Shining Flycatcher Switch

Explanation: One of these things is actually just like the other. This is a pair of Shining Flycatchers, the dark male on the left sitting on the tiny nest, and the female on the right, coming in to relieve her mate from nest-tending duties.

This is a rather remarkable case of sexual dimorphism, where different sexes of the same species look utterly unalike. Sexual dimorphism is not uncommon in the animal world, but this species exhibits it to quite a high degree. As to how and why this evolved seems to be unstudied, and perhaps may be difficult to impossible to unravel.

But, back to the story. Both sexes incubate their clutch of tiny eggs. The female here, likely out feeding on insects, has returned and is taking over. It is the switch.

Watch the following video I shot of how incredibly careful she is in approaching and inspecting the nest, before settling in. She may be inspecting for viability of the eggs, maybe if one has hatched, perhaps to see if any insect predators or parasites are present, perhaps to see if an avian "nest parasite" has laid its egg in her nest as they do, or other reasons.

Male Shining Flycatcher on watch.

We are in a native forest at Manton Dam Recreation Area
near the town of Palmerston in the northern "Top End" portion
of Northern Territory, Australia. It is early October,
springtime in the southern hemisphere here, and breeding season.

Shining Flycatchers are found mostly in Australia,
but also in Indonesia.

Male on the nest, good boy.

Female on the nest, good girl.

Note the orange-red "gape" (inside of the mouth).
This might serve as a signal device to express aggression, mate
signaling, or other behaviors. Here, she is briefly engaged in
"gular fluttering" or quick breathing, to cool her down
after being out hunting.

Information:
Shine, R. 1989. Ecological causes for the evolution of sexual dimorphism: a review of the evidence. The Quarterly Review of Biology 64(4):419-461.

EPOW - Ecology Picture of the Week