British Birds Established 1907; incorporating 'The Zoologist', established 1843

Status and behaviour of the Tenerife Kinglet Hans LohrL, Ellen Thaler and David A. Christie

ABSTRACT The Tenerife Kinglet Regulus teneriffae appears to be a little-studied taxon, despite the fact that its taxonomic status has given rise to much debate. This paper summarises our knowledge of this attractive bird.

Over the years, the small kinglet Regulus which is endemic to the Canary Islands has been treated both as a subspecies of the Goldcrest R. regulus (e.g. Hartert 1932-38; Bannerman 1922, 1963; Cramp 1992) and as a subspecies of the Firecrest R. ignkapittus (e.g. Seebohm 1883; Vols0e 1951; Vaurie 1954, 1959; Etchecopar & Hue 1967), the latter view being followed also, though with some reservation, by Nicolai & Wolters (1971), Mauersberger & Stubs (1971) and Niethammer & Wolters (1972). More recently, A. van Loon (in Cramp 1992) and Beaman (1994) included it as an island race of Goldcrest, though both admit that their decision is not incontrovertible, whereas Sibley & Monroe (1990) considered that these two forms were better treated as allospecies. The current treatment by British Birds (86: 1-2) follows that of Sibley & Monroe (1990), the Canary Islands species being given the English name of Tenerife Kinglet Regulus teneriffae. This view is adhered to below, but the situation is by no means fully clarified. Despite the interest in the taxonomy of this delightful little bird, very little appears to have been published on the species in the last few decades. Indeed, the only major paper of which we are aware is that by Lohrl & Thaler (1980), which detailed observations made on Tenerife and of a captive female. The present paper is largely a summary of that work.

{Brit. Birds 89: 379-386, September 1996] © British Birds Ltd 1996 379 380 Lohrt, Thaler & Christie: Tenerife Kinglet General appearance The immediate impression given by Tenerife Kinglet is that of a Goldcrest, but with a broad black band on the upper forehead joining the two black stripes that border the central crown, and with narrower pale tips to the tertials. It shares with Goldcrest a prominent, very broad pale surround to the eye and does, in fact, bear little resemblance to Firecrest, lacking that species' bold pale supercilium, black eye-stripe and obvious bronzy 'shoulder' patch.

Distribution The Tenerife Kinglet is restricted to the outer islands of the Canaries: Tenerife, La Palma, La Gomera and Hierro. It appears to be not uncommon, at least in the Anaga mountains in the northeast of Tenerife, where it occurs in the region of the former laurel (Lauraceae) forests. This area is today dominated by the tree-heaths Erica arborea and E. scoparia, which would seem to be essential for nesting purposes. It becomes rare in the pine Pinus forest, where it occurs only in areas with tree-heath. Not unexpectedly, the species appears to be wholly resident. Nevertheless, it is interesting to note that a female reared in captivity demonstrated migratory restlessness, largely coinciding with the timing of autumn and spring passage periods of central European Goldcrests and Firecrests; its nocturnal unrest was less intense than that of Firecrest, but more continuous than that of Goldcrest. To what extent this single captive reflects the migratory disposition of a Tenerife Kinglet population remains to be seen. A more or less pronounced migratory disposition has, however, been confirmed also for Blackcaps Sylvia atricapilla living in the same area (Berthold 1978).

Voice Volsoe (1951) interpreted Lack & Southern's (1949) description of the Tenerife Kinglet's song as being typical of Firecrest, although he was probably unfamiliar with the latter's song. In playback experiments in Germany, however, Becker (1978) found that both Firecrests and Goldcrests showed little, if any, reaction to the song of Tenerife Kinglet, although Goldcrest reacted well to the kinglet's excitement call; the song was similar in structure to that of Goldcrest, though somewhat more variable. Sonagrams showed the calls of the captive female Tenerife Kinglet to be Goldcrest-like, though somewhat lower in pitch; 63 Goldcrests and 18 Firecrests showed hardly any recognisable individual variations (Thaler 1979). A clear difference exists, however, in the use of the 'short alarm-call'. This call, used very frequently by Goldcrests and Firecrests, apparently indicates low-intensity alarm when danger is not immediately threatening, and is given by both sexes in various other situations as an excitement call (Thaler 1979). In a densely occupied breeding area on Tenerife, males (apparently only males?) uttered it frequently at the start of the breeding season during territorial disputes, the call in this case probably having the function of deterring rivals ('rival-call': see Thielcke 1970). It seems that Tenerife Kinglets (especially females?) require a much stronger stimulus to utter the short alarm, which is clearly of lower threshold level in the cases of Goldcrest and Firecrest. British Birds, vol. 89, no. 9, September 1996 381

Plate 139. Captive female Tenerife Kinglet Regulus teneriffae, October 1983 (Ellen Thaler). Plumage of male is identical unless the crown feathers are raised.

Plate 140. Aggressive display by captive female Tenerife Kinglet Regulus teneriffae, March 1981 (Ellen Thaler). Male would show more orange in crown.

Plate 141. Captive female Tenerife Kinglet Regulus teneriffae wing-flicking while foraging on snow, January 1981 (Ellen Thaler). Note taxon's diagnostically broad black stripe on forecrown. 382 Lohrl, Thaler & Christie: Tenerife Kinglet Breeding Pre-laying period At one site 725 m above sea level, a female was carrying nest material on 1st March; the following day, a completed nest was found. If nest-building takes 15-20 days (Thaler 1976), construction must have started no later than mid February, bearing in mind that building activity ceases in wet and cool weather (which at this time of the year is frequent in the breeding area). Another pair had fledged young on 7th April, which means that eggs were laid in the first few days of March. The breeding season is doubtless later at higher altitudes. As with Goldcrest, the male shares in nest-building. During 1979-80, a captive female Tenerife Kinglet paired with a male Goldcrest was observed nest-building: all building activities were typical for Goldcrest, and the male prepared most of the foundation; the rapid 'vibrating' of the material that is characteristic of Firecrest (Thaler 1976: 135) was lacking, and the nest hollow was not arched over by a rim of inward-pointing feathers. The female kinglet spent a total of 4.5 days on the lining, somewhat shorter than observed among Goldcrests (minimum 5.5 days) and Firecrests (minimum 5 days), though this may be due to the smaller clutch (five, incubation from third egg); she used only 121 feathers, whereas captive Goldcrests used at least 1,151 and captive Firecrests at least 673 feathers. Several nests, including two freshly built ones, were located on Tenerife, all suspended 4-7 m above ground in thin horizontal branches of tree-heath. Although tree-heath facilitates the construction of suspended nests in the same way as spruce Picea does, it offers little protection against rain; in addition, the nests are more visible. Completed nests are ball-shaped and, as with all Regulus nests, the entrance is at the top and not, as Bannerman (1963) suggested, at the side. Both fresh nests were collected after use. One was still fully intact, and its attachment to the branches could be examined: two stronger branches (diameter 2-5 mm) passed along the interior of the nest wall for lengths of 50 and 70 mm respectively, and a further 17 twigs barely 1 mm thick were woven more or less horizontally into the wall. Both were true 'suspended nests', ideally adapted to the growth habit of the tree-heath. In their horizontal suspension they differed clearly from Goldcrest and Firecrest nests, which (almost always) are interwoven into vertical side twigs of spruce branches (Palmgren 1932; Thaler 1976). The materials used, however, were very similar: about 80% spiders' web, moss and lichens, 5% other soft vegetable material (grass panicles, rootlets, fibres), and 15% soft lining. They were somewhat lighter (8.9 and 8.6 g) than Goldcrest or Firecrest nests, and contained fewer feathers in the lining (194 and 116 feathers, against average of 1,773 for Goldcrest and average of 618 for Firecrest), but more aerial seeds, especially long, silky thistledown. When the female was at or in the finished nest, the male often sang for 2-4 minutes at a distance of 1-3 m. The song was usually shorter than the territorial song, and always with a highly variable end section or terminal flourish. Sometimes only a few elements preceded this, so that the 'song' consisted almost wholly of the end section. For the Goldcrest, the terminal section plays a major role in 'intimate behaviour' between male and female (Becker 1976; pers. obs.). When foraging during this period, most prey captured were minute insects. On British Birds, vol. 89, no. 9, September 1996 383 one occasion, one of the kinglets spent much time searching moss-covered branches and narrow trunks in a high-lying misty area.

Incubation and fledging periods During 41 minutes' observation on 18th March, incubation stints lasted for 12 and 11 minutes, with intervals of 10 and 8 minutes; and, on the foEowing day, for 3, 10, 20 and 12 minutes, with breaks of 7, 13 and 10 minutes. On 21st March, after heavy showers, the female returned very hesitantly to the sodden nest: between 10.53 and 12.05 hours, she incubated for 11 and 24 minutes, with intervals of 13, 16 and 8 minutes. During the incubation period, the male no longer sang near the nest, but always some distance away. Only when the female was reluctant to enter the nest after heavy rain did he sing from 3 m, but almost solely the end section of the song. When the parents appeared together and the female did not go straight to the nest, the male raised his crown feathers in a threat display: the female then perched on the nest rim, before finally entering; a few minutes later the male once more sang at 1 m from the nest. The male never approached the nest itself, and during the whole period of observation never fed the female. Thaler (1979) found that mate-feeding was not performed by the Goldcrest, either, although it was by the Firecrest Feeding of the young was observed on 28th March, from 10.50 to 11.52 hours; the weather was very cool and windy, with clouds of mist sweeping over the site. During this period, both adults fed the young 13 times, and faeces were removed once. The young, probably only a few days old, were brooded three times by the female, for 1, 12 and 6 minutes. When the male arrived during brooding, the female left rather hastily, waited at 10-20 cm distance, and when the male flew off immediately resumed brooding.

Nest bsses Although both Goldcrest and Firecrest suffer nest predation, no nests appear to be lost through the effects of weather (Thaler 1979). In the Canary Islands there are no natural nest predators, but introduced Common Rats Rattus norvegicus and House Mice Mus musculus are widespread and could possibly prey on nests. Domestic Cats Felts cams are present, but it is doubtful that they can reach kinglet nests; there appear to be no feral cats anywhere on Tenerife. The weather, however, is a regulating factor. At one nest, following heavy downpours, the eight-day-old young perished. Around this age, Goldcrest and Firecrest chicks are no longer brooded by day, their spruce-tree nests offering sufficient protection against the weather; but not so with nests built in tree-heath, and at eight days chicks are still quite inadequately feathered. A few days later, young from another brood at the same place fledged intact; thus the degree of feathering was decisive, unless the second nest had been unusually well sheltered. The last of these fledged young, not yet capable of flight, had landed on the ground and was taken into captivity (see over). 384 Lohrl, Thaler & Christie: Tenerife Kinglet Nestling diet The stomach contents of the four nestlings that died were examined, and in three of these the undigested constituents could be identified: the diet was dominated by adult and larval bugs (Hemiptera), but bush-cricket nymphs (Tettigoniidae) were also well represented (full details of analysis in Lohrl & Thaler 1980). Compared with the prey of central European Goldcrests and Firecrests, bush-crickets are notable as an adaptation to the different type of insect fauna. A corresponding preference for Orthoptera was shown by the captive female Tenerife Kinglet.

Development and behaviour in captivity Development of young The flightless young which had been retrieved from the ground was reared in captivity. When it left the nest, at 19-21 days of age, its tail feathers extended only 1.8-1.9 cm out of the sheaths but nevertheless projected 0.8-1.1 cm beyond the remiges, which had not fully grown out. It looked plumper, more compact than Goldcrests or Firecrests of the same age, whose wings are longer compared with the (equally short) tail (Thaler 1979). The body feathers were largely grown. The back and especially the head were greenish, brighter than on young European Goldcrest and more like a juvenile Firecrest. The head feathers, especially on the forehead, showed a distinct dark margin, corresponding to the black head markings of the adult. Goldcrest nestlings, however, sometimes also show an indication of a dark area on the forehead, even though no such marking is present on adults. The Tenerife Kinglet appeared darker and more 'colourful' than Goldcrest or Firecrest of the same age.

Behaviour of the fledgling At first, the young kinglet refused food and had to be 'force-fed'. Subsequent development was typical for the genus, and the vocal repertoire continued to be Goldcrest-like. Independent foraging began on day 27, and on day 38 the juvenile song (see Cramp 1992) was heard for the first time; on day 45 post-juvenile moult started, this lasting for nearly 60 days, and the bird finally proved to be a female. The Tenerife Kinglet differed from Goldcrest and Firecrest in its bathing behaviour, which was far more strongly pronounced. The kinglet became highly excited when confronted by wet twigs, always bamed in such circumstances, and as early as day 26 discovered bathing spots on the ground, where it subsequenuy bathed four or five times per day. (Goldcrests and Firecrests initially bathe only in branches made wet by rain or dew, and at most twice per day; ground water is not visited until much later: by Goldcrest, accompanied by parents, on day 48 at the earliest, otherwise on day 108; by Firecrest on days 52 and 114, respectively.) This behaviour is possibly determined by the environment, the frequently damp, heavily matted vegetation in its natural habitat enabling the Tenerife Kinglet to bathe safely at any time. For the Goldcrest and Firecrest, bathing in branches is dependent on weather conditions; ground bathing, being much more dangerous, is resorted to only by birds with full capacity for flight. British Birds, vol. 89, no. 9, September 1996 385 Behaviour following independence After the post-juvenile moult, the kinglet continued to behave essentially like a Goldcrest: for example, it flicked its wings sideways, not upwards like a Firecrest. In behaviour directed towards the mate-rival, it frequently gave a weak 'feather-raffling display', as well as the Goldcrest-specific 'forward display' with head bowed and stiff bobbing movements. When inviting copulation, it sometimes (in first year of breeding) performed wing-quivering, but later (second year) more often did not. In choice of prey the kinglet was less 'fussy' than its European congeners. Even when barely independent, it showed a liking for long-winged or long-legged insects; it was particularly fond of bacteriid larvae (Orthoptera: Bacteriidae), which are often shunned by Golderests and Firecrests. The preference for springtails (Collembola), so typical of Goldcrest, was not so pronounced; the kinglet did not bother with these tiny prey until winter and, later, the breeding season. This unusual selection perhaps reflects the availability of insects in its natural environment. A particularly interesting behaviour, apparently unrecorded for other Regulus species, was seen at the start of the brood-feeding period. The kinglet parcelled up minute prey, especially spiders, until its bill was full, with items hanging out of both sides; it then placed its bill under its foot so as to rearrange the items, enabling it to retain the food in the bill. (This behaviour could subsequently be provoked by supplying similar food by hand.) Despite detailed observations of foraging and food-carrying Golderests and Firecrests, we have never seen them use this action, which is very similar to the habit of tits (Paridae) of clamping food under the foot. Further study is required to show whether an individual habit was involved or whether this is a behaviour specific to the Tenerife Kinglet. Interestingly, however, on 12th February 1980, on Tenerife, a wild female demonstrated this same behaviour while gathering nest material.

Hybridisation and behaviour in mixed flocks At 11 months (January), the Tenerife Kinglet was placed with a male Goldcrest, but the pair failed to achieve sufficient synchronisation and did not complete nest-building. In the following year, however, synchronisation was complete: courtship (with strong pursuits), nest-building (initially with predominant male activity) and all aspects of pairing were typical of Goldcrest; at no point did either species show any of the paradoxical behaviour which is so striking in mixed pairings of Firecrest and Goldcrest. The nest was freely suspended in a spruce, which the kinglet accepted immediately (in the first breeding year it had shown less affinity to spruce than to juniper Juniperus). During 21st-26th May, the female laid five eggs which were unmarked and Goldcrest-like, but paler-looking, almost pure white. All hatched after 16-17 days. After the breeding season, the Tenerife Kinglet was placed with four Golderests and three Firecrests. Casual observations revealed that it behaved as a Goldcrest: it associated more closely with the Golderests, especially the females, than with the Firecrests (which are in any case less of a contact species), and roosted mostly with 'its own' male. It was, however, the most aggressive individual of the group and would violently attack another individual, especially a Goldcrest, 386 Lohrl, Thaler & Christie: Tenerife Kinglet for no apparent reason, jostle it in flight, and seize it with its claws so that both fell to the ground. In such attacks, it showed no preference for any particular individual; certain confrontational situations, perhaps intrusions within individual distance, seemed to be enough. It remains to be shown how close Tenerife Kinglet flocks will approach each other when roving about outside the breeding season.

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Dr Hans Lohrl, D72227 Egenhausen, Bei den Eichen 5, Germany Dr Ellen Thaler, Kirchgasse, A-6020 Innsbruck, Austria David A. Christie, 4 Steventon Road, Harefield, Southampton SOIS SUA, England