Partitioning of parental care in the leaden flycatcher

Leaden Flycatchers Myiagra rubecula are sexually dichromatic spring and sum mer visitors to south-eastern Australia. Twelve pairs were observed for 661 hours throughout the 1993-94 breeding season. These pairs made repeated ne sting attempts, due to a high failure rate (young fledged from only 23% of nests that received eggs). Investment by male and female parents wits very similar at all stages of nesting, though females contributed slightly more to incubation (55% of time) and brooding of nestlings (58% of time) and inc ubated eggs and brooded nestlings overnight. The pattern of parental invest ment is similar to that shown by the Willie Wagtail Rhipidura leucophrys, a sedentary, sexually monochromatic flycatcher. We suggest that parental inv estment is so similar between the sexes in these flycatchers because the ve ry low breeding success means that the potential benefits of seeking extra- pair copulations by males will be lower than the benefits of investing in t he few nests that reach the later stages of breeding.