Saturday, 22 February 2014

Interesting items from Miranda News Issue 91.

Copyright: Miranda
Naturalists' Turst
We have just received our latest copy of Miranda News, the journal of the Miranda Naturalists' Trust and I wanted to share a few interesting points from it.

There are a couple of articles written by Tony Habraken about those long-distance migrants, the Bar-tailed Godwits. The first telling of the sheer fluke that led to the collection of data proving the 11,000 km+, eight day, single flight from the breeding grounds in Alaska to New Zealand. It was as a result of a battery outlasting its expected lifespan, by a few months, that this data was made available. The transmitter was originally fitted to a female bird sporting the leg flag E7 (she features on the front cover, left) to track her as she flew north to discover where her stop over sites in the Yellow Sea region were and then onward to discover where she bred in Alaska. All batteries fitted to the other birds at the same time then ceased to function as was expected but E7's transmitter battery just kept going and continued to send signals detailing her return to New Zealand! Since this epic flight, and discovery, she has held a special place in the hearts of those that were studying her and she continued to be monitored by visual observations. In the course of a few years, since 2008, she  had lost a leg which stopped her from feeding sufficiently well to enable her to make further migrations and she seems to have retired to New Zealand. She had moved from her usual haunt in the Firth of Thames to the Bay of Plenty, the theory is that the substrate at the latter is softer thus making it easier to feed, offering her a kinder environment in which to spend her remaining years.

Bar-tailed Godwit (not E7) Limosa lapponica baueri; Foxton Beach, New Zealand.
The second article is about another of these great long-distant migrants, one of the first ever Bar-tailed Godwits to be fitted with a transmitter, a female with the flag E0. This was done in Alaska with the express intention of plotting her migration south to New Zealand, but the transmitter failed so no data was achieved. Her appearance in New Zealand however at least showed that the species was capable of migrating successfully with a transmitter implant and led to the study that ultimately proved what they had set out to do in the first place, albeit by pure chance. E0 has now disappeared with no records for two years so is presumably deceased, but E7 has been reported as recently as February this year, seven years after her transmitter was implanted.
Bar-tailed Godwit Limosa lapponica baueri; This bird had just arrived from its marathon flight from Alaska. Phil Battley who studies the species in the Manawatu Estuary, told us that new arrivals could often be told by their droopy wings. Foxton Beach, New Zealand. October 2013.
In another article by Richard Fuller (University of Queensland) there are some horrendous statistics about the Yellow Sea's destruction rates and the resulting migratory bird population crashes. Some migratory populations have crashed by up to 80% in 20 years, Curlew Sandpiper being one of the worst hit.
Curlew Sandpiper Calidris ferruginea; Khok Kham, Thailand. February 2014.
The bar-tailed Godwits are faring badly too, the bauri population of eastern Australia and New Zealand is falling by 1% per year which is quite fast and the menzbieri population of western Australia is faring worse at something like 6% per year. The difference between these two populations is that the latter, menzbieri, travels through the Yellow-sea on both its northerly and southerly migrations thus is probably being more adversely affected by the habitat loss in its stop over points. A study showed that 29% of the mudflats present in the 1980s had gone by the late 2000s. Historical maps suggest that that figure could be as high as 65% since the 1950s. The main culprit for this is obviously land reclamation (land grab in my eyes, it is not being reclaimed, it was never lost in the first place), but in addition sediment flow from the rivers is much reduced resulting in some mudflats disappearing entirely over the past few decades. This destruction looks set to continue and will certainly have a drastically negative effect on wader populations that pass through there, add into this boiling pot the threat of rising sea levels and it is not hard to see that some migratory wader populations could easily become extinct if it continues. One study showed that a 23-40% loss of intertidal habitat would result in a 72% reduction of  population size due to the loss of important stop over bottlenecks.

Red Knot Calidris canutus rogersi; juvenile Western Treatment Plant, Victoria, Australia. September 2013.
On the same subject, Keith Woodley the centre manager writes that between 1990 and 2008 an average 285 sq km of tidal flats were destroyed annually around the Yellow Sea and from 2009 to 2020 it is predicted to be more than 500 sq km annually. From 1994 to 2010 450 sq km of offshore area including 218 sq km of tidal flats were destroyed in just two projects in Bohai Bay where reportedly 80% of the shoreline has been built upon with factories and other buildings. All very depressing reading, but important information that we need to make more generally known in the wider world.

Broad-billed Sandpiper Limicola falcinellus; Pak Thale, Thaialnd. January 2014
Changing the subject a little to something a little lighter, in the Miranda Snippets section I noted a report that Adrian Boyle had photographed a Variable Oystercatcher nesting 4m up a tree! It seems that this is unique although our friend John Dowding reported some other strange nesting choices by these ground nesting birds, including on a small ledge 5m up a cliff face!

Variable Oystercatcher Haematopus unicolor; Plimmerton, New Zealand. October 2013
Wader Quest even got a mention with a quote from our blog about visiting Miranda. Fame at last!

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