Dreary day on the beach.

As the wind was blowing on this dreary October day, I was watching this Red knot as it rain around the edge of the water looking for food.. I lowered myself to my normal shore bird position, on my belly with a ground pod holding my lens. I was shooting off pictures at a distance when I noticed my camera would not auto focus anymore.. What could be the problem??? Oh as I looked up from my viewfinder I noticed the Red Knot had walked right up to the front of my lens and well within my focal distance of my 500mm F4 lens.. Not a bad situation to be in..