Introduction
During the spring/early summer of 1978 a survey on behalf of the Nature Conservancy Council was carried out to determine the structure of the breeding bird community in the Aber Bogs, Loch Lomondside.
The Aber Bogs are a mesotrophic mire complex of some 30 hectares, situated adjacent to the Endrick Water where it enters the south-east corner of Loch Lomond (Map 1). There are 4 named divisions, the Ring Bog (16 hectares), Aber Bog (5 ha), Gartocharn Bog (6.25 ha) and Bell Moss (2.8 ha), which are separated by the Ross Drain and the old and new courses of the Aber Burn (Map 2). Comparable with English and Welsh eutrophic fens, the bogs show 3 distinct vegetative associations (Map 3):
1.A mixed mire community characterised by Juncus acutiflorus, Juncus effusus, Iris pseudacorus, Valeriana officinalis, Equisetum spp, Carex vesicaria and Deschampsia cespitosa based on the Ring Bog;
2.A fen area of Phalaris arundinacea stands with understoreys of Urtica dioica and Filipendula ulmaria centred along the Ross Drain and the old bed of the Aber Burn;
3.A wet meadow characterised by Filipendula ulmaria, Poa pratensis and Holcus lanatus at the southern end of the bogs.
As a result of several centuries of attempted drainage, the cutting of 'bog hay' and grazing of cattle, the vegetation shows a parallel zonation rather than the classical radial zonation (Ratcliffe 1951 and 1977). Annual hay and reed cutting declined during the 1930s and the last recorded cut was made in 1952. There was also an associated decline in the maintenance of the drains, while the central Aber Burn channel becoming completely overgrown, diverted its water into the Bell Moss. The bogs were totally fenced off on the north side in 1968 following the drowning of several cattle (NCC file records), but up to 34 cattle were recorded grazing the Bell Moss, on the south side, during the census period. The cessation of hay cutting and/or regular grazing has resulted in an accumulation of organic debris leading to the bogs drying out in some places. The resultant colonization by Willow (Salix spp) scrub in the drier areas is very similar to the situations described for East Anglian fens and broads by Godwin et al (19740 and Mason (1978). The bogs are bounded by mixed woodland to the north east (Oak/Birch) and to the south east (Willow/Alder).
The importance of the Aber Bogs was formally recognised with their inclusion in the Endrick River Mouth SSSI, which was notified by the Nature Conservancy in 1959. Due to legal difficulties, only the Ring portion of the bogs was incorporated in the mainland section of the Loch Lomond National Nature Reserve when it was established in December of 1962. The entire Aber Bogs, together with other marshes around the Endrick Mouth, have been assessed as a Grade 1 Peatland site in the recent Nature Conservation Review (Ratcliffe 1977).
Bibliography
Batten LA and Marchant JH (1977) Bird Population Changes for the years 1975-1976. Bird Study 24: 159-164
Bell BD, Catchpole CK and Corbett KJ (1968) Problems of censusing Reed Bunting, Sedge Warbler and Reed Warbler. Bird Study 15: 16-21
Bell BD, Catchpole CK, Corbett KJ and Hornby RJ (1973) The Relationship Between Census Results and Breeding Populations of some Marshland Passerines. Bird Study 20: 127-140
Bibby CJ, Green RE, Pepler RM and Pepler PA (1976) Sedge Warbler Migration and Reed Aphids. British Birds 69: 384-399
Cramp S and Simmons KEL (Eds) (1977) The Birds of the Western Palearctic Vol 1. Oxford University Press
Fuller RJ and Glue DE (1977) The Breeding Biology of the Stonechat and Whinchat. Bird Study 24: 215-228
Glue DE and Morgan R (1972) Cockoo hosts in British Habitats. Bird Study 19: 187-192
Godwin H, Clowes DR and Huntley B (1974) Studies in the Ecology of Wicken Fen v. development of fen carr. Journal of Ecology 62: 197-214
Hawthorn I (1975) Wrens Wintering in a Reed-bed. Bird Study 22: 19-23
International Bird Census Committee (1969)Recommendations for an international standard for a mapping method in bird census work. Bird Study 16: 248-255
Mason C (1978) Problems in Broadland. Birds 7: 32-35
Mitchell J (1978) Aber Bogs - Selected Ornithological Records. Unpublished NCC report
Phillips JS (1970) Interspecific competition in Stonechat and Whinchat. Bird Study 17: 32-35
Ratcliffe DA (1961) Aber Bogs - Botanical Description. Unpublished NC report
Ratcliffe DA (1977) A Nature Conservation Review. Cambridge
Sharrock JTR (1976) The Atlas of Breeding Birds in Britain and Ireland. BTO/IWC. Tring
Shaw G (1975) The Breeding Birds of Crom Mhin, Loch Lomond. Scottish Birds 8: 356-363
Williamson K (1964) Bird Census work in Woodland. Bird Study 11: 1-22
Williamson K (1975) The Breeding Bird Community of Chalk Grassland Scrub in the Chiltern Hills. Bird Study 22: 59-70
Williamson J, Idle ET and Mitchell J (1973) Bird Communities of the Mainland Section of Loch Lomond National Nature Reserve. The Western Naturalist 2: 15-28
Wilson J (1978) The Breeding Bird Community of Willow Scrub at Leighton Moss Lancashire. Bird Study 25: 239-244
Winstanley D, Spencer R and Williamson K (1974) Where have all the Whitethroats gone?. Bird Study 21: 1-14