I found it interesting watching the way the elongated tufts of feathers on some of the birds that we saw change shape. Crest plumes enhance the outline of a bird and are raised as a visual display to either attract the opposite sex or as a threat display.
Bohemian Waxwings (above) spend most of the time with their smooth, sleek, perfectly coiffed crest retracted. During courtship the male feeds the female with a berry and will raise the crest as part of the courtship display. It was noticeable that when two birds went for the same berries that one of them would lift the crest slightly.
I often see Blue Jays (right) land on a branch, squawking away with their brilliant blue head feathers erect. Like the woodpecker this is to show who is in charge and let the others know exactly where they are. One of the Blue Jays that we saw in Algonquin, had its back to the wind, which produced a somewhat ruffled and comical head dress.