Chick Growth Patterns of Three Sympatric Tern Species on Nakhilu Island, the Persian Gulf

This study compares the chick growth patterns of the Bridled Tern (Sterna anaethetus), Greater Crested Tern (S. bergii) and Lesser Crested Tern (S. bengalensis) on Nakhilu Island, Persian Gulf, Iran in 2010 and 2011. Chicks at different ages and adults were captured and their growth parameters were measured at one-week intervals. Body weight, wing, tail, bill, tarsus and head to bill lengths of chicks measured on weekly basis were significantly different for all these three species (P<0.01). The average ratio of the fledging weight to the adult weight was 1.01 for Bridled Tern, 0.85 for Lesser Crested Tern and 0.96 for Greater Crested Tern. Regarding the complex effect of growth parameters, the growth rate of the Bridled Tern has discriminately been increased from the third week while for the Greater and Lesser Crested terns it increased from the fourth week. However, adults and the last week chicks had not showed significant difference of growth parameters (P>0.05). The study result supports the hypothesis that the growth rate represents an optimum balance between the low energy requirements and short development period of terns.