Written by J.V. Lloyd and J. Friese
History and Current Status
Dillwyn, writing in 1848, described the Tree Sparrow (Passer montanus) as frequently “obtained” around Llanelli. This was the first record of the species in Carmarthenshire. There was a pair near Cilycwm on 18th April 1903, a record from Glyn Abbey (near Pontyates) in December 1945 and Ingram & Salmon had a record of a few seen occasionally with House Sparrows near Nantgaredig. Describing the situation more recently, it is probably most convenient to split the county into two parts; the Tywi floodplain and the rest.
Away from the Tywi floodplain there has been a steady decline and contraction in range. The decline to the east of the Tywi came first. There was a record of possible breeding at Pembrey Burrows in 1981 but there has only been one record since- of 6 at Commissioner’s Bridge on 7th March 1992. In the west of the county records have come from the parish of Llansadyrnen in 1989 and from Three Lords (Pendine) over an extended period. The population was never large and the largest recorded count was 14 at Ginst Point on 12th December 1995. The only other double figure count was of 10 birds on stubble at Three Lords on 16th October 1994. Since the Millennium, there have been fewer records from this part of the county and it is probable that there are few if any birds left.
There has been an opposite trend in the Tywi Valley. An early notable flock was c.30 at Abergwili in August 1961. A pair used a nest box at Llangadog in 1972 and in 1980 breeding was confirmed at Dryslwyn and a flock of 12 at Manordeilo on 29th August 1984 was notable. By 1987 breeding was considered widespread in the valley from Whitemill to Llangadog and a post-breeding flock of 39 was found at Dryslwyn on 25th September. There were 45+ including juveniles at Dinefwr Ponds on 8th August 1989 and 55 at Tygwyn Pond on 22nd October 1995. In 1999 this project commenced with winter feeding and nest boxes. 38 pairs were found in 1999 with 6 of these in boxes. The number of occupied boxes built up to 82 in 2005 but it is believed that the population in the valley is well over 100 pairs, possibly more than 200.
The importauce of the Tywi population There has been a steep decline in the numbers of Tree Sparrows across the United Kingdom. This has resulted in the species being included in the red list at both UK and Wales level. In Wales the Tywi Valley population is the only one remaining with substantially more than 100 individuals- the level considered the minimum for long term survival of an isolated population (Meffe & Can-oil 1997). In South Wales there are approximately 50 pairs east of Brecon town (A King pers. comm.) but numbers have collapsed recently in the Vale of Glamorgan and Gwent ( R. Facey & R. Morris pers. comm.). There are probably less than twenty pairs in each county. The one spark of good news comes from Gower where breeding was confirmed in 2007 for the first time since 1992 ( A. Lucas pers. comm.).
The number of pairs breeding in nest boxes has made it possible to collect much data on breeding performance. Tree Sparrows make up to three attempts in a year, with the breeding season stretching from April to August. The earliest and latest dates for the first egg of a clutch being laid are 3rd April and 27th July. The distribution of dates is shown in Figure 1, the season being divided into 5 day intervals. This shows three peaks caused by the three attempts. The first peak is steep and sharp, reflecting a high degree of synchronicity at the start of the season. The second peak is more spread out as attempts are made by a mixture of pairs whose first attempt failed and those who completed successful first attempts.
Figure 1. Breeding Season 1999-2006
The most common clutch size is five eggs; the mean is 4.96, slightly less than the figure from the BTO Nest Record Scheme of 5.13. The number of young reared in this study is, at 3.43, substantially lower than the national BTO figure of 4.28. This might be a matter of concern if the population was not apparently maintaining itself.
Habitat – the importance of the floodplain
The Tree Sparrows in this population do not wander far from the floodplain and breeding attempts off from the floodplain are rare. Some nestboxes are sited on the edge of the floodplain but are rarely occupied. A group of four boxes in the orchard at Typicca Farm was compared over the period of 2002-6 with the four nearest boxes on the floodplain. The orchard is 13 metres above the floodplain and 60 metres horizontally from the nearest part of the floodplain. A comparison of the two groups of nestboxes is shown in Figure 2.
Figure 2. A comparison of nestboxes on the floodplain and in the orchard at Typicca 2002-2006
This, backed up by the species the species being so closely associated with the floodplain, would appear to suggest that there is something that the breeding Tree Sparrows need that can only be found on the floodplain. In 2002 faecal samples were taken from the pulli in 40 broods and these were analysed for remains of the food items fed to the pulli. The results are shown in Figure 3. 32% of the diet is from three groups of insects with strong aquatic associations: Culicidae (Mosquitoes), Chironomids (Midges) and Zygoptera (Dragon Flies). Other groups found in the diet such as Arachnida (Spiders) and Coleoptera (Beetles) have aquatic species.
Figure 3. The diet of Tree Sparrow Pulli 2002
The Tywi Floodplain is a flat piece of land bisected by slow-flowing ditches, ox-bow lakes and backwaters of the main river channel. This habitat of slow-flowing or stationary water is rare in the rest of inland Carmarthenshire. It also abounds in insect life and as is well-known, mosquito larvae are only found in stagnant water. This study has not confirmed the connection between the Tree Sparrow’s range-restricted to the floodplain- and the habitat of slow-flowing water but it seems that this connection is probable. More work is needed to confirm the preponderance of aquatic insects in the pullus diet, the insect biomass on and off the floodplain, habitat differences between the floodplain and the surrounding countryside and where the adult Tree Sparrows gather the food to take back to the nest.
Outside the breeding season, Tree Sparrows are totally dependent on seeds for food. Naturally the food supply would have come from the weedy parts of the floodplain, particularly the shingle banks, and also “high water” marks of vegetation washed down from further upstream. Winter feeding is a means of substantial augmentation of these natural resources. Tree Sparrows are not continual in their use of feeding stations but do utilise them on a regular basis. Without this supplementary feeding, it is improbable that the population could continue at its present level.
Movement of birds within the Floodplain
Ringing of pulli has been carried out since 2004 and colour-ringing since 2006. So far there have been five recoveries, all by workers in this study. Three of the five come from the breeding season, two from winter. Only one movement has been greater than one kilometre (1.8 kms.from Ro Fawr to Tywi Cot- both in Gelli Aur parish) and the others have all been a matter of a few hundred yards. Although the data is limited, there is every indication that the population is extremely sedentary.
The population of Tree Sparrows in the Tywi Valley is the largest in Wales of this red-listed species. It is of importance at UK level because of its geographic position, far away from other similarly viable populations. The population is highly tied to the floodplain of the Tywi and it is believed that the availability of prey items for feeding to the pulli is the limiting factor, these items being strongly associated with the static or slow-flowing water found on the floodplain. Winter feeding is important in maintaining the population at its current level. Limited recoveries of ringed birds suggest that the population is highly sedentary.
This study would not have been possible without the help and forbearance of the landowners. Approximately 20 landowners have given us permission to access their land. A team of people resident on or close to the floodplain have worked hard at providing feed on a regular basis. Some of these have been provided with feed but others have been totally unsupported. We thank them all for playing a key part in maintaining this key population. We have also received financial assistance from the Countryside Council for Wales, the Royal Society for the Protection of Birds, the British Ornithologist’s Union and Carmarthenshire County Council and are duly grateful. The pulli faecal samples were collected as part of a Royal Society for the Protection of Birds study and were analysed by their staff.
Dillwyn L. Weston: Materials for a Fauna and Flora of Swansea and its Neighbourhood. Swansea 1848
Meffe G.K., C.R. Carroll and contributors: Principles of Conservation Biology. Massachusetts. 1997
Ingram G.C.S. & H. Morrey Salmon: Birds of Carmarthenshire. Narberth 1954