129 Rusty 



the guard bird that did the calling, but both birds sometimes 

 called together, usually when a turkey vulture, Ward's heron, or 

 caracara flew over, close to the nest. This call seemed to be both 

 a warning and a challenge, and it also seemed to be a way of re- 

 lieving the tension of comparative inactivity. To remember this 

 particular call I wrote down symbols indicating one double note 

 that swooped (or "whooped") on a downward scale, followed by a 

 more rapid series of four triple notes, punctuated in the middle. 



When one of the birds took over at the nest it carefully placed 

 a foot on each side of the eggs, then lowered itself to a sitting 

 position, wriggling or twisting slightly to get the eggs settled 

 properly against the brood patches. Sometimes it stood up again 

 at once then tried a second time. Less frequently, a third and 

 fourth attempt were necessary. In rising, especially after a long 

 time setting, it often had to make quite an effort to pull itself 

 up, for it rises entirely by muscular action and control, without 

 pushing with the bill as, for example, the incubating flamingo does. 

 The incubating bird frequently reached under its breast feathers 

 to touch the eggs lightly, perhaps to move them a little. When 

 turning or rolling the eggs it usually stood, but sometimes it sat 

 "on its elbows," as it were, and, reaching under its breast, moved 

 the eggs slightly. 



The bird that was relieved at the nest often showed real 

 pleasure at its release. Both Pete and Jo exhibited this reaction. 

 Once Jo stepped off the mound and Pete took over, turning around 

 and around on the nest in a standing position and touching the 

 eggs briefly with his bill before sitting down. Jo stood for a 

 moment and then went running and skipping off toward the open 

 marsh, her wings flapping gaily. Another time she walked as far 

 as the nearest salt pond and, standing on the bank, did a wonder- 

 ful little dance apparently through sheer exuberance twirling 

 and leaping around and around, dipping her body low, wings ex- 

 tended, and then leaping sideways as if seeing how cunning she 

 could be. Usually the free bird started feeding very soon after 

 being relieved. On May 18, I noted two species of small, semi- 

 aquatic mollusks, the usual grass shrimps, several spiders, a number 

 of small frogs, and miscellaneous crickets, grasshoppers, bees, and 



