SAND M \irri N 



nearly so instantaneous or simultaneous a manner: ami this may be 

 repeated for a greater or less, r number of times. . . . At the moment 

 of each sudden exodus ;i certain number sometimes about half of 

 these sand-martins will be more or less hidden within the holes they 

 are excavating, yet out they all dart with the rest" 1 Such simul- 

 taneous movements are common to many species of birds, and have 

 yet to be explained 



It 'IB probable that the departure of a colony of sand-martins from 

 its breeding-place is a gradual one, as some broods are more forward 

 than others. It is certain that in July, instead of roosting in their 

 nesting-holes, they begin to betake themselves to the reed and osier- 

 beds to which they resorted on their arrival in the spring/ Here 

 they may be joined by other colonies, so that, toward the end of July 

 or the beginning of August, the total number may reach thousands. 

 The changes in the roost from reed-bed to nesting-place, and from the 

 latter back to the reed-bed, is well illustrated by the following record 

 kept by Mr. T. A. Coward of the arrivals and departures of sand- 

 martins from the roost at Knutsford Moor, in Cheshire : ' 



1 Hirtl- Watching, p. 824. See above, p. lift 



' Not all. Mr. Parren tella me he baa found neat* with young and frnth fgtt* in the seoomi 

 week of July. ' Fauna o/ Chrthirr. \. 1HW. 



VOL. II. 2 8 



