20 Mattingley, Cormorants in Relation to Fishes. [^^^ "j"iy 



annually inundated, and what is dry land for part of the year is 

 then covered with water. It is at this period that the large and 

 mature fishes retire from the main stream and deposit their ova 

 amongst the aquatic vegetation of the swamps. Crustacea of 

 many kinds repair also to the swamps at this time, and prey 

 upon the ova and minute fry in an appalling manner, billions 

 of either fishes' eggs or young fishes disappearing into their 

 hungry maws ; turtles, likewise, lay their eggs in the sand 

 adjacent to the swamps, so that their young, when hatched out 

 by the solar heat, can readily find their way to them and 

 banquet upon the tremendous supply of fish eggs and fry. It 

 is precisely at this period that some species of Cormorants — viz., 

 PJialacrocorax vielanolaiciis, P. sulcirostris, P. carbo, and Plotus 

 novcB-Jiollandice — nest together in rookeries in these swamps, well 

 knowing that an abundant harvest of Crustacea is to be reaped 

 from them at this time. The knowledge of this fact is a 

 necessity to them, since their energies are taxed to their utmost 

 to satisfy the voracious appetites of their young ones. At this 

 period there are no fish of suitable size, such as are commonly 

 captured by Cormorants, to be found in the swamps, with very 

 few exceptions only the large spawning adults being found. It 

 is obvious that destruction of fish by Cormorants in these 

 localities does not occur at the nesting period, Cormorants 

 disdaining the capture of the small fry when there is a plenteous 

 supply of larger-sized and more readily captured slow-moving 

 forms of life suitable as food for their young ones. Hence the 

 Cormorants at this period allow more fish to be hatched out 

 than is eaten by the adult birds throughout the balance of the 

 year when they prey upon them in their more advanced stages 

 of growth, and when they have a better chance to escape. It is 

 during the nesting period that Cormorants and their young are 

 destroyed wholesale, owing to their being more easily 

 approached at this time — a time at which their usefulness is 

 greatest. If you notice a Cormorant diving after a shoal of 

 fish in a river or in the sea you will observe that he reappears 

 many times without having achieved success. The number of 

 times he dives is out of proportion to the number of fish caught, 

 probably once in six tries being a fair average. This shows 

 that, being a bird, the Cormorant is not equal to a fish in its 

 own domain, and that only the weakest and physically unfit fish 

 are caught — fish that probably would not be competent to 

 propagate their species, or if they did so would beget a 

 decadent stock. A question simply of the survival of the fittest. 

 The Cormorant is one of those aids to nature by which her 

 balance is kept level as regards the. fishes. Cormorants have, 

 therefore, been evolved by nature for the special work of 

 eliminating those fishes which are unfit to live, and which are 

 unnecessary in her economy. Other aids are utilized by nature 



