etc.), that there was no adverse effect on the bird 
!!!

Irene Denton
Sydney   NSW