186
THE ESSEX NATURALIST
Captured adders have, however, disgorged small mammals and
young birds. It seems very likely that they feed on the Short-tailed
Vole which is often abundant in overgrown pastures in the Forest
such as this. Common Shrews are also abundant here and they also
may form a proportion of the diet: they are taken readily in cap-
tivity. Small adders have disgorged small nestling mammals, and
probably the nestlings of both shrews and voles are eaten. Less is
known about the birds which are potentially available as food, but
the bird fauna in the area is rich in species which may nest on the
ground or low down. Skylark, Tree Pipit, Willow Warbler, all
corne into the first category, while Dunnock, Robin and Blackbird,
with others, would enter the second.
It is hoped that future work will throw more light on the feed-
ing relationships of the adders in this area of Epping Forest.
Acknowledgements
We would like to extend our thanks to John Davison. Geoffrey
Davison, Simon Townson and Roger Thorpe for the help and
assistance we received from them throughout the year.
References
Wheeler. A, Malenoir, G. Davidson. J. (1959). A First Report on the
Reptiles and Amphibians in Epping Forest. Essex Nat., 30: 179-188.
Smith. M. (1951). The British Amphibians and Reptiles. London. 318 pp.
On the Occurrence of the Guppy Lebistes
reticulatus in the River Lee
By B. S. Meadows
The Guppy, Lebistes reticulatus Peters, 1859, a cyprinodont
or tooth carp, native to northern South America and the West
Indies, has recently been reported by Dumbill (1957) as occurring
in an apparently wild state in St. Helens Canal, Lancashire. In-
vestigations of the River Lee at Hackney during the period of
July 1966 to February 1968, inclusive, have shewn that this river
also supports a population of Lebistes reticulatus. This paper
discusses the salient physical, chemical and biological features of
the River Lee that would seem responsible for the maintenance
of the colony.
In the River Lee the species is distributed only in that part
of the river being affected by the cooling water discharge from
the Central Electricity Generating Board's Hackney Power
Station (Grid Ref.: TQ 360863). This discharge, which increases
the normal river temperature up to about 9°C, is normally a
constant one and the river is only subjected to relatively minor
temperature fluctuations. The increased river temperature is