Last week, my brother and I were fortunate to see (briefly) a pure white White Goshawk fly out from the ridge to the east, and then do a circuit, before being attacked by the resident Magpie clan. They really behave like "bovver-boys".
Technically, this is not a new species for me, as the "experts" regard this bird as a white "morph" of the Grey Goshawk (Accipiter novaehollandiae) which is an occasional visitor here, from the dense rainforest below the escarpment (only a few minutes flying time away).
At first, we thought it might have been a White Cockatoo, but the Magpies do not bother to harass the Cockies. plus, Cockies seldom fly by themselves.
Later in that afternoon, in warm sunny weather, Brendan asked me what bird was calling. A gentle, high pitched trilling call, descending gently. At first I thought it could only be an Eastern Spinebill, but then I realised it was not giving the fast repetitive trill which Spinebills give. I suggested possible a Scarlet Honeyeater, and Brendan immediately replied: "Of course". What he did not know was that it is a new bird for me here. He is quite familiar with them from the moist gullies in the far South Coast. For me, I was going back to last New Year's Day when I heard many of them calling high in the Eucalypt trees when searching for Christmas Orchids, south from Ulladulla, also on the South Coast.
The Scarlet Honeyeater is on the bird lists from the Barren Grounds, approximately 15 Kms from here (presumably from the rainforest patches there, not from the Heathlands). But this was my first record. Although only an auditory record, as there were two observers present, and we both agreed with the ID, I am prepared to put it down on my list.
Other birds have been as per normal for a long, warm Autumn. The migrating Yellow-faced Honeyeaters and White-naped Honeyeaters have been passing through. Their passage had appeared to dwindle (in numbers) over the previous week, when it was very cold, but the last few days of warmer weather has seen the numbers pick up again. The ratio of Yellow-faceds and White-napes has reversed now (finally). This is expected, as the YFHEs always move first, and the WNHEs come though later.
Today I saw several flocks of 30 or more birds pass through, and they were predominantly White-napes. Their in-flight calls are totally distinctive, and these species, and their migratory habits are very familiar to me, as I grew up banding hundreds of these birds with my father, every autumn, during the years of huge migrations from the Brindabella Ranges, west of Canberra. I found many hundreds of these migrating birds in the Budawangs, last year, near Tianjara Falls.
Christmas Bells
Christmas Bells - Blandfordia nobilis
Showing posts with label Migration. Show all posts
Showing posts with label Migration. Show all posts
Monday, May 10, 2010
Sunday, January 24, 2010
Bar-tailed Godwit from Alaska visits Tuross, NSW
What I am about to write here is probably not news to some of our keen "Wader Studies" participants (and Bloggers) namely Mick, from Sandy Straits and Beyond, and Duncan (from Ben Cruachan) and Gouldiae. They all report periodically on Wader studies they participate in. Mick reports on such outings very frequently indeed, frequently on Bar-tailed Godwits.
Today I am writing about the migrations of several specific Bar-tailed Godwits (Limosa lapponica).
Interestingly, Sebastian wrote about the flexibility of the beaks of these birds, which use their long beaks to probe into wet sand, to find Marine worms and other tiny marine creatures. And several days ago he reported on them feeding on grass, on The Esplanade at Cairns.
Another Blogger, Steve Happ has also written about a"flagged" Godwit from New Zealand
So, many of my Blogging colleagues know about Godwits. So this might not be news to them - but it is to me. Hopefully some of you will find it of interest too. To me, these journeys sounds a positively "heroic".
I have today posted two messages on the Canberra Ornithologists Group "Chat Line". My brother, Brendan, who lives at Dalmeny, has sent me this interesting report of an article in the "Narooma News" about a Bar-tailed Godwit (a migratory "Wader" bird) which seemingly has been flagged with a clearly visible marker code indicating it was banded in Alaska.
Brendan says: There is a story (and photo) in the Narooma News this week.
A Bar-tailed Godwit banded "flagged" with a tag that can be read without capturing the bird. I take it the flags are not individual but are a batch number - P1 black with white letters. It is quite clear in the photo.
******
Details of the bird's history are as follows:
Banded at Punoaray Point - Yukon-Kuskokwim Delta - Alaska on 9th September 2009
Identified 21st November 2009 - Tuross estuary
January 12th 2001 still at Tuross.
11,500k in 10 weeks.
*****
Brendan then asks: More significantly is this the "normal" north south migration? Has it gone across the pacific - or maybe across the top end of the pacific and then south. (I have looked on the electronic version of the Narooma News, but it has not rated an electronic entry.)
*****
The following report might help answer some of the questions which Brendan was hinting at - which way do the migrating Godwits go: (a) around the top of the Pacific or (b) directly across it?
I have located the following report from the Alaska Science Centre (part of the USGS - i.e., their "Geological Survey" Department) which provides a likely answer:
"We used satellite telemetry to follow the migrations of two populations of Bar-tailed Godwits, a group of 9 from New Zealand (NZ) and a group of 15 from Western Australia (WA). The birds from WA represent a subspecies that nests in eastern Siberia whereas the New Zealand birds nest in Alaska."
Map of the basic migratory route of Bar-tailed Godwits
from north-west Australia to Asia.
This represents the largest population of
migratory Godwits visiting Australia
There is a special report on one particular individual bird (E7) which took the "short cut" non-stop directly across the Pacific from Alaska to New Zealand. She flew for 9 days, non-stop.
* "On the early morning of August 29, she took off southeast back across the Alaska Peninsula, went out over the vast North Pacific and headed towards the Hawaiian Islands. When less than a day's flight from the main Hawaiian Islands, she turned southwest, crossing the Hawaiian Archipelago over open ocean 125 miles west of Kauai, heading towards Fiji. She crossed the dateline about 300 miles north-northeast of Fiji, and then appeared to fly directly over or slightly west of Fiji, continuing south towards New Zealand.
* "In the early afternoon of September 7th she passed just offshore of North Cape, New Zealand, and then turned back southeast, making landfall in the late evening at the mouth of a small river, eight miles east of where she had been captured seven months earlier." (a distance of 7,200 miles according to the USGS) Source: "Bird Completes Epic flight across the Pacific"
9/12/2007 7:27:02 AM U.S. Department of the Interior, (U.S. Geological Survey)
This is clear evidence that some Godwits fly the Pacific - seemingly without even landing once. There are very small numbers in the survey, of course.
But if one can do it, and knows the way, then that's pretty impressive evidence as far as I am concerned. (In fact, thanks to radio telemetry several other records confirm this is more or less the regular southerly migratory route for Godwits which breed in Alaska).
I have done some reading up about the (Shorebird) Wader Study research done in Australia.
JOURNAL OF THE VICTORIAN WADER STUDY GROUP
VWSG BULLETIN
Number 31, August 2008
If we now add in the extra information from Steve Happ's report, we know some Godwits migrate across the Tasman.
Indeed, many seem to do that, as a preparation for a return journey northwards along the Asian (Pacific) coastline. One theory I have read today is that they follow this route, to avoid the perils of catastrophic weather on the northern end. By not flying directly, they can "stop off" safely till the weather clears - in Korea, or Kamchatka Peninsula, or Siberia, or Alaska.
By contrast - the theory goes - the southerly migration is not likely to meet such catastrophic weather (as they are not migrating to such extreme latitudes in the Southern Hemisphere) on their southerly journey.
Makes sense to me.
Wikpedia reports a modification of this story, namely that the New Zealand birds mostly fly directly north-west from New Zealand, (skirting around Papua New Guinea) across the equatorial and sub-tropical zones of the Pacific Ocean, until they reach the Yellow Sea (China).
Post Script:
I was thinking about whether the Godwits follow the "Great Circle Route". I hope readers understand the basic concept there. It is the plot of the shortest route between two point on the surface of the oddly elliptical shaped Globe we call home. It is not the straight line between two points on a map.
Here is the Great Circle Route from Anchorage, Alaska to Auckland, New Zealand. It goes south-west from Alaska. but after an initial s-w departure, the birds go south-east from Alaska. (Refer to the second map above - the plotted chart of E7's flight.)
Short answer is the Godwits do not closely follow the Great Circle Route. They are more influenced, especially in the early part of the trip, by prevailing Northern Pacific storm winds (Low pressure systems have anti-clockwise winds in the Northern Hemisphere, so, with a storm north from them (in Alaska), they get pushed south-east).
The following is my own interpretation of the information in a highly technical paper by Bob Gill of the USGS, who has done the flight analysis and all sorts of energy consumption modelling, flight efficiency (drag) coefficients, and more besides. His excellent paper was referred to me by Mick of Sandy Straits and Beyond.
In fact the Godwits' route follows the best prevailing winds. They appear to "ride" low-pressure storms as they leave Alaska, heading south-west initially with a strong tail wind kick off, then turning south-east from Alaska, parallel to the Pacific Coast (but a long way out, given that they are starting from the peninsula in the west extreme of Alaska), with the tail wind from the storms, which may assist them for up to 1500 miles. By then they have crossed into prevailing westerlies. They then head south-west towards Hawaii. Then they follow the northern Hemisphere Trade Winds, which flow south-west. After they cross the Equator, the birds can again gain some benefit from the southern Trade Winds, which take them towards Fiji. Some juveniles do appear to stop there. Flagged bird "E7" headed past, going directly to New Zealand. Remember they are doing this in September/October when weather in the last part of their route is generally benign.
The birds obviously "bulk up" prior to departure:
Today I am writing about the migrations of several specific Bar-tailed Godwits (Limosa lapponica).
Interestingly, Sebastian wrote about the flexibility of the beaks of these birds, which use their long beaks to probe into wet sand, to find Marine worms and other tiny marine creatures. And several days ago he reported on them feeding on grass, on The Esplanade at Cairns.
Another Blogger, Steve Happ has also written about a"flagged" Godwit from New Zealand
So, many of my Blogging colleagues know about Godwits. So this might not be news to them - but it is to me. Hopefully some of you will find it of interest too. To me, these journeys sounds a positively "heroic".
Female Bar-tailed Godwit - known as "E7"
Photographed in Alaska by the USGS.
Photographed in Alaska by the USGS.
I have today posted two messages on the Canberra Ornithologists Group "Chat Line". My brother, Brendan, who lives at Dalmeny, has sent me this interesting report of an article in the "Narooma News" about a Bar-tailed Godwit (a migratory "Wader" bird) which seemingly has been flagged with a clearly visible marker code indicating it was banded in Alaska.Brendan says: There is a story (and photo) in the Narooma News this week.
A Bar-tailed Godwit banded "flagged" with a tag that can be read without capturing the bird. I take it the flags are not individual but are a batch number - P1 black with white letters. It is quite clear in the photo.
******
Details of the bird's history are as follows:
Banded at Punoaray Point - Yukon-Kuskokwim Delta - Alaska on 9th September 2009
Identified 21st November 2009 - Tuross estuary
January 12th 2001 still at Tuross.
11,500k in 10 weeks.
*****
Brendan then asks: More significantly is this the "normal" north south migration? Has it gone across the pacific - or maybe across the top end of the pacific and then south. (I have looked on the electronic version of the Narooma News, but it has not rated an electronic entry.)
*****
The following report might help answer some of the questions which Brendan was hinting at - which way do the migrating Godwits go: (a) around the top of the Pacific or (b) directly across it?
I have located the following report from the Alaska Science Centre (part of the USGS - i.e., their "Geological Survey" Department) which provides a likely answer:
"We used satellite telemetry to follow the migrations of two populations of Bar-tailed Godwits, a group of 9 from New Zealand (NZ) and a group of 15 from Western Australia (WA). The birds from WA represent a subspecies that nests in eastern Siberia whereas the New Zealand birds nest in Alaska."
Map of the basic migratory route of Bar-tailed Godwits
from north-west Australia to Asia.
This represents the largest population of
migratory Godwits visiting Australia
There is a special report on one particular individual bird (E7) which took the "short cut" non-stop directly across the Pacific from Alaska to New Zealand. She flew for 9 days, non-stop.
* "On the early morning of August 29, she took off southeast back across the Alaska Peninsula, went out over the vast North Pacific and headed towards the Hawaiian Islands. When less than a day's flight from the main Hawaiian Islands, she turned southwest, crossing the Hawaiian Archipelago over open ocean 125 miles west of Kauai, heading towards Fiji. She crossed the dateline about 300 miles north-northeast of Fiji, and then appeared to fly directly over or slightly west of Fiji, continuing south towards New Zealand.
* "In the early afternoon of September 7th she passed just offshore of North Cape, New Zealand, and then turned back southeast, making landfall in the late evening at the mouth of a small river, eight miles east of where she had been captured seven months earlier." (a distance of 7,200 miles according to the USGS) Source: "Bird Completes Epic flight across the Pacific"
9/12/2007 7:27:02 AM U.S. Department of the Interior, (U.S. Geological Survey)
Complete Migratory Route of Godwit known as "E7"
She was flagged with the numbers E7
and tagged with a small satellite transmittor.
She was then tracked from New Zealand to China,
then to her nesting grounds in Alaska and back to New Zealand.
Source: USGS
She was flagged with the numbers E7
and tagged with a small satellite transmittor.
She was then tracked from New Zealand to China,
then to her nesting grounds in Alaska and back to New Zealand.
Source: USGS
This is clear evidence that some Godwits fly the Pacific - seemingly without even landing once. There are very small numbers in the survey, of course.But if one can do it, and knows the way, then that's pretty impressive evidence as far as I am concerned. (In fact, thanks to radio telemetry several other records confirm this is more or less the regular southerly migratory route for Godwits which breed in Alaska).
*****
I have done some reading up about the (Shorebird) Wader Study research done in Australia.
- "Sightings of Waders Leg-flagged in Victoria" Report Number 15 Clive Minton, Roz Jessop and Heather Gibbs. "Full details of all sightings are of course kept in the Leg Flag Database and updated versions of this are periodically exported to the Australian Bird Banding Scheme in Canberra for incorporation into their data storage facilities".
- "Sightings of Waders Leg-flagged in South Australia" Report Number 8 Clive Minton, Roz Jessop, Maureen Christie, Iain Stewart and Heather Gibbs "Bar-tailed Godwit 24/5/07 (2 birds) Yukon-Kuskokwin Delta, S.A. ALASKA 11,195 km. NNE 28/5/08 ..... 3/7/08 (breeding – with chicks) Aropuk Lake, Y-K Delta, ALASKA. Note: Only a handful of Vic-flagged Bar-tailed Godwits have been recorded on northward migration or during the breeding season in Alaska.
- "2007 Breeding Success, based on juvenile ratios of Northern Hemisphere waders which spend the non-breeding season in Australia" Clive Minton, Rosalind Jessop, and Chris Hassell (REPRINTED FROM STILT 53: 15-19) A flag sighting in South Korea on southward migration is unusual as baueri Bar-tailed Godwits (a sub-species), normally make a direct return to Australasia from Alaska across the Pacific. Maybe this bird was on its first northward migration and didn’t make it all the way to Alaska?
- Recoveries of Waders Banded in Victoria" Clive Minton, Roz Jessop and Maureen Fitzgerald Alaska 86403144 Juv 7/9/04 Yukon-Kuskokwim Delta, S.W. ALASKA 5/3/08 Corner Inlet (Victoria) Note: The individually leg-flagged (AO) bird from Alaska seen in Corner Inlet in March was the first Alaskan-marked bird recorded in Victoria. In contrast, there have been a few recoveries and many flag sightings of VWSG-marked Bar-tailed Godwits in Alaska.
JOURNAL OF THE VICTORIAN WADER STUDY GROUP
VWSG BULLETIN
Number 31, August 2008
If we now add in the extra information from Steve Happ's report, we know some Godwits migrate across the Tasman.
Indeed, many seem to do that, as a preparation for a return journey northwards along the Asian (Pacific) coastline. One theory I have read today is that they follow this route, to avoid the perils of catastrophic weather on the northern end. By not flying directly, they can "stop off" safely till the weather clears - in Korea, or Kamchatka Peninsula, or Siberia, or Alaska.
By contrast - the theory goes - the southerly migration is not likely to meet such catastrophic weather (as they are not migrating to such extreme latitudes in the Southern Hemisphere) on their southerly journey.
Makes sense to me.
Wikpedia reports a modification of this story, namely that the New Zealand birds mostly fly directly north-west from New Zealand, (skirting around Papua New Guinea) across the equatorial and sub-tropical zones of the Pacific Ocean, until they reach the Yellow Sea (China).
Post Script:
I was thinking about whether the Godwits follow the "Great Circle Route". I hope readers understand the basic concept there. It is the plot of the shortest route between two point on the surface of the oddly elliptical shaped Globe we call home. It is not the straight line between two points on a map.
Here is the Great Circle Route from Anchorage, Alaska to Auckland, New Zealand. It goes south-west from Alaska. but after an initial s-w departure, the birds go south-east from Alaska. (Refer to the second map above - the plotted chart of E7's flight.)
Short answer is the Godwits do not closely follow the Great Circle Route. They are more influenced, especially in the early part of the trip, by prevailing Northern Pacific storm winds (Low pressure systems have anti-clockwise winds in the Northern Hemisphere, so, with a storm north from them (in Alaska), they get pushed south-east).
The following is my own interpretation of the information in a highly technical paper by Bob Gill of the USGS, who has done the flight analysis and all sorts of energy consumption modelling, flight efficiency (drag) coefficients, and more besides. His excellent paper was referred to me by Mick of Sandy Straits and Beyond.
In fact the Godwits' route follows the best prevailing winds. They appear to "ride" low-pressure storms as they leave Alaska, heading south-west initially with a strong tail wind kick off, then turning south-east from Alaska, parallel to the Pacific Coast (but a long way out, given that they are starting from the peninsula in the west extreme of Alaska), with the tail wind from the storms, which may assist them for up to 1500 miles. By then they have crossed into prevailing westerlies. They then head south-west towards Hawaii. Then they follow the northern Hemisphere Trade Winds, which flow south-west. After they cross the Equator, the birds can again gain some benefit from the southern Trade Winds, which take them towards Fiji. Some juveniles do appear to stop there. Flagged bird "E7" headed past, going directly to New Zealand. Remember they are doing this in September/October when weather in the last part of their route is generally benign.
The birds obviously "bulk up" prior to departure:
- "The small-sized juvenile Bar-tailed Godwits with a lean mass of only 166 g and a fat store of 200g (Piersma and Gill 1998) are predicted to be able to cover more than 11 000 km nonstop". (Gill)
- In fact, they are predicted to lose all fat, and have reduced pectoral muscle mass in the course of the flight. It is obviously on the limits of their endurance, but they make it - mostly.
- Other immature birds are said to divert to Fiji if they cannot make the full direct flight. Presumably they then resume the journey after rebuilding fat and muscle tissue.
Saturday, November 21, 2009
Do you get Migratory Waders in your area?
I have received this notice from "Birdpedia".
Just as well somebody is watching what the DEWHA is up to.
A Latham's Snipe at Kangaloon
This "Policy Statement" review will impact upon most major wetland sites in Australia, but particularly Ramsar Sites, notably the Coorong, and Lower Lakes, other wetlands in the MDB, and the Victorian coastline, especially Gippsland, and the Great Sandy Straits area, within the Mary River estuary, south of Fraser Island.
Please feel free to send this on to other persons who might be interested to comment.
Dear Shorebirds 2020 volunteers & friends,
The Commonwealth Government has been developing an EPBC Act Policy Statement for Migratory Shorebirds, to provide guidance in relation to actions that may impact migratory shorebird populations in Australia. An important element of this policy statement is the adoption of criteria to identify nationally important sites for migratory shorebirds in addition to internationally important sites, to increase the amount of habitat protected for shorebirds nationally (see pages 9-10 of the draft policy statement).I would encourage you to take a look and make comments if required.See the following Birdpedia Notice for full details.
>> http://www.birdpedia.com/au/bi.dll/bipu01?m=550&id960=9756653697_0001&id509=ALL
Regards,
Jo Oldland & Rob Clemens.
DJW note:
I found the links suggested by Birdpedia (within their article) did not take me where I needed to go.
This one will:
I would point out that not all "Migratory Shorebirds" are restricted to Australia's ocean shores. This is acknowledged in regard to the Latham's Snipe (only) in the relevant papers.
Public comments are now being sought from interested parties on the draft policy statement, particularly in relation to its usability and suggestions for improvement. We would also be interested in any new research or information on these 36 migratory shorebird species to contribute to future policy revisions.
Comments will be accepted until COB Monday 14 December 2009.
At the end of this comment period the policy will be finalised, taking into consideration any comments received. The policy will be updated as substantial new information becomes available.
Comments should be sent to:
Email: speciespolicy@environment.gov.au
Mail: Species Information Section
Department of the Environment, Water, Heritage and the Arts
GPO Box 787
Canberra ACT 2601Fax: 02 6274 2875
This might be the required strategy for Snipe - FLEE!
Only sites where 18 Latham's Snipe of more gather regularly
are regarded as worthy of protection - under their proposed policy.
Only sites where 18 Latham's Snipe of more gather regularly
are regarded as worthy of protection - under their proposed policy.
Cheers
Denis Wilson
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.
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.
Monday, March 27, 2006
Autumn evenings, and migratory Honeyeaters.
The wonderful cool freshness of Robertson evenings is seldom as comforting as in early Autumn.
Another comfort is Anni's blog, where she continues to intrigue us with the breadth of her imagination, and occasional clever photographs, such as today's self-portrait in a teaspoon (the photo is relevant to her story)
We have had a string of balmy days, with clear air, and temperatures in the high 20s, but dropping to the low teens, over night. Weather watchers could do worse than visit the "Mittagong Weather and Weather Cam" website. It is a weather statisticians dream.
My personal gauge of the changing of the seasons is the first sign of migratory Honeyeaters passing through. Yesterday I saw my first migrating Yellow-faced Honeyeaters (Lichenostomus chrysops) for the season. Today I saw a few more. There is no spectacular wave of migration with these birds, unlike images from Europe and North America of migrating Geese and other wildfowl.
These little birds drift to warmer climates, and to coastal feeding grounds, from their summer nesting grounds in the high country in southern NSW and Victoria. But they form small flocks, currently a mere handful of birds. They fly in small groups from one tall tree to another, in short distances of perhaps 200 metres at a time, then rest for a few minutes, then fly on. In a few weeks time, the numbers of birds in these groups will swell to 50 or maybe 100, and the frequency of the passage of these groups will also increase. Just because it is not a spectacular flight of passing birds, does not mean it is not a real migration.
I can tell these birds are migrating, quite simply, because they do not reside in the Yarrawa Brush over the summer. These Honeyeaters are birds of the tall Eucalypt forest, primarily. But they migrate to coastal heathlands, to arrive when the nectar-rich Banksias are coming into flower. So, over the summer I see none of these birds here in Robertson. But they pass through in autumn, and again pass through on their way back, in spring.
Incidentally, these birds do reside a mere 5 Kms away, on the sandstone based forests, down along the Belmore Falls Road. I am not saying that these migrating birds come from there, simply, just pointing out how specific their choice of habitat is. Belmore Falls, has sandstone-based scrubland and Eucalypt forests, with many proteaceous shrubs in the understory. That environment suits them as a breeding ground. The Yarrawa Brush, cool temperate rainforest country does not. The difference is primarily that our trees do not produce the kind of nectar supplies that these birds need. So they do not breed here. They fly through to get to other environments which suit them, for the autumn and winter seasons. Typically, that is the coastal heathlands of the NSW coast where many Banksias flower at the suitable time for them - autumn and winter. (Photo above is courtesy of the Macleay Valley Coast birdlist, on their Tourism website.)
Food sources is the limiting factor in this migration, by the way, not temperature. This is demonstrated by the fact that every year a small number of these Honeyeaters overwinter in the Australian National Botanic Gardens, in Canberra. Canberra has far colder winters than the Southern Highlands. But the Botanic Gardens has a cultivated collection of suitable food plants for these birds, with thousands of Grevilleas and Banksias, which flower over the autumn and winter seasons. So, a number of birds stay there, instead of migrating through to the coastal heathlands.
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