354 BULLETIN 16 7, UNITED STATES NATIONAL MUSEUM 



food conditions. M. P. Skinner's notes give the dates of arrival in 

 Yellowstone National Park as ranging, over a period of seven years, 

 from April 9 to 25. 



Courtsliip. — I believe that ospreys are mated for life, as is the case 

 with many other large birds. Dr. Harry C. Oberholser (1897) tells 

 the following pathetic story, illustrating the constancy of a bereaved 

 mate: 



At a time when one of the birds, presumably the female, was ou the nest, a 

 bolt of lightning struck the tree, killing the bird and demolishing the nest. 

 Strangely enough, the other osprey when retui'uing only to find his home deso- 

 lated, took up his station upon the top of one of the uninjured trees close at hand, 

 and throughout the remainder of the summer was seen day after day, month 

 after month, keeping his lonely vigil, apparently mourning the loss of his 

 mate. * * * He remained until late in September, but at the time that the 

 other ospreys departed he too disappeared. The next spring, however, found 

 him again at his post, and throughout the whole summer he continued just as 

 before ; but in the ensuing autumn, joining the company of his fellow ospreys in 

 their journey to the southland, he departed, this time to return no more. 



But such constancy is not the invariable rule. I have known of sev- 

 eral cases where one of a pair has been shot and the survivor has 

 secured a new mate. I also knew of a case where both of a pair were 

 shot and a new pair appropriated the nest. 



As soon as the ospreys arrive on their breeding grounds they inspect 

 the old nest and begin repairing it. One bird, probably the female, 

 stands on the nest, and receives and arranges the material brought in 

 by her mate ; it is interesting to see these great birds flying home with 

 a long string of seaweed or cornstalks trailing out behind. Mrs. Irene 

 G. Wheelock (1904) says that the osprey breaks off the dead twigs 

 from a tree, sweeping down on them and seizing them in its feet. 



All is activity in the colony, as new birds are arriving at intervals, 

 looking up their old nests or seeking locations for new ones. As most 

 of the birds are already mated, courtship is mainly a nuptial display, 

 an expression of joy at their home coming, or an exhibition of exuber- 

 ant spirits. It consists mainly of aerial gymnastics in which both 

 sexes indulge, chasing each other in swift pursuit-flight, soaring, 

 scaling, circling, dodging with rapid turnings or quick dashes down- 

 ward, as they sweep, now low, now high, in wide circles. Several pairs 

 are often seen in the air together, and sometimes trios, all screaming 

 their notes of love or excitement. 



Copulation is performed on the nest or on a branch of a tree ; the 

 male stands on the back of the female, balancing himself by waving 

 his wings, and making connections for a few seconds. 



William Brewster (1925) saw what was probably a male — 



mount to an immense height above the Lake near Great Island, to drift slowly 

 eastward over the forest, poising or hovering all the while on set or loosely- 

 flapping wings, uttering almost ceaselessly a shrill, screaming cree-cree-cree 



