274 
W. BICKERTON-NOTES ON BIRDS 
develop unusual tastes in the way of nesting-sites. Dr. Langston 
Day (Baldock), however, reports the following very unusual 
circumstance:—“In a large wooded garden in Stevenage, a small 
nesting-box is placed against a tree, four feet from the ground, 
and this year a pair of willow-wrens nested in it.” 
Wood-Wren (Phylloscopus sibilatrix ).—I am glad to state 
that this year I have received more notices of the presence of 
this rather rare little warbler than ever before, so I hope this 
points to the fact that it is increasing its range and its numbers 
in the county. Mr. Headley reports wood-warblers as rather 
more plentiful; Mr. Oldham has heard them in rather larger 
numbers in the Aldbury district, and I am glad to say that 
I have again heard the bird singing in a private wood near 
Watford, in June. I tried hard to find the nest, but without 
success. During the past two years I have now heard the birds 
in three different localities near Watford, whereas in the previous 
nine years I had never heard a single bird in the district. 
Keed-Warbler (Acrocephalus streperus ).—That this continues 
to be a very local, if not rare, bird in Hertfordshire is shown by 
the fact that I scarcely ever hear of it except from Tring, and 
from the Lea Valley (Hertford), where Mr. Headley reports 
a nest having been found this year. There is, of course, my 
own little colony near Watford, and I am strongly inclined to 
believe that this is actually the largest colony of the species in 
the county. In my last report I referred at length to my 
observations on the Watford birds, and I think I showed 
conclusively: (1) That while the majority of the birds sling 
their nests like so many cradles to the reeds, a fair number 
attach them to the twigs of trees. (2) That the cuckoo is 
very largely parasitic on the reed-warbler, and deposits its eggs 
both in reed-nests and tree-nests. (3) That new nests of this 
species may be found from about the third week in May to the 
third week in July, and that the later nests are mostly those 
built in trees. I have again continued, with increased interest, 
to watch the doings of these birds during the past season, and 
the conclusions as stated above have been fully confirmed. By 
way of reminder, I may perhaps state that during 1909 I found 
in all twenty-one reed-warblers’ nests, of which fifteen were 
built in the reed-beds and six in trees adjacent to, or not very 
far away from, them; that of the sixteen nests whose contents 
I was able to examine, seven contained each one cuckoo’s egg, 
three of the seven being tree-nests, and the remaining four 
reed-nests. This year has proved, on account of the weather, 
much less favourable than last year for these birds, some of 
which I first found back in their old haunts on April 21st. 
I did not find any traces of a nest until May 17th, and this was 
in the reeds. Between that date and August 4th I continued to 
find additional nests to the number of sixteen in all, and of 
these, eleven were built in the reeds and five in the trees, and 
the whole of these were suspended either from the reeds or from 
