332 Field Observations on the Biology of the Marsh Tit
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332 FIELD OBSERVATIONS ON THE BIOLOGY OF THE MARSH TIT. BY AVERIL MORLEY. (Continued from page 287.) (4) BREEDING BEHAVIOUR. MAY (1949) asserts that as pair-formation behaviour patterns "are not related to the sex act, which is the criterion for 'sexual behaviour' ", pair-formation is not sexual behaviour, at any rate in the Willow Warbler (Phylloscopus trochilus) which he studied, but apparently social. The male's resistance to a companion is worn down by the female's persistence in invading his territory and continuing to do so in spite of all rebuffs. But surely her behaviour at least must have a sexual element in it, otherwise what is there to prevent her, if all she wants is sociability, from forming mono-sexual groups? It would surely not be possible to maintain that pair-formation and pair-persistence are purely social actions in such a species as the Marsh Tit, which maintains pairs throughout the year and at the same time for most of the year has a social life in the flock where it meets plenty of other Marsh Tits. Formation and persistence of pairs in the Marsh Tit was con sidered in a previous paper (Morley, 1950). Let us now follow a little the life of the pair throughout the year, starting from June, the close of the breeding-season. Figure 1 attempts to portray diagrammatically the approximate annual pattern of behaviour shown by the adult Marsh Tits in the study area. It shows the dramatic change in the adult's life which takes place from January onwards due to the onset of breeding behaviour, and the equally sudden return to ordinary life when the breeding-season is over. The pair remain together on the territory, sometimes alone, sometimes moving about with the flock, keeping in touch with small soft sip notes or an occasional pitsu. They support each other if there should be a dispute with other Marsh Tits. Nothing more than this was observed in June and July, but from August onwards, proximity to hole-bearing shrubs such as elder occasionally revived a significance which such shrubs held for them earlier in the year. For example, a pair on their way back from a border skirmish with neighbours paused by a hole in an elder, and the male looked at it closely with twitching wings, uttering the nasal ter-cher note (see p. 279). Signs that the pair are not indifferent to each other as male and female were given in August, 1941, when a landless bird showed attachment to a pair, or rather to the male member of it. While it was keep ing close to the male, the female repeatedly flew at it, evidently resenting the proximity. The male took no notice of it and the VOL. XLVI] OBSERVATIONS ON THE MARSH TIT. 333 FIG. I: APPROXIMATE PLAN OF ADULT MARSH TITS' ACTIVITIES THROUGHOUT THE YEAR. HATCHED PORTIONS INDICATE TRACE ACTIVITIES. interloper made no retaliation but would not be dislodged. P. S. Burns (1952) records a Marsh Tit carrying beakfuls of nesting material—lichen and moss to an elder in September. A slight but steady interest in holes was shown from October by all the tits of the genus Parus in West Wood. The same holes were investigated by the four species. My own impression is that the Marsh Tit showed its interest in a somewhat tame manner compared to the other species, especially the Blue Tit. It would perch by the hole, fly off a little way and wipe its bill on its new perch, then return, call su, and so on. Alongside the autumnal incipient interest in holes develops an interest in the places where holes occur. From the end of Novem ber the scattered patches of elders on the borders of territories began to be contested between neighbours and fights became more 334 BRITISH BIRDS. [VOL. XLVI. violent and prolonged in the vicinity of these shrubs. On December ioth, 1938, a female began flying rapidly from perch to perch, calling pitchou. The male replied and flew up to her, whereupon she uttered the high sibilant trill heard from the female in the breeding season. The male flew off to some blackthorn scrub, and she followed him, uttering the note again. She then became interested in a shallow cavity in the, rotten bough of an oak, flying in and out of it and not retreating more than a yard or two before returning, uttering excited sip, sip cries. Skutch (1946) in his life history of the Costa Rica Tityra (Tityra s. costaricensis) notes how this hole-nesting bird shows interest in holes at all times of year, and that, as is apparent with the Marsh Tit, the first stage is one of looking in, rather than going in to, holes. The Tityra begins to visit holes in earnest in November while nest-building apparently begins from the end of February. From November also were seen, in brief and soon-vanished form, chases between mates, small commotions and fuss, flying close around each other with soft excited sip notes. Mid-January saw the beginning of the proper song-period of the West Wood Marsh Tits. During this month, the vicinity of hole-bearing shrubs and the canopy above them became ever more attractive to the birds so that the ties with the flocks were loosened and the birds were found more frequently alone in these parts of their territories. From this month, too, the above-mentioned chase or emotional fuss became more frequent, the pair whirling round each other for a few seconds. Or they might move rapidly from perch to perch attacking oak buds, bark and moss, with twitching wings. Emotional fusses might end with visits to holes, both birds alternately going in and out, or they might be per formed between the pair after the close of a skirmish with neigh bours. A fairly representative section of behaviour was shown by a pair which made a chase, then clung 8-9 inches apart upside down on twigs, the bark of which they pecked and tore, then the male flew at the female as if she had been an interloper and darted off to the tree tops, there to burst into song. This pouncing action is widespread among birds and has been thought to be a means whereby one partner (usually the male) attempts to impress its dominance over the other. Female Marsh Tits occasionally pounced on their mates but were not recorded doing so after the end of March. During February the twitching of the wings while the bird is foraging becomes marked, showing that the apparently passive bird is really in a state of tension which is likely at any time to be fired into more definite expression. A pair may move rapidly about, sometimes almost bouncily and clumsily, in the canopy above a group of elders, and go from group to group in this manner, perhaps with no pretence of feeding at all. Or they may VOL. XLVI] OBSERVATIONS ON THE MARSH TIT. 335 descend to the base of the shrubs' trunks, moving round and round them, or perching" near the holes without going in, calling noisily—especially the male—the pitchou, the loud tew and tsup, or the nasal ter-char-char note. Though the males were noisier than the females in the vicinity of holes, the females sometimes had more vigorously twitching wings and a greater restlessness, visiting elders in quick suc cession, or occasionally inspecting the snag ends of rotten oak boughs. The males might be hard put to it to keep up with their mates. Attractive patches of elders, in or out of their own terri tories, became objects for visiting, and excursions were made which ordinarily were not attempted. March saw a peak in the activity of hole-visiting. The birds clung to the entrances, bobbing their heads with excited sip notes and many pitchou calls. Two pairs visiting the same batch of elders led, of course, to noisy strife. A female en route for the scene of battle between her mate and a neighbour perched at the entrances of three successive holes with twitching wings before throwing herself into the fray and another female visited holes at intervals during the fight. The pair may visit holes when alone or when arriving in the vicinity with a flock. The male may sing somewhat softly in the elder clump, and one male, whose soft song verged on the low yu-yu throbbing version (see p. 274) also strung together small whispered shrew-like notes and twitters merging into a sub-song. Bachelor males occasionally visited holes, but were not seen to set out purposefully to visit, as did mated pairs. The bachelors were often noisy, giving long loud series of pitchou from their winter scrub haunts as well as song from canopy and shrub, but they did not cling to the vicinity of hole-bearing shrubs. A deserted male whose female ultimately returned to him after 5 weeks' absence, was seen during his grass- widowhood to visit a woodpecker's disused hole with twitching wings and loud puts calls. A male which was silently and un obtrusively sidling up to the future nest hole was driven off by the female. The pair had used this hole for nesting the previous year. The female also drove off Blue Tits from the hole, but could only watchfully retire when Great Tits decided to inspect it. Any excitement, such as strife with neighbours, the male feed ing the female, the presentation of bait by me or even my appear ance would incite Marsh Tits to visit holes.