RUDDY SHELDUCKS IN BRITAIN AND IRELAND, 1986–94 K. E. VINICOMBE AND A. H. J. HARROP Ruddy Shelducks Tadorna ferruginea (Tony Broome) ABSTRACT An invasion of Ruddy Shelducks Tadorna ferruginea into Fenno-Scandia in summer 1994 coincided with the occurrence of flocks in Britain. The patterns of the records and status in Europe are documented and discussed in an attempt to determine whether wild birds, escapes from captivity or individuals from feral populations were concerned in these movements. ogers (1982) analysed the occurr- more together, including five instances ences of Ruddy Shelducks Tadorna involving five and one flock of eight, all R ferruginea in Britain during 1965- within the period 16th July to 16th 79. He traced a total of about 123 October. There was a strong bias towards individuals (eight per annum), roughly the Southeast. Of the ten parties of three or two-thirds of which occurred in the more, only three were in the North or second half of the year. There was some West, but these included the largest flock: increase in spring, from late March to early eight at Llyn Alaw, Anglesey, on 26th May, including several instances of two or July 1979. Only two groups were reported more together. Most first occurrences, to have contained juveniles. Rogers however, took place from early June and in concluded that the number of records was particular from mid July onwards. The increasing, probably as a result of a largest numbers of individuals (as combination of greater observer activity opposed to records) were present from and a larger number of birds wandering July to late August, with smaller peaks from wildfowl collections. There appeared from September through to the end of to be no grounds for presuming that any November (fig. 1). In late summer and record during at least the previous 50 autumn, there was a far higher incidence years related to a wild vagrant. This of groups, with ten reports of three or view was endorsed by the British British Birds 92: 225–255, May 1999 225 RUDDY SHELDUCKS IN BRITAIN AND IRELAND, 1986-94 12 10 8 6 4 2 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 1. Monthly occurrences of Ruddy Shelducks Tadorna ferruginea in Britain in seven-day periods during 1965-79. Number of records, filled columns; extra individuals, open columns. (From Rogers 1982) Ornithologists’ Union Records Committee, individuals which they regard as ‘obvious and the species currently resides in escapes’. In addition, some bird reports Category B of the British List. have not bothered to publish the records. In recent times, however, there has In an attempt to obtain as many records as been a growing suspicion that wild Ruddy possible, KEV wrote to all the county Shelducks are still occurring, and this recorders in whose areas Ruddy view was given credibility in the summer Shelducks were thought to have occurred of 1994 when there was a large and during the period. Their response was widespread invasion into Fenno-Scandia, excellent, and a large number of involving some 262 individuals. This additional records came to light. Finally, paper attempts to analyse the current Lee Evans (in litt.) provided additional position in Britain and Ireland, with records which he had obtained from the particular reference to the 1994 invasion. more recently published bird reports. KEV collected and analysed the British Inevitably, some records will have been and Irish records and also data relating to missed, but it is unlikely that their the general occurrence patterns on the absence will have significantly affected Continent. AHJH also collated the the general patterns of occurrence. Continental information, particularly The Ruddy Shelduck is a large, that relating to 1994, and arranged for a colourful and conspicuous duck and it request for information to be placed tends to occur in wetland habitats, in the newsletter of the Russian Bird which are very well covered by Conservation Union. birders. Consequently, a few wandering individuals may account for many records. METHODS Indeed, the raw data collected comprised Obviously, there is no point in analysing records of some 907 individuals, so an the 1994 invasion year in isolation, so this attempt had to be made to rationalise these paper deals with the period 1986-93 in and estimate the true numbers occurring. comparison with 1994. That period is used This was done by dividing Britain and simply because the initial records were Ireland into eight regions: (1) Scotland, taken from Pete Fraser’s rare-bird and (2) Northeast England, (3) Northwest scarce-migrant database, which, for this England and North Wales, (4) the species, goes back to 1986. Although the Midlands, (5) Eastern England, (6) Ruddy Shelduck is an obvious and Southwest England and South Wales, (7) conspicuous bird, it quickly became clear Southeast England, and (8) Ireland. In each that PF’s data were not complete. This is region, the numbers of individuals because many observers do not bother occurring were estimated, adopting a to report the species, especially those minimalist approach. Little attempt was 226 British Birds 92: 225–255, May 1999 RUDDY SHELDUCKS IN BRITAIN AND IRELAND, 1986-94 made to correlate movements between as the pattern produced in the Southeast by regions, unless there were obvious reasons the high proportion of escaped birds, for so doing. For simplicity, the data are particularly in the London area, was presented here in four regions (see also fig. different from that in the Southwest. 11 on page 235): In the analysis, no attempt was made to differentiate between those birds 1. Northern Britain: Scotland, northern considered to have been escapes and those England and North & West Wales; with apparently better credentials as 2. Southern Britain, subdivided into: wild individuals. a. East and Southeast England; b. Southwestern Britain: the Midlands, ANNUAL TOTALS Southwest England and South Wales; Fig. 2 shows the annual totals of Ruddy 3. Ireland. Shelducks estimated in Britain and Ireland The above regions may seem arbitrary, but during 1986-94. The total number of the boundary lines were drawn to take individuals was 435, an annual average of account of marked clusters of records. It 48, a marked increase on Rogers’s (1982) seemed desirable not to split such clusters, annual average of eight. His annual totals which involve the same birds moving varied from just one in 1965 to 12 in 1978, around. For example, there is a cluster of whereas during 1986-94 they varied from records around the Wirral, in Cheshire/ 23 in 1986 to 62 in both 1992 and 1993. Lancashire, and records farther north in It is immediately apparent from fig. 2 Lancashire and Cumbria, as well as those in that, for Britain and Ireland as a whole, North and West Wales, often relate to birds 1994 was unexceptional by recent from this cluster. Also, the patterns of standards. Indeed, it was only the fourth- occurrence in northern England are similar best year during the period of analysis. In to those farther north in Scotland, so it seems this period, there has been a gradual build- sensible to treat this region as one. Similarly, up in numbers, with peak years in 1988 there is another cluster of records around the and during 1991-94. From these data, one Severn Estuary, so it makes sense to include could draw the surprising conclusion the records from South Wales with those that, given the events in Fenno-Scandia, from the English Southwest Peninsula. Britain and Ireland did not experience a Southern England was subdivided into two, significant Ruddy Shelduck influx in 1994. 70 60 50 40 30 Number of birds 20 10 0 86 87 88 89 90 91 92 93 94 Year Figure 2. Estimated annual totals of Ruddy Shelducks Tadorna ferruginea in Britain and Ireland during 1986-94. Note marked upsurge in 1991-94. (Note that a flock of 18 known escapes in Wiltshire in June 1988 has been omitted.) British Birds 92: 225–255, May 1999 227 RUDDY SHELDUCKS IN BRITAIN AND IRELAND, 1986-94 20 15 10 5 0 Number of birds 86 87 88 89 90 91 92 93 94 Year Figure 3. Estimated annual totals of Ruddy Shelducks Tadorna ferruginea in northern Britain during 1986- 94. Note that 1994 was the peak year, coinciding with the invasion into Fenno-Scandia, with a flock of up to 12 in North Wales and on the Wirral, Cheshire/Lancashire. 20 15 10 5 0 Number of birds 86 87 88 89 90 91 92 93 94 Year Figure 4. Estimated annual totals of Ruddy Shelducks Tadorna ferruginea in southwestern Britain during 1986-94. The 1994 peak was produced by two flocks, of five and six in Somerset and Cornwall. (Note that a flock of 18 known escapes in Wiltshire in June 1988 has been omitted.) 35 30 25 20 15 Number of birds 10 5 0 86 87 88 89 90 91 92 93 94 Year Figure 5. Estimated annual totals of Ruddy Shelducks Tadorna ferruginea in east and southeast England during 1986-94. This area failed to receive a significant influx in 1994. 8 6 4 2 0 Number of birds 86 87 88 89 90 91 92 93 94 Year Figure 6. Estimated annual totals of Ruddy Shelducks Tadorna ferruginea in Ireland during 1986-94. Surprisingly, none was recorded in 1994. 228 British Birds 92: 225–255, May 1999 RUDDY SHELDUCKS IN BRITAIN AND IRELAND, 1986-94 63. Three Ruddy Shelducks Tadorna ferruginea, Hayle Estuary, Cornwall, October 1994 (Steve Young/ Birdwatch) REGIONAL ANALYSIS year, with just 12 (only the seventh best in To make more sense of what happened in the period reviewed; fig.