About Lemon-bellied Flyrobin

Habitat

Diet

Distribution

Life Cycle

Nest

First is that its nest is the smallest of all Australian birds. The nest is tiny and blends in with the tree fork in which it is built. Without the bird sitting on it, it is difficult to spot the nest at all. As can be seen in the photos, the nest is a tiny shallow rim of fine strips of bark and grass, tightly bound with spiders’ webs. Pieces of bark on the outside help it blend in to the tree limb so that it is well camouflaged. There is plenty of room for the mother and egg/chick until the later stages of brooding (11-12 days) when the mother struggles to find room.

Egg

Yes, egg, not eggs, as only one is laid. At 18% of the female’s body weight, the egg is enormous for a passerine. The female incubates the egg without the help of the male. It has been observed that she spends very little time on the nest during the heat of the day but more in the earlier and later part of the day. Where other female brooding insectivorous species spend an average of about 65% of the day brooding, this species spends an average of only 30% of the time on the nest. It may be assumed that this is possible only because of the consistently warm temperatures in the birds range during its breeding seasons. Of the seven Australian passerines that lay a single egg per clutch, only two are tree-nesters (Cicadabird and Varied Triller).

Breeding Seasons

While only one egg per clutch is laid, and only one brood per season, the Lemon-bellied Flyrobin has two distinct breeding seasons. The first is March/April and the second starts in August. Our bird times it well, as the breeding seasons sit between the coolest months and the wettest months and coincide with peak flying insects in the mangroves where they often nest. Cooperative breeding behaviour has been observed, with help provided by likely offspring from previous broods.

The incubation period is about 14 days, brooding 11-12 days and the birds fledge 18-21 days after hatching.

Courtship

Lemon-bellied Flyrobins are monomorphic and monochromatic, but the observer can distinguish the sexes by their behaviour. In studies involving banding, it has been established that females incubate the eggs unassisted by the male. Males show their attentiveness in other ways. While females sing simple phrases typical of the species, males take it up several notches with improvisation and mimicry. In their pre-dawn song, they blast out a dozen or more phrases per minute, for around 15 minutes, equating to 160-250 little bursts of song. His calls can be heard 100-150 metres away. Then after sun rise, the male adds aerial choreography to the mix. He launches into the air singing, slowly rising 15-40 metres in wide spirals then in tight circles for 1-3 minutes, still singing, then drops down to a favourite perch at the top of a prominent tree, and sings some more. This can happen at any time of the day and takes place at the peak of the breeding seasons. (No wonder he doesn’t have time to help with incubation, though the male will help with feeding.)  

As with many Australian passerines, male Lemon-bellied Flyrobins are accomplished mimickers. They have been heard imitating Beach Stone-curlews, Grey-tailed Tattlers, Figbirds and Mistletoebirds. I have seen a male at the top of his tree belting out the harsh metallic sounds of a Spangled Drongo. It lacked the depth and volume of the Drongo but the rendition was unmistakeable. The female must have been very impressed, I was!

Success

The Lemon-bellied Flyrobins breeding cycle shows the bird has a style that is very unique. Is it successful? In terms of its relative abundance within the many habitats it chooses to live in, the answer is definitely yes! At risk of sounding anthropomorphic, this bold little bird likes to be seen and heard. It will approach human observers and follow them. My theory is that it knows we attract flies and is hoping for a feeding opportunity.

*Nominate species occurs in NT, two other sub species exist, some with variations to the behaviour discussed here.

Sources - Research on Darwin Lemon-bellied Flyrobins by Dr Richard Noske published in Wingspan Summer 2011 and personal observations.