The record of nests in the Whipsnade Bird Sanctuary in 1936 and 1937 shows that the latter year was less favourable to avian reproduction.
This is manifested in number of species nesting (20 as against 21); reduction of total number of nests (about 11 per cent.); and of nests in nest-boxes (17-5 per cent.).
For the three abundant species of which complete records were taken (Starling, Great and Blue Tits, taken together), it was manifested in reduction in the number of nests where eggs were laid (11-8 per cent.) and those in which eggs hatched (6-5 per cent.); in reduction of mean size of clutch (2–4 per cent.); of mean number of young hatched per brood (8-7 per cent.); and of mean number of young fledged per brood (14-4 per cent.). The Blue Tit showed the greatest decrease in 1937.
The only change in conditions was a reduction in the amount of underbrush; this, however, could not be responsible for most of the decreases noted.
Records by Mr. Kendrick of Blue Tits in the Birmingham area indicate that there also 1937 was less favourable to avian reproduction than 1936.