138
THE ESSEX NATURALIST.
proceed by a direct westerly course." Dr. Clarke gives a list
of the species which follow this route, one of which is the Martin.
In the systematic list it will be seen that I make reference to
Martins steadily passing up the river, that is from east to west,
on 22 Sept., 1924. It occurred to me that this movement of the
Martin might form part of this east to west migration described
by Dr. Clarke. I do not wish to read into my observations what
is not there, but it is only by endeavouring to analyse the in-
formation that we collect that we shall be able to form con-
clusions. This isolated case, taken by itself, is of little value,
but placed side by side with further records the position might
be changed.
The great migratory movement, which takes place towards
the end of July and the earlier part of August, and is mostly
composed of Limicoline birds, but also includes Gulls, obviously
must follow a different route to that of the September north
to south migration, as large gatherings of these types of birds
make their appearance on the Essex coast. Either these birds
must come overland or follow closely the line of the coast, perhaps
both. On 2 August, 1924, there were manifest signs of a migra-
tory movement at Hamford Water. Dunlin in breeding plumage
were very numerous, Whimbrel were abundant. The Green-
shank was present in some numbers and the Green Sandpiper
was identified. There was a marked increase in the number of
Gulls, including the two Black-backs. In September all the Whim-
brel had gone, no Green Sandpipers were seen, most of the
Greenshank had moved on, and there was a distinct reduction
in the number of Dunlin. It is less easy to deal with the Gulls,
with the exception of the two Black-backs, whose numbers were
increased at the time of this July—August movement, but their
numbers did not decrease until after the end of September.
My survey of the valley, which has been confined to the Essex
side, was carried out at first by day journeys from London, but
latterly by two days' stays, with Manningtree as headquarters.
The river has been traversed from Dedham to the mouth, and
southwards along Mill Bay to the old decoy at Great Oakley ;
visits were made during all months of the year, except May,
June and October. I have included a few records obtained in
April. 1923. Altogether 106 species were identified, and follow-
ing the plan adopted in the previous notes of the series, I quote