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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".

Female Bar-tailed Godwit - known as "E7"
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
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.
  1. "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".
  2. "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.
  3. "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?
  4. 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.
Source for all these reports:
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).

Godwit northerly migration route from New Zealand
(Source: Wikipedia)

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.)
Map generated by the
Great Circle Mapper -
copyright © Karl L. Swartz.

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.
I am sure no Doctor would recommend such an extreme wait loss program as these birds engage in.

18 comments:

Snail said...

I'm with you, Denis. Those are prodigious feats!

As for the NZ bird --- that's one heck of a short cut!

mick said...

Great posting, Denis. You have done a lot of background reading and your links are great. Godwits are fascinating! Maybe you'll even decide you have to see them from up this way where they actually arrive and depart!!

Mark Young said...

Hi Denis,

These and other waders species are so impressive in their migratory flights.
As the picture shows their destinations in Korea and China, which are currently under threat, are so important as refueling stations for them to get back home. Can you imagine what would happen if those places are gone?

Regards,
Mark

Denis Wilson said...

Hi Mick, Snail and Mark
Thanks for the comments.
.
Yes, it is an impressive feat, indeed.
.
We have known about the Shearwaters doing a "Figure of 8" loop of the entire Pacific for a long time, but they can feed and rest along the way.
.
The Waders cannot do that (although they probably can swim for a while). But clearly the records show E7 flew for 9 days non-stop. A massive effort.
Mark is right to point out that the feeding grounds in China and Korea are under threat. There are huge pollution problems coming down the Chinese rivers.
.
Also humans are starting to use some of the same areas for harvesting food for themselves, so that may well alter the habitat there.
.
Mick I would love to see some of your waders, one day.
.
It is interesting that the your East Coast Godwits have not yet been tracked.
.
There has been a lot of study, and they even reckon they are a different sub-species from the West Coast birds and the New Zealand ones. But they seem to not know too much about their flight route. Do they drift west and mix with the WA birds, or go north-east, and follow the New Zealand birds?
Does your local Wader Study group know the people in Victoria? I assume so. They seem to be well resourced.
.
Maybe its time for some "boom netting" at Sandy Straits, to "flag" some of your birds. If that ever happens, I'd love to see it.
.
Cheers
Denis

Denis Wilson said...

Incidentally, my brother wonders that the Americans are so interested in our birds.
Actually, as they breed there, they are "their birds".
None-the-less, he might be right about one thing. He suggests the Yanks are looking as vectors of "Bird Flu"

Denis Wilson said...

Further to Mark's comment about the importance of the Yellow Sea area as a "fly way" and en route feeding ground. There is an important paper on Shorebirds of the Yellow Sea
which reports on this.
It says: "Status of key sites: The 3 Chinese sites and a small part of 1 site in South Korea (Dongjin Gang Hagu) are within Protected Areas. The Dongjin and Mangyeung estuaries are currently being reclaimed as part of the Saemangeum Reclamation Project."
.
So human population pressures leading to land reclamation might pose the greatest threat to these migratory shore birds (Waders).
.
Regards, Mark
.
Denis

mick said...

Hi Denis, re the sub-races of Godwits - menzbieri WA and baueri - Eastern Aust and NZ - can you reference where there are questions raised about the ones from NZ and Eastern Aust perhaps being different races? Young birds have been tracked traveling between E.Aust and NZ. Also adverse weather on the migration can send birds off track. Older birds seem to remain site specific - see the numbers of sat.-tagged birds that returned to the same place. Also a pair of birds tagged on the Alaskan breeding grounds and one went to NZ for the summer and one came to East Aus.

Denis Wilson said...

Mick is a bit shy, it seems.
.
It transpires that our own Mick from "Sandy Straits and Beyond" has personal experience with a flagged bird from Alaska. She has written me a longer note, which in part states:
.
"Then E3 - one of the tagged birds - disappeared off their tracking and turned up here at Tin Can Bay and I took photos of it.
.
"My photos (Mick's) went all round - to Australia, NZ and Alaska - as its only by direct sighting such as this that tagged birds without satellite tags can be followed.
.
E3 was apparently uncomfortable with the satellite tag and had gotten rid of it then decided not to continue the migration that year.
.
Phil Battley from NZ was also closely involved in those studies and his web page has some very interesting material. http://www.nzshorebirds.com/
.
He also links to this pdf of one of Bob Gill's papers http://www.nzshorebirds.com/downloads/gillCondor2005.pdf
.
This has a lot of material about the weather systems which aid the godwits in their flights - and in fact make it possible.
.
When I was following the updates on the web tracking site in '07 it was obvious from the figures listed that different birds were picking up different winds.
.
None of the birds were flying at "normal" godwit speed! All were faster because of the winds they were riding/surfing - whatever might be the right term for it.
.
The weather patterns also explain why the northward migration is over a different track than the southward migration."
End of quote from Mick's email.
Fascinating stuff, Mick.
Great to hear of your personal involvement.
Steve Happ has also photographed one from NZ.
Cheers to all.
Denis

Denis Wilson said...

Hi Mick.

It was in a copy of "The Stilt" I found, but it was in a bad format (scanned in from a typed document) and I could not copy from it. (Unlike a proper .pdf file).
.
Unfortunatley I cannot relocate it on the web this morning.
.
I read VWSG and "Stilt" articles mostly yesterday. Google Searched: Bar-tailed Godwit + migrations.
.
Gill's paper (Intro Page 2) makes mention of: ""(In the Anadyr
Basin area of Chukotka is a third, much smaller breeding population of unresolved taxonomic
affinity and nonbreeding area [Engelmoer and Roselaar 1998, McCaffery and Gill 2001].)""
.
Reading between those lines, somebody has proposed splitting this group into another sub-species. But it has not been "accepted" as yet.
.
That's what I seem to recall reading yesterday.
.
Of course, it is not yet clear where this separate group (which has been identified as breeding at an intermediate stage along the North Asian coastline) takes their southern holidays (East coast Oz, or NZ?)
.
So, I think you have to just take it that some people want to break up the group with another SSP, but not everyone agrees.
.
Cheers
Denis

mick said...

Thanks Denis, I do remember reading about that other breeding area but had not realized that it was proposed to make that a separate race.
btw - I just didn't want to 'bog down' your blog comments with too much extra info :-)

mick said...

Fantastic Post Script. You have done a great job of simplifying some highly technical but fascinating concepts.

Denis Wilson said...

Well, Thanks to you, Mick for the llnks.
.
I hope I have done the researchers justice - and the birds.
.
Cheers
Denis

Gouldiae said...

Excellent stuff Denis.
Even held me up from watering. Got to read it again to absorb a bit more. I recall seeing my first Godwit and standing in awe while I pondered its probable journey.
Thanks,
Gouldiae.

Denis Wilson said...

Thanks Gouldiae.
.
If I held you back from the watering on Australia Day, then I have achieved something (perhaps).
.
I know it turned into a very long post - thanks to comments, which sent me off for more research.
Indeed it is fascinating.
.
Of course, the Red-necked Stints and many other tiny waders make similar trips.
.
I suspect it is easier to flag the larger waders, and to see their "flags".
.
Amazing efforts by the Victorian Wader Studies Group have been well rewarded. No doubt they are working to get more records of banded and flagged birds.
.
Cheers
Denis

steve said...

Hi Dennis,

Fantastic research. I have photographed a tagged bird which was tagged at Jalu Jiang in the Yellow Sea in China near the Korean border. That is a stop-off on the way home to Alaska, I believe.

cheers,
steve

Denis Wilson said...

Thanks Steve.
I enjoyed this reporting, but credit goes to you and to Mick who have done the field work to report "flagged" birds".
I believe I have presented the migration pattern in a straight forward manner - hope so, anyway.
Cheer
Denis

Russell Constable said...

Wonderful Story Denis and you obviously put a lot of work in so even a non twitcher like myself can get a handle on the concept.
It's one hell of a migration however you look at it and whatever route is taken!
cheers Russ

Denis Wilson said...

Thanks Russell
Its well out of my normal range of discussions, but I found it very interesting.
Glad you did, too.
Denis