18 
Introduction: 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-grounds; 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, pp. 122, 150, 159) are common, and 
the food-supply 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. 
Monsoojis of the East Indian Archipelago. — In consequence of the superior- 
power of the sun about the equator, the heated atmos|)here 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 
(cf. Maury, Phys. Geogr. Sea, IT^ 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 Archipelago. 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 Hemisphere 
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 
1) “L’ete de Pekin, qui est sous le quarantieme degre de latitude, donne une moyenne de chaleurs egale a 
celle du Caire (30° lat.), et son hiver, une moyenne de froids egale de celle d'Upsal (60° lat.)” (David, N. Arch, du 
Mus. 2e ser., 1885, YlJl, 5). 
