27 November 2008

The migrants

Jesse at Foxton
A cold wind sweeps the Manawatu estuary, bringing a few light spots of rain from the overcast sky. The tide rises visibly, creeping across the mud flats, beginning to encircle the flock of bar-tailed godwits. A handful of birds lifts into the air, then more join them, then all but a few stragglers take to the wing and fly towards their high tide roost on the beach on the far side of the flats. As they recede into the grey distance the individuals disappear into the collective movement of wingbeats and the arc of flight; the cloud and the flock begin to merge.
Jesse Conklin looks up from the spotting scope. He seems thoughtful, slightly pensive, somewhere in the nebulous region between puzzled and concerned.

“A lot of birds are missing,” he says.

He's counted 178 birds, but last week more than 200 had occupied the estuary. The usual places small groups or stragglers might be hiding are devoid of birds. Jesse should know where to look—barring midwinter, he's here every week; he was waiting when the first godwits arrived in spring after their astonishing 11,500 km non-stopJesse inspects the godwits flight from Alaska; he watched them all last summer until the last birds rose into the air and headed north-west to a stop-over on the shores of the Yellow Sea and eventually on to their breeding grounds back in Alaska.

The spring flight from Alaska to New Zealand is the longest recorded non-stop flight of any bird. The flight takes about nine days; not bad for a bird that averages about the weight of a can of beer (roughly 350 g). Elite human athletes can maintain an equivalent effort for only about one hour; you or I might manage 10–15 minutes before collapsing. The birds do have a singular advantage, though. Shortly before they take to the air their digestive system begins to shrivel—anything not essential for the flight atrophies; every gram might make the difference between a safe arrival and death.

Why do they do it? At first the answer seems obvious—during winter, Alaska's locked under ice and snow. Stay late and if the cold doesn't kill you starvation will. But why not fly to the Tropics? Why fly to the other end of the Earth—New Zealand?

Jesse shrugs.

“Good question,” he says. “We have a few theories, but we don't know for sure. The Tropics are dangerous places — lots of predators, parasites, diseases, and competition. It might simply be safer, despite the effort, for them to fly all the way here. Or, their adaptations for the Arctic cold might make it too difficult for them to survive tropical heat.”

It's the usual story. The more we learn, the more questions the knowledge raises. For example, bands on the birds' legs showed individuals returned to the same place each year.

“We now know they have very high site fidelity,” Jesse says. “Manawatu estuary birds return to the Manawatu estuary; Miranda birds return to Miranda, and so on. But we don't know if there's a genetic component. We don't knowBlackbacked gull, Pencarrow head if the offspring of Miranda birds migrate to Miranda, for example, or whether they choose somewhere else—and if they do choose somewhere else, why, and how?”

A group of godwits appears from somewhere and circles the roosting flock before settling down with them. Jesse turns back to the spotting scope and resumes counting, the clicking of the mechanical counter sounding like another kind of bird. There's no shortage of those, either. Red knots mingle with the godwits; a few of the ubiquitous black-backed and red-billed gulls fly overhead, the larger black-backs spreading a flutter of agitation through the godwit flock. White-fronted and Caspian terns cluster near the water's edge, the big, powerfully built caspians looking like rugby players among a group of dancers. A spoonbill flies upriver and skylarks hang, fluttering and singing above the marram and lupins from where a pheasant calls repeatedly. A kahu cruises on the far side of the river where tight, gnarled, wind-shorn trees rise beyond a patchwork of mud flats and rushes.

The rarest bird here is also the least conspicuous. Five thrush-sized wrybills rest in the shelter of a vehicle track in the sand, each bird resting on one leg, each with its unique, sideways-curved bill tucked under a wing. Soon they'll migrate back to the South Island. A few non-breeding birds remain in the North Island, but most return to the wide, braided Canterbury and Otago riverbeds to breed. New Zealand's—and therefore the world's—entire population totals just 4–5000 birds. But Canterbury farmers are clamouring for more water for dairying and to irrigate crops which, as droughts become more frequent and more severe, are harder to grow. Expanded irrigation schemes might keep these types of agriculture viable for a while longer, giving farmers the chance to find forms better suited to the changing climate, but not all farmers are willing or able to adapt, preferring to demand still more water from the rivers—the only home the wrybills have to rear their young.

Right here, though, there's no shortage of water. The tide nears its peak; the sea fights the relentless flow of the evil olive-brown Manawatu with its shameful load of agricultural run-off and effluent dumped daily from the Fonterra factory not far upstream. This is not water one would swim in, let alone drink. What impact does it have on the birds and other wildlife living in and on the estuary? Sometimes one prefers not to know, but the thought arises: what we do here affects birds that spend half their lives in Alaska; our choices in Aotearoa directly influence the Alaskan environment.

...

How do the godwits know when to leave? Timing is especially crucial on the return journey from New Zealand to Alaska—leave too soon and the breeding grounds might still be covered in snow; too late and other godwits might have taken the best sites.

Researchers noticed that some male birds left early, still largely in their pale, non-breeding plumage, while others left later but with more developed, redder breeding plumage. Which birds might be more successful—those leaving early and claiming the best breeding sites, or those leaving later and arriving later but with more attractive plumage? And what about birds that leave early but take a break in Asia, eventually arriving in Alaska in similar breeding condition to the late-leaving birds?

“It gets even more complicated,” Jesse says. “Birds in southwest Alaska can start breeding up to 3–4 weeks earlier than those on the North Slope, which thaws later. Birds heading for the northern sites have to wait an extra monthWhite-fronted tern with fish for their breeding grounds to thaw, so why not go later and grow more breeding plumage? In other words, the late-leaving, redder males may simply be northern breeders.”

Although he's still a month short of one full year of collecting data, Jesse already has some insights into these and other questions. He's confirmed that male birds do vary greatly in the state of their breeding plumage at the time they depart. More information comes from tiny dataloggers fitted to some birds; these record changing daylight levels, and from the estimated times of sunrise and sunset, latitude and longitude can be estimated to within roughly 150 km—accurate enough to determine how long a bird stayed at the Yellow Sea feeding grounds, and roughly where it settles to breed. As the data accumulate, he might finally be able to say whether or not the late-departing, redder birds do indeed breed further north.

...

In the pub a few days later, Jesse grins.

“Saturday was one of the best days ever for recording data,” he says. “When the flock took off I got photos showing full wingtips in 31 colour-banded birds.”

Photography, as well as other recent technological developments like the miniscule dataloggers, is vital for Jesse's study. Beautiful photos aren't his aim (although he has plenty of those)—it's the information in the photos that's important. Wingtips let him gauge the stage of the bird's moult, but shots in flight are seldom useful because the legs are tucked up so the bands are hidden and the individual can't be identified. It's that moment Godwits & red knots flyingwhere they're stretching their wings to take flight, or lowering their legs to land—when leg bands and wingtips are visible in the same photo—that delivers the data. Given the total number of colour-banded godwits on the estuary is about 55–60, his high spirits are understandable. Information on half the birds in just one session seems worth celebrating.

Photos record that crucial information about the degree of development of breeding plumage. He can also score the condition of the bird from a side-on photo by comparing the area of the bird's body to the length of the lower leg (the tarsus); the length of the tarsus doesn't change, and it's known from measurements taken when the bird was banded. This lets Jesse determine the bird's condition when it leaves New Zealand — in other words, how well prepared it is for its migration. Between January and mid March, they'll add 60–70% to their body weight.

“A study like this wouldn't have been possible even a few years ago,” he says. “The recent advances in digital photography let me shoot hundreds of photos and extract the information from them in a way that just wouldn't have been feasible with film. The cost would have been prohibitive.”

...

A man and a woman with two small children come over to ask about the spotting scope and the birds. The small boy offers treasure in his hand — a small, dead crab. Places like this, with animals that fly and scuttle and burrow and swim; with the excitement of what might be under that driftwood log, still fascinate most children despite the temptations of TV and CGI. Maybe one day that small boy will carry on Jesse's work, helping us understand more about the astoundingly complex and beautiful world we share with these other lives—and on which we depend.

The man asks how many godwits live on the estuary.

“Do you know them by name?” he asks, in jest.

“I can identify most of them individually,”Jesse replies, and the man laughs and shakes his head. The couple and their children wander off, and Jesse returns to his counting. He looks up.

“That's it,” he says. “They're all here.”
Wrybill at Foxton

Acknowledgements:I'm grateful to Jesse for most of the information and for taking the time to check over a draft of the post; and to Anne-Marie for guidance on the style. Any errors of fact, misrepresentations, typos, and failures of style are inadvertent and mine alone.

Notes:
1. Four subspecies of bar-tailed godwit (kuaka, Limosa lapponica) are now recognised, with the subspecies baueri migrating to New Zealand.
2. Other birds mentioned: Red knots (Calidrus canutus); black-backed gull (Larus dominicanus);
red-billed gull (tarapunga; Larus novaehollandiae); white-fronted tern (tara; Sterna striata); Caspian tern (taranui; Sterna caspia); spoonbill (Platalea regia); skylark (Alauda arvensis); pheasant (Phasianus colchicus); kahu (Australasian harrier, Circus approximans); wrybill (Anarhynchus frontalis).
Photos (click the smaller photos to enlarge them):
1, 2. Jesse at work on the Manawatu estuary near Foxton, Manawatu, New Zealand (all photos from the Manawatu estuary are dated
15 November 2008).
3. Black-backed gull near Pencarrow Head, eastern shore of Wellington harbour.
4. Lupins and some other unidentified flowering plant among the marram, Manawatu estuary.
5. White-fronted tern with fish, Waipapa Point, Southland, New Zealand.
6. Godwits and red knots in flight, Manawatu estuary.
7. Wrybill, Manawatu estuary.

Photos and words © 2008 Pete McGregor

35 comments:

Anne-Marie said...

An excellent post, Pete; interesting and informative.

It was a thrill to see godwits and wrybills for the first time. The godwits are lovely birds and yet so ordinary – they don’t look remarkable enough to make such remarkable journeys.

You touched on the quality of water in the Manawatu estuary, which pretty much resembles industrial sludge [which is probably exactly what it is]. The godwits don’t seem to be bothered by it – yet – but I can’t help wondering if at some point in the future, the bad water will affect the creatures the godwits feed on. When that happens, will the godwits return?

Great pictures, too. Jesse’s hat is a classic :-)

Bob McKerrow said...

Loved the srtory Pete Full of wholesome Kiwi values and our interface with mirants. I was stunned to read

"The spring flight from Alaska to New Zealand is the longest recorded non-stop flight of any bird. The flight takes about nine days; not bad for a bird that averages about the weight of a can of beer (roughly 350 g)."

Thanks for sharing. Came home today after 11 days in hospital with my new knees. Walking a 100 metres is a big achievement for me at the moment. Take care. Bob

Duncan said...

Good one Pete, waders are special, Jesse's doing a great job. Off to (hopefully) count waders myself soon, conditions aren't too good with the dry but fingers crossed.

Relatively Retiring said...

What astounding information there is here. The more we learn, the less we know.

Emma said...

I agree -- an excellent post, Pete. I just heard a story on the migration of godwits a few weeks ago, on the radio, and was astounded. How beautiful and mysterious our world is!

Ruahines said...

Kia ora Pete,
Eco-journalism at its best. Like Anne-Marie I wonder how that sludge is really impacting the bird life. Growing up in Green Bay, part of Lake Michigan, back in the 60's it took finding new generations of birds with twisted beaks and other mutations before they realized dumping pdp's and raw sewage into the lake was no longer working. Thanks for the information, and the reminder of connected we really all are.
Cheers,
Robb

Frontlawn said...

Hi Pete,

A great post. Some of those manawatu godwits spent some time in the wildlife ward at the Massey vet clinic. I went to have a peek at them and learned (amazing godwit factoid coming up!) that godwits can bend the tips of their bills. While the rear 2/3rds of the bill remains shut they can bend the top of the front 1/3rd up and down. It makes the end of their beak like a finger and thumb. Unfortunately, I didn't get any photos of bill flexing in action --- just lots ones of sad, sick looking godwits.

pohanginapete said...

Anne-Marie, despite the rhetoric, the quality of our rivers has actually deteriorated over the last several years. At this rate many of our native fish will be extinct in the near future — and they're pretty good indicators of what's happening to other species. When I used the word “shameful”, I meant it, and was probably being diplomatic.

Bob, great to hear you're walking so soon after the op., even if it's only short distances. Best wishes for a speedy return to full fitness, and when you're weight training with those cans of beer, remember the average weight of a godwit ;^)

Duncan, you're right; Jesse's work is showing us so much, not just about godwits, but about migrations and the complex web of interactions in which they take place. Best of luck with the wader spotting.

RR, I've often wondered about the observation that every answer seems to pose many questions, and the logical consequence of that, which is that the number of unanswered questions must be increasing rapidly. I suppose we do know more, but as a proportion of what remains to be known, our knowledge seems to be getting smaller.

Emma, it's something of a paradox that we're so curious about our world, yet we seem so strongly to want it to remain mysterious.

Kia ora Robb. Unfortunately, the example of Lake Michigan seems to carry little weight here. I suspect we'll have to see those same awful consequences happening here before we get serious remedial action. But let's hope I'm unduly pessimistic.

Frontlawn, that is indeed an amazing factoid. I wonder how they manage it? I tend to think of bills as being largely inert, but I suppose other birds have similarly strange adaptations (the fleshy flaps on the end of the bill in whio, for example.)

peregrina said...

I did enjoy this post, Pete, and it was so informative. I knew quite a bit about them, but it filled in gaps. I've been down to our estuary at low tide to try to see them, but they're far more shy than our other seabirds and feed well out on the mudflats. They're so far away it's impossible to see any detail at all. There's a research team banding some of them here, too.

Did you know that every spring, when the first little group of godwits arrives, the change-ringers go in and ring a peal on the Cathedral bells to announce their arrival to the city? (They warn the nearby tourist hotels first!) In autumn, when migration in groups of twenty or thirty birds has begun, there's a Farewell to the Godwits ceremony down at The Spit. It's notified in the paper, but I haven't been yet. I think some of the juveniles (perhaps from a later brood?) over-winter here.

butuki said...

Hi Pete, I was very surprised to hear of the Godwit's migration flight being the longest in the world; I'd always read and heard that it was the Arctic Tern:

The species is strongly migratory, seeing two summers each year as it migrates from its northern breeding grounds to the oceans around Antarctica and back (about 24,000 miles) each year. This is the longest regular migration by any known animal (Wikipedia)

You did say "the longest recorded non-stop flight of any bird.", so maybe it is the "non-stop flight" part that makes a difference? I assume Arctic Terns land a lot along the way and eat upon the sea's surface, since they are truly sea birds.

pohanginapete said...

Peregrina, I love that idea that these small, seemingly nondescript birds capture the imagination (and hearts) of people enough to get the bells ringing. Among other things, it reminds me that not everyone's utterly obsessed with economic crises and material comfort; that many of us still value the spirit of wild things. And yes, some juveniles do stay here over winter. I suppose if you're not ready to breed, it's a pointless and enormous effort to fly back to Alaska.

Miguel, yes, my understanding is that the Arctic tern's migration is longer (although not by much), but includes stops. On that note, I can never hear mention of the Arctic tern without thinking of Chatwin's wonderful account, in The Songlines of his meeting with the tramp:
He then said, slowly, and with great seriousness:
"It’s like the tides was pulling you along the highway. I’m like the Arctic tern, guv’nor. That’s a bird. A beautiful white bird what flies from the North Pole to the South Pole and back again."

peregrina said...

Pete: I forgot to say that I think those mauvy-pink flowers among the yellow lupins are a cineraria species. When I travelled down the North Island by bus earlier this year I noticed them colonising the roadside verges, particularly south of the Volcanic Plateau.

pohanginapete said...

Thanks Peregrina :^)

Beth said...

Wonderful post, Pete. I cheered when I got to the end - and realized I had a stupid grin on my face from smiling at that last bird. Thanks for enlightening me on a migration and bird species I knew nothing about before, for letting me meet Jesse, and, as always, for the spectacular photographs.

Jamie said...

Pete, that is an amazing post. Thanks!

pohanginapete said...

Beth, Jamie — thanks! Very pleased I could share the delight.

mm said...

Oh my Pete. So packed with information, so well written. Thank you.

Your sense of reverence for the natural world comes through. As does that of Jesse.

pohanginapete said...

Thanks MM. I just wish all the others who enjoy the beaches and riverbeds shared a similar reverence. Sadly, it's not the case, and many forget or ignore the presence of these other lives. For example, wrybills lose nests every year to the trailbikers.

Gustav said...

Pete

My 10 year old daughter and I are grateful for this post. We love birds and the godwits are quite a bird.

Alaska and New Zealand are two of my favourite places on Earth and if I were lucky enough to be a godwit I would surely prefer these places over most others on Earth.

Maybe godwits have an eye for beauty that prefers rugged cool beauty than hot tropics?

Thanks for sharing Pete.

pohanginapete said...

Thanks Gustav; it's great to know you and your daughter enjoy and have so much respect for birds. Some of these species need all the appreciation and help they can get.

Don't Feed The Pixies said...

I've been saving this post for a moment when i had enough time to digest and enjoy it properly.

I love the way you tell this story - bringing us into your experience: and the photos are fantastic.

pohanginapete said...

Cheers, pixie. Thanks for taking the time to do it justice :^)

Vickie said...

Bird migration is fascinating in general, but to read that these relatively small birds can travel for nine days w/o stopping from Alaska to New Zealand is amazing. Studies of this sort are inspiring, both answering questions and generating new ones. Great post and images.

On a slightly different subject, you have a beautiful blog site here! (I would love to change the format of mine, but I'm afraid I'll lose everything.)

pohanginapete said...

Thanks Vickie. Actually, I have a similar problem — I'd love to switch the blog to the new blogger layout, but it's not simple to replicate the appearance. Fortunately, it still works, but I suspect the blogger people will eventually force a change. Oh well, I'll face that problem when I have to.

Beverly said...

Wow, awesome post. Like you, I’m appalled by the quality of our water…and have railed about it a number of times; but not so gently as you have.

In addition to fascinating information about birds and migrations…you give us a gentle hint to consider that everything we do affects our environment. Thank you!

pohanginapete said...

Cheers Beverly. I do get pretty wild about what's happening to our water. A recent report also indicated our favourite swimming places — beaches, rivers, etc. — are in an appalling state. Apart from the inherent shame of that, it's not a good look for a country that markets itself as "clean and green".

ehunter said...

Beautiful photos! I love the wrybill. I even knew what it was and it is definitely a bird I would love to see someday.

Can't wait to check out more of these posts.

pohanginapete said...

ehunter — thanks! Wrybills are lovely little birds, and I'm sure you wouldn't be disappointed to meet them. Jesse was at the estuary just before New Year and apparently while he was squinting at distant godwits through his scope, he had masses of little wrybills running around his feet, just a few metres away. I must get out there again soon...

Lydia said...

This post was extremely moving for me. I learned so much (about birds I had never heard of). Along with my new-found awe of their curved bills, the astonishing migration, how digital photography assists in the count, my edgy global warming concern was working overtime. I'm so glad that you ended the post with the hopes that perhaps the little boy would grow up to carry on the work.....

pohanginapete said...

Thanks Lydia; very pleased you appreciated it :^) We have to hold on to hope, and the comments I get here help me to do that. They convince me that many good, concerned people still survive and value more than just economic growth and material well-being.

Patry Francis said...

Once again, you take my breath away.

pohanginapete said...

I'm deeply honoured, Patry. Thank you.

It's good to see you back.

Peregrine's Bird Blog said...

Hi Pete
This takes me right back to my visit to Manawatu Estuary even down to meeting Jesse.

Great Post

Larry said...

An excellent post on the Godwits and the Manawatu estuary Pete! You have some great information here. My hats off to all those hard working scientists, working hard for bird conservation and extensively, our own.

I found it very interesting that the best photos for gathering information on these birds was at take off and landing. I guess I never thought about it before.

pohanginapete said...

Peregrine, thanks :^) That must have been quite a migration for you, to make it all the way here. Good that you got to meet Jesse, too.

Larry, thank you. I'm pleased I could share some of the information; even small things like the optimum time for recording information can sometimes spark an insight that leads to greater things. You're right, too, about scientists like Jesse — like you, I greatly appreciate their hard work (and believe me, some of it's miserable and mind-numbing!)