TRANSACTIONS OF SECTION D. 505 
MONDAY, AUGUST 30, 
The following Papers were read :— 
1. Paleobiology and the Age of the Earth. By Professor 
A. B. Macatuum, F.B.S. 
2. The Pre-Nuptial Plumage in Calidris arenaria. 
By C. J. Patten, Sc.D. 
It may be well to state very briefly what led up to this investigation. 
Repeated observations on the Sanderling during its vernal migration show 
that the species occurs in varying numbers throughout the breeding-season 
on different parts of the British coast. A certain proportion of the migrants, 
pushing northward, appear to sojourn with us during the summer. These 
birds, while assuming what might easily be mistaken for the nuptial 
plumage, show no evidence that they remain to breed, for the flocks keep to 
the coasts and do not split up into pairs. Based upon the above data I have 
elsewhere put forward the hypothesis that the birds were immature (vide 
Naturalist, 1909, pp. 84, 85). Here I hope further to strengthen this 
hypothesis by direct objective evidence obtained from an examina- 
tion of the plumage-markings. The rich variegated markings of 
chestnut, brown, and black, which appear on the head, neck, breast, 
back, and wings, are found in the summer plumage in Sanderlings 
in all ages, after the first winter plumage. It is generally known as 
the nuptial plumage. When, however, the tertials of those birds which 
tarry with us till late June, July, and the beginning of August are 
examined it may be noticed that they, like the tertials of the first winter 
plumage, are relatively short, the longest not reaching to the tip of the 
fourth primary feather, the wing being folded in the natural position. By 
far the majority of Sanderling which I have collected in late spring and 
summer have short tertials, and to such plumage I give the name of 
pre-nuptial, from its close resemblance to the true nuptial plumage which 
. it precedes. But a few specimens collected towards the end of April and in 
early May, from small flocks, showed on examination to have longer tertials 
which reached halfway between the tip of the fourth and third primary, 
and in some cases almost to the tip of the third primary. Such birds I 
believe have assumed the adult nuptial plumage of the second or subsequent 
springs. This plumage follows the plumage of the second or subsequent 
winters, in which the long ashy-grey tertials are easily distinguishable from 
the darker shorter ones of the first winter plumage. With reference to the 
flocks which may be seen early in August (before the advent of the birds of 
the year), I may cite that out of a large flock which appeared on the Dublin 
coast on August 7, 1900, I secured several, all of which had short tertials ; 
moreover, the birds were very fat and in good condition, and showed no 
signs of having gone through the task of hatching and rearing a family, 
while their liveliness on the beach indicated that they were not suffering 
from migration fatigue. Such evidence tends to disprove the idea that 
these early August birds have descended from their breeding-haunts in 
northern regions. They have probably remained throughout the summer, 
but at the beginning of August have mustered into large gatherings. It 
may be added that in both pre-nuptial and true nuptial plumage there 
seems to be a considerable amount of variation in the distribution and 
intensity of the rich brick-red colouration which is so characteristic. Both 
plumages are assumed by an extensive vernal moult, involving not only the 
feathers of the upper and under-parts, but also the wing-coverts. It would 
appear, however, that the winter primaries are not shed. 
