 Great white pelicans on Dyer Island , in the Western Cape region of South Africa , were culled during the 19th century because their predation of the eggs and chicks of guano @-@ producing seabirds was seen to threaten the livelihood of the guano collectors . More recently , such predation at South African seabird colonies has impacted on the conservation of threatened seabird populations , especially crowned cormorants , Cape cormorants and bank cormorants . This has led to suggestions that pelican numbers should be controlled at vulnerable colonies . 
