Ixii 
INTRODUCTIOI^- 
seems to be by small flocks in the beginning ; though we frequently find 
that hosts of them appear, as it were instantaneously, about the latter end 
of April. The Swallow leads the van, the House- martin and the Sand- 
martin arrive next, and the Swift brings up the rear. The business of 
choosing their mates employs them a few days after their arrival. They 
assemble together, their twitterings are then loud and constant, whether 
seated or in their flight. About the middle of August, when the first 
broods have attained some strength of wing, they assemble in vast numbers, 
on trees, or on roofs of houses, towers, and other lofty buildings, crowding 
the sides most exposed to the genial warmth of the sun. A few meet at 
first at the place of rendezvous, to form the nucleus, round which numbers 
are continually collecting. They line the roof, hang pendent from the 
walls horizontally and perpendicularly, and differently from their usual 
habits. Many weeks elapse before their assemblage is complete ; but no 
time is lost in preparing themselves for their intended journey. Some are 
pruning their feathers as a preparation for flight, while others wave the 
wing, in circles round the building, in trial of its vigour and its strength ; 
now they launch into the air, and wheeling round in an extensive circuit, 
return and alight. The movement is often alternate, others supply their 
places in the atmosphere, till at once, as if obedient to a signal of com- 
mand, all the members of the colony spread their wings. These prepa- 
ratory exertions are continued commonly from twenty to thirty days, until 
they are ready to depart. On the morning of their departure their unusual 
garrulity increases, and their chirpings may be heard at a considerable 
distance. At first, some of the individuals of the wandering host begin 
the chirping, to which the others attend in silence ; but after a short period 
“ Dans un sage conseil par les chefs assemble 
Du depart general le grand jour est regie : 
II arrive ; tout part, le plus jeune peut-etre 
Demande, en regardant les lieux qui I’ont vu naitre,. 
Ouand viendra ce printemps par qui tant d’exiles 
Dans les champs paternels se verront rappeles !” 
