406 BULLETIN 179, UNITED STATES NATIONAL MUSEUM 



Stoner (1936b) gives an excellent account of the excavating 

 activities of the bank swallow : 



With the onset of the breeding season the first excavating efforts of the bank 

 swallow are intermittent and seemingly aimless * * * not until about May 10 

 did the excavation of burrows begin in earnest. * * * 



When starting a burrow it appears that the birds first cling to some slight 

 projection on the face of the bank from which they can reach the point of attack, 

 either with the claws or bill or both. After a slight concavity is formed, its 

 sides are creased with the marks of claws and bill. As the work proceeds, 

 the ceiling takes on a distinctly arched form, while the floor is practically flat. 



Observations indicate that the more deeply scarred appearance of the inner or 

 apical part of the cavity is due to the use of the bill. The bird clings to the 

 walls and dislodges the particles of sand or gravel by pecking with a rapid side- 

 to-side movement of the head. As soon as the shelf has resulted the feet with 

 their long sharp claws are brought into action. Both biU and claws of captured 

 individuals were caked with the moist earth. In digging, the tail is frequently 

 used as a support, as in the woodpeckers. 



Dissection of a few specimens taken showed that both male and female 

 take active part in the task of digging. Often one individual of the (apparently 

 mated) pair remains clinging to the face of the bank immediately beside the 

 one that is working. When the latter hesitates or flies away its place is imme- 

 diately taken by the other. 



Until about May 15, the bank swallow seems to have a strong impulse to 

 dig, but many more burrows are begun than are later occupied. However, as the 

 season advances the impulse evidently becomes stronger, and excavating is con- 

 fined to single burrows which increase in depth rapidly and steadily. At this 

 time, too, the birds exhibit sensitiveness to disturbance. 



With the deepening of the excavation the dislodged materials fall to the 

 floor of the shallow burrow whence they are ejected by frequent vigorous 

 kicks accompanied by a kind of wriggling movement of the body. In this 

 action the wings also are "shuffled" rapidly in a backward and forward direction 

 as well as from side to side, thus aiding in whipping the sand out behind the 

 bird. Ordinarily, excavating is interrupted by frequent flights, probably at 

 times to feed, but at other times for no very evident reason. 



When a swallow returns to a burrow under construction it often enters im- 

 mediately, and at once sends forth a shower of sand from the burrow by the 

 rapid backward kicking action of its feet. After a few seconds, digging evi- 

 dently is resumed and a new pile of loose material results ; this is ejected by 

 the same individual or its mate. In colonies where the burrows are close 

 together the considerable amount of sand which is thus dislodged from them 

 often accumulates in distinct windrows on the bank below. 



When old burrows are renovated, the labor involved, in many if not most 

 instances, is probably less arduous, the task then being mainly that of enlarging 

 or extending the tunnel, and clearing out the remains of the old nest as well 

 as other debris. 



Generalizing the results of his study of the bank-swallow excava- 

 tions at colonies in the Oneida Lake region, N. Y., Stoner (1936b) 

 states that the excavating activities were most marked between May 

 7 and 21 and little was accomplished after May 26. In general, bur- 

 row excavation progressed at the rate of 3 to 4 inches a day. The 

 greatest rate of excavation was a burrow that was increased 65 inches 



