VOL XIV.] NOTES. 165 



nesting-site in Delamere Forest, which he had previously 

 reported to be deserted in 1917 ; but I find from my note- 

 book that on May i8th, 1918, I saw a fair number of birds 

 and nests, at the old gullery, as well as at the new one — the 

 " submerged forest " — and again on May i8th, 1919, I saw 

 a small number of birds at the old guUery ; whether or not 

 these successfully brought up their young I cannot say. 



The decrease at their original site is, however, partly 

 explained by the formation of a third colony at the end of a 

 mere, one and a half miles from the " submerged forest " ; 

 here I first noticed them on May 18th, 1919, and was told 

 by the keeper that they had arrived two days before ; probably 

 they had been disturbed too much at their old site, but they 

 soon settled down, and on June 2nd I calculated there were 

 between fifty and one hundred pairs, many of which had eggs. 



This year (1920) the third colony seems to be well established ; 

 on May 15th they were nesting and by July 3rd a number 

 of the young were flying. A. W. Boyd. 



The Altitude of Migratory Flight. — In an interesting 

 paper in the Ibis (1920, pp. 920-936) Col. R. Meinertzhagen 

 brings together all the evidence he has been able to find on 

 this subject and shows that exact observations are few. 

 Indeed the author's own observations made with theodolites 

 and others recently made from aeroplanes are the most 

 reliable. His conclusions are that birds need not and do not 

 ascend much beyond 5,000 feet for the purposes of migration, 

 and that those met with above that height are the exception 

 rather than the rule, while the greater part of migration takes 

 place below 3,000 feet ; that nocturnal flight need not be and 

 in fact is not, higher than diurnal ; and that under normal 

 conditions difterent species travel at different altitudes. The 

 question of altitude is certainly a very important one, because 

 it is one of the factors which should help in elucidating the 

 mystery of how migrating birds find their way. Unfortunately 

 there is very great difficulty in making exact observations 

 at night, and those species which migrate at night do not as 

 a rule also perform long journeys by day. We know that 

 Carrier Pigeons are carefully trained to find their way by sight 

 and that notwithstanding many lose their way, but they are 

 descended from a species which is not a migratory one, and 

 it is not therefore reasonable to argue that migratory birds 

 find their way in the same manner. There is indeed a con- 

 siderable amount of evidence, some of which is brought 

 forward by Col. Meinertzhagen in his paper, to show that in 



