when there is enough direct incident light to see it, whereas the necklace of the same bird in the second
image appears black when there is insufficient light. See article by James E. Cavanagh in Florida Field
Naturalist, Vol.32,No. 2, pp. 56-59, where Figure 1 in that article is the same image as the first photo
below but is shown there only in black and white. Photo 1 below has been cropped only to better show the bird.
