14. December 2009

56 Coll, Strathclyde Region

Site map
History: Very little is known about Greenland White-fronted Geese on Coll, which is striking given that they have become so numerous in the very recent past.  Berry (1939) recorded the species as a comparative rarity on the island, and A-W (1963) mentioned that flocks were “…reported from parts of south-west Coll, but numbers have always been small”.  R&O (1979) considered that between them, Tiree and Coll probably together held over 200 and that, by inference, Coll supported c.50 regularly.  That said, a reliable count found 500 birds on the island in March 1970 suggesting there may have been many more birds that were thought over a longer period.  The only coordinated count of both islands that they specifically reported was of 610 on Coll in April 1978, when a simultaneous check on Tiree found none, although the date suggests these numbers could relate to passage movements at this late stage in the winter.  Two thorough searches of the island in November 1982 and April 1983 found 343 and 330 White-fronted Geese respectively, making Coll of international importance.  This rather suggests that there had been substantial numbers on the island for some years, but alas there were no previous counts to really assess the status and trends in their abundance, indeed local opinion was that if anything, numbers had fallen somewhat during winter 1982/3, so these numbers were likely at least to reflect the norm.

Status: International importance (part of R&O 49). Despite very recent declines on Coll since the peak of over 1100 birds in 1998, the island remains of outstanding importance for the population and has suffered less than many resorts in the magnitude of the declines since the peak numbers in the late 1990s.  The site has mostly supported lesser numbers than on neighbouring Tiree, but then the extent of improved grassland is substantially less.  Since 1982, efforts have been made to standardise the counting to avoid double counting whilst ensuring total coverage of all potential sites.  Very major changes between years in these counts suggest that there is often movement to and from the island, most likely involving exchanges with Tiree, although potentially also with other resorts further afield, including Islay.

Maximum winter counts:

Breeding success: Like neighbouring Tiree, the production of young on Coll was variable through the 1980s and 1990s (although the fluctuations did not correlate well with each other).  However, the proportions of young during the period since 2000 do not seem to have been especially low.  Nevertheless, like Tiree, the annual production of young birds resembles those on nearby Islay.

56coll   56coll2

Feeding sites and habitat: Three distinct areas hold Greenland White-fronted Geese on Coll.

1. Acha/Totamore/Ballard.  Six discrete feeding areas are known and recognised and the geese presumably shift between as disturbed by agricultural disturbance and local food depletion and availability.  It seems highly likely that in addition to those mentioned below, there may be other peatland feeding areas to which the geese regularly resort which are not evident to the passing observer that have yet to be discovered.  The most important feeding area is the Totronald-Lonban-Totamore area (NM1656 and NM1756) which comprises both blown machair pasture, improved grass ley, some root crop fields and wet buttercup-rich (Ranunculus), sedge dominated grazing land.  In addition there are some areas of Juncus marsh and old rushy pasture which are also utilised by the geese.  Further west, geese use the fields south of Breachacha Castle, grazing the reseeded fields and the short maritime turf down to the shore (at NM1552 and NM 1553). Geese are also frequent in the Acha area, immediately north of the road on rich improved pasture that leads up to Loch Anlaimh (where these birds roost).  Evidence of bog feeding on Eriophorum angustifolium has been found in this area (e.g. around NM191555 and NM 189554), but these geese are usually to be found in the wetter parts of reseed in this small valley.  Birds will also resort to Friesland (NM194538) on recent improved pasture very close to the farm there, often in the company of Greylag Geese.

2. A second discrete group of birds have been frequently seen feeding on the machair, dune grassland and fields claimed for agriculture at Crossapol and Caoles (NM1253) in the extreme southwest of the island, with records of birds amongst the rough pasture and bogs around Lochan a Chuirn (NM119522).  This flock also feeds on the far side of the bay around the MacLean’s graveyards. It is not entirely clear whether these are a discrete group separate from those resorting to Acha and Totronald.

3. Cliad/Arnabost/Gallanach/Arinagour.  Four distinct areas are exploited in this general area.  Improved pasture southeast of Gallanach (NM218603) include reseeded leys favoured by the flock and Greylag Geese which also feed in the area, which have led to claims for damage, although the grazing pressure from geese is slight compared to that on areas (e.g Islay); rough pasture near Arnabost (NM215597); improved and rough pasture south and west of Cliad (NM2059) including the northern edge of Loch Cliad; and very rough pasture/Molinia blanket mire to the north and west of the Lodge (NM2157) including Loch Duin.  In addition, geese have been reported feeding in fields to the north of Arinagour farm (NM222572).

Roosting sites:
1. Birds from these feeding areas will flight to Loch nan Cinneachan/Loch Anlaimh when disturbed or to roost.  It is not clear where the birds feeding south and west roost, but in all likelihood they are part of the Totronald-Breachacha complex and so may flight to the roosting loch further east.

2. Observations of birds flying to and from Gunna (where these birds may also spend the day feeding) hint that this may be the night time roost of this group of birds as speculated by A-W (1963).  Geese are also frequent in the Acha area, immediately north of the road on rich improved pasture that leads up to Loch Anlaimh (where these birds roost).  Evidence of bog feeding on Eriophorum angustifolium has been found in this area (e.g. around NM191555 and NM 189554), but these geese are usually to be found in the wetter parts of reseed in this small valley.  Birds will also resort to Friesland (NM194538) on recent improved pasture very close to the farm there, often in the company of Greylag Geese.

3. The main roost is in the hill area to the northeast of the feeding fields.  Bog pools and small lochans in NM2360 were seen to have been used in this way and it is possible that they use a large expanse of upland mire habitat in the course of the winter in this general area.  Geese are also likely to roost on Loch Cliad and/or Loch an Duin, but more frequently seem to fly into the hills.

Habitat change: There was some drainage and enclosure on Coll in the 1980s, but less so than on Tiree.  Although the geese have benefited from reseeding, they often seem to prefer more rushy fields and still rely upon the peatlands for supplementary feeding.  However, there has been relatively little recent change in agriculture in recent years likely to affect the geese, which tend to use improved pasture for their feeding habitat throughout.

Aircraft disturbance: There has been some infrequent but regular helicopter traffic associated with one of the owners on the island that causes disruption when approaching the helicopter landing area and when taking off.

Hunting disturbance: Not known.  There was some hunting and scaring of geese using shot guns on the island in the past.

Agricultural disturbance: Not known, but not thought significant.  Generally the geese will take to the hill lochs to which they resort at night to roost when severely disturbed by day.  Generally, the geese on Coll are fortunate to be able to resort to a suite of alternative feeding areas if disturbed from any one favoured site, a feature which probably minimises the effects of any disturbance.

Site safeguard:  Parts of feeding and roosting areas of the geese lie within the Hough Bay and Ballevullin Machair SSSI and the Totamore Dunes SSSI on the island.  Both are NCR sites and lie within the larger Tiree and Coll proposed Ramsar Site and SPA.  The RSPB has recently acquired a large reserve in the south-west part of the island, including significant areas used by the geese.

SNH Natural Heritage Zones/Area: Coll, Tiree and the Western Isles.

Threats:   Not known

Linkages with other sites:
Three of the 96 geese ringed in Eqlungmiut Nunaat west Greenland in 1979 turned up on Coll, two seen first and last in 1983.  Another, A06 was first seen at Endrick Mouth, Loch Lomond in March 1980, then at Loch Ken in November 1983 before appearing at Lonban, Coll in February 1985 in company of two geese ringed in the same area of the breeding grounds in summer 1984 (a pair, K61 and K62), and again at Totronald in April 1986.  Another Greenland ringed collared bird, A0V was marked in Isungua, west Greenland in summer 1992, appeared on Coll in winter 1992/3, on Kintyre in  October 1993 and Loch Swilly in January 1994.  A further 9 Wexford ringed geese have been seen on the island, one of them 2CF clearly an autumn migrant, briefly staying between at least 22 October and 8 November 1993 before wintering in Wexford the rest of the year and ultimately until winter 2004/5.  Most of the other observations involved birds that exhibited unusually high likelihoods to switch winter sites.  AN moved from Wexford to Islay in 1993/4, where it was regular most winters until 2001/2 and 2002/3 when it was on Coll.  3XH wintered at Wexford in 1990/1, the Dyfi Estuary in Wales 1991/2, Kintyre 1992/3, Coll 1993/4 but was back at Wexford by October 1996.   7RT was a spring migrant visitor on 18 April 1987, having wintered at Wexford, was seen on Kintyre the next winter and on Islay in 1990/1.  D7J ceased wintering at Wexford in 1993/4 and showed up on Coll in 1996/7 and 1997/8.  Finally 4 marked birds out of a family of 6 goslings captured in December 1986 on Wexford Slobs turned up on Coll in winter 1987/88, these were the father (5PF), two sons (2PJ and 8PK) and a daughter (6PF).  The mother and two sibling had evaded capture, but it was not possible to judge whether they were also present on Coll with the rest of the family.  2PJ was seen on Islay alone the next winter, but 6PF and 8PK showed up on Coll the next winter as well.  Finally 6MM was ringed at Sheskinmore in County Donegal and turned up on Coll in April 1989.

References

Bowler, J. & Hunter, J. (2007)  Birds of Tiree and Coll. Paircwood Publishing, Balphuill.

Fox, A.D., Francis, I.S. & Stroud, D.A. (1989)  Greenland White-fronted Geese in Coll and Tiree.  pp.129-142. In: Stroud, D.A. (ed.) The Birds of Coll and Tiree: status, habitats and conservation.  NCC­/SOC, Edinburgh.