418 
ENEMIES OF MOLLUSOA — BIRDS AND BATRACHIANS. 
largely upon Helix nemoralis, H. Iwrtensis, and other species, seizing 
the shell by the outer lip, and striking it repeatedly against a stone 
until broken, or fixing the shell in some suitable crevice and pecking at 
it until fractured, a particular stone being often selected to which the 
shells are carried for the purpose of 
being broken thereon. These sacri- 
ficial stones, known as “ Thrushes’ 
altars,” are usually in open posi- 
tions and easily recognized, not only „ , 
° ■' Figs. 731 and 732, W/jT L., 
by their slimy surface and the shell- illustrating the manner in which these 
shells are broken by Thrushes, etc. 
fragments adherent thereto, but by Kmerlng'"^ 
the little heaps of broken shells which are strewn around them. 
Starlings, Fieldfares, Redwings, and many other birds devour great 
(piantities of the smaller species during the winter months, Zua 
luhrica being a fiivourite food of the Starling, while the Fieldfare and 
Redwing search for Helix virgata and other species. In times of stress 
the (foldcrest resorts to the same food, seeking out from their hiding- 
places Hdlea, Cldusilia hidentata, Pupa mnsconim, etc. The Bearded 
Titmouse and Reed Bunting devour great quantities of the Succinecv] 
the 'I’itlark searches for Helix capemta to vary or make up for the 
deficiencies of its more fiivourite coleopterous diet, and the Grey 
Wagtail preys upon Ancyluff fluxiatiUs and Sphcerium corneum in 
our streams and ponds. 
The Heron feeds upon Limnaea stagnalis and other species and also 
upon the Anodonti, with which it will fly up into the trees, breaking 
the shell against the branches; the Hooded and Carrion Crows, which 
also feed upon the same species, have been observed to carry them to 
a considerable height and to drop them to the ground to break the 
shell, so that they can more readily get at the animal. 
The Dipper haunts the rocky streams, and the Water-Rail the 
])Ools, preying upon the mollusks and other aquatic creatures therein, 
while the Land-Rail is said to become quite fat in the summer months 
by feeding upon the various snails. 
'I'he Batraciiians are also very partial to mollu.sks. Frogs and Toads 
more especially devouring considerable quantities on occasions, and 
this is so well known that the garden attached to the laboratory of 
Agricultural Chemistry at Rouen by the introduction thereto of 100 
toads and 90 frogs was in a month completely cleared of the slugs and 
snails which had previously so infested it that the growth of any useful 
