Pintail in the Severn Vale

By Les Brown and Mike Smart

(Although much of this review covers Gloucestershire it doesinclude parts of the Severn and Avon flood plains of Worcestershire, and Worcestershire's Longdon Marsh. In times of floods the two counties probably contain nationally and internationally important numbers of pintail. In this context it is important that their numbers, distribution and requirements are better understood. Ed)

Introduction

In February/March 2002, unusually high numbers of Pintail were observed in the Severn Vale, notably at the Ashleworth/Hasfield Hams and the Coombe Hill area (the "Severn Hams"), the principal floodplain of the Severn between Tewkesbury and Gloucester, but also at Walmore Common, below Gloucester. Numbers in the Severn Hams were estimated at around 1500, possibly as many as 2000, with over 200 at Walmore, mostly feeding on flooded grassland. These numbers are unusually high for the area, though there has been a general increase in Pintail in the Vale floodlands in recent years. There had already been high counts in the Severn Vale in the previous winter (2000-2001), at Ashleworth/Hasfield, Coombe Hill, Walmore Common and Longdon Marsh (just in southern Worcestershire), not to mention the New Grounds at the top of the Severn Estuary at Frampton/Slimbridge. But the counts in early 2002 have been exceptionally high.

To put these figures in context, the agreed figure for national importance is 280, and for international importance (ie qualifying for inclusion on the Ramsar List of wetlands of international importance) 600, if these figures are reached on a regular basis.

In a review of long term population trends in Pintail between 1966 and 1995, based on the results of the WeBS (the Wetland Bird Survey) counts, Kershaw (1998) pointed out that "Pintail is one of the only two wildfowl species for which the international 1% level for northwest Europe has been reduced in the latest review, following a downward revision of the winter population estimate from 70,000 to 60,000 birds". Furthermore, "the northwest European wintering population of Pintail is relatively small compared to other areas of Eurasia, but Great Britain holds almost half of these birds, the highest population of any species". The conservation status of the British wintering populations of Pintail is therefore a matter of national and indeed regional importance.

Kershaw added that northwest England/North Wales is by far the most important region for wintering Pintail in Great Britain, with a mean peak annual count between 1966 and 1995 of 13,907 birds, three times higher than the second most important region, east/central England with a mean of 4061. The mean peak for the southwest England/South Wales region over this thirty-year period was 1842 (about equivalent to the number recently seen on the Severn Hams!). Kershaw noted that in the 1991-95 period the ten main British sites for Pintail were, in order of importance: Dee Estuary, Ribble Estuary, Morecambe Bay, Mersey Estuary, Solway Estuary, Burry Inlet, Ouse Washes, Duddon Estuary, Nene Washes and North Norfolk Marshes. It is evident that most of these sites are estuarine. According to the annual WeBS report for 1999-2000, the most recent available, the Great Britain maximum of 17,333 in November 1999 was the lowest since the late 1970s. However, the "top five" sites remain the Dee with a five year mean (for the 1995-2000 period) of 4900, Morecambe Bay 3830, Solway 3610, Ribble 2982, and Burry Inlet 2783. The Ouse Washes (with a five year mean of 2720) and Nene Washes (1023) are the only inland sites in Britain that met the international criteria between 1995 and 1999. The very large Severn Estuary WeBS site (covering not just the New Grounds at Slimbridge/Frampton but the whole of the Severn Estuary from Newnham (below Gloucester) to Cardiff on the northern shore and Newnham to Bridgwater in the south) just reaches the international threshold with a mean of 641.

Pintail breed in Iceland (about 500 pairs according to Birds of the Western Palearctic), but most of the Pintail wintering in Britain originate from breeding grounds in northern and central Europe, so it is perhaps surprising that the top five British wintering sites should be on the west coast. Numbers wintering in Ireland are small, and the All-Ireland threshold is only 60, so the Severn Vale birds are not likely to be migrants returning from Ireland.

Review of Records

Past records of Pintail in Gloucestershire

Swaine's "Birds of Gloucestershire" (1982) indicated that "numbers have increased considerably during the past thirty years". The author noted that the New Grounds formed the main winter resort in the county, and that numbers of 100 to 200 were quite usual there, with counts of 400 in December 1957 and 600 in January 1977. He added that large numbers at Ashleworth, Coombe Hill and Walmore depended on flooding, and that counts of 200 had been made at Coombe Hill and 300 at Ashleworth. Finally, Swaine noted that the Pintail was virtually unknown in the Forest of Dean and the Cotswold dipslope, though up to twelve had been recorded in the Thames Valley gravel pits (now the Cotswold Water Park).

WeBS counts have been carried out at Ashleworth since 1974-75 and at Coombe Hill (not every year) since 1961-62. Before 1992-93, the annual maximum at Ashleworth reached 100 only once, in 1974-75, and was usually less than 50, generally occurring in February or March, though once or twice in January. At Coombe Hill, Pintail were not recorded every year in the WeBS counts and numbers never exceeded 25 birds before 1991-92, with the low peaks reached in any month between December and March.

Numbers of Pintail recorded at Coombe Hill and Ashleworth/Hasfield have increased in the 1990s, both in the WeBS counts and in records from other sites published in the Gloucestershire Bird Reports (GBR) - latest available 1999 - as follows

There are thus indications throughout the 1990s of somewhat higher numbers being recorded at Ashleworth/Hasfield and Coombe Hill (though, since the two sites are close together and birds move back and forth especially when flooding is high, it is important to obtain co-ordinated counts from both sites).

The Gloucestershire Bird Reports also give details of appreciable counts at Walmore Common: 300 in January 1990, 175 in January 1993, 130 in December 1993, 150 in March 1997, 200 in January 1998, and 87 in January and 120 in December 1999.

Pintail numbers in the Severn Vale usually seem to peak in late winter, in February or March, though there are sometimes high counts in December or January.

In the New Grounds sector of the Severn Estuary at Frampton and Slimbridge, maxima from the Gloucestershire Bird Reports are: 245 in March 1990, 275 in February 1993, 238 in December 1994, 350 in January and February 1995, 286 in March 1996, 320 in February 1997, 210 in January and February 1998 and 321 in January 1999. Dave Paynter pers comm has checked the Wildfowl and Wetlands Trust's records of maximum counts and notes that between 1945 and 1977 there was a gradual increase from a maximum of 100 to a maximum of 300, with the high count of 600, mentioned by Swaine, in 1977. The increase has continued since 1977 with the maximum count generally between 300 and 400. The only count of 1000 occurred in exceptional circumstances (see below) in December 2000.

Numbers have remained low at the Cotswold Water Park, rarely reaching 20 individuals, though there was also an unusually high count of 225 Pintail at Pit 41 in the Cotswold Water Park (West) on 19 February 2002 (A. Jayne pers comm).

Recent counts in the Severn Vale

It is important to emphasize the difficulty of obtaining accurate counts in the Severn Hams area when floods are high. Many of the access roads are then impassable, and there is a broad stretch of floodwater some five miles by three miles, the edges of which are exploited by surface feeding ducks. G. Peplow pers comm notes that at Longdon Marsh too, precise counting is difficult in times of flood as some birds are hidden behind partly flooded hedges. If the flood is very high, ducks may decrease in the central area of the Severn Hams, using sites further north in Worcestershire, such as Longdon Marsh and marshes along the Avon. If the floodwater freezes over in a cold spell, these surface feeders may disappear, presumably to the Severn Estuary. WeBS count dates often do not coincide with flood episodes, and so may fail to pick up any large numbers present in time of flood.

In order to throw more light on these numbers, LAB, who carried out the WeBS counts in most of the 1990s and who has visited Ashleworth once or twice a week throughout the period, with more frequent visits to Coombe Hill at the end of the decade, has reviewed his observations over the last ten years, in order to link count dates and periods of flooding. The following paragraph summarizes his observations, giving the period when the floods were high and the highest counts of Pintail in each winter.

In 1991-92, with little flooding, numbers of Pintail did not exceed 35. In 1992-93, with flooding in early December and mid January, peaks of up to 190 Pintail were noted between December and mid-February. In 1993-94, with flooding from mid-December until mid-January, peak Pintail numbers of between 130 and 240 were recorded until late February. In 1994-95, with flooding from mid-December to mid January, then from late January until mid-March, peak Pintail numbers ranged from 165 (late December) to 245 (early March). In this same winter the 1995 GBR notes high counts (by other observers) at Coombe Hill of 140 in January, 500 in February and 60 in March. In 1995-96, with flooding from mid-January to mid-February and a freeze-up in early February, peak numbers of 245 and 205 were noted before the freeze-up (while the 1996 GBR gives a record of 300 at Coombe Hill for this period); numbers after the freeze-up were less than 50. For 1996-97, with a freeze-up in late December and January but little flooding, there were no records of more than 100 Pintail. In 1997-98 there was a high count of 115 in November before the flooding which lasted from late December until early February; the highest Pintail counts of the winter (165 and 185) occurred in late January and early February. Winter 1998-99 brought an early flood in late October/mid-November and a count of 130 Pintail in November, followed by a flood from mid-December to early February, with a count of 520 Pintail in February. In 1999-2000, flooding was from mid-December to early January, with a count of 300 at Ashleworth in January. In the very wet winter of 2000-01, extensive flooding (from late October-December, from mid-January to mid-February and from mid March to early May), plus the effects of the Foot and Mouth outbreak, often made counting very difficult. There were combined counts of 500+ at the two sites in November, over 350 in December, up to 400 in January after a freeze-up in late December, and about 500 in February, with 230 in March. Finally in winter 2001-02 there were brief late October and early December floods, with a freeze-up in early January, followed by extensive flooding from late January until mid-March; numbers of Pintail reached 240 in January then rocketed to figures of nearly 2000 in early March.

In addition, Andy Jayne, who has been watching Walmore regularly since the late 1970s, comments that numbers have definitely increased there since then, and that the high counts occur in periods of extensive flooding. He adds the following counts from Walmore for winter 2000-01: 12 on 3 November, 150 on 18 November, 76 on 19 November, 100+ on 26 November, 90+ on 25 December; records in early 2001 are limited because of the Foot and Mouth outbreak.

The above detailed observations show clearly:

Increase in numbers:

Whereas numbers of Pintail in the Severn Hams only exceptionally reached 100 birds before the 1990s, counts of over 100 have become commonplace in the last decade, particularly in the last five years. February 1995 saw counts of 300 at Ashleworth and 500 in Coombe Hill (very probably the same birds). Again in February 1999 there was a count of 520. In November 2000, an early date coinciding with early flooding, there were over 500 Pintail present in the Severn Hams), and it was estimated that the numbers of Pintail in late 2000 approached 1000 birds. Finally, winter 2001-02 has produced the highest numbers so far, with at least 800 at Coombe Hill in February and 1500 (and perhaps as many as 2000) round the edges of the flood at Ashleworth/Hasfield in March 2002.

Occurrence after flood events:

Such large numbers of Pintail occur only during and after floods which cover the whole floodplain. In conditions when there is no flood, an area of open water is maintained by a sluice on the Gloucestershire Wildlife Trust reserve at Ashleworth Ham, but numbers on this area of water and marshy vegetation are typically below 100 birds. The large concentrations occur on the edges of the floodwater beyond the boundaries of the Ashleworth reserve and of the new GWT reserve at Coombe Hill.

In November 2000, the whole of the Coombe Hill meadows were flooded, and a set-aside field below Deerhurst Walton proved particularly attractive to ducks and Bewick's Swans (most of the Bewick's that normally spend the autumn at Slimbridge were in this area in November-December 2000). On 19 November - an early date for such numbers - a minimum of 330 Pintail were counted over the flooded set-aside, and the total present was probably 500. At the same time, the unusual figure of 190 Pintail was recorded from Longdon Marsh, in south Worcestershire. This illustrates the tendency for Pintail to go to Longdon in numbers when the flood is very deep on the Severn Hams.

At Coombe Hill in 2002, 800 were seen in the area of the same set-aside field on 7 February, soon after the first big flood of the winter, and there were at least 400 there on 9 February. Large numbers were recorded in the Ashleworth/Hasfield area in February with 600 on 9 February, and on 26 February at least 1100, and perhaps 1500, in shallow water around the edge of the floods, just outside the GWT reserve, mainly in the area of Hasfield Ham. Up to 1500 and perhaps 2000 were recorded in early March, by which time the floods at Coombe Hill had gone down, and it seems clear birds from Coombe Hill had moved to the Ashleworth/Hasfield flood. These numbers were maintained as long as there was natural flooding (outside the Ashleworth reserve), until 10 March. By 12 March, however, when the only open water remaining was on the Ashleworth reserve and was not fresh flood water, numbers dropped dramatically and on 16 March there were no more than 350 Pintail left on the reserve.

A similar situation occurred at Walmore Common, in the Severn Vale below Gloucester. In February 2002, as soon as the floods began to rise, large numbers of Pintail occurred. There were 180 on 2 February, 220 on 5 February, 240 on 10 February, about 200 on 12 and 15 February, and 100+ on 18 February; these birds disappeared from Walmore as rapidly as they had arrived when the floods receded after about 20 February, so that only 14 were recorded on 2 March (many records from A. Jayne pers comm).

Low numbers in absence of flood:

There is extensive flooding in the Severn Hams most winters, but outside periods of flooding, the large numbers of Pintail disappear. Similarly in winters like 1991-92, 1996-97 or 1999-2000, when flooding is light or absent, large numbers are not recorded.

Thus the large concentrations coincide with the time of flooding, rather than with any periodic movement. When there is a November or December flood, good numbers of Pintail occur in these months. The most frequent months for flooding are December to February, hence the frequent peaks of Pintail at this time.

Departure in case of freeze-up:

In winter 1995-96, numbers of Pintail dropped from the region of 300 in December before the freeze-up to about fifty afterwards. There was a week's cold snap in the very wet winter of 2000-01; after counts suggesting the presence of up to 1000 Pintail in the Severn Hams area in November/December, the Bewick's Swans and Pintail which had been frequenting the set-aside field disappeared in a cold snap between Christmas and the New Year, when most of the floodwater was heavily iced over. It is known (from ring numbers and face patterns) that the Bewick's returned to the New Grounds. A quite exceptional count of 1000 Pintail on the New Grounds in late December 2000, when there had been no count remotely approaching this figure throughout the preceding autumn (nor at any other time since 1945!), suggests that the Pintail did likewise.

Counts from South Worcestershire

Gavin Peplow pers comm agrees that the trends noted in the Gloucestershire sections of the Severn Vale are mirrored in south Worcestershire, and that the highest counts there occur just at or after the peak of flooding. The following notes on the situation in South Worcestershire have been collated by him. Prior to the 1980s the highest Worcestershire count would appear to have been of only 36 at Bittell Reservoir (NE Worcestershire) in 1949! A count of 110 at Ripple in March 1985 (on the Severn near Tewkesbury) was a record for county of Worcestershire county and West Midlands region.

Longdon Marsh, a basin west of the Severn which floods when the Severn is high, only began to be regularly surveyed in the 1990s. It produced counts of 70 Pintail in February 1990, 112 in January 1993, 70 in December 1993, 26 in January 1995, before another county and regional record o 475 on January 1998 (a period when numbers at Ashleworth were not particularly high). There was a count of 120 at Longdon in January 1999, when the floods at the Severn Hams were at their height, then 50 in late December 1999. In November 2000, there was a count of 190 (probably some of the birds first seen in the Severn Hams), with 100 in December 2000 and 200 on 3 January 2001. Winter 2001-02 produced a count of 600 on 9 February (an all-time county and regional record) just when the floods in Gloucestershire were at their highest. At Longdon, Pintail are generally observed to be feeding actively.

Bredon's Hardwick Pits, near the Avon just north of Tewkesbury, has had records up to 80 Pintail since 1993, but these are restored gravel pits with fairly deep water, and birds there appear to be loafing rather than feeding.

Elsewhere, there are records of 54 at Pirton Pool (Worcestershire) in February 1998, and of 152 in October 1991 and 68 in September 1999 at Blithfields Reservoir (Staffordshire), a site where higher counts generally occur in autumn and early winter.

Habitat preferences of wintering Pintail

Kershaw's 1998 study noted that "wintering Pintail are highly aggregated according to habitat type in Britain. Pintail in northwest Europe tend to winter in coastal areas, particularly floodlands, estuaries and wetlands near the coast. The most recent five year peak mean for estuaries and coastal habitats is more than seven times greater than the five year peak mean for the second most important habitat, rivers/freshwater marshes." However, Kershaw added that "Pintail are extremely mobile, enabling them to use habitats which are temporarily available due to flooding. However this mobility also causes major local changes in distribution and means that numbers tend to fluctuate considerably between years on individual sites".

Ringing results

Pintail are regularly caught and ringed at Slimbridge. There are a number of recoveries from the breeding area in western Russia and Finland (but no indication of birds of Icelandic origin), together with some more short range recoveries in UK (Dave Paynter pers comm). Recoveries in UK include birds on The Wash, Lancashire, the Mersey, Essex, Northern Ireland, Norfolk, Cambridge, the Ribble, Herefordshire, Dorset (Abbotsbury), and four in Gloucestershire. Two of the latter are at Slimbridge itself, one at Berkeley and one at Walmore Common. There are thus inadequate data to provide new insights into the local movements of the birds.

Disscussion

These large numbers of Pintail have appeared in the Severn Vale marshes in the last few winters, at times when the meadows become flooded (as already noted by Swaine in 1982). Such numbers are generally recorded at, or to be precise, immediately after, times of high flood, when the birds seem to be taking advantage of optimal feeding conditions. They like to feed around the edges of the flood, either upending or dabbling in shallow water. The literature suggests that Pintail feed mainly on vegetal matter, chiefly seeds or parts of plants, by upending or swimming. Perhaps the seeds are easier to find when they float on shallow floods, and uprooting of plants is easier. In March 2002, most of them appeared to have been already paired, and to be feeding as couples. However, as noted by Juliet Bailey (pers comm), the Birds of the Western Palearctic points out that, while plant materials dominate Pintail food in autumn and winter, Hydrobia snails predominated in the food in the Medway from December to February, and that there was a rapid change from vegetal to animal matter after a thaw in the Mologa floodplain. She speculates therefore that flooding may produce a glut of drowned and half-drowned animal prey, on which the Pintail feast.

The distribution pattern of wintering birds in UK indicates that the most important sites are estuarine. But could it be that the estuaries are sub-optimal feeding sites, where Pintail congregate, waiting opportunistically for the chance to move to inland freshwater marshes when optimal feeding conditions occur there? Perhaps the WeBS counts, organized on a regular monthly basis on pre-set dates, identify the areas of concentration in the estuaries, but undervalue the inland feeding areas. If this is the case, there are considerable implications for management of wintering Pintail in Great Britain, and for greater emphasis to be placed on the conservation of these inland feeding sites.

Comparison with other inland marshes favoured by Pintail

Carl Mitchell pers comm notes that at the Ouse Washes in autumn Pintail generally arrive at the WWT centre at Welney from the coast on The Wash in mid-morning and use the relatively small flood of the main lagoon. Annual peaks are very variable and depend on water levels; larger numbers tend to occur with higher water levels, but with some land still showing. In winter 2001-02, numbers at Welney were initially low when the washes were only lightly flooded, but increased as water levels rose. Numbers correlate well with increased water levels, but complete bank to bank flooding, submerging the washes completely, provokes a departure to other sites.

Kershaw (1998) notes that Martin Mere is very close to the Ribble, and like the Ribble, numbers have fluctuated to a large decree. The following additional details have been provided by C. Liggett and C. Tomlinson (pers comm). While numbers at Martin Mere have been declining, those on the Ribble have been increasing; there is a feeling that there is some interchange between Martin Mere and the Ribble but this is unquantifiable. During the 1970s flocks of three to four thousand were recorded at Martin Mere; influxes tended to occur in September/October just after the duck marshes were re-wetted, allowing the seed of sedges, rushes, knotweeds and dock to float on the surface. Since the mid 1980s numbers have decreased to a few hundreds, possibly because of a reduction in plant productivity in the two seasonally flooded duck marshes. However, it is not known precisely what the Pintail were feeding on. These lower peak numbers have been in winter and tend to coincide with severe weather on the coast.

In recent years (Mark Pollitt pers comm) it seems that much greater number of Pintail have been recorded in the inland marshes of the Dee, presumably coming from the northwestern estuaries to feed.

Origin of the Pintail in the Severn Vale

Another question is where such large numbers in the Severn Vale come from. Received county ornithological wisdom is that Pintail winter on the Severn Estuary and move inland to marshes in the Vale for short periods when the floods rise and feeding conditions are at their best. But there is no indication of the numbers recently recorded in the Severn Vale being seen on the Severn Estuary beforehand, nor of a sudden decrease there when the floods rise. On the contrary, it seems that the Pintail from the Severn Vale take refuge in the estuary, as in December 2000, when the floods ice over. If they have not been displaced from the New Grounds, have they come from some other site? Not the Somerset Levels, which does not figure in the sites of national importance in UK, though 570 were recorded in January 2000.

One obvious possibility is the Burry Inlet, the nearest of the big five Pintail estuaries to the Severn Vale, with a five year mean of 2783 birds from 1995 to 2000. Do the Burry Inlet numbers perhaps decrease in the early months of the year when the floods rise inland? Bob Howells (pers comm) has kindly provided extremely detailed information on the situation on the south side of the Burry Inlet. He notes that Pintail numbers there usually build up to 1000 or more in October/November, peaking in January/February, before rapid declines in early March. Regular and detailed monitoring of Pintail numbers is carried out and in general, numbers are increasing. There is no sense that birds are simply sitting there all the winter, waiting for good feeding opportunities to occur inland; on the contrary there is abundant feeding material for the birds on the muddy fringes of the numerous pills that cross the site, and comparatively little disturbance. He suggests however that the increased numbers in the Severn Vale might be due to departures from the Burry Inlet of birds making their return migration to breeding grounds in northern Europe. Thus, a peak of 3000 in November 1999 was followed by a count of 1345 in February 2000; a peak of 4275 in November 2000 was followed by a count of 400 in February 2001, and a peak of 2675 came before a high of 1175 in February 2002. This possibility clearly needs further investigation, but would not explain the occurrence of high numbers of Pintail at times of Severn floods earlier in the winter season (eg November 2000).

Another possibility is that these large numbers in the Severn originate in the nucleus of wintering Pintail in northwest England. If this were the case it might be expected that birds would be observed in larger numbers in the Midlands en route to the Severn Vale, unless they fly "straight over the top" or move at night.

Some Directions for Future Investigations

The authors, in consultation with the Wetlands and Wildfowl Trust hope to develop the enquiries presented above and to seek answers to some of the questions raised. Among the questions that might be raised are the following.

Counts:

There is clearly a need for better co-ordination of future counts, especially at times of high flood, in the Vale floodplain sites to establish the numbers involved with greater precision. Such counts would need to be carried out over and above the current WeBS counts, and to be much more flexible. Co-ordination with the Severn Estuary and Burry Inlet counts would be desirable. It might well be of interest to operate such flexible counting systems in other inland floodland sites.

Feeding ecology:

Little is known about the food taken by Pintail in these inland sites. It would be of great interest to study this question in more detail, either through examination of shot birds, or through examination of birds caught for ringing.

Ringing:

To learn more about local movements of the Pintail, it would be necessary to ring them in the floodplain area, using either rocket nets or swim-in traps, preferably marking them with radio tags or picric dye.

Habitat conservation:

If it should prove that inland feeding areas in the Severn and elsewhere are of more importance to Pintail than was previously thought, some change in management strategies may be required, especially if the birds are (as in the Severn Hams) mainly using only freshly flooded area, rather than permanent water areas.

UK statutory obligations.

Given the importance of British wetlands for wintering Pintail in a northwest European context, this issue takes on national and indeed international significance. There may be a need to look again at UK's statutory responsibilities under national legislation, and in the context of international conservation instruments.

Acknowledgements

Thanks are due to all those who have provided information for this text and commented on the issues raised. Many field observers have provided information from their own often unpublished notes. These include (in Gloucestershire) Gordon Avery, Eddie Butters, Colin Evers, Rob Homan, Andy Jayne, George Parsons, Dave Paynter, John and Viv Phillips; in Worcestershire Gavin Peplow; from the Ouse Washes Carl Mitchell; from Martin Mere Christine Doyle; from the Burry Inlet Bob Howells who provided a detailed overview of Pintail in the Burry Inlet in the last decade. At the Wildfowl and Wetlands Trust, Melanie Kershaw, Mark O'Connell, Dave Paynter and Mark Pollitt contributed greatly to the discussion of the issues. Brian Smith of the Environment Agency contributed greatly to thoughts on monitoring needs in the Severn Vale. Juliet Bailey looked over the text with a botanist's sharp eye.

References