Page:Popular Science Monthly Volume 76.djvu/406

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402
THE POPULAR SCIENCE MONTHLY.
 

PSM V76 D406 Noddy gulls nesting on bird key tortugas.png

Fig. 5. Noddy Gulls nesting on Bird Key., Tortugas.

 

so doing is quite shy, but if an egg be placed in the nest the mere sight of it causes the bird to lose all shyness, and it sits upon the egg as if it were its own. Both male and female cooperate to build the nest, but the male alone procures food for both during this period, the female constantly guarding the nest. After the egg is laid, both male and female fly away to fish and take their turns in brooding the egg at intervals of about two hours. The egg hatches after 32 to 35 days. But the noddy gull does not recognize its own egg, but will readily incubate the egg of the sooty tern or any object colored or uncolored bearing more or less resemblance to an egg. It recognizes the locality of its nest however, and returns to the old locality if the nest be moved, but it will accept an artificial nest placed in the old nest locality without hesitation. Dyeing one of the mates in strange colors causes the undyed bird to attack it, and indeed all other birds upon the island displayed excitement at the appearance of a dyed bird.

The sooty tern nests upon the ground, and recognizes the exact lo-