(50) NOTES ON THE BIRDS OF PUFFIN ISLAND.

Transcription

1 (50) NOTES ON THE BIRDS OF PUFFIN ISLAND. BY W. ASPDEN. OFF the extreme eastern point of Anglesey known as Penmon or Head of Mona, and marking the eastern entrance to the Menai Straits, lies the small island of Priestholme or Puffin Island. This little scrap of land, some two-thirds of a mile long and half that breadth, has from time to time received considerable attention from eminent naturalists including ornithologists of repute. It is therefore possible, owing to the notes made by such observers, to compare existing conditions with those pertaining to the past. Amongst such early references are the ones made by Oliver Goldsmith in his History of the Earth and Animated Nature, published first in 1774, wherein he states with reference to the Puffins that their numbers may be likened to swarms of bees, and also cites the island as one of the noted breeding haunts of the Guillemot. It is, however, with later and more modern observers that I have been able to make comparisons. I do not propose, however, to make, in these notes, more than a mere reference to one or two features which seem of interest respecting the changes brought about on the island by the increase of certain species of birds. About forty years ago the Liverpool Marine Biological Society had a station on the island, and in 1891, when the Society transferred its activities to the Isle of Man, the station was handed over to the University College of North Wales at Bangor. The station was active from 1892 to 1897 and during that period published bi-annual reports. Professor Newstead, now of Liverpool, visited the island in 1895 and published a list of the birds he noted.* An interesting footnote to the list reads as follows : " The almost entire absence of cover gave the birds little or no chance of concealment and it is doubtful therefore if a single species was overlooked at the time of the visit." There is certainly no absence of cover to-day and each season sees an increase. The Monks who inhabited the Priory on the island grew as a pot herb the common Alexanders (Smyrnium olusatrum), and this plant has remained down the centuries. For many years before the War a small herd of goats inhabited the island, and these served to keep the upper surface and the slopes clear of cover, even cropping the few stunted elder bushes which are the only trees on the island. When the *Report of the Puffin Island Biological Station, , University College of North Wales, Bangor.

2 VOL. XXII.] NOTES ON BIRDS OF PUFFIN ISLAND. 51 Biological Station was working the Alexanders were practically confined to the south-western corner of the island, and mainly on the slopes. Now quite half the upper surface is also covered with a breast-high growth of the plant, along with considerable quantities of common hemlock (Conium maculatum) and patches of nettle (Urtica dioica). The goats have gone, and so a positive check on the plants is removed, but the great increase in the numbers of the Herring-Gull (Lams a. argentatus) and the Lesser Blackbacked Gull (Larusf. affinis) has, I think, provided a positive aid, especially to the Umbellifera. Wherever these two species of Gulls nest on the upper surface of the island the close turf of tiny, dwarfed and closegrowing plants is soon worn away by the constantly alighting birds, and the subsequent scramblings of the young, and the soil is laid bare. The umbelliferous plants seem to have the power of colonizing these bared patches before the smaller plants can re-establish themselves, and in consequence the island is rapidly becoming covered with a thick growth. This means that the area inhabited by Puffins (Fratercula a. grabce) is being restricted, as that bird prefers a clear front exit to his burrow. The Puffin once was the dominant bird here but has now lost that place to the Herring-Gull. This latter bird really seems to prefer open situations for nesting, but the Lesser Black-backed Gull shows a very decided liking for cover. I have noted this at another large gullery in Anglesey where the two species nest together. The egg-stealing habits of these two Gulls are well known and I doubt if there is much to choose between them. There is, however, a difference of some three weeks between the nesting time of the species in most years, and the Herring- Gulls are, as a rule, well started before the Lesser Blackbacked Gulls begin to build. During this period there is bitter strife between them, but when both have eggs they turn their attention to the Guillemots (Una a. albionis) which frequent the north-western cliffs. The Puffins in the vast majority of cases make use of burrows in the turf of the upper surface, but many use holes in the cliff faces, which being of carboniferous limestone provide a multitude of crevices. When the young Gulls begin their wanderings they often get into the Puffin burrows and this is strongly resented. I have seen a Puffin, dragging a Gull chick, emerge from its burrow, and the chick was just killed and quite warm. " Tommy Noddy " can bite cruelly hard,

3 GUILLEMOTS ON PUFFIN ISLAND. On uncrowded ledges the birds adopt the prone position when incubating. (Photographed by W. Aspden.)

4 LESSER BLACK-BACKED GULL ON PUFFIN ISLAND. In June the vegetation attains a height of 4 to 5 feet, and provides very effective cover to the majority of nests of this species. (Photographed by W. Aspden.)

5 54 BRITISH BIRDS. [VOL. XXII. The Guillemots are in some hundreds on the narrow ledges, but they congregate in their greatest numbers in two low caves some distance down the cliff. The caves run back a good way but the roofs are so low as to prevent a human being getting far in. The floors of these caves are paved with eggs, far back beyond sight, and it is only when the birds pour out, like water from an opened sluice gate, that one can get an idea, of the numbers of birds using the place for breeding. Most visitors to the island can have but little conception of the numbers present, as they cannot be seen without going down to the caves. I have long been intrigued by the statements made by professional cliff-climbers that they are able to say with a high degree of certainty just where a particular type of egg will be found each year and Puffin Island seemed to me to provide an opportunity for testing this statement. I therefore selected two small portions of accessible ledge, whereon I found certain uncommon and well-defined types of eggs, making sketch maps and carefully marking the positions of the chosen eggs. I took careful notes and chose ten specimens. This was in In 1926 I kept watch on these two places and six of the specimens were duplicated. In no case was an egg more than eighteen inches from the position of its prototype of the previous year. One case was particularly interesting. The 1925 egg was of the common blue colour, but uncommonly marked with white blotches outlined with black, giving the impression that the white patches had been outlined in ink. In 1926 there were three eggs of that particular type all close together. This raises an interesting point: Do the daughters inherit the colour scheme from the mother? This may be perhaps solved by further observations and the use of rings. In 1927 five of the eggs were duplicated eventually, though my observations were temporarily broken down by a collector. Fortunately I met him leaving the ledge and he very kindly showed me what he had got, a brown egg and a white with red scribblings, which were like two I had plotted on my maps. One of the eggs was replaced in less than seven days, but this was much less heavily pigmented, though undoubtedly laid by the same bird. I have known a bird to lose three eggs and still lay a fourth. There can be little question that a considerable number of Guillemots do return year after year to the same place for egg laying, and even to the same part of the same ledge.

6 VOL. xxn.] NOTES ON BIRDS OF PUFFIN ISLAND. 55 The statement is often made that this bird always sits upright on its egg when incubating. This is by no means the case and applies only to crowded ledges. The majority of Guillemots when there is room adopt the same position as any other bird, i.e., prone upon the egg. The photograph of the group of birds taken on an open ledge where they are not too crowded shows this clearly and my own observations over some years bear it out. When a ledge is very crowded and an individual has literally to fight its way into the crush, then the upright position is the only one possible, and facing inwards to the cliff-face is a necessity to avoid being pushed off from behind. Razorbills (Alca torda) are quite as numerous as the preceding species but are not confined to the western face. They are, however, somewhat restricted on the opposite side of the island owing to lack of suitable sites. On many little overhung ledges Razorbills and Guillemots may be seen sitting together on their eggs and showing no dislike for each other's company. Shags (Phalacrocorax a. aristotelis) are scarce but regular nesters, and I found one nest in 1926 on a cliff-face within a few feet of the nest of a Raven (Corvus c. corax) in which there were three half-grown young. The Shag had also three young and was particularly assiduous in guarding the nest. On the turf above the Raven's nest there are often disembowelled corpses of Puffins, but I am inclined to attribute this to the visiting Greater Black-backed Gulls (Larus marinus), a bird which does not nest regularly on the island, though I have found the nest twice and seen the birds frequently. The Raven I think takes toll of the carrion but is not responsible for the killing, in spite of Stanley's Book of Birds. A small colony of Cormorants (Phalacrocorax c. carbo), about half a dozen pairs, nest at the foot of the western cliff but they are sadly harassed by trippers. About the Kittiwakes (Rissa t. tridactyla) the same tale is to be told, and not more than a couple of dozen pairs now use the island. A list of other species, none of which are numerous and some confined to one or two pairs, may be of interest, and covers the nesting species*. Jackdaw (Colceus m. spermologus) A little colony in rockcrevices at the south-eastern corner. Starling (Stumus v. vulgaris) A few pairs in the ruined buildings.» Hedge-Sparrows were also resident on the island in (F.C.R.J.).

7 56 BRITISH BIRDS. [VOL. XXII. Meadow-Pipit (Anthus pratensis) Common but decreasing. Rock-Pipit (Anthus s. petrosus) Common. Song-Thrush (Turdus ph. clarkei) Three nests noted. Blackbird (Turdus m. merula) Two nests noted. Wheatear ((Enanthe m. ananthe) Not numerous. Sheld-Duck (Tadorna tadorna) Varies in number, but nests most years high up on the cliff edge in rabbit burrows. Stock-Dove (Columba anas) Two or three pairs only. Oyster-Catcher (Hcematopus o. ostralegus) About six to eight pairs annually.