Owlet Nightjar

It's not often that we see a night-bird, which usually roosts in a hole by day, out in the open. So this little bird, an Owlet Nightjar Aegotheles chrisoptus, surprised me when it flew up into a tree in front of me. Seemingly from nowhere.

The bird did not seem sure what to do next and it gave me a good look, watching me as if to determine whether I was a threat to it or not. It did not seem to think so, probably because I had not moved or chased after it.

This is where the bird had flown from, inside the hollow heartwood of this long-ago felled tree stump. The hole was straight down from the top and about 40 cm deep. That is rather low and shallow for an Owlet Nightjar to roost in, so I think it was a young bird of the year, now out on its own to find a territory with food and suitable tree holes to roost in, and nest in next year. It probably felt vulnerable in the small hollow and could see me walk past through the cracks in the timber. I do usually check such sites for animals, and I probably would have discovered it, so it did the right thing.

This is the habitat the stump was in, old farmland, partially cleared for grazing, which is now part of  the nature reserve network in Canberra. Owlet Nightjars hunt invertebrates at night, mostly on the ground, and the leaf litter around the stump would be good habitat for them. However the taller grass would not be so good as the birds can't see their prey so easily, nor land and walk about in tall grass - they have short legs.

I walked past the nightjar, on the far side of the bird from the stump. That way, if it was hoping to go back to its hole to continue its daytime roost it would be less likely to think that I would follow it. And I did not go back to check it, to find out if it had. If I had done so then I would have flushed it twice from its precious home and so might abandon it. It might not be the perfect home for an Owlet Nightjar, but it might have been all it had for now.

Most daytime views of Owlet Nightjars are of faces peering from roost holes. To see this one completely out, was a special occasion. But I do wonder, why do they have such long nasal bristles.

Mist-netting birds

Owlet Nightjar Aegotheles cristatus

I was out mist-netting birds last weekend at The Charcoal Tank Nature Reserve, New South Wales, on a trip organised by Mark Clayton. The aim is to catch a sample of birds several times a year as part of a long-term study of the changes in the numbers and species in the bird population. The nets were set the evening before and opened at first light, hence we caught this nocturnal bird, an Owlet Nightjar. This is the first I have seen caught in almost-daylight. Perhaps it had been feeding late because it was a cold night at the end of winter and there were few insects about.

Small, quiet, with big dark brown eyes, a long tail, and dark grey plumage
- all ideal for a nocturnal woodland bird

Owlet Nightjars are neither owls nor nightjars, they are classed in a family of their own, Aegothelidae. They roost by day in tree hollows and hunt at night, feeding on invertebrates, mostly insects, which they can catch in flight although they spend much time foraging on the ground. They are small dainty birds, only about 50g in weight, and they have a soft plumage similar to owls and frogmouths, for quiet flight.

Horsfield's Bronze-Cuckoo Chalcites basalis
  - the broad dark stripe over its ear coverts and the scalloped,
 buff tips to the wing coverts are diagnostic markings of the species. 

As the day opened up we heard four species of cuckoo calling: Pallid Cacomantis pallidus, Fan-tailed C. flabelliformis, Shining Bronze-Cuckoo Chalcites lucidus and this one, Horsfield's Bronze-cuckoo. We caught four of this last species and all were males, indicative of how male cuckoos, and many other species of birds, tend to migrate to their breeding grounds ahead of the females. The tail patterns, both topside and underneath, are diagnostic of the species' sex - the females have russet colouring on the outer tail feathers, the males, like this one, have black and white outer feathers.

     Top-side of Horsfield's Bronze-Cuckoo's tail     

    Underside of tail

We caught a good number of regular breeding birds of the area especially White-plumed Honeyeater Ptilotula penicillata and White-eared Honeyeaters Nesoptilotis leucotis for comparisons of biometrics. Our sample included a good mix of species; some resident, some returning to breed and some migrants passing through. There were examples of two races of Silvereye, Zosterops lateralis; the local Z.l. westernensis and the migrant Z.l. ochrochorous which breeds on King Island in the Bass Strait. We also caught fifteen Striated Pardalotes Pardalotus striatus at once in one net and there were three races in that flock; P.s. striatus which breeds in Tasmania, P.s. substriatus which breeds in the interior of the continent and P.s. ornatus which breeds in the south-east.

Z.l.ochrochrous

Z.l. westernensis 

                       

Z.l.w. Rufous flanks

Z.l.o. Tawny flanks

Z.l.w. Yellow throat

Z.l.o. White throat with yellow flecks

Perhaps, the most spectacular bird we caught was a male Brown Goshawk Accipiter fasciatus in full breeding plumage. Accipiters are aggressive and can inflict cuts with their bills and talons, so great care is necessary when handling them. This powerful predatory bird was such a contrast from the docile Owlet Nightjar we began the day with.

The talons are grasped firmly and the head held up away from our hands.
The whole bird is kept well away from our faces.

The bird had clean, slate-blue upper coverts and head. Its breast and underwing coverts were solidly barred.
All its flight feathers were complete, no moult.

The rounded tail is one of the better features to look out for if in doubt whether a bird seen is a
Brown Goshawk or a Collared Sparrowhawk Accipiter cirrocephalus, which has a square-ended tail.

The bright yellow eyes of an Accipiter - a determined hunter.

Note the heavy eyebrows, these shield the eyes, not only from sunshine, but against twigs and leaves when a goshawk crashes through thick vegetation in pursuit of its prey. The brows are unfeathered and the skin shows signs of abrasion. One of the honeyeaters we caught had a 4mm long thorn stuck in the skin on its crown, an example of what birds have to contend with when flying through woodland. I pulled the thorn out cleanly and the honeyeater flew off happily.

All the birds we caught flew off back into the bush. No animals were harmed in the making of this blog. 

Owlet nightjar

The weather is warming up now with a predicted high of 35 degrees tomorrow. The cicadas are singing loudly, very loudly, and most of the birds have fledged their young. Two late frogmouth nesting attempts have failed. I suspect the eggs were infertile as the birds had been sitting on them for longer than the usual incubation period with no sign of chicks hatching. There are chicks in two other nests and one pair are sitting on their third clutch of eggs having failed to rear chicks from two earlier attempts.

While checking one of these nests, I walked past a tree where Anthony had owlet nightjars last month. And there was a bird sitting at the entrance to one of the holes. It ducked back a little more into the hole as I approached, but stayed there looking out. These birds favour trees with multiple holes or with other suitable holes in trees within fifty or a hundred metres. If flushed by a predator they dart from one to another, with a confidence that says they know exactly where they are going.

I left this bird at peace and wondered at its plumage and posture. The big black eyes look so like knot holes in the tree and the stripes on its head blend well with the crack lines. Perfect camouflage. Or have they adapted a plumage pattern similar to that of sugar gliders which are common in the same habitat, and so gain benefit of less predation. The central stripe over the head, round face and large eyes all fit. Perhaps potential predators are less likely to attack a glider, e.g. a sparrowhawk which only take birds.