Banding also permits us to relate plumage changes precisely to age. At fledging, the young pelicans’ first suit of soft white down has been replaced with brown feathers on the wings, back, head, and neck, and by white feathers on the belly.
Over the next three to five years, the birds undergo successive costume changes leading to adult plumage. The white belly of the immature bird changes to black, the brown back and wings to silver gray, and the head and neck to white.
Upon reaching full adulthood, the brown pelican displays seasonal transformations that are perhaps the most elaborate among water birds. During fall and winter the head becomes yellow, the neck white, and the bare skin around the eye dark blue, while the bill takes on varying shades of orange. As the breeding season nears, the distensible throat pouch becomes deep black, the iris straw yellow, and the eye ring bright pink (page 118).
When the birds move to Tarpon Key in late February, the neck undergoes a very rapid molt from white to chocolate brown. While the adults are incubating in March and April, the yellow feathers fall out of the head and are replaced by white ones. The eye turns dark brown, and the pouch and bill fade to gray-green.
In six years of study I have enlarged our understanding of the biology of this appealing, ungainly bird—and acquired a deep, unsettling awareness of its vulnerability to the growing pressures of man.
Curious visitors and sun worshipers increasingly disrupt the birds’ normal routine on the beaches and sandspits, the offshore islands, and in the mangrove thickets that provide the pelicans’ daytime loafing areas and nocturnal roosts.
Four-fifths of all free-flying pelicans I’ve handled have had either anglers’ hooks or fishing lines attached to them somewhere, or have shown the scars of such encounters. I regularly find pelicans hanging in the mangroves entangled by monofilament line and dead of starvation.
Pelicans mooch food from fishermen—from their bait boxes and from the anglers’ catch. Unfortunately the birds are not wise enough to avoid hooks and lines. I offer fishermen this advice: If you suddenly find a pelican on your line, reel in the ensnared bird, grab his bill, and fold up the wings. Then remove the hook and line—and save a life.