Christmas Bells

Christmas Bells
Christmas Bells - Blandfordia nobilis

Sunday, February 22, 2009

Dollarbirds become obvious in late summer

There have been a few Dollarbirds (Eurystomus orientalis) around the Southern Highlands over the last week.
They are not common in the region, as a summer (breeding) migrant. They nest in large hollows, typically in old Eucalypt trees. I have never seen them in Robertson. I photographed this bird near the Bong Bong Racecourse, east of Bowral.

Its population status is described in the COG "Annotated Checklist of the Birds of the ACT" as "Widespread in suitable country in small numbers. An uncommon breeding migrant." That must be right - it was based upon research done by my father, Steve Wilson!

From discussions about these birds on the Canberra Ornithologists Group on-line forum in the last few days, it seems that they become highly visible at this time of year (after breeding) - sitting on power lines, while waiting to spot a flying insect, which they fly after, and catch on the wing.

As with most aerial hunters, these birds are very alert, even when sitting still - moving their heads around, forever on the lookout for a passing insect. I made a similar comment about a Grey Goshawk last week, which did not move for more than 16 minutes, but never stopped "hunting" - looking for potential prey. Back to this Dollarbird, you will notice it has a very large eye, necessary for such challenging hunting as catching flying insects. It also has a very sharply hooked beak on the tip - "The better to eat you with, my dear" as the Wolf in the "Little Red Ridinghood" Nursery Rhyme might have said - if he had been a Dollarbird. Click to see the details of the head.Geoffrey Dabb, (who spoke at REPS two weeks ago) has just written (on the COG forum): "Yes, this is the time of year they move around. .... The distinctive shape on a powerline is very evident. In 2003 this (normal) seasonal movement gave rise to a widespread misapprehension that those numbers were caused by the fires."

This bird was once known as the "Broad-billed Roller", but these days, that name is used exclusively for a related African species. You can see how the genus got that name - from this image. The beak is very broad at the base.
The species was named by Linnaeus in 1766 - obviously from Asian specimens, as that pre-dates European settlement of Australia. The generic name means wide-mouthed, which is of course, an advantage for birds which catch insects "on the wing".
"Eurystomus
- Gk, eurus, broad; stomus, mouth, thus wide-mouthed" (Source: Birdpedia)

"Roller" is the internationally preferred name for this family of birds, which occurs in what is described as the "Old World"- Africa, Europe, and Asia. They get that name from their aerial acrobatics, as they fly up in the air, snatch a passing insect, and fly back to their perch. They have very long wings, and are powerful fliers, and are extremely agile in flight.
This species gets its "common name" (Dollarbird) from a prominent light blue patch in the wing, said to resemble the (former) "American Silver Dollar" (it looks white when the bird is in flight). A slight patch of light blue colour on the wing is just visible in this image (just lower than the powerline). As the bird flies, the patch in its wing becomes highly visible. (Click to enlarge the image.) This species is found in east Asia, Japan and northern Australia, although the birds found in Asia are regarded as different sub-species. Our Australian-breeding Dollarbirds breed in the north and east of Australia. They are apparently "common" in northern Australia. It is regarded as a "straggler" to South Australia, Tasmania, New Zealand and Lord Howe Island. Our Australian-breeding birds winter to the north of Australia in the Moluccas, Celebes, New Guinea and the Bismarck Archipelago. ("Straggler" is a term used of migratory species, which cover vast distances, and on occasions stray out of their normal range.)

As I mentioned this bird is an extremely powerful flier, and it is a full migrant in this region, meaning that it disappears from our area entirely in the non-breeding season.

5 comments:

mick said...

A very interesting post of a bird I have only seen from a distance. I know they are around here but haven't yet been in the right place at the right time.

Duncan said...

Dollarbirds get to their big old redgums on the Avon near here about October 25 every year Denis, regular as clockwork.

Denis Wilson said...

Hi Mick and Duncan.
The books refer to them being more common further north, Mick, but perhaps they don't like your local area's trees. They do need big old trees with hollows - typically Eucalypts.
Duncan, they were "regular" breeders in old Red Gums in Canberra, too. Nice to know they are such regular time keepers. Sounds like the Rufous Fantails here - similar "late" arrival.
Cheers
Denis

swampythings said...

I love seeing Dollarbirds and you've managed to capture it from some good angles Denis. Their colours are vibrant in contrast with the red bill when the light is at the right angle. We see them here feeding during the summer months but I wouldn't describe them as 'common'. I would imagine that habitat destruction would have had a big impact on suitable breeding sites.

Denis Wilson said...

Hi Barbara
They can be very colouful, but my specimen seemed a bit drab. I wondered if it was a juvenile, or moulting, or something.
In really good plumage, they are almost as pretty as their relatives the Rainbow Birds.
But as it was an unusual sighting for me, I decided to publish anyway.
I have fond memories of watching them in Canberra catching Christmas Beetles on the wing on hot summer evenings.
Cheers
Denis