Cape Town - Fine feathers do make fine birds, according to researchers at Stellenbosch University. "The bright white feathers of the male ostrich may be one of the best indicators of faster-growing and healthier chicks," they said in a statement on Monday. The team, of the university's department of botany and zoology, has been investigating why ostrich chicks vary so greatly in size, hoping to find answers to the high chick mortality rate within the first three months after hatching. "With ostrich chick mortalities of between 10 and 50%, one of the greatest challenges facing ostrich farmers is raising chicks that will survive beyond the first three months." Bird and animal behaviour specialist Prof Michael Cherry says female ostriches appear to prefer males with bright plumage. "Having bright plumage comes at a cost, so only the fittest males can afford to have both a strong immune system and bright feathers. "At the same time, females might prefer bright males because they are better able to resist disease and pass on to their offspring copies of genes for resistance."