INTERBREEDING OF BLACKBIRD AND THRUSH. 
585 
Tho tree \v:us in a secluded spot some distance from any thoroughfare, 
therefore it is not likely tho eggs were placed in tho nest by any one. I also 
found, on May 0, a Blackbird’s nest witli one egg of a clear light blue, 
without markings. This variety of egg, mentioned by Mr. Saunders 
(‘ Manual of British Birds,’ p. 14), may be the result of a cross between 
a Blackbird and a Thrush. I saw a pair of Blackbirds, which undoubtedly 
owned the nest and spotless egg, and to all appearance were true Blackbirds. 
Probably the nest with the Thrush-like eggs may more likely belong to such 
a cross.— F. W. Fboiiawk.” 
Here, then, are ten additional cases, in all of which there are more 
or less good grounds for supposing that Blackbirds and Thru.shes 
have interbred. The evidence of their having actually done so is, 
however, both .slight and un.satisfactory, as there are several 
suppositions on which it is possible to account for these supposed 
cases, without necessarily at once accepting them as authentic and 
reliable cases of interbreeding. Thus in the case of the first two 
(XIX. and XX.), it seems possible that a hen Blackbird, with her 
brown plumage and spotted throat, may have been mistaken for 
a Thrush by ignorant observers. Comparatively few persons, who 
are not professed students of ornithology, are aware that the hen 
lUackbird is not wholly and uniformly black, like tho male. 
Several other instances, notably Xos. XXL, XXIV., XXV., and 
XXVI., may bo c:vses of Blackbirds laying their eggs in the old and 
deserted nests of Song Thrushes. Similar cases among other species 
of birds, and especially among game birds, have been frequently 
recorded. For instance, Mr. T. 0. 1 lall relates in the ‘ Field ’ for 
June 10th, 187G, “that a Missel Thrush built a nest in his garden 
and laid three eggs. Soon after he found two Blackbirds in the 
same nest. Upon these five eggs the Missel Thrush sat until they 
wore hatched. Tho place at which this occurred is not stated.” 
I have long known that almost every bird will sit upon the eggs 
and rear tho young of any other species laying eggs of somewhat 
similar size if they are introduced into her nesL As a result of 
a largo number of experiments in this direction, I published an 
article “ On the Kesult of Interchanging the eggs and young of 
different species of Birds,” in the ‘Journal of Proceedings of the 
Essex Field Club’ for 1883 (vol. iii. p. xciv.). The following 
case, which I have clipped from the ‘ Essex County Chronicle ’ of 
^lay 25th, 1888, seems very much to the point : — 
