Dippers - white eyelids?

I was recently lucky enough to see my first dipper in the flesh - a beautiful little bird. It was standing on a large stone in the middle of a shallow, fairly fast flowing river. I had a good view of it and it seemed to blink a lot with what looked like white / pale eyelids. Can anyone confirm this? Is there any reason why:

a) it was blinking a lot

b) their eyelids are the colour they are

 

Cheers