AN ORNITHOLOGIST ON THE DANUBE. 545 



generations, herons and cormorants have nested on the tall trees of 

 the island, among the much older residents the rooks; and, though 

 the cormorants have greatly diminished in numbers since the begin- 

 ning of the sixties, they have not yet entirely disappeared. Forty 

 years ago, according to Landbeck's estimate, there nested here about 

 one thousand pairs of night-herons, two hundred and fifty pairs of 

 common herons, fifty pairs of little egrets, and a hundred pairs of 

 cormorants; but now the rooks, of which there are from fifteen 

 hundred to two thousand pairs, form the great bulk of the colony, 

 while the common herons have dwindled to about a hundred and 

 fifty, the night-herons to thirty or forty pairs, the egrets have 

 disappeared entirely, and only the cormorants remain in approxi- 

 mately the same numbers as formerly. Yet at least an echo of the 

 former life rang in our ears as we set foot on the island, and here 

 and there the forest still presents the old picture almost unchanged. 

 The various birds in such a mixed heronry appear to live in the 

 best accord, yet there is neither peace nor friendliness among them. 

 One oppresses and supports, plunders and feeds the other. The 

 herons invade the rooks' colonies to save themselves the labour of 

 nest-building; the rooks collect twigs and build their nests, and the 

 herons drive them away, that they may take forcible possession of 

 the nests, or at any rate of the building material; the cormorants 

 dispute with the herons the possession of the stolen booty, and 

 finally assume despotic authority over the entire colony. But even 

 they, thieves and robbers as they are, are plundered and robbed in 

 their turn, for the crows and kites the last being seldom absent 

 from such settlements feed themselves and their young to no 

 slight extent on the fish which the herons and cormorants have 

 brought for the sustenance of their mates and young. The first 

 meeting of the various kinds of brooding birds is hostile. Violent 

 and protracted battles are fought, and the ten times vanquished 

 renews hostilities for the eleventh time before he learns to submit 

 to the inevitable. But in time the inter-relations are better 

 adjusted, as the individual members of the colony recognize that 

 there are advantages in social life, and that there is room enough 

 for peaceable neighbours. Fighting and quarrelling never cease 



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