Common Shelduck (of Unknown Provenance), Rye, NH - August 2017

An interesting report of an immature Common Shelduck came across my eBird NH Needs Alert.  Of course I needed Shelduck for my NH list – not only are there no accepted records in NH, there are no records accepted by the ABA.  Not surprisingly, my initial thought was this bird was an escapee from a local waterfowl breeder.  Slowly additional details came to light – first of all the bird was unbanded and not pinioned.  And then came a report that a local breeder was contacted and he had not lost any Shelducks.  Eventually photos showed the bird had both hind toes.  And there were reports that wild Shelducks in Europe are indeed migrating this time of year.  With this information, several birders were starting to think that it could be a wild bird.  So although I was still very skeptical, not wanting to take any chances, I decided to head out to try to find it.

I pulled up to the pools just south of Odiorne Point State Park where the Shelduck had been hanging out for the last week, and instantly spotted a large, pale duck at the edge of the southernmost pool.  With a quick binocular view it was obvious that it was the immature Common Shelduck.  I headed over to the pool and watched the bird for the next hour as it fed in the shallows with a slow side-to-side sweeping motion.  As I continued to study this very attractive bird, I couldn’t help but think I would have had no idea what species it was if I had discovered it.  Although lighting was harsh, I got these passable phonescoped photos of the bird. 

This isn’t my first encounter with Shelducks in the ABA.  Back in the 70’s there were breeding populations of both Common and Ruddy Shelducks in DE at Bombay Hook NWR, and I saw them on several trips to the region.  Needless to say everyone thought those local populations were from escaped birds and not wild countable birds.

Now some thoughts on whether the NH bird might be a wild migrant from an expanding population in Iceland, or an escaped feral bird -

First of all, one can only prove with 100% certainty that a bird is wild if it has been banded as a wild bird likely in its native land.  Though you can prove that a bird is an escapee in multiple ways such as if the bird is pinioned, missing hind toes, or banded by a breeder.  This bird is unbanded, unpinioned, and has its hind toes.  So without any feature to conclusively determine the provenance of the NH bird, one has to use a "weight of evidence" approach - is there more evidence that the bird is wild than it is an escapee? 

I’ve read a report that native Common Shelducks in Europe are indeed migrating at this time of year.  But it’s unclear if juveniles are migrating now, or just adults, or both.  Plus, how far are they migrating this early in the season?  For instance we might call a mid-summer Yellow Warbler at Odiorne a "migrant", but it may just be a post-breeding wanderer from a nesting location a mile away.  By comparison, the Stilt Sandpiper seen recently in the same pools the Shelduck is frequenting is certainly a long-range migrant - its closest breeding area in Manitoba is 1,300 miles away, and its breeding area in Nunavut is 2,300 miles (as the sandpiper flies). 

Could the Iceland Shelducks be "migrating" from their nest sites but still staying in country, going to a post-breeding feeding area still in Iceland?  For instance there is an eBird report of 120 birds at the Andakill mudflats in Iceland on 6/27/17 – perhaps a post-breeding dispersal site?  Or could they be migrating a greater distance, say to somewhere in the UK?  That would be about 1,200 straight-line miles to the southern end of England.  Or maybe they've already arrived in southern Spain, one of their typical wintering grounds - the straight-line distance is 2,000 miles.  They typically winter no farther south than coastal Morocco and Algeria - 2,200 miles away on a straight line. 

By comparison, the minimum straight-line distance from Iceland to the NH coast is something like 2,400 miles.  In other words - for this to be a truly wild migrant in NH, the distance the bird would have traveled would be roughly the same distance that a bird could have migrated from the species' farthest northwest breeding area (Iceland) to its farthest southwest wintering area (coastal Africa) - all before mid-August.  That is assuming that birds breeding in Iceland would winter all the way south to Africa in the first place (instead of birds breeding closer to Africa being the source of the individuals wintering in Africa). 

Muddying the waters - not all Shelducks leave Iceland for the winter - note an eBird report of 160 birds on 1/29/17 in Grunnafjordur, Iceland.  And Shelducks are breeding in Spain and Portugal - they are reported every month of the year in eBird.  So could birds breeding in Spain and Portugal be the source of those wintering in Africa, rather than birds from farther north?

Then there is the issue of when Shelducks normally appear on their wintering grounds in northern Africa.  Using eBird data, the first scattered reports are in October, and they don't seem to arrive in any real numbers until December.  Note that there are 4 reports of 26 to 46 birds in central Algeria in summer last year and since May of this year - likely a local feral flock I would imagine rather than migrants.

One point to note though is that there aren’t nearly as many users of eBird in Europe and Africa as there are in the States.  So one has to use a grain of salt when evaluating data from those regions. 

In summary - for the NH bird to have migrated from the closest breeding area in Iceland in August, it would have had to migrate a distance roughly equal to the distance the species might take from its farthest northwest breeding area (Iceland) to its farthest southwest wintering area (coastal Africa), and it would have had to do this migration at least a couple months before the first birds normally appear in coastal Africa.  Not to mention all of this migration would be along a route not typically taken by wild birds.

Can more eBird research shed additional light on the bird?  I'm sure it can, but with my limited effort it seems that the possibility that this is a true wild migrant is remote.  I wouldn't say 0%, but certainly a low probability.  But as I said initially - one cannot be 100% sure on this unbanded/unpinioned bird, so probabilities are the best we can work with.

Now for local sources of Shelducks - I’ve heard that a local waterfowl breeder has not lost any Shelducks.  But I found a couple websites that sell Shelducks - anyone could go online and purchase a pair for just $135.  So it would be easy enough for anyone to buy one – you wouldn’t just have to be a breeder to own Shelducks.  And if a breeder somewhere nearby in say MA or ME lost a bird, it sure could have wandered easily enough to the NH coast.  This is obviously the time of year when post-breeding dabbling ducks wander and congregate in favorite feeding locations.  In summary – it’s plausible that the NH bird is a local escapee - though again I can't say 100%.  But it is certainly a higher probability than the wild migrant option.

And a further complication – an adult Common Shelduck was discovered in far northeastern NY at about the same time the NH bird was discovered.  Were both of these two birds blown off-track from Iceland by the same forces?  Or were both birds escapees from the same breeder?  Or maybe the two sightings were just a coincidence?  Seems like this last option is the least likely, but who is to say.

In conclusion, given the weight of evidence as I know it now, I could not accept the NH Common Shelduck as a wild vagrant.

Now show me a bird in suitable habitat in December and I could change my mind.  Oh wait a minute - that's exactly what happened in MA in 2009 and even that record was rejected.  Though it’s notable that there was a group of 3 adult Shelducks seen in New Brunswick this past winter that local birders are thinking could be wild birds.  And apparently at least one older record from the east coast of Newfoundland (on 4/2/14 per eBird) has been accepted by the province’s committee.  So perhaps if this is the beginning of a future pattern of accepted wild Shelducks, the NH and MA rare bird committees could come back and re-evaluate the recent New England records.