30 Coward, Fauna I Survey of Rostheme Mere. 



The Lesser Tern is 

 Sterna minuta niinuta Linnaeus, not so frequently- 

 met with inland as 

 the two larger birds, and one which was feeding over the 

 mere on July ist, 191 3, was probably a wanderer from 

 the estuary and not a passing migrant. 



The Blackheaded Gull 

 Lams ridibundus Linnaeus, has, within late years, 



become an almost regu- 

 lar Rostherne bird ; it is even present in small numbers 

 during the nesting season, but there is no evidence that it 

 has nested near the mere. Most if not all the birds which 

 frequent the water in April and May are immature. On 

 April 4th, 1910, we saw a pair of mature birds repeatedly 

 stoop at a Heron which was standing on one of the moor- 

 ing stumps ; their angry cries resembled those of breeding 

 birds when attempting to drive intruders from the neigh- 

 bourhood of the nest. After the breeding season is over 

 young birds of the year appear with the adults and begin 

 to roost nightly on the water ; as autumn advances the 

 number of birds which come in every evening increases, 

 and it reaches its maximum in the winter. From 

 December to February there are usually several hundred 

 gathered at dusk in a dense flock in the centre of the 

 mere. The birds arrive from all directions, but the largest 

 number come from the north and north-west ; those also 

 which have been feeding on Tatton Mere during the day 

 leave in a body in the afternoon and join the congregation 

 at Rostherne. The birds straggle in for several hours in 

 the afternoon ; they arrive singly or in large or small 

 parties, often flying in chevron formation. On the after- 

 noon of February i6th, 191 4, we estimated that there 

 were between 600 and 1,000 Blackheads on the water at 

 about 4-30 p.m., and others were arriving. At the end of 



