120 



absent the day before. Tbeir departure was siinibir. On April II, 

 17, 27 and May 1, the less vagrant sniumer resident l'ro(jne was the 

 only Swallow remaining of the motley companies of the day before. 

 In other years this mode of migration has been just as marked; in 

 1!)02. two species arrived together on the fifth of April and three on 

 the thirteenth; and in 1SS5. four species, the Bank, Tree, Barn and 

 Cliff SwalloAvs arrived in one flock on the 15th of April, and were 

 seen together again on the next day. Tree and Cliff Swallows became 

 common on the 22d, the Barn Swallow a day before, and on the 25th 

 the Bank and Roughwinged Swallows became common. 



A more detailed discussion of the migration of the Hirundinidce 

 in 1903, will bring out another point, i. e., the relation of weather con- 

 ditions to the pliases of the migratory movement. 



From April 10, the date when three species had arrived, to May 3, 

 inclusive, when the last flock of migrants was seen, there were just 

 fifteen cloudy or rainy days, with an average temperature of 47° at 5 

 a. m., and ten clear days with a temperature of 44.° Swallows, some- 

 times, with the exception of the Purple Martin, were absent [three spec- 

 imens of Hirundo seen one day and two of Petrochelidon another] during 

 the ten days, and were very much in evidence fifteen days. South winds 

 prevailed during this period and migration was high among all the small 

 land birds, especially on the 28th and 29th; but on these dates no fiocks 

 of swallows were seen. If a clear or partly clear period was succeeded by 

 a rainy, cloudy, or misty one, swallows were surely to be found. 

 As long as the Aveather remained cloudy, these birds remained, but on 

 the first fair day they disappeared. The only species that arrived on a 

 clear day was the Tree Swallow; but after its arrival its movements 

 agreed with those of its cousins. There was only one cloudy day on 

 which the crowds of swallows were absent and even that day brought 

 an increase in the number of Martins. 



A synopsis of the period follows: April 10, cloudy, 3 species; April 11, 

 cloudy, an increase in number of Purple Martins; April 12, fair, no Swal- 

 lows (Martin ignored); April 13-16, inclusive, cloudy and rainy, all species 

 present; April 17-18, clear, no Swallows; 19-25, inclusive, cloudy or rainy, 

 all species present in considerable numbers; 26-29, fair, few Swallows 

 seen and their number decreased during this period; April 30, cloudy, 

 a large flock of four kinds; May 1-2, clear, no Swallows; May 3, rainy, a 



9— A. OF SCIENCK, '04. 



