What follows is a personal account of Greater Yellowlegs behavior prior to and including copulation. In addition, I've included text from Arthur Cleveland Bent, author of the 21-volume work, Life Histories of North American Birds , published between 1919 and 1968.
[Note: The “Undulating Flight Display” is characteristic of male Greater Yellowlegs when engaged in pre-nuptial activity and is performed both in migration (practicing for the real thing) and on the breeding territory.]
*From my field notes, 12 May 1998, Plum Island, MA*
“The male flapped his wings to rise quite high above the ground and then abruptly stopped flapping and began to glide briefly upward on open wings before stooping, wings folded, like a hawk, downward, before again wing-flapping to once again fly upward [Thus the “Undulating Flight Display”], calling incessantly whenever he entered a stoop! This sequence was repeated 8 more times! This was all done above a presumed female as following the flight sequence, the presumed male landed near her and began to run around her, occasionally approaching with wings held above his head. The presumed female remained in one small area, watching the male’s movements until the male alighted atop her for a cloacal kiss.”
*From Bent, A. C. 1927. Life histories of North American shore birds: order Limicolae*.
Note: This 21-volume life history series should be on the shelf (or on the electronic desktop) of every North American Natural Historian. Electronic versions of many of these volumes are free to download (e.g., from https://www.gutenberg.org/ ). My favorite account (from Bent's Life histories of North American Raptors) is that of the Cooper’s Hawk (sorry, no spoilers). These and similar volumes from before the age of computers attest to the fact that electronic intelligence will never take the place of the natural historian . . . that is, until all the plants, animals, fungi, etc. have gone extinct.
*Courtship. Mr. Whitaker writes to me:* “The time for nesting varies as much as 10 days between the few pairs which frequent the lower levels and the bulk of the birds which nest on the high grounds. On the lowlands a pair of birds will take up their quarters near the place they intend to nest soon after their arrival and the cock bird may be seen high up in the air uttering his nesting song. He will sometimes be so high that he appears but a speck against the blue sky. His loud notes carry a long distance and sound like tweda-tweda-tweda uttered quickly and continually for quite a long time.”
*"Dr. Charles W. Townsend (1920)* *writes:* “The courtship song of the greater yellow-legs comes up from the marshes of Essex County throughout the month of May but is heard in greater volume during the two middle weeks. It has a sweet and pleading character and seems to say wull yer? wull yer? wull yer? Although it differs from the flickerlike call described in the original Memoir, which may be heard at the same time, it, too, has a decided flickerlike flavor. It is heard throughout the day, but in the evening until it is nearly dark the marshes often resound with the plaintive callings.”
*" H. S. Swarth (1911)* observed some greater yellow-legs on the wooded islands of southeastern Alaska in April, of which he says: “At this time, the males were going through various courting antics, posing with upraised, quivering wings, or running in circles on the sand bars around the object of their attentions, and incessantly uttering the shrill whistle peculiar to the species.”
