A tale of nature, wildlife and birding from Cheshire, North Wales and across the globe....

A tale of nature, wildlife and birding from Cheshire, North Wales and across the globe....

Thursday, 5 March 2015

Pacific Diver in Marazion

As we had a whole weekend free after visiting the Little Bunting, me and Alex decided to head back down to Cornwall to try and spot the Pacific Diver that overwinters around Mounts Bay near Marazion each year.

Pacific Divers have only recently been split from the near-related Black-throated Divers, and with only 8 accepted records for the UK, is a real mega. There were no accepted records in the UK or Europe even prior to 2007, but early that year 3 different individuals were identified, a first winter inland at Farnham Gravel-pits in Yorkshire from the 12th January to the 4th February, another first winter on the Llys-y-fran Reservoir in Pembrokeshire from the 2nd Feb to the 20th March, and this adult bird in Mount’s Bay, Penzance which first arrived on the 17th February. What caused this mini influx is unknown, although the fact that the species became wider known to birders, with more people aware of the ID features, may have contributed to the 2 other birds being found and subsequently IDed that very same winter.

Remarkably this is the 9th winter the Marazion bird has been back, although vagrant Pacific Divers do seem to show a tendency for remaining faithful to a site, as incredibly the Llys-y-fran bird returned again in the Februarys of both 2008 and 2009! Who knows how long the Cornwall bird will continue coming back for, although it has been showing far more regularly and reliably this winter than in previous years.

St Michael's Mount, Marazion
A view of St Michael's Mount from the Station Car Park
On arriving at the Station Car Park, we soon picked up several close in Great Northern Divers, but after determining the Pacific wasn’t anywhere near this car park, we adopted a different strategy to our first visit and decided to make our way along the bay, stopping off at various points. We headed over to Penzance, viewing from the road, where another GN was picked up along with a Black-throated not too far away in front of the rocks – the white diagnostic flank patch visible even at a distance. 2 Eiders fishing near the marina were nice to see, as were a pair of Gannets diving just off shore.

Deciding the best point to view from would be Long Rock Car Park itself, especially as that was where all the reports had been coming from lately, we the headed that way – managing to find it this time tucked away over a level crossing down one of the small lanes (on our last visit we just viewed from the Station Car Park, unaware of this better viewing point).  With just a few Great Northerns hanging around, there was still no sign of the Pacific, having last been reported at 10:30am that morning. Several other birders turned up as it neared to high tide, including the birder that had reported it this morning, but with still no sign we decided to head back round to Penzance and check the Jubilee Pool area. With no luck there, we returned to Longrock for one last check before the light faded, and joined the birder who had seen it that morning.

Alex spotted a different looking diver relatively far out beyond the rocks and as we got our scopes on the bird it was clear to see it wasn’t a Great Northern – structurally different with an exceptionally dark back, rounded head, and a clear, bright white contrasting throat and chest. The black line along the throat was also solid – no white collar indentations or dark curves around the neck. As divers tend to have a habit of doing as their name suggests, we were lucky that this one was busy preening, allowing us to really study the features. Despite the distance, our bird was clearly visible above the water, and the absence of the white flank patch that would otherwise indicate a Black-throated was apparent from all angles – the bird was a solid black colour all over down to the waterline. It had to be the Pacific. The man who had seen it earlier was also confident that this was the bird that he had seen this morning, and with it being way to far to determine a definite chinstrap, the absence of the white flank patch clinched the ID for me.

Sadly the light faded at this point, rendering viewing much harder (especially in my scope!) and we watched in dimming light until the bird eventually took off from the water and flew out far to sea – presumably to roost.

On our previous visit we had encountered a similar looking diver at very close range, and on seeing the bird again it was now clear that it was the same that we had been watching 2 weeks earlier. On our first visit we just weren’t armed with enough knowledge on the ID, and actually talked ourselves out of it being the Pacific back in the hotel! Having never seen one before and being alone with no one else to confirm, we just weren’t 100% confident on the ID to add it to our lists.

This brilliant video taken by Mark Hipkin in November 2014 was really useful in getting to know how the Pacific Diver would look in the field.

A lone diver’s proportions and size is always difficult to assess when it’s on its own with no other birds to compare it to, although the much smaller size (at one point I exclaimed it was nearer GC Grebe size) and the much shorter, stubbier bill that we noted should have told us it was the Pacific that we were watching and not a GN diver or BT, especially as there was a clear absence of a white flank patch.

It just goes to show that a little bit of research, knowledge and ID insights can go a long way (my excuse is that Pacific isn’t well document in my Collins!) and that you really need to know what you’re looking for in the field (as demonstrated on our first visit, when a couple were adamant that a young GN diver was the Pacific over and over again!). Having only ever seen one Black-throated Diver before (extremely distantly at Carsington Water, where it was the only diver present) I also wasn’t familiar or experienced enough with the structure of smaller divers in the field – another point that meant I just wasn’t 100% sure what we were looking at on our first visit. I always like to be 100% sure of a bird’s ID myself before I add it to my list, so I’m really glad we made the huge effort to come back to Cornwall in order to be fully sure that we had indeed seen the Pacific Diver.

For anyone looking to visit, the best vantage points can be seen on the map below. 

Pacific Diver Marazion Map

Pacific Diver Marazion Map
We saw the diver at points 1 and 3, and it apparently favours the area around the rocks (2)

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