Pelican Feeding Time


Very dull and overcast day, bad light and the threat of rain showers.
Can anyone help explain the lines across the pelican necks (looks like a split image focussing screen).
This was one of about 45 shots taken within about two hours on one afternoon recently and this was the only one affected. I know this is not a prizewinning shot, just a family gathering memory but I am intrigued and would not like this to happen on something important.
Would appreciate any help on this.