Abstract
Two theodolites were used with a base line 50m long to measure the height of hovering skylarks (Alauda arvensis japonica Temm et Schl), June 11-27, 1951 almost exclusively in the afternoon, in an open field near Tokyo.The skylark usually remain, in the sky flying at the level of 80-100m (see fig. 2) discribing a nearly horizontal circular path of a diameter about 60m lore.The heights are not seemingly affected by any meteorological element-temperature, wind etc, -so long as the temperature ranges from 20 to 28°C and the wind velocity is within 5m/sec (fig. 3).However the same bird is found flying at a height scarcely exceeding 20 m high, in the Kuril Islands.It is too low in altitude to attribute it to the different variety of Alauda arvensis and such low altitude may be owing to the intense coldness of the locality. So some climatic element seem to control the hovering height to a certain extent.
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