ON THE NEST AND EGGS OF THE COMMON TEEIN 
{S. FLUVIATILIS). A COOPERATIVE STUDY. 
W. ROWAN, E. WOLFF, and the late P. L. SULMAN, Field v.orkers. 
K. PEARSON, Reporter. 
E. ISAACS, E. M. ELDERTON, and M. TILDESLEY, 
Tabulators and Computers. 
(1 ) Origin of the Material and Method of Measurement. 
This paper may be looked upon as a continuation of that published in Biometrika, 
Vol. X. pp. 144 — 168. It is based upon a census of the eggs made July 3rd — 20th, 
1914, and contained in Rowan's Fifth MS. Report on the Faunistics of Blakeney Point, 
the Field Station under Professor F. W. Oliver's direction on the Norfolk coast. The 
year was a record year for the common tern, a marked contrast to 1913, the young 
were abundant as well as the eggs, and many of the birds were still laying. Some 
peculiar nests were found : (a) one entirely of seaweed, {h) another of large wood 
shaving.s, (c) one of selected small pebbles, (d) a very large nest— the largest yet met 
with. Some of the nests are illustrated in Plate II and will suffice to indicate the con- 
siderable differences between their make up and environment*. The range of ground 
colour with extent and distribution of mottling are indicated in Plate III, which 
should be taken in conjunction with Plate VIII of the earlier paper. There is 
every reason to believe that the two clutches, each of three eggs, were in both cases 
due to a single bird ; the seventh egg, from a one-egg clutch, represents a peculiar egg 
found in the examination of this year's material. In all 515 clutches were recorded 
as against 203 in 1913. In that year there were 13 clutches with 3 eggs each ; in 
1914 there were 198, and many of those with one or two eggs at the time had also one 
or two newly hatched chicks, bringing the total up to chree. Even the nests with 
one egg (122 as compared with 119 in 1913) were actually nests with the first egg 
only of the clutch, for the birds were still laying, while most of the one-egg 
clutches in 1913 were either deserted or the egg addled. 
Plate IV gives some further photographs taken of the Ternery. Fig. a is an 
attempt to catch the bird alighting in order to indicate the great length of the 
* The following illustrates a method of nest building, that of nest (</) above. "A common tern laid 
close to the observation tent. At first there was no material whatever. But on the same day a few of 
the Psamma leaves from the tent were taken and deposited round the egg. The next day another egg 
was laid and more stuff was added. None of the Psamma had then been broken and the leaves radiated 
from the centre in all directions. On the second day the first few were broken and tucked neatly in 
all round. Then a third egg was deposited. More pieces of Psamma were added and the nest then had 
a very ragged appearance. It took two more days before the nest was completed and tidied up. " 
