ILLINOIS AUDUBON BULLETIN 25 
same place. During that time the gulls turned slightly, but did not move their 
location. But the slight shift in the angle of reflection from their backs has 
changed their apparent mantle color. In one slide it is the dark gray expected for 
the particular race involved; in the other slide, however, the mantle color is 
slaty-black, as in a Greater Black-backed Gull. The angle of light affects 
especially the sheen of iridescent feathers. Look for a purple-headed Mallard 
drake when one swims directly away from you, especially when it is backlit. 
After you find one, you'll be more reluctant to identify scaup based on the head 
colors given in the field guides. 
Finally, reflected light from a bird’s surroundings can affect the colors you 
see on the bird. Once in Florida I saw House Sparrows whose underparts were 
quite noticeably tinged with yellow. Before I could speculate about a possible 
different race, I realized that they were standing on a yellow translucent plastic 
feeder tray! In a similar fashion, light filtering through the foliage of a tree can 
give a greenish or a yellowish cast to the plumage of a bird. 
Distance: Birds that are too far away certainly can’t be identified. But how far is 
too far depends on what you need to see. An albatross can be identified over two 
miles away; but to see that the pale rump of a possible Hoary Redpoll is actually 
unstreaked may require you to be within thirty feet. You may think that you see 
an unstreaked throat on a fairly close waterthrush, and put it down as a 
Louisiana; however, the spots on a Northern Waterthrush’s throat often cannot 
be seen more than 25 feet away (not to mention the fact that a few Northern’s 
throats are unspotted anyway). 
Incomplete views: The problem here is in knowing that your view has been 
incomplete. For example, a rounded-winged accipiter may look more like a 
pointed-wing falcon when viewed from behind, going away. Foreshortening 
makes the separate primary feathers appear overlapping. Similarly, foreshorten- 
ing can make the tail of a bird flying directly away seem shorter than it really is. 
Another example, where an apparently adequate view can be misleading, is the 
tail of a Cooper’s Hawk. If it is completely folded, it may appear more 
squared-off, like a Sharp-shinned Hawk’s tail; only when it is spread somewhat 
does the rounded shape become apparent. 
If the examples I’ve cited represent only some of the instances where our 
observations can be misleading, how can we trust our identifications? The 
answer, of course, is that an identification takes several factors into account. 
Furthermore, it is possible to minimize observational problems, if you make an 
effort. You must go into the field enough to learn by experience what the problem 
possibilities are, and you can develop a critical attitude that leads you to consider 
what the effects of light, distance, etc. might be at the time of an important 
observation. The question of attitude brings me to the last factor giving rise to 
field identification problems: 
