The Chimney Swift 221 
gradually softens and then it not infrequently happens 
that the nest, weighed down by the young birds, falls 
to the bottom of the chimney. If the fall does not 
kill the nestlings, they usually climb up the sides of 
the chimney for a short distance, and here they 
remain in a hanging position, being fed by the old 
birds until they are ready to fly and shift for them- 
selves. 
The young swifts are very interesting, although 
somewhat uncanny in their actions, resembling in 
their constant movements a bunch of wriggling snakes. 
At first I thought they were irritated by the vermin, 
<0 common about birds’ nests, but as I failed to find 
anything of the sort, I looked for another cause. 
After careful observation I concluded that the move- 
ments were due to an innate desire on the part of 
the young birds to preen their feathers, although the 
feathers had scarcely started. One does not become 
thoroughly aware of the constant motion of the young 
birds until one attempts to “take their picture,” 
when their restlessness becomes painfully apparent; 
it being almost impossible to catch the whole brood 
motionless, even for the fraction of a second. For 
this reason, in addition to the fact that their surround- 
ings are such that the light is poor at the best, they 
are most difficult young birds to photograph. 
