NORTHERN CLIFF SWALLOW 479 



pied by cliff swallows in 1935. This colony was closely observed by 

 Grinnell and others, who reported on its progress from time to time. 

 In 1936 the sparrows arrived and Grinnell's comments are as follows : 



On May 27, I first became aware of the presence of English Sparrows 

 (Passer domesticus) . At the southeast corner of the btiilding I saw males of 

 this aggressive species behaving as if evicting cliff swallovps from the latter's 

 nests. Male sparrows, calling loudly, were either perched on the coping under 

 the nests or were actually ensconced within the entrances of the swallows' 

 nests. Furthermore, on the southeast steps at 1 p. ni. of May 27, I found 

 remains of eggs. Ou May 30, at 1 p. m., in the same location, I saw on the 

 steps two dead young swallows of about hatching age, a splashed. Incubated egg, 

 and many fragments of eggshells — the latter definitely of the swallows because 

 of the umber spotting ou the shell fragments. Directly above, along the row 

 of 48 swallows' nests, were several male English Sparrows. * * * 



When I made a census of swallows' nests on June 4, I counted 11 English 

 Sparrows, 7 of which were males perched on the coping near swallows' nests 

 from which protruded wIsps of nesting material ; the birds were singing, if 

 English Sparrows can be said tO' sing, as though sitting females were Inside 

 certain of the nests. Again and again, a sparrow was seen to enter a swallow's 

 nest; but I did not see a swallow and a sparrow enter the same nest. Oa 

 the southeast steps, I saw more, dead, naked, seemingly just hatched swallows, 

 and also two more splashed eggs. The same sort of observations were made 

 on June 5 and 6. On the latter date, sparrows were seen carrying nesting 

 material into swallow's nests at the southwest corner of LSB, so that all of 

 the three corners of the building patronized by the swallows had also attracted 

 sparrows. * * * 



I was amazed at the aggregate large numbers of English Sparrows around 

 LSB, where before 1936 I could not recall ever having seen any, since its 

 construction, in the summer time. Again we have Illustrated how the fortunes 

 of one kind of animal may be influenced favorably by some circumstance in 

 the economy of another. The swallows, by furnishing appropriate nest sites, 

 brought the sparrows into a territory new for them. Partial supplaulatiou, or 

 succession, was in evidence. 



Dayton Stoner (1939b) cites an interesting case, wliich he terms 

 parasitism, in which English sparrows confiscated the nest of a 

 cliff swallow and later were driven away or abandoned it after the 

 female sparrow had deposited an egg. Three eggs of the cliff swal- 

 low were added. The sparrow egg hatched first, followed several 

 days later by the hatching of the swallow eggs. The young swallows 

 perished, but the young sparrow thrived through the diligent care 

 of the foster parents, the cliff swallows. 



Friedmann (1931) writes as follows concerning the parasitism by 

 the cowbird: "Mr. J. Hooper Bowles informs me that he has a 

 parasitized set of four eggs of the Swallow and one of the Cowbird 

 from La Anna, Pennsylvania, June 30, 1914, and that three nests of 

 this Swallow [Cliff Swallow] at that place contained Cowbird's 

 eggs." 



