The Philippine Journal of Science, 



]). General Biology, Ethnology and Anthropology. 



Vol. VI, No. 4, August, 1911. 



HYBRIDISM AMONG BOOBIES. 



By Dean C. Worcestee. 



On the morning of June 29, 1911, while observing the boobies on 

 Usong Island at the northern end of Tub-bataha Beef, I saw and shot 

 an extraordinarily colored individual -which had ever}- appearance of 

 being a hybrid. This led me to walk the length of the island several 

 times, carefully searching among the thousands of nesting birds for other 

 similar individuals. I found two, and I am satisfied that there were 

 no more. 



What interested me still more was to find a female Sula cyanops mated 

 with a male Sula leucogastra. The latter was in full breeding plumage 

 and his sex was conclusively proved by the color of his legs and feet 

 and of the bare skin of his head. 



The strangely matched pair had a nest to wdiich they promptly returned 

 whenever I drove them away. It contained no eggs, but this was 

 a lack which was evidently soon to be remedied ! There w^as no possible 

 doubt that the birds were mated, and it seems not improbable that the 

 three hybrid individuals observed, all of which proved to be fully adult, 

 may have been their ofiispring. - 



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