 The greater crested tern has a widespread distribution range , estimated at 1 – 10 million square kilometres ( 0 @.@ 4 – 3 @.@ 8 million square miles ) . The population has not been quantified , but it is not believed to approach the thresholds for either the size criterion ( fewer than 10 @,@ 000 mature individuals ) or the population decline criterion ( declining more than 30 % in ten years or three generations ) of the IUCN Red List . For these reasons , the species is evaluated as being of Least Concern at the global level . However , there are concerns for populations in some areas such as the Gulf of Thailand where the species no longer breeds , and in Indonesia where egg harvesting has caused declines . 
