Richard Jenkins

Despite a relatively wide distribution in Britain and Ireland, the true breeding population of the Water Rail is imprecisely known (Gibbons et al. 1993). The secretive nature of Water Rail and its preference for inhabiting tangled stands of emergent vegetation denies the casual birdwatcher the opportunity to observe this species Using standardised methods, which are considered unsuitable for surveying Water Rail, Gibbons et al (1993) reported a 34% distributional decline in the breeding population between 1968-1972 and 1988-1991. However, until a better technique is used to first measure, and then to monitor population abundance, the true conservation status of this little studied rail will remain poorly understood.

The regional picture of the breeding Water Rail population is no clearer. Lovegrove et al (1994) considered it to be a scarce breeder in Wales, but qualified this judgment by suggesting that many of the breeding attempts were unrecorded. In Carmarthenshire, Hunt et at. (1996) highlighted the need for clarification of the breeding status in the county A survey of breeding Water Rail was undertaken at 40 wetland sites in south-east Carmarthenshire during April 1996 using a tape recording of a Water Rail territorial call to provoke birds into responding (Jenkins 1996). This survey was successful in providing a minimum county estimate of the breeding population and also provided some clues as to the importance of habitat type and wetland size.

As most breeding bird surveys are conducted over a two to three year time period to account for natural variation in population size (e.g. Gibbons et al. 1993), it was important to repeat the Water Rail surveys in other years. In this article I report on surveys of breeding Water Rail at Llangennech reed beds and Ffrwd Farm Mire from 1995-1998.

METHODS

Llangennech reed bed (Burry Inlet and Loughor Estuary SSSI; SN 566 015; c. 10 ha) consists largely of a monodominant stand of Phragmites and is prone to regular tidal inundations. Ffrwd Farm Mire 5551 (SN 420 025; c. 17 ha) is similarly dominated by Phragmites, but also has areas of wet marshland characterised by Juncus spp. Both sites were visited on three early mornings in April from 1995 to 1998.

The surveys consisted of a series of point counts, where a tape recording of the territorial call of a Water Rail pair was broadcast for 30 seconds. All Water Rail responses within one minute of the broadcast were logged as either from a pair (i.e. a territorial duet Cramp and Simmons 1980) or from a single bird (i.e. an individual screech). Water Rail abundance was either the maximum number of pair vocalisations recorded from all visits or the mean number of individual birds (i.e. pairs counted as two birds) per visit. The same number of point counts and routes were used in all four years.

Rainfall data from Gelli Aur Country Park were collected to aid in the interpretation of the results.

RESULTS

The abundance of Water Rail at Llangennech was relatively stable in all four years, with a difference of only 1.5 birds between the minimum and maximum population counts (Figure I) The years of lowest Water Rail individual abundance were 1995 and 1997, although an increase was noted in each of the subsequent years (Figure 1).

The abundance of Water Rail at Ffrwd Farm Mire fluctuated more than at Llangennech, but the patterns were generally similar (Figure 2). There was a difference of ID birds between minimum and maximum abundance at Ffrwd Farm Mire, 1995 and 1997 were years of low abundance, but just as at Llangennech, whilst 1996 and 1998 produced larger populations.

Note that the number of maximum pairs recorded in each year was more consistent at both sites than the mean number of individual birds, suggesting that there are fluctuations around a core-breeding population.

Rainfall for April was lowest in 1995 and 1997, whilst April 1998 was the wettest late winter and spring of all four years (Figure 3). Interestingly, 1998 was also the year of highest population abundance in Ffrwd Farm Mire (Figure 2).

DISCUSSION

The repeated surveys of Water Rail at these two important Carmarthenshire wetlands revealed a stable population of breeding pairs. The total numbers of individual birds varied more, especially at Ffrwd Farm Mire, and this could have been caused by the presence of non-breeding birds. Similarly, the breeding success from previous years or over-winter mortality may determine the number of extra birds around the core-breeding population.

The results from this study are important because they have provided the information with which to interpret previous, one-off surveys. For example, although the breeding survey of Water Rail in 1996 provided valuable and unprecedented information on Water Rail (Jenkins 1996), the results over four years indicate that 996 was a year of high Water Rail abundance. However, given that the Water Rail populations at the two sites did not show extreme changes in abundance and that such surveys required a specific method, one-off local surveys will continue to provide acceptable estimates of the breeding Water Rail population.

References

Cramp, S. & Simmons. K.E.L. (1977) The Birds of the Western Palaearctic, Volume 1, Oxford University Press.

Gibbons, D West, Reed. J. B. and Chapman, R. 1993. The New Atlas of Breeding Birds in Britain and Ireland 1988-1991. T & AD Poyser. London.

Hunt, R. O. H. (1996), Carmarthenshire Birds 1995

Jenkins, R K. B. (1996). A survey of breeding Water Rail Rallus aquaticus in south-east Carmarthenshire, Carmarthenshire Birds 1995 Hunt, R. O. (ed.).

Lovegrove, R, Williams, G. and Williams, 1. 1994. Birds in Wales. T & AD Poyser. London.