A Strange Aparition in the Woods

I have a mystery on my hands and I sure hope that it doesn't involve aliens.

If you look carefully at the sequence of pictures taken below you will see a string of four, small vertical bright spots - evenly-spaced - move from right to left.

Initially they appear just to the left of the larger birch tree on the right and directly above the hind quarter of the deer.  Then they move to center.  They continue moving left and are last seen just to the right of the larger birch tree on the left.

And they're gone!

Any ideas?