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National Geographic : 1982 May
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part of the world of this mysterious spe cies-to hear what a grebe hears and see what it sees, to live through its trials and feel its excitements... in short, to think like a grebe. To accomplish this, I would have to learn the meaning of the western grebe's vocal signals, then somehow establish com munication with the shy birds. In 1975 Iobtained grants from the Nation al Geographic Society, and the Bell Museum of Natural History at the University of Min nesota, in association with the Delta Water fowl Research Station. These enabled me to continue the project four more years and to complete my doctorate at the university. In the Delta Marsh the largest grebe colo nies all included nesting Forster's terns. The nesting grebes, having very limited perspec tive from the water surface, appeared to use the jittery terns as aerial sentinels. When terns sounded their alarm call at my ap proach, grebes hidden within the reedbeds would leave their nests and make for safer open water. To reach the wary grebes, I would have to fool the ever watchful terns. Muskrats abounded in both tern and grebe colonies; the terns often used their houses for nest sites. Somewhere I had heard of hiding in a blind that simulated a musk rat house. Within a week I had fabricated a portable, floating muskrat-house blind from a truck inner tube and cattail-thatched chicken wire. Sitting in the rude contrap tion, I wore chest waders to protect me from the cold water and marsh muck. On my first venture into a grebe colony a pair of terns landed atop my blind, inches from my head (pages 628-9). As I slowly walked the blind about in the shallow water, the pair vigorously defended their newly gained turf from all intruders. While the terns helped to allay the grebes' wariness, they also prompted me to modify my blind: Above my head I added a plastic shield; one tires of ending the day covered with guano like a park statue! Camouflage Allows Closeup Study Over the years my reed blinds took many shapes-from small, collapsible compacts to more spacious models. From these cozy mobile lookouts, with room for tape record er, notebook, and camera, I began studying western grebes almost within arm's length. I found that with a tree sprayer and hair dyes I could mark birds on their nests with out interrupting their incubation routine. Preening the dye into its feathers, each bird acquired a distinctive pattern that allowed me to log its activities as an individual. During live-capture operations I found that I could simply place grown grebes in the Beak to beak, a small-billedfemale, at left, and nasal-taggedmale square off in a preliminarycourtshipmove called "ratchetpointing" (above). With the help of voiceprints Dr. Nuechterleinunscrambled some of the mysteries of grebe language and can tell a bird's sex, mating status,and individualidentity by its advertising NationalGeographic, May 1982 630
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