Treshnish Birds Spring 2008

This year is an important year for British and Irish birdwatchers. 2008 is the first of four years contributing to the forthcoming Atlas of Breeding and Wintering Birds. The previous New Atlas of Breeding Birds in Britain and Ireland covered the years 1988-91 and the only Atlas of Wintering Birds in Britain and Ireland 1981-84. This time the records for winter and breeding atlases are being collected over the same time period.
The new atlas is exciting as it will show changes of bird populations over the last 15-20 years and even further back to the first Atlas of Breeding Birds in Britain and Ireland of 1968-72. In participating we also take more notice of what is happening locally to our birds.

We know that Fulmars breed on the cliffs of Treshnish but when do they arrive back to breed or do they occasionally turn up at their breeding grounds in the winter? Well, through taking part in the winter bird survey we know that at least some visit these breeding cliffs during the winter. They were not actually seen sitting on the ledges but it is very possible that they do. Perhaps they are only exploiting a food source near the breeding cliffs but the way they patrol the cliffs is identical to the way they patrolled and landed on the cliffs in early spring in mid and late March 2006 and late March 2007. Then they departed before returning to breed from mid-April until mid-August.

Many of our so-called resident birds actually leave Treshnish for the winter. Some only disperse locally within Britain and may not even leave Mull but a few may even migrate southwards across the channel or westwards to Ireland in the same way that British resident birds are augmented by Scandinavian visitors. Lesser Black-backed Gull, Pied and Grey Wagtail, Goldfinch, Greenfinch, Siskin, Linnet, Twite, Lesser Redpoll, Reed Bunting and probably Gannet, leave Treshnish for the winter (although one Lesser Redpoll was seen in the winter survey of 2007-2008). The previous atlases tell us that Lesser Redpoll move to the south and east of Britain according to the presence of birch seed and Siskin to the south of Britain to feed mostly on Alder cones. Twite move to form flocks at prime coastal sites; Southern Mull, Coll, Tiree, Colonsay, Oronsay, Jura and Islay being the closest winter hot-spots with the highest concentrations in Scotland appearing in Uist, NE Scotland, Shetland and Orkney. Even Meadow Pipit and Skylark become much less common in the winter.

Most ‘resident’ species arrive back in early spring from March onwards to take advantage of the first warm weather and so gain the advantage over the true summer migrants. Some appear to arrive later than the first true migrants so Wheatear is back singing in its territories in mid-April before residents such as Greenfinch, Linnet, Siskin, Lesser Redpoll and Twite have made an appearance. Of course conditions contributing to the breeding of resident species change from year to year. Perhaps that early singing Song Thrush that you may have heard has had an early success but two of our local species that usually lay early are Tawny Owl and Golden Eagle. Tawny Owls become more silent in early spring and in Britain start laying in mid-February although in Scotland it is a little later but by mid-April chicks may have hatched. This year it appears that one nearby Golden Eagle nest had a sitting adult in mid-March and another in early April.

Noticing the arrival of local and long distance migrants is a lot easier than the departure of winter visitors but it appears that the last Woodcock had left our woods by mid-March.
Fieldfare were very scarce this winter only being seen in the autumn and Redwing too were only seen in early winter and early spring. Probably each year is different but certainly this year Treshnish was only visited on passage by these northern thrushes; this may have been an effect of the mild winter. A severe winter would push birds further south but a mild winter with a good Rowan crop might mean Scandinavian thrushes have less need to migrate so far, although Fieldfare is less versatile in its feeding and so less able to stand harsh conditions than for example our Blackbirds. Redwing on the other hand can forage in fields and woods but is also more sensitive to cold weather than our resident thrushes.

Golden Plover flocks can be seen occasionally at Treshnish in the spring and autumn but less frequently in the winter. This year a flock was found on one of the nearby hill tops and so they may only be moving very locally and not leaving the area at all although flocks seen in the winter may not actually be the breeding stock at all.

Dipper which has been seen on the Ensay Burn in the summer was, as expected, still present in the winter but should weather conditions become harsh would this species disperse? In the unlikely event of the streams freezing solid, this species would also have to move towards the shore but apparently as long as it can reach any flowing water below the ice, though air holes, it can survive and will probably remain in its breeding grounds. But interestingly the winter atlas tells us that it breeds early and can even lay eggs in late February, so in Scotland breeding is probably a little later.

Puffin is the odd one out as the auks go. Razorbill, Guillemot and Black Guillemot can all be seen offshore in the winter but the Puffin leaves our coastal waters during the winter. Kittiwake are also pelagic during the winter but can still be seen from the coast throughout the year although they have been seen roosting on tidal rocks here in September. In the British Isles as a whole there is a general displacement of birds further into the Atlantic but not a true migration. Breeding birds start arriving back in their colonies in February and some still visit their colonies up until November. The nearest breeding colony to Treshnish is on the Treshnish Isles.

At Treshnish the most common true winter migrant, assuming that Redwing and Fieldfare are mostly on passage, is the Great Northern Diver. In winter plumage it can be a little difficult to separate from the much less common (resident) Black-throated Diver but the pale breast side has square dark patches projecting forwards and this is usually easy to see. Red-throated Diver which breeds on Mull is more common than Black-throated Diver and can be separated by its upward pointing bill. In April Great Northern Diver is starting to moult into its breeding plumage and before leaving for its arctic breeding grounds we can see it in all its splendour. Some birds may stay until early June and it is not uncommon to see them until mid-May.
Whooper Swan another enigmatic winter visitor can usually be seen at Loch an Torr and Mishnish Lochs but this year I have seen none there and again this could be due to the mild winter. We see this magnificent swan occasionally at Treshnish in October and April when it sometimes settles on Treshnish lochan. Winter ducks are rare at Treshnish and so Goldeneye for example is best looked for at Loch an Torr and Mishnish Lochs.
Sanderling another winter migrant can sometimes be seen on passage in autumn on Calgary beach and Turnstone can be seen there throughout the winter if the beach is not too disturbed.

In late March a Short-eared Owl was seen along the road about 1km south from where the Treshnish farm-track meets the paved road. In early April a pair was seen hunting in the same area and again one was seen hunting in mid-April so it looks like the abundance of voles this winter has benefited this species and hopefully it will remain. It has certainly chosen a perfect spot as the deer fence protecting the broad-leaved plantation here must be excellent for voles. Another species which seems to have benefited from the ‘vole year’ is the Buzzard. Nine were seen circling together above Treshnish Point in early April. Another vole predator is the Hen Harrier, which is virtually a year round speciality here at Treshnish; although they do not breed on the farm but nearby and therefore the only time they are difficult to see here is at the peak of the breeding season when they will be hunting closer to the nest site. Hen Harriers are polygamous and so numbers can increase quite quickly if they are not prosecuted. The new plantation is ideal habitat and hopefully we will have them breeding there soon.

Spring is probably the best time to see Merlin but again they probably do not breed very close by and so we do not see them in the breeding season. They can also be seen throughout the rest of the year. Peregrine sightings are quite scarce but scanning the sky when the Common Gulls are alarmed could provide results. Golden Eagle is THE Treshnish bird speciality and is very easy to see throughout the year but especially in January, February when at least one pair seems to spend hours soaring together. I can only conclude that this is either for pure enjoyment or is part of the mating and bonding ritual or both because during breeding period they fly much less. If you disturb a Golden Eagle during the breeding season (mid-March until end of July) please leave the area immediately as some pairs are very prone to disturbance and will abandon the eggs especially in the early stages. White-tailed Eagle can be seen throughout the year, usually flying along the coast. On one of the timed winter surveys two or three juveniles were seen near Port Haunn. All had white wing tags and one was perched long enough to identify it as a 2007 chick from Skye which had not yet been seen on Mull. During the summer the Loch Frisa adults frequently come to Treshnish to hunt but last year the chicks fell out of the nest and afterwards they were not seen at Treshnish probably because they had fewer mouths to feed. This was good for the Fulmars, which reared at least 7 chicks around Treshnish Point in 2007.