CHAPTER XXXVIII 
THE “CORROS,” OR MASSING OF WILDFOWL IN 
SPRING FOR THEIR NORTHERN MIGRATION 
THe withdrawal of the wildfowl at the vernal equinox affords an 
unequalled scenic display. It forms, moreover, one of those rare 
revelations of her inner working that Nature but seldom allows 
to man. Her operations, as a rule, are essentially secretive. A 
little may be revealed, the bulk must be inferred. Here, for 
once, a vast revolution is performed in open daylight, coram 
populo—that is, if the authors and a handful of Spanish fowlers 
be accepted as representative, since no other witness is present at 
these scenes enacted in remote watery wilderness. 
Up to mid-February the daily life of the marisma continues 
as already described. From that date a new movement becomes 
perceptible—the seasonal redistribution. Daily there withdraw 
northward bands and detachments counting into thousands apiece. 
But no vacancy occurs since their places are simultaneously filled 
by corresponding arrivals from beyond the Mediterranean. 
It is at this precise epoch that there occurs the phenomenon 
of which we have spoken. 
Towards the close of February, dependent on the moon, a 
marked climatic change takes place. A period of sudden heat 
usually sets in—a sequence of warm sunny days, breathless, and 
at noontide almost suffocating. But each afternoon with flowing 
tide there arises from the sea a S.W. breeze, gentle at first and 
uncertain but gaining strength with the rising flood. 
Already, shortly before this change, the duck-tribes had 
partially relaxed their full mid-winter activities—owing to 
abundant spring growths of food-plants, had become more 
sedentary ; if not sluggish, at least reluctant to move. After 
the brief morning-flight not a wing stirred. But now, scan the 
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