J^ Inti-oduction : Seasons and Winds. 



batrachians hibernate; consequently, most insectivorous, granivorous and other 

 birds betake themselves at this season to warmer latitudes, the majority invad- 

 ing the countries and islands of the tropics, where specimens often fall to the 

 gun or blow -pipe of the collector, sometimes to be named as new species or 

 subspecies by learned ornithologists at home. Amongst the endemic birds of 

 tropical countries, such as the East Indian Islands, periodic wanderings across 

 the sea are very rare (though not unknown amongst certain Pigeons); the birds 

 do not as a rule shift their quarters in an extensive manner, for they have not 

 far to go to find the needed food, since one side of an island often has its dry 

 season when the other has its wet one, and the highlands in general an entirely 

 different climate from that of the districts near the sea-shore or the plains. 

 Birds, therefore, need not cross the sea to find new feeding-gi'ounds; it is 

 probable however that local movements, depending upon the ripening of certain 

 fruits or blossoming of flowers (see, for instance in the text, Meyer's obser- 

 vations on some small Parrots in Celebes, pji. 122, 150, 159) are common, and 

 the food-sujjply seems to be regulated by the season. The seasons are determined 

 in the East Indies by the monsoons, the monsoons themselves by the position 

 of the sun over the greater masses of land. 



Monsoons of the East Indian Archipelago. — In consequence of the superior 

 power of the sun about the equator, the heated atmosphere there rises, and 

 an indraught of the cooler air from the north and the south flows in to supply 

 its place, taking the form of N.E. and S.E., instead of due North and South, 

 winds, owing to the rotation of the earth. These are the Trade-winds, which 

 blow with a general regularity from year's end to year's end over most of the 

 Pacific and over parts of the other great Oceans. The return of the rising 

 equatorial air through higher strata towards the north and south, its meeting 

 in the upper atmosphere with high N.E. and S.E. Trade-winds blowing from the 

 Poles, their stopping one another, piling up and descending to the globe about 

 lat. 30° — 35" N. and S., giving rise to a high barometer and zones of calms 

 icf. Maury, Phys. Geogx. Sea, 14"' ed. 1869 p. 80), the starting from these belts 

 of the true Trade-winds and of low winds returning towards the Poles, are questions 

 upon which the meteorologist may be consulted, but which need not further 

 concern the weather-chart of the Ai'chipelago. Here, there are four principal 

 winds, two north of the equator and two south of it, which blow alternately 

 throughout the year generally speaking without much interruption, except at 

 the periods of the shifting of the winds, the N.E. and S.E., which blow each for 

 about half a year, when they are displaced by other winds, the true Monsoons. 



The South-west Monsoon. — When the sun in the Northern Hemis))here 

 draws towards the Tropic of Cancer (our summer), the plains and table-lands 

 of Asia become greatly heated'), and the N.E. Trade-wind, instead of continuing 



'j "L'ete de Pckin, qui est sous le quarantieme degre de latitude, doime unc moyenne de chaleurs egale a 

 celle du Caii-e (30" lat.), et son hiver, une moyenne de froids egale de celle d'Upsal 60° lat.;" iDavid, N. Arch, du 

 Mus. ■2<^ sir., 1885, Vm, 5). 



