98 



F. BOURLIERE 



2^9S. , ■ I I I . , , , I 



I I I » » 



< 1 T T I I f 



Years of age 



Fig. 4. Survival curve of a cohort of common 



terns banded as chicks in 1934 in Cape Cod 



colonies (After Austin and Austin, 1956). 



Austin and Austin (1956). Adults (6,965) banded as chicks in 

 the Cape Cod colonies were subsequently trapped in the same 

 places by these ornithologists. To overcome the usual bias 

 caused by band loss in long-lived sea birds, the Austins took 

 the precaution of adding new bands to every bird wearing a 

 band it had carried eight or more years. Their results are 

 therefore more reliable than those of other observers. Fig. 4 



