Digital camera shots which contain unknown object not seen until photos were downloaded to computer.

I was using my Epson PC500 digital camera to take exterior shots of the view from a Bed and Breakfast for a web page.  No objects were observed with my naked eye except for the seagull which appears in photo no. 2.  Photos were transferred to my computer and were being reviewed in Corel PhotoPaint ver. 7 when I noticed the bright white dot on Photo no. 2.  I then reexamined photo no one to see if the object was present there also.  I discovered the object, only this time appearing as a dark spot.  I then increased the resolution from 288 dpi to 1200 dpi and cropped the object.  I then increased the size 300 percent and was surprised to find what I did. The physical shape of the object appeared to change as well as did the color.  The photos were taken approximately 1.5 minutes apart. I am e-mailing both photos 1 and 2 as well as the enlarged cropped object image of both.