Wednesday, 31 January 2018

The arrival of a new English goose ?

Pink-footed Geese flock over the marshes at Lady Anne's Drive

Ever since the days of the Victorian ‘gentleman gunners’, the wildfowlers and collectors of the distant past, Holkham has maintained its place as being one of the most consistent spots in the UK for attracting large numbers of wild geese. It was only during and after the Second World War with disturbance from heavy artillery fire that the vast skeins of Pink-footed Geese, the species that Holkham became synonymous with, temporarily deserted us. Holkham fits nicely into the ornithological history books not only for having one of the largest concentrations of ‘Pinkfeet’ in Norfolk when some 90,000 were estimated to be present on a single day back in 2006 but also for providing the county with its very first example. Pink-footed Geese, with their pink legs and feet are very similar to Bean Geese (with their orange legs and feet) and in Victorian times they were deemed one and the same. It took until 1833 before it was realised that two species were actually involved and how fitting it was that the first Norfolk Pinkfoot should be shot at Holkham. Incidentally that very first one was preserved and is still on display within Holkham Hall. This year Pinkfeet numbers have only managed to reach 33,000 on the reserve, still a significant total but far less than the 2006 count! Reasons for such a drop include less sugar beet being grown locally (the harvested yet unwanted tops and leaves left in fields are the main winter food source) and milder weather and more food in Scotland.

A flock of Dark-bellied Brent Geese rise up from Burnham Overy marsh.

Apart from the Pinkfeet there are other species of wild geese that arrive each winter to seek food and sanctuary on the protected marshes of the north Norfolk coast, Holkham in particular. Probably most well-known to casual observers, second after the Pinkfeet would be the Brent Geese. Brents are smaller and darker and part of a different family of geese. Our geese come into two distinct groups; Anser or ‘grey geese’ like the Pinkfeet and common feral Greylags or Branta otherwise known as ‘black geese’ such as Canada, Barnacle and Brent Geese. Like many species of geese there are distinct sub geographical groups; different populations from distinct parts of the World. They might all nest in a certain area and then winter in another distinct area well away from others of their kind. Birds such as Barnacle Geese cover several widely separated areas of the Arctic in which they nest yet usually stay well apart in the winter but essentially they all look identical. The difference in the various Brent geese is that they have evolved so that they actually look different in different parts of their range. Here at Holkham we have been lucky as we have been able to see and compare these different forms. At the moment they are all deemed as identifiable sub-species yet with evolution still ongoing and the taxonomic scientists working overtime they might at some point all become species in their own right.

The common form of Brent Goose seen in Norfolk is the 'Dark-bellied'

The common form we see here in north Norfolk is the Dark-bellied Brent Goose. It arrives every September from breeding grounds on the tundra from northern and central Siberia and peaks at about 5000 feeding on short coastal grassland, cereal, saltmarshes and mudflats although numbers are far less than they were 20 years ago. Less common is the Pale-bellied Brent Goose. It nests in the Greenland, Canadian High Arctic, and Svalbard. Small numbers from the latter two populations appear in Norfolk amidst the Dark-bellied birds, with the Greenland birds most likely to be seen amongst the wintering Pinkfeet. A far rarer form, the Black Brant can be seen in even smaller numbers here in Norfolk, usually a couple per year. This form breeds from the central high Arctic Canada across to the Pacific coast of both North America and Asia. This is where things really start to become confusing (or interesting!) as where Dark-bellieds and Brants meet there is occasionally inter-breeding. 

The less numerous Pale-bellied Brent Goose

The striking looking black and white goose in the centre is the rare Black Brant

All geese traditionally remain a tight family unit during their first year, even during their migration south, it means when we see goose flocks here in the winter we can see both parentage and the amount of youngsters in each family. This year has seen an almost complete failing of the breeding Brent Geese, hardly any young in evidence and a phenomenon that frequently occurs. The success and failings of Arctic breeding Brent Geese is linked to the availability and abundance of rodents for predators such as Arctic Foxes. No Lemmings means baby geese are sought after as prey. What we have seen here at Holkham currently amidst the flocks of Brent Geese are all the different forms together in the same flock including some of those hybrids. Such identification conundrums have stirred up much interest from visiting birdwatchers at Lady Anne’s Drive, where the flock habitually frequents.

The birdwatcher's conundrum - one of our regularly occurring hybrid birds

Even more unusual for us this year is a potential English first – a Grey-bellied Brant. This fourth form in the Brent goose group of sub species has only recently been truly recognised (although some scientists are still arguing this!). It breeds in a relatively small area of western High Arctic Canada and winters solely in Puget Sound, western USA. In looks it appears intermediate between Black Brant and Pale-bellied and some observers initially thought they were hybrids although ongoing work has suggested that is not the case. The odd bird has turned up in Ireland but never in England so when a bird turned up amongst the Pinkfeet this October at Wells and then at Burnham Overy in November it proved a very exciting find for avid local goose-watchers. With scientific work continuing and evolution obviously very much ongoing it could be we have to wait quite some time before the mysteries of the whole Brent Goose group truly unravels. In the meantime have a look and you will see that everything is not quite just black and white!

This year's Grey-bellied Brant - a potential English first ?

Andy Bloomfield