ESSEX BIRD-MIGRATION.
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Denmark in May was found at Colchester in October of the same
year, and a Dunlin ringed at Rossitten, Germany, in August,
was found at Southend in December of the same year. Two
Curlews born in Sweden were recovered in Essex after the lapse
of two and four years respectively. Two Terns, either Arctic,
or Common, born in Schleswig-Holstein, one in July, 1912, and
the other in July, 1913, were recovered in Essex September, 1913.
The object of ringing birds is to obtain knowledge of their migra-
tions, but its usefulness does not end there, for we are gaining some
knowledge of the longevity of birds. There are several instances,
some have been mentioned, of Essex birds carrying the ring for
four years. A Starling was recovered after the lapse of just
under five years, and a Common Gull had been ringed nearly
six years, but the most striking case was of a Black-headed Gull,
which had been ringed in Denmark on June 25th, 1920, and
found at Tilbury on November 16th, 1929, a period of well over
nine years.
REVIEW.
We have covered much ground, and it may be well to glance
back on the condition of our knowledge of the subject. In so
far as what may be observed within the county much good
work has been done over many years and many points settled.
The dates of the departures of the migrants, however, is one
which calls for further attention ; it is difficult but not im-
possible. The second aspect of migration is that which has been
observed off the Essex coast. These movements have been
shown to be of very complex nature. Seventeen of the species
which have been observed at the light-stations are included in the
list of birds which are resident in the county. The migrations
of some of these species, particularly those of the Skylark and
Starling, reach extraordinary dimensions. The frequency of
the appearance of the name of the Kentish Knock light-vessel
is very remarkable, and it will be noticed that the greater part
of the information of the movements off the Essex coast came
from this station. These migrations were performed to and
from many points of the compass, but broadly they were from
north to south and east to west. It is the latter which is of chief
interest to us. There is no doubt as to the existence of these
great migrations. They were revealed by the investigation of
1879-1887, and if we compare the results then obtained with