Two photographs of the male. The male is distinguished by his black
collar feathers. In fact, in good light, up close, the feathers appear
slightly steely blue. The female, by contrast, has yellow collar feathers.
I don't have any really good photographs of the female. I apologize for
the horizontal lines across the second photograph.
A visitor to the nesting site. When the chicks were almost ready
to leave, some other sunbirds came to visit the nesting site. The even
tried to steal some of the nesting material and enter the nest. They could
not steal the nesting material, since by that time, the top of the nest
was attached to the line with sticky tape. See the Sunbird
Letters page for details. They could not enter the nest because the
chicks inside rejected them.
Notice the collar feathers of the visitor, that they are not as
black as the male's. This leads me to suspect that the dark collar appears
after the chicks have left the nest, so that it is impossible to determine
the gender of a baby bird still in the nest.