544 THE POPULAR SCIENCE MONTHLY 



ously eaten than in others, and there can be no doubt that habit often 

 decides the question. Fear, however, is another variable to be reckoned 

 with, for if this sense is aroused at the moment the bird has seized a 

 sac to bear it from the nest, it seems to be eaten as the easiest solution 

 of the difficulty. Perhaps a counterpart of this sort of behavior is seen 

 when a bird with food in bill suddenly encounters the naturalist, or 

 any other fearsome object, for it immediately sounds the alarm, and 

 promptly swallows the insect. When more than one sac is taken, all are 

 usually eaten. It is not an uncommon sight to see a bird walk around 

 the nest and take a "' white marble " from three birds in succession, 

 for in muting, a bird is sometimes followed by one or more of its mates, 

 and anything which soils the nest is quickly removed. More than once 

 I have seen a sac, which had dropped from a nestling snapped up by 

 the old bird before it had fallen two feet in the air ; and birds will even 

 descend to the ground for the sacs, if necessary. Twice I have seen the 

 male chestnut-sided warbler take a sac to carry it off, and the hungry 

 female snatch it from him, devour it and settle down to brood. 



Removing the excreta piecemeal and dropping them at a safe dis- 

 tance is the common instinctive method not only of ensuring the sani- 

 tary condition of the nest itself, but, what is even more important, of 

 keeping the grass and leaves below free from any sign which might be- 

 tray them to an enemy. Bluebirds and redwing blackbirds often carry 

 the sacs a long distance before letting them fall. Crow blackbirds some- 

 times drop them in the water, and house wrens and nuthatches implant 

 them on the bark of trees. This instinct, like so many others in the re- 

 productive cycle, after running its course, begins to wane, and even be- 

 fore the close of nest-life, so that it is not correct to say that the nest 

 of the cuckoo or the nicker is always sweet and clean. I examined a 

 hoopoe's nest in upper Egypt, near Luxor, on March 26, which was 

 filthy in the extreme, but hardly worse from a sanitary standpoint than 

 is a woodpecker's hole at a corresponding period. This nest of the 

 hoopoe was on the ground in the midst of a pile of sun-dried brick, 

 and was composed wholly of weeds and lentil-pods. Tbe five young 

 ones, which were at this time nearly ready for flight, showed their fear 

 by erecting their beautiful crests and crawling down among the bricks 

 to hide. There is the further curious anomaly regarding this practise, 

 that some of our most attractive birds, which have delicate and artistic 

 nests, of which I can mention the American goldfinch, do not appear 

 to possess the cleaning instinct at all, or the attendant instinct of in- 

 spection, and shortly after the young emerge their surroundings be- 

 come encrusted with filth. This singular fact is, I believe, correlated 

 with the method of feeding described above. The young are fed at 

 rather long intervals ; at one period, of nearly seven hours, the aver- 

 age was once every twenty-five and one half minutes, and all are rapidly, 



