4. Coastal Dykes and Marshes
(a) Old Hall Marshes Reserve (R.S.P.B.), Tollesbury
This is one of the few remaining large areas of rough grazing marsh on the Essex
coast which still retains its traditional character. Running parallel with the extensive
sea walls are invertebrate-rich borrow dykes, which vary widely in their salinity, depth
and vegetation. Sea Club-rush is the dominant emergent plant species in the dykes,
some of which hold little or no free water. Wide 'fleets' cross the reserve, but these suffer
from nitrogenous pollution, and are less rich in dragonflies than are the dykes and
associated pools. Several observers including K. M. Rowland, J. Shanahan and myself
have recorded ten species of dragonfly on the reserve since 1980. The dykes support a
strong breeding population of the local Sympetrum sanguineum, and Aeshna mixta
probably breeds here. too. Significantly, one female of Lestes dryas was seen here by K.
M. Rowland in 1984. though it is not yet clear whether the reserve supports a breeding
population of this species. Appropriate management of the borrow dykes must clearly
be an important priority if the reserve is to continue to support its rich dragonfly
fauna.
(b) Langenhoe Marsh (M.O.D. Range)
Another very fine area of coastal marshes, with many characteristics in common with
Old Hall. Access to the marshes is limited, and this is probably one reason why the
number of recorded species is relatively low at six species. No doubt the full total of
species is considerably higher. However, the six species which have been recorded
include the strongest colony Lestes dryas so far discovered in north Essex, and the only
Essex breeding colony so far discovered of Brachytron pratense. The very local (in Essex)
Libellula quadrimaculata has also been recorded at the site and there is a strong breeding
population of Sympetrum sanguineum. Despite the small number of recorded species,
this site is one of the most important in the county for its dragonflies.
(c) Hadleigh Marshes and Benfleet Downs
This area of the Thames estuary has long been known as a high quality dragonfly
locality. It was regularly visited by C. O. Hammond, E. B. Pinniger. C. Longfield and
others because of its association with two rarities - Lestes dryas and Coenagrion scitulum.
Though the latter is probably extinct. L. dryas has been re-discovered at several
locations within the area in 1984 and 1985 by R. G. Payne and C. W. Plant. Eight other
species, including Sympetrum sanguineum and Lestes sponsa have been recorded since
1980, and there is a 1979 record by B. Watts for Libellula depressa.
(d) Foulness Island (M.O.D. Range)
As with Langenhoe, Foulness remains to some extent under-recorded because of
limitations on access. Nevertheless, it has been visited on a number of occasions by K.
M. Rowland, R. G. Payne. A. Stubbs and others. Eight species have been recorded here
since 1980. including Sympetrum sanguineum. Lestes sponsa and Orthetrum cancellatum,
but the site is most important as a national stronghold for Lestes dryas. The uncommon
Coenagrion pulchellum occurred on Foulness in 1943, but appears to be now absent.
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