10 



among migrating birds is enormous. The section dealing 

 with the light-records in the spring of 1913 will give some 

 idea of the magnitude of the migration-stream at that station, 

 while the amount of material supplied in the autumn of 1913 

 far surpasses that received from any other light with which 

 the Committee have hitherto had to deal. A summary of the 

 records will be published in the next Report. 



Considerable numbers of summer-residents appear to have 

 passed the winter in the south and west of our islands, 

 and this fact may account for a good many of the early 

 records during January, February, and the first part of 

 March. As will be seen from the Report, the weather 

 during the latter month over the area defined on p. 13 was 

 wet and accompanied by many severe gales, but the tempera- 

 ture was above the average and unusually uniform. It was 

 probably owing to this last condition, that several different 

 species of our summer-residents arrived at such early dates, 

 the numbers of the birds usually regarded as early stragglers 

 being considerable. During the remaining period of the 

 spring-migration, the weather-conditions seem to have had 

 but little effect on the progress of the movement. The 

 period covered by the migration lasted from the 6th of 

 March till the 6th of June. Up to the end of March the 

 number of arrivals was small, and the first considerable 

 increase, recorded on the 13th, coincided with a rise in the 

 general temperature. With the exception of small influxes 

 on the 23rd and 25th no increase was noted until the 31st, 

 when an alteration in the force and direction of the wind and 

 a rise in the temperature marked the arrival of large numbers 

 of migrants. Thereafter a gradual increase was apparent, 

 though a temporary lull noted on the 11th of April was 

 accompanied by a fall in the temperature. The migration 

 reached its height between the 14th of April and the 11th 

 of May. After the latter date it rapidly waned, and by 

 the 20th of May only very small numbers of birds appear to 

 have arrived on the south coast, though passage-movements 

 of some importance were still in progress in other parts of 

 the country. 



The migrations of the Swallow between the 8th of March 



