Richardson 1937 54. Yellow Warbler (Dendroica aestiva) May 29, 1937 - opening of 20 mi. G. into Warner Valley, Oregon Two birds seen in and around thickets in this principally sagebrush area. The birds, staying the whole time within an area say 30 yards across, were almost incessantly chasing each other. This went on for about 10 minutes - was still continuing when one bird was collected. No fights were seen to occur. The birds typically stayed well apart (5-10') during the chase. Several times they both perched for a few seconds but still well separated. Both birds chased the other though no reg ular alternation could be detected. Tentatively this was a pair (?+?) and the chasing was a type of mutual courtship seemingly very much like playing.