There must be then more to it: when I do that with coots, the "bald" spot might not end up blown out, but if the pinkish hue of the beak is visible, most of the bird will be uniform black and the eye hard to find. I suspect it's also about relative size of the subject in frame before any crops (and thus, focal lengths available).
I can imagine the difficulties in trying to figure out the correct exposure for these guys with the stark back and white coloring. You did a wonderful job of it though. I'm enjoying these "Glass Reflections" series