Birds in Lincolnshire

Black Brants in Lincolnshire and the first hybrid records

The Brent Goose complex is generally considered to consist of three species, or sub-species, depending on current taxonomic opinion. These are:

• Dark-bellied Brent Goose Branta bernicla - chiefly wintering in the coastal belt between the Humber estuary and the Exe estuary
• Pale-bellied Brent Goose Branta hrota - birds from the Canadian population wintering in Ireland and the Svalbard population wintering mainly in the area of Lindisfarne, Northumberland
• Black Brant Branta nigricans - an increasing winter vagrant, mainly amongst flocks of Dark-bellied Brent.

Dark-bellied Brent Goose at Frieston Shore, Feb 2002 © Neil Smith 2002

Black Brant, Gibraltar Point 26th January 2003 © Stephen Botham 2003

Of the three, the Dark-bellied Brent Goose is the main species encountered within Lincolnshire. With an average of almost 21,000 birds in recent winters, the Wash is a Site of International Importance for the species in the UK as well as being the top location for wintering birds in the country. Flocks can be found all along this stretch of coastline from Gibraltar Point to Terrington Marsh on the Norfolk border. The Humber estuary, with a mean of almost 2,350 birds in recent winters also qualifies as a Site of National Importance in Great Britain. Within the county the main sites lie between Grainthorpe Marsh and Saltfleet. An exciting prospect for the watchers of these goose flocks is to find a vagrant Black Brant amongst them.

Records of Black Brant in Lincolnshire

Up to 1996 there had only been three records of Black Brant in Lincolnshire. Since then, allowing for duplication and returning birds at least another seven have been found. All records listed below concerned adult birds and, as would be expected, all were found with flocks of Dark-bellied Brent Geese. The breeding range of Dark-bellied Brent Goose has expanded eastwards in recent years following a population increase. This has brought them into contact with the westward expanding populations of Black Brants in the area of the Taimyr Peninsula; increasing the likelihood of their becoming caught up with westward migrating flocks of Dark-bellied Brent. On 30th January 1993 three Dark-bellied Brent Geese (2 female and 1 male) were caught at Kirton Marsh; one female had been ringed on 23rd July 1989 while the male and the other female (presumably a pair) had been ringed on 31st August 1990. These birds had originated from the Taimyr-Delta West, Taimyr, Siberia and had travelled a distance of 5,125km south-west to reach the wintering site at Kirton (LBR 1993). These recoveries provide firm evidence of the origin of some of our wintering Brent Geese and suggest a route by which a vagrant Black Brant might arrive on the east coast. This, and increased observer awareness, is the most likely cause of this recent increase in sightings. Records to the end of 2001 are as follows:

1982 Skidbrooke, 21st and 23rd January
1987 Kirton Marsh, 19th February
1991 Wainfleet, 10th January
1996 Holbeach Marsh, 10th November
1998 Butterwick Marsh, 26th April
Frampton Marsh, 16th October
1999 Gibraltar Point, 2nd-8th & 28th February and 11th?22nd March
Frampton Marsh, 18th March
Kirton Marsh, 5th-6th April and 5th December
Butterwick Marsh, 12th December
2000 Kirton Marsh, two 15th-16th January with one until 25th. Single 25th-26th November, then up to two in December remaining to 2001
Holbeach Marsh, 26th March
Cleethorpes & Humberston, 9th November into 2001 (two on 18th November)and finally 2001, a year which firmly established the Black Brant as an annual wintering species in the county:
2001 Humberston, the wintering bird remained until at least 29th January
Tetney, 9th April (possibly same as the above)
Kirton Marsh up to two wintering birds remained until February and then two returning birds 28th October into 2002
Holbeach Marsh, a single in January and on 18th February
Gibraltar Point, 21st February and possibly a returning bird during December remaining into 2002Welland Mouth, 21st April (possibly same as Kirton above).

As can be seen from the above records most were found amongst the large flocks of Brent that winter on the Wash. It is interesting to note, however, that the record at Cleethorpes and Humberston in winter 2000/2001 was the first record for the North Sea coast since the very first county record at Skidbrooke in January 1982. It appears that a pattern of occurrence has now emerged and it is presumed that several of the records involve returning wintering individuals. Providing that observers are prepared to keep searching these flocks there is no reason to presume that the recent increase in county sightings should change. Up to seven individuals have wintered with the Dark-bellied Brent in north Norfolk in recent winters, however, a record of a Black Brant at Spurn and Kilnsea, East Yorkshire, appearing intermittently between 18th February and 23rd May 2001 was the first for Yorkshire. This single record no doubt reflects the small numbers of Brent that winter in the Yorkshire.
Just as observers are getting to grips with the finding of Black Brants, another twist to the tale now emerges. In February 2001 I observed at least two hybrid Black Brants with the flock at Kirton, and it appears that this may not be the first time a hybrid has been recorded in the county.

Hybridisation in the Black Brant

The Dark-bellied Brent Goose breeds in north-west Siberia eastwards to the Taimyr peninsula while the Black Brant breeds in the Canadian Arctic from Melville Island westwards to Alaska, and in northeast Siberia westwards to the Taimyr peninsula. As already described, it is presumed that the Black Brants turning up on the East coast of England originate from the Siberian population breeding around the Taimyr peninsula which then attach themselves to the migrating flocks of Dark-bellied Brent, subsequently arriving on the east coast. In Finland, single Black Brants recorded migrating ENE with flocks of Dark-bellied Brent Geese in May 1982 and 1984 seem to support this theory.
In the summer of 1997, Syroechkovski et al (1998) visited a number of breeding colonies of Brent Geese in northwest Yakutia, East Siberia. At all sites both bernicla and the American wintering nigricans were present. Six American colour rings and one Dutch ring, collected from local hunters, revealed the presence of two flyways and two populations mixing in the Olenyok/western Lena Delta region. In addition, there were mixed pairs and individuals of intermediate plumage observed in one of the colonies. Of 22 geese ringed on the trip, one bernicla ringed on an island in the western Lena Delta was controlled on Vlieland in the Netherlands and had therefore travelled more than 5,500km, the longest distance known for a migrating Dark-bellied Brent Goose. Birds in this area must account for several of the Black Brant records in Britain and perhaps the records of hybrid individuals.

Hybrid Black Brants in Britain and Europe

There appears to be few documented reports of hybrid Black Brants in Britain and Europe, so it must be presumed that their occurrence is rather rare. In Britain the first record of a mixed pair of Black Brant and Dark-bellied Brent Goose with hybrid young was at Thorney Deeps, West Sussex, from 8th January to 18th March 1989. This pair had six young, all of which closely resembled nigricans. In 1997 one or two apparent Black Brant x Dark-bellied Brent Goose hybrids were reported on the Fleet in Dorset on 4th-15th January, while even more recently a mixed pair with four hybrid young was present with a Dark-bellied Brent flock at Burnham Deepdale, Norfolk from 9th January to 2nd May 2001. These birds were a tight-knit family group comprising a presumed adult male Black Brant and a female Dark-bellied Brent Goose. The only known record of hybrids in the Netherlands came between 15th December 1991 and 9th February 1992 when an adult male Black Brant and a Dark-bellied Brent Goose with two hybrid young were present in the vicinity of Grevelingendam. It is also interesting to note that between 15th-22nd March 1998 a pair of pure Black Brants with two young stayed on Texel, Netherlands and on 16th February 2002 a pair accompanied by one juvenile was observed at Snettisham, Norfolk. These records represent the only pure family groups to be identified in Europe.

Hybrid Black Brants in Lincolnshire

The first documented record of a hybrid Black Brant for Lincolnshire was the report of a bernicla/nigricans intergrade at Moulton Marsh on 11th January 1992 by A.H.J. Harrop (LBR 1992). Unfortunately no further details of this individual were published at the time. In recent winters, along with fellow South Lincs birders, I spent many hours studying the flocks of Brent Geese that winter at Butterwick, Frampton and Kirton Marshes. The rewards of this searching were several records of Black Brant; the flock at Kirton proving particularly interesting and educational on the complexities of Brent Goose identification. The possibility of some birds being hybrids was mooted several times and early in 2001 this was confirmed in the following way.
On 17th February conditions for goose-watching at Kirton Marsh were ideal. The weather was sunny with virtually no wind and during the course of the morning the Brent flock gradually flew in to feed close to the seawall. By late morning up to 4,000 Dark-bellied Brent, 4 Pale-bellied Brent and 2 adult Black Brants were present. Careful scanning and close scrutiny of the flock provided some interesting looking individuals; two birds that fed close to, but not necessarily associated with, one of the adult Black Brants showed signs of hybridisation. Having never seen such a hybrid before, I took notes on these individuals, but was reluctant to claim them as such until I had had a chance to investigate further. Shortly after these sightings details of the Norfolk family were published, along with photographs. After studying these photographs, and those of the hybrids in the Netherlands, I was convinced that the birds I had seen were in fact Black Brant x Dark-bellied Brent hybrids; only the second time such birds have been recorded in the county.

The Kirton Hybrids

The two hybrids were both adult birds and plumage features indicated the mixed parentage. Both birds showed a broad neck collar which, although not quite as extensive as that shown on adult Black Brants, was more extensive and well developed than that of any of the Dark-bellied Brent present. The flank patches showed an obvious Black Brant-type pattern but also showed some 'dusky' feather fringes giving it a rather washed-out appearance. The back and belly of these birds appeared to be slightly less concolourous with the neck compared to the two 'classic' Black Brants present, but were darker than those of the Dark-bellied Brent. In size and structure they appeared little different to the accompanying Dark-bellied Brent and tended to feed towards the outer edges of the flock (as did the two adult Black Brants).
To bring things right up to date, in January 2002 Steve Keightley located a mixed pair of a Black Brant and a Dark-bellied Brent Goose with five hybrid young in the Brent flock at Kirton Marsh. A second adult Black Brant at the site apparently did not associate with these birds. Video footage obtained of these birds will prove valuable in the identification of any future hybrids.

Summary

Whether or not hybrid Black Brants will remain identifiable when they attain full adulthood is perhaps debatable. Close scrutiny of Brent flocks in recent winters has shown that some of the birds present do look rather strange. During the past two winters up to six Pale-bellied Brent have been present at Kirton, and with a presumed adult Black Brant x Pale-bellied Brent Goose hybrid having been reported from Ireland could this perhaps account for some of the strange looking geese on the Wash? An adult Brent Goose sp. present at Wells, Norfolk during autumn 2001 defied positive identification. It was not a Dark-bellied Brent, so could have possibly been a hybrid, an aberrant Pale-bellied Brent or possibly even a Grey-bellied Brent, which breeds solely on two islands in the Western Canadian High Arctic. One thing is certain, Brent Geese are no longer just Brent Geese; spending time studying these fascinating birds on the Wash is a challenge and an education in itself.

References

Catley, G.P. Black Brant at Skidbrooke, January 21st 1982 Lincolnshire Bird Report 1982. Lincolnshire Bird Club.
Lincolnshire Bird Reports 1987, 1991 and 1992 Lincolnshire Bird Club.
Lorand, S. and Atkin, K. 1989 The Birds of Lincolnshire & South Humberside Leading Edge
Lewington, I, Alström, P. and Colston, P. 1991 A Field Guide to the Rare Birds of Britain and Europe Harper Collins
Mullarney, K, Svensson, L, Zetterström, D and Grant, P.J. 1999 Collins Bird Guide Harper Collins
Beaman, M and Madge, S. 1998 The Handbook of Bird Identification for Europe and the Western Palearctic Helm
van den Berg, A.B. and Bosman, C.A.W. 1999 Rare Birds of the Netherlands. East Sussex
Cranswick, P.A., Pollitt, M,S., Musgrove, A.J. and Hughes, R.C. 1999. The Wetland Bird Survey 1997-1998: Wildfowl and Wader Counts. BTO/WWT/RSPB/JNCC, Slimbridge.
Pollitt, M.S., Cranswick, P.A., Musgrove, A.J., Hall, C., Hearn, R.D., Robinson, J.A., and Holloway, S.J. 2000. The Wetland Bird Survey 1998-1999: Wildfowl and Wader Counts. BTO/WWT/RSPB/JNCC, Slimbridge.
Millington, R. Separation of Black Brant, Dark-bellied Brent Goose and Pale-bellied Brent Goose Birding World 10: 11-15
Bloomfield, A, and McCallum, J. Changing fortunes of the Black Brant. Birding World 14: 66-68

Acknowledgements
I would like to thank Steve Keightly for useful discussion on Brent Geese in the Wash and for information on the hybrid family in January 2002.

Matthew Harrison

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