of an intruder, 
uttering a loud 
snake-like hiss 
“\, as she does so. 
When the eggs 
are hatched, the little ones are fed with the utmost 
regularity, one of the parents visiting the nest about 
every two minutes and a half, always with one grub or 
caterpillar in its beak, and often with two or three. And 
as this work begins before sunrise, and continues without 
intermission till at least half an hour after sunset, it will 
be seen that a pair of blue-tits, during the nesting season, 
must supply their family with at least five 
hundred grubs a day. Multiply this total by the 
number of weeks which elapse before the little birds 
can take care of themselves, and add the 
