Northern Shoveler at Miranda

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Les Feasey
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Joined: Wed Jul 06, 2016 1:03 pm

Re: Northern Shoveler at Miranda

Postby Les Feasey » Wed Aug 01, 2018 7:52 pm

I was with Grahame when we saw the Northern Shoveler at Miranda on Tuesday. My photo didn't have the Kotuku, though. We had good views for about 20 minutes at least until I went back to the car to get the camera. With regards the mating activity, Ian, the Northern Shoveler was running up and down the mudbank for a period, and I did wonder about that activity, because it wasn't prompted by other Shovelers.
Les Feasey
Opua, Far North
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RussCannings
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Joined: Wed Sep 24, 2014 5:23 am

Re: Northern Shoveler at Miranda

Postby RussCannings » Thu Aug 02, 2018 7:27 am

Hi Sav,

This is perhaps what Ian was getting at but here are two possible theories why they're all in breeding plumage:

1) Many vagrants (especially long distant migrants) will delay moult until established in a suitable wintering spot with sufficient food etc., (ie of you're flying around lost on a big ocean, you need every feather at your disposal), sometimes this can lead to them missing/repressing/delaying a seasonal hormonal change that triggers molt. Once they set up in a favourable place then things can be a bit out of whack. Something similar can be seen in young nomadic crossbills as depending on when they under go a second pre-basic molt, immature males can be all yellow, all red, or a mix. So these birds may have been wandering juvenile males that are now off kilter with their northern brethren.

2) Perhaps related to the above theory, it seems that many northern hemisphere breeders that get lost (or in the case of our exotic Europeans) and end up down here, adjust to the opposite seasons along with their molt cycle. Consider the Leach's Storms on the Chathams and in South Africa (always nesting in the boreal winter--opposite to 'normal' LSP) or our South Island nesting WW Black Terns (that interestingly have never been recorded nesting in Australia despite being vastly more common during our summer season). So maybe these shoveler have made an adjustment to the southern hemisphere. What exactly triggers the adjustment? Don't know. Will they stick around in spring and try it on with some female Australasians? Dunno. On Ian's thoughts about northern waders, remember that the long-staying Miranda Marsh Sandpiper fell into an opposite molt cycle and I was there the day a second Marsh sandpiper arrived and can tell you that the local bird (who was in breeding plumage in Nov) was VERY excited to see another Marshie. Had it been an adult of the opposite sex I'm sure it would have done the deed (or at least tried to) ;)

Interesting stuff to think about..

Russ C
Morrinsville, NZ
Clinton9
Posts: 888
Joined: Sat Aug 07, 2010 10:22 pm

Re: Northern Shoveler at Miranda

Postby Clinton9 » Fri Aug 03, 2018 4:20 pm

If the Northern shoveler were to remain thought austral winter and spring here, its flight feathers now one year old, would be very worn on January (austral summer), and when in eclipse plumage, it might not be told from eclipse-plumaged Australasian shovelers.

If the Northern shoveler marry an female Australasian shoveler, the future hybrid Northern X Australasian drakes would be a mixture between parents, like Australasian shoveler, but with lighter breasts and stronger green glossy to bluish-grey heads.

There is no studies and photos of birds change their moulting seasons from Northern hemisphere to Southern hemisphere.

Northern shoveler that decided to stay in New Zealand and not be bothered to migrate back to Asia, once moulting to eclipse plumage on December (austral summer), would be in trouble trying to fly away if an Swamp harrier arrive, as its 19-month-old flight feathers will be very worn and almost useless for flying. Once it shed all 19-months-old fight feathers on January, it will be flightless for 3 weeks, and flight feathers are not fully grown until 4 weeks old. Normally the flight feathers last 12 months between moulting seasons in Northern shovelers.

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