Wednesday 22 April 2015

More migration news on the GFN satellite telemetry project - Chris Hassell: Global Flyways Network

Well there is lots going on in the world of migrating birds with a mix of good old fashioned observations (scanning and migration watch) and modern technology (the Platform Terminal Transmitters PTT’s) on the ‘GFN” Great Knot and Bar-tailed Godwits. 

Mixed flock of waders containing Greater Sandplover Charadrius leschenaultii, Bar-tailed Godwits Limosa lapponica, Black-tailed Godwits Limosa limosa, Great Knot Calidris tenuirostris,  Red Knot Calidris canutus, Curlew Sandpiper Calidris ferruginea, Red-necked Stint Calidris ruficollis, Ruddy Turnstone Arenaria interpres, Terek Sandpiper Xenus cinereus and Grey-tailed Tattler Heterocelus brevipes: Australia September 2013.

Six Great Knots are sending signals from China and two are sending signals from Australia. One of these is in the Northern Territory (1,000km north east from Roebuck Bay, where we banded it) and the other is at 80 Mile Beach (200km south from Roebuck Bay) it would seem these two will remain in Australia this dry season. All the Great knots did a single flight from Roebuck Bay to the coast of China except one that stopped in Vietnam. The general strategy has been a single long flight then short stays of less than one day but up to eleven days before the next leg northward of between 500 and 1,800km. Four birds are in Yalu Jiang on the China/North Korea Border, a site that gets tens of thousands of Great Knots. 

Great Knots Calidris tenuirostris: Thailand, January 2014.

A few examples: one bird did a direct flight to the south coast of China of 4,600km then spent eleven days there before flying 1000km taking a very brief stops of one or two days ‘hopping north again for 700km then another very brief stop before the final hop of 450km to Yalu Jiang. Another did the single leg to the Chinese coast did two very short stops and then after a ten day stop went the final 1,800km to Yalu Jiang. One bird made only one stop it went 5,200km and then after seven days zipped the other 1,200km to Yalu Jiang. It will be interesting to see if this apparently ‘strong bird’ leads up to the breeding grounds. All birds have travelled at about the mid 40km’s per hour during the big leg from Roebuck Bay to China.

Great Knot Calidris tenuirostris: Australia September 2013.

One bird was transmitting as it left Roebuck Bay on migration and this gives us very good timing, direction and speed of the initial leg of its journey. It left at 6PM on April 7th (it was no doubt logged in the observational data of the BBO team at migration watch.) 

Bar-tailed Godwits Limosa lapponica: New Zealand October, 2013.

The Bar-tailed Godwits with PTT’s left later than the Great Knots and have experienced some head and cross winds. three of them have stopped in the Philippines and seven are in china. One is still in Roebuck Bay. The first leg of the birds that got to China were between 4,600 and 5,200km. The most interesting aspect of the godwits is that I saw a flock of fifty-five Bar-tailed Godwits exhibiting pre-migration behaviour at a roost on the afternoon of April 11th. In this flock were three colour-banded birds and two of those had PTT’s on! I wrote to Lee saying these birds would migrate that night and when she checked the data; sure enough, they had left at 6PM that evening. And just to add to the mix it was the BBO “public Migration Watch’ day and seventy-two people watched a flock of one hundred and thirty bar-tails head out at 6PM! I am afraid they were fairly distant so no images of antennas trailing behind migrating birds! But I am pretty certain our two birds were in that flock. What a great mix of field observation and modern technology. 

Bar-tailed Godwit Limosa lapponica: Australia September 2013.  
This was the first time we have had two PTT birds apparently in the same flock. And a question I am always asked is ‘when they leave together do they stay together’. ‘I don’t know’ I was the honest answer. These two didn’t stay together the whole way one stopped in the Philippines after a flight of 3.430km while the other went all the way to China in a 4,800km leg. The Philippine site only has narrow mudflats but three suitable looking river mouths for a godwit to feed at and only a low population of people nearby. Two other godwits are just 80km south of this site on the west coast of the island of Mindoro. This also looks a very suitable stop-over location. It has mudflats, river mouths, mangroves and aquaculture ponds which potentially offer good roosting opportunities. 

Bar-tailed Godwits Limosa lapponica and Great Knots Calidris tenuirostris: Australia September 2013.
One of the birds at this site I find particularly interesting. Initially it landed on an island 125km due west of its current location. That site is a rocky coast with no mudflats and completely unsuitable. So the bird went somewhere with mudflats! A very sensible thing to do. This says to me, that the bird ‘knew where it was’ it didn’t go north or south or west as there is nowhere suitable (close by) for it to feed at so it went due east to where it ‘knew’ there was suitable habitat. Another PTT bird is on the same mudflat but it got there in a direct flight. Interesting stuff.

Chris Hassell, Curtis Robinson and Phil De Bruyn (Last two Dept of Parks and Wildlife) : three big blokes releasing three rather small godwits. Photo: Ying Chi Chan

Note: All distances and flight times in this update are preliminary. Further statistical analysis will be done at a later stage. So all information in this document is approximate. 
The GFN PTT Team 

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