COMMON TERN AND BLACK-HEADED GULL. 139 



I found the Gulls first of all nesting on the low margins of 

 the triangle, their nests being built amongst the long growth of 

 sea-purslane. But at the very beginning of their efforts at 

 nidification they met with disaster, the tide coming high enough 

 to cover the nests and wash out the eggs. I found these nests 

 on May 11th, one nest already having a full clutch of three 

 eggs, another two eggs ; and perhaps a dozen more ready for 

 eggs scattered over the purslane-covered hummocks. On this 

 occasion I saw about half a dozen Terns amongst the Gulls, but 

 could not find any of their nests. Between that date and 

 May 19th a tide had covered this low ground, leaving only a few 

 traces of the more substantially made Gulls' nests, and all the 

 Gulls were scattered. But the Terns were then much more in 

 evidence — to the number of quite a hundred birds ; and a care- 

 ful search all over the higher level of the triangle resulted in 

 the finding of two nests, one containing two eggs, and the other 

 one egg. 



My next visit was on May 31st. The Terns had by then 

 made good progress. Fifteen nests were found — three with 

 single eggs, three with clutches of two, and nine with full 

 clutches of three eggs. The Black-headed Gulls were about the 

 marsh, but still showed no signs of nesting. 



On June 7th I began a system of marking the nests by 

 means of white wooden pegs — such as are used to label seed 

 patches in a garden — stuck into the ground about a yard off the 

 nest, each peg with a reference number on it. I continued to 

 do this until I stopped my observations, and thus kept a more 

 or less complete record of each nest found. I marked fifteen 

 Terns' nests in this way on June 7th. Between May 31st and 

 June 7th the Gulls had begun to nest, and I marked seven of 

 their nests on that date containing one and two eggs. 



I paid weekly visits to the colony after that, with an extra 

 visit now and again, until July 20th. During that time I 

 marked fifty-one Common Terns' nests, and thirty-five Black- 

 headed Gulls' nests. The bulk of the Terns' nests were all 

 -marked by June 28th, although I found two nests unmarked 

 as late as July 12th, which might perhaps have been over- 

 looked earlier. The last of the Gulls' nests were marked on 

 July 11th. 



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