6
back from the brink of extinction in Victorian
times. From an estimated national population
of 32 pairs in 1860 (the popularity of "grebe-
furs" nearly brought about their extinction)
the Essex -figure has now stabilized at 90 pairs
- the increase in part due to colonisation of
our many gravel pits and reservoirs. The
presence of more, observable, stretches of
water has produced more records of Red—necked
Grebes whilst the increased Scottish breeding
success of Slavonian Grebes has led to larger
flocks (the record is 52) wintering in Essex.
Since 1970, the Dutch populations of Night
Heron, Purple Heron and Spoonbill have
increased, making these species more frequent
vagrants to Essex, whereas our own Grey Heron
has declined by 90 pairs since 1973, presumably
as a result of drainage of marsh land and loss
of feeding sites during hard winters. At
Walthamstow reservoir the breeding colony has
fallen from 128 pairs in 1981 to 72 in 1986.
In contrast, the Cormorant, which may have bred
at Wrabness in 1920 and Bures in 1937, occupied
151 nests at Abberton Reservoir in 1986. In
most of Britain the Cormorant is a cliff-nester
but the Dutch population prefers trees and
Abberton may well be a satellite colony from
Dutch "invaders".
Of our swans, the Mute has declined (as it has
nationally) whereas the Bewick Swan is seen
more often in Essex. There were just 7
records in the 19th century, yet it has
occurred annually since 1953, many Essex flocks
probably being part of groups commuting between
the Ouse Washes and Slimbridge.