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.

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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.

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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.)

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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).

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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.