(326) ROOSTING HABITS OF THE IRISH GOAL-TIT, WITH SOME OBSERVATIONS ON OTHER HABITS BY ROBERT F. RUTTLEDGE. (Plate 43). THE observation in The Handbook, Vol. i, p, 256, stating that data on normal roosting habits of the Coal-Tit were scanty, led me to pay particular attention to this subject. My observations are confined to the Irish Coal-Tit (Parus ater hibemicus). The results are those of over three years' study of a limited number of birds in Co. Ma}'o. The locality where observations were made is fairly exposed, but with considerable shelter in the form of gardens, outhouses, trees and scrubby woods. There are a number of difficulties in the way of detailed study of this species, chief of which is the extreme difficulty of seeing rings on marked birds in thick foliage and on such a restless bird. In summer, in particular, it is very hard to trace birds to their roosts, with the result that there is a paucity of observations at this season. When working alone, or with only one companion, it is extremely difficult to follow up the rapid movements of the birds as they travel through thickets or in high tree-tops prior to going to rcost. Observations have, therefore, at times been rather disjointed, especially when a bird changes its roost, thus necessitating renewed search. Although primarily the work was in connexion with roosting- habits, other habits have claimed attention and some notes on them are given. I am much indebted to John Barlce for the photographs of two typical roost-sites. BEHAVIOUR PRIOR TO ROOSTING. This varies to some extent. Coal-Tits are inclined to become silent about half-an-hour before roosting-time, whereas Great Tits and Blue Tits are inclined to call and scold up to roosting-time. Coal-Tits often go up into the tops of trees or high bushes and there sit silently, perhaps preening. They then suddenly fly off or travel rapidly through the tree-lops or lower bushes for an appreciable distance to arrive at the vicinity of the roost. - Often birds arrive and hang about in the vicinity of the roost either to preen or sit quietly for 7-10 minutes, even 20 minutes or exceptionally 25 minutes, before entering the roost. Very rarely have I seen a bird come from a distance and go straight into the roost. Such instances seem to occur only when a bird is very much behind the normal time of going to roost (e.g. a bird which arrived from a distance, calling and seeming agitated, 33 minutes after sunset, went straight into its roost.). Coal-Tits are normally very suspicious prior to entering their roost. There is individual variation, but on the whole their anxiety is more pronounced than at their VOL. xxxix] ROOSTING HABITS OF IRISH COAL-TIT. 327 nesting-site. Most birds, before entering finally, will either sit just outside the roost for a few moments, or will enter the roost, then re-appear just outside, perhaps several times. If conscious of being watched they delay entering and may even depart to an alternative roost. Such enforced delays must be avoided when timing birds into their roosts. Timings have been taken from the birds' final entry into the roost. Once in the roost individuals vary in their alertness, even in similar forms of roost. Some are very wakeful 20 minutes or even 30 minutes after entry; others are not easily disturbed even a short time after entry. At night they are not very responsive to noise or even to light, but they awake immediately and leave the roost if the tree-trunk or branch, etc., is lightly tapped or jerked. (cf. Dunsheath and Doncaster [1]),

ROOSTS. The following have come under my notice. Holes in rotting tree-trunks—usually of ash-trees—-(illustration No. 1). Frequent. These holes are frequently enlarged from Tree-Creepers' scrapings as Messrs. Rankin [2] have pointed out, but are also made by the tits themselves. I have found them to be very uniform in shape, as the following dimensions of three typical ones show. Defth; entrance to back. Diameter at entrance Vertical Horizontal 3 ins. 2 ins. if ins. 3 ins. 2I ins. " 2| ins. 2 ins. 2 ins. 2 ins. The difference in depth of the last one may be due to the roost not having been fully excavated at the time of measurement. Ivy-covered hawthorn trees {Illustration No. 2). Frequent. Ivy on gable of house. Three. Ivy-covered fork of sapling. Three. Ivy-covered fork of tree. Two. Ivy-covered stump. One. Between thick ivy stems around a branch. One. Short ivy around a sapling. One. Garden arch covered with ivy and creepers. One. Crevice between masonry and corrugated-iron roof. Two. Haystack. One. Hole c. 3 ins. deep. Hole in hollow end of snapped-off branch. One. Hole excavated by bird in dry mat of dead ivy on a gable. One. Depth 2| ins. Entrance 21 ins. x z\ ins. On ledge in split of rotting stump. One. Ledge 3 ins. front to rear, 2 ins. broad. 328 BRITISH BIRDS. [VOL. xxxix.

Branches of Cupressus macrocarpa. One. Old Wren's nest. One. Thick hedgerow. One. Reference to the use of holes in Sequoias has been made by Rankin [2] and in cedars and old nests of birds of the British race, by Dunsheath and Doncaster [1]. Height of roosts from ground.—The average height of twenty roosts was 9 feet 10 inches. Maximum, 21 feet in one case, in ivy on the gable of a building. Minimum, between two and three feet in two cases, in ivy-covered forks of holly bushes. In addition there were several at c. 15 feet in ivy-covered trees in which it was not possible to obtain completely accurate measure­ ment. In one instance a marked bird was found to roost in an excavated hole 8 feet from the ground in May and June. In the following November it was roosting at c. 15 feet in an ivy-covered hawthorn tree c, 300 yards away. Aspect.—It seems immaterial what aspect is used. Prevailing winds (S.W. here) and weather conditions do not seem to have any marked effect. I have note of the following aspects. N. 2. S. 2. E. 3. W. 3. N.W. 2. S.W. 2. S.E. 1. TIME OF GOING TO ROOST. From 13 roosts at which I have made observations, the following four are given in detail. They were used fairly consistently (roosts are very frequently changed or deserted, often only temporarily), and they bring out one or two points of interest. As in no case was a marked bird constantly observed there is no proof that the same bird would return after a temporary desertion of a roost, though there was in most cases evidence pointing 'to the probability. Marking a bird at the roost always entails desertion with consequent breaking Of any sequence of observations, and with the added difficulty of finding the new roost. All times given are in relation to local sunset.

ROOST I. Date Time Weather Conditions 10-12-42 2 rains, before Fair. 9-4-43 3 mins. before Fair. 13-4-43 5 mins. before Very fine; mild. 22-4-43 16 mins. before Very fine; warm. 23-4-43 14 mins. before Very fine; mild. 19 mins. before 25-4-43 Full gale; rain. This roost was not seen to be in use again until 1945. Impossible to say if the same bird returned, but the roost was in exactly the same place. The difference of time in relation to sunset is, however, strange, though on the September dates sunset is approximately half an hour earlier than on the April dates given. VOL. xxxix] ROOSTING HABITS OF IRISH COAL -TIT. 329

Date Time Weather Conditions 14-9-45 10 mins. after Bright, warm, occasional showers. 15-9-45 Not in use Gloomy, drizzle, strong wind, S.E. 18-9-45 19 mins. after Calm, warm, bright. 20-9-45 16 mins. after Cool, strong wind, S. 10-10-45 33 mins. after Bright, warm, calm. This is an exception­ ally late record. 12-10-45 Not in use.

ROOST II. Date Time Weather Conditions 4-^-43 5 mins. before Fair. 5-1-43 5 mins. before Bright, Fine. 6-1-43 2 mins. before Dull, foggy. 12-1-43 Not in use Dull, foggy. 14-1-43 In roost before sunset. Thick fog. 26-1-43 5 mins. after Bright. 3I-I-43 Already in roost Fine, bright. Great Tits and Blue Tits were 19 mins. before still abroad 30 mins. later. sunset. 2-2-43 Roost finally vacated. The same bird used this roost throughout. Note that on the evenings oi January 26th and 31st, there was considerable variation in time of roosting under similar weather conditions.

ROOST III. Date Time Weather Conditions 10-10-45 23 mins. after Calm, bright, cool. 11-10-45 24 mins. after Calm, bright, cool. 12-10-45 23 mins. after Calm, overcast, warm, I3-IO-45 20 mins. after Overcast, rather cool, light breeze, S.E. A bird roosting 4 paces distant entered its roost 12 mins. after sunset on 13th. 16-10-45 Not in use Overcast, cool, light breeze, S.E. 19-10-45 19 mins. after Very gloomy, wind moderate, S.E. 24-10-45 Not in use Gale W. High wind and rain on succeeding days. Roost very sheltered. From. October 28th, weather was fine, calm. 4-i i-45 30J mins. after Stil), warm, clear. 6-11-45 24 mins. after Still, warm, clear. Not in use. 10-11-45 It is noteworthy that on November 4th, when the bird went to roost at the rather unusually late time (30I minutes after sunset), its companion with a roost four paces away went into its roost late also (30 minutes after sunset). On most days when both were noted there was never more than one minute's difference between their respective times of going to roost. These birds, though very regular in their time of going to roost, are noticeably later than the average.

ROOST IV. Date Time Weather Conditions 8-8-45 19 mins. before Still, fine, clear, warm. 2-9-45 20 mins. before Still, fine, clear, warm. 8-9-45 18 mins. before Calm, clear, cool. V VOL. xxxix] ROOSTING HABITS OF IRISH COAL-TIT. 331 Shapes of territories naturally depend considerably on the layout of cover. I have found that between one year and another, territorial ground may be gained to one flank, but it is then lost to the other flank.

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Both the marked birds disappeared entirely at the end of the periods mentioned. In six other cases unmarked pairs could always be found in what was obviously their restricted territory. 332 BRITISH BIRDS. [VOL. XXXIX. Mr. W. A. Wallace showed me two restricted areas in his woods at Oldhead in which he could always find, within a short space of time, one or a pair of Coal-Tits. This I was able to confirm. These territories seem to be defended by song in winter (see under Song Period), but no exception is taken to other Coal-Tits passing through the territory when members of the "hunting bands" of small birds. NEST-SITES. It may be interesting to compare the heights of nesting-sites in relation to those of roosting-sites. The latter I have shown to average 9 feet 10 inches above ground level, with a minimum of 2 feet to 3 feet. Ten nests of which I have note averaged 3 feet 2 inches above ground level, with a maximum height of 5 feet 2 inches, above which I have never found a nest.* Nests are not infrequently placed below ground level. In one such case, where the male was marked, it was found that the bird had its roost 96 paces distant and at a height of 8 feet. Another male roosted 13 feet above ground 23 paces from its nest, which was 1 foot 8 inches above ground. In each case where nest and roost has been found both have been in territory as defined not only in summer, but also in winter. The most favoured site in this locality is a hole in an unmortared wall. NESTING MATERIALS. Ussher [3] found feathers used very sparingly. I find that there are usually not more than two or three and that most nests contain no feathers. I have one record of a nest containing eight feathers, six white, two black. Otherwise material is as given in The Handbook, Vol. i, p. 256, with the addition in one case of some dried stems of bracken, and in another of a small proportion of thistle­ down. SONG-PERIOD. Ussher [3] considered that the song sometimes commenced at the end qf January. He believed that, although heard until the end of June, it was improbable that the song of nesting individuals was continuous. The period as observed in the north of Ireland by Campbell [4] conforms generally to Ussher's observation. Benson [5], quoting Kinahan's observations near Dublin, gave the song period inclusive from January to June. I do not find that these observations apply normally in Co. Mayo. Marked birds have been observed singing in every month. Song is quite usual by these birds from mid- December until the end of February, There is then usually much increase with periodical slackening in accordance with weather conditions. From mid-March output increases, more so in April. Song may be heard in short bursts through May, June and July. *Since writing this I have found a nest at a height of 16 feet 6 ins. in a deep cavity where a rotten branch had fallen away. I consider both the height and the site quite abnormal. VOL. xxxix] ROOSTING HABITS OF IRISH COAL-TIT. 333 All through August in some years there is occasional song. Marked individuals that were singing in winter did so constantly in May. I have (still referring to marked birds) one note "silence, birds feeding young from May 10th to May 17th," but on occasions I heard song when there were young in the nest. The song-period of Coal-Tits in general, taken as a whole, is much in accordance with the pattern given in The Handbook, Vol. i, p. xl. except that song is normally quite exceptional in September and early October. In late winter and early spring especially, though indeed at all times to some extent, the volume of song is much dependent on birds of adjacent territories being close to one another. Meeting on the boundary causes much song until one or the other bird retires farther into its own territory, when song will cease. A bird whose territory is seldom invaded or which spends much time in the centre of its territory is seldom heard to sing. It follows that in areas where population is dense song is more frequent. Early in spring most song is delivered from the top-most branches of trees and bushes. Later Coal-Tits sing as they work along hedgerows or from tree to tree. Song in flight is frequent, especially in spring and during aerial chases. FOOD. During September and October, Coal-Tits habitually hide beech- mast and other nuts and seeds, though I have found no case of storing them together. A species of Chironomns is a favourite food in spring, caught in short hawking flights. I can confirm Ussher's observation that it fee "s on alder seeds. I have seen Coal-Tits taking grains of oats and possibly wheat from the ground when threshing of these cereals had recently taken place. I have seen birds taking grains, one at a time, from stacks of oats. The grain is carried to a distance to be eaten, as is the normal procedure when feeding on beech-mast. Seeds are also extracted from sallow catkins. MISCELLANEOUS. All my observations go to show that the sedentary individuals at any rate, remain paired for life. Pairs -keep together, or when widely separated, regain contact by the use of the call-note, As in the case of the British Coal-Tit, as described by Nethersole- Thompson [6], I find that both sexes prospect for nesting-sites. I have several records of birds hovering to obtain insects from the leaves of trees and from tall grasses. REFERENCES. [1] DONSHEATH, M. H. and DONCASTER, C. C. (1941). Brit. Birds, Vol. xxv, p. 143. [2] RANKIN, M. NEAL and RANKIN, DENIS H. (1940). Brit. Birds, Vol. xxxiv, p. 60. [3] USSHER and WARREN (1900). Birds of Ireland, p. 31. [4] CAMPBELL, D. C. (1921). Irish Naturalist, Vol. 30, pp. 76 and 77. [5] BENSON, C. W. (1901). Our Irish Song Birds, appendix, p. 189. [61 NETHERSOLE-THOMPSON, CAROLINE and DESMOND (1943). Brit. Birds, Vol. xxxvii, p. 90. British Birds, Vol. XXXIX, PL 43.

IRISH COAL-TIT. IRISH COAL-TIT. TYPICAL ROOSTING HOLE IN ROTTING ASH TREE, TYPICAL IVY-COVERED HAWTHORN USED FOR ROOSTING : 11 FEET ABOVE GROUND. ROOST WAS IN SHADED CAVITY NEAR CENTRE. (Photographed by J. S. Barlee). (Photographed by J. S. Barlee).