150 BIRDS DECEIVED BY WEATHER. [PART II. 
egg is deposited quite tally with the one above 
mentioned. From the similarity of the Hydro- 
campa potamogeta’s arrangements (described by 
Réaumur—see Rennie’s Insect Architecture, p. 154. 
Murray, 1857) I should however conclude that 
the one in question was of that family. The Cater- 
pillar, indeed, appeared to me thicker than I 
should expect to find that of a Hydrocampa, 
but my eyes may have thus far deceived me. 
From ‘the mistakes which birds occasionally 
make with regard to the time of incubation, it 
would appear that their instinct affords them no 
other guide to the approach of summer, than that 
of the increasing warmth of the temperature. A 
remarkable proof of this occurred in the winter 
of 1857-8, when two of the chimnies of a house 
in the Isle of Wight, where I was staying at the 
time, were between Christmas and New Year’s 
Day blocked up by Jackdaws’ nests, which must 
have been constructed then, as the chimnies had 
been swept less than a fortnight before. The 
birds were indeed, I believe, actually seen carry- 
ing in materials. In these nests, besides the quan- 
tity of sticks and rubbish of which they usually 
consist, the jackdaws had taken the odd fancy to 
insert some pieces of glass, whether for use or 
