The Corsican nuthatch (Sitta whiteheadi) is a species of bird in the nuthatch family Sittidae. It is a relatively small nuthatch, measuring about in overall length. The are bluish-grey, the greyish-white. The male is distinguished from the female by its entirely black . The species is sedentary, territorial and not very shy. It often feeds high in Corsican pines (Pinus nigra var. corsicana, syn. P. nigra subsp. laricio), consuming mainly pine seeds, but also catching some flying insects. The breeding season takes place between April and May; the nest is placed in the trunk of an old pine, and the clutch has five to six eggs. The young fledge 22 to 24 days after hatching.
The Corsican nuthatch is found only on the island of Corsica, where it populates the old forests of high-altitude Corsican pines, descending lower in winter. Its scientific name comes from John Whitehead, the ornithologist who brought the bird to the attention of the scientific community in 1883. The Corsican nuthatch is closely related to the Chinese nuthatch (S. villosa) and the red-breasted nuthatch (S. canadensis). It is threatened by loss of nesting sites and habitat fragmentation, with an estimated population size of about 2,000 individuals, possibly in moderate decline. Due to the small population size and the limited range, the conservation status of the Corsican nuthatch is classed as "vulnerable" by the International Union for Conservation of Nature.
Taxonomy Discovery and studies
The Corsican nuthatch was discovered when ornithologist John Whitehead went to observe alpine swifts (Tachymarptis melba) on 13 June 1883. Whitehead, who had spent much of the previous years in Corsica, spotted and shot a male Corsican nuthatch. He kept the specimen's skin and did not bother with it until October, when he asked Richard Bowdler Sharpe for help in naming some small birds he had collected; although the bird's head was damaged by the collection method, Sharpe assured him that the species was not yet described. Whitehead thought the bird was extremely localised and did not give the precise locality where he collected the first specimens for fear that the species would be exterminated by additional collections.
Whitehead returned to Corsica in May 1884 and found a male, which he recognised by its black . After killing it, he waited to see the accompanying female, killed it as well, and then collected three more specimens from a small flock. In the following days, he observed a pair coming and going with nesting material in a hole six metres above the ground in the trunk of a very old pine. He located other nests, some above the ground, and opened two of them, finding 5 eggs in each, which he collected.
The Italian ornithologist Enrico Hillyer Giglioli reported in 1890 that he had observed the bird on 16 September 1877 at Ponte Leccia, almost six years before Whitehead, but mistaking it for a Eurasian nuthatch (S. europaea), he did not bother to shoot it. In the spring of 1896, the German naturalist Alexander Koenig visited the forest of Vizzavona and collected with great difficulty five specimens; in the early autumn of 1900, Arnold Duer Sapsworth brought back some skins. For the first, the breeding season had not begun at the time of his visit and for the second, it was over; no additional eggs were therefore brought back during this period. The next collections were made between 1908 and 1909 by the British ornithologist Francis Charles Robert Jourdain, who provided some additional field notes and explained the difficulty of accessing the nests.
The first works concerning the biology of the bird were only carried out in the 1960s by the German ornithologist Hans Löhrl, who studied the reproduction, feeding and behaviour of the species. In 1976, Claude Chappuis described the voice of the species in an article dedicated to the vocalisations of birds from Corsica and the Balearic Islands. In the 1980s, the Italian ornithologists Pierandrea Brichetti and Carlo Di Capi studied the reproduction of the Corsican nuthatch. Since the 1990s, the species has been studied closely by local groups, and in particular by ornithologists Jean-Claude Thibault, Pascal Villard and Jean-François Seguin.
In the summer of 2006, a Dutch group participating in an entomological expedition incidentally observed a pair of nuthatches in the Altai, near the meeting point of China, Kazakhstan, Mongolia and Russia, in a pure Siberian larch (Larix sibirica) forest. The male had a black crown, and the female did not, and both had a dark topped by a white supercilium. The closest species geographically that might fit this description is the Chinese nuthatch (S. villosa), which would then be far from its known distribution, and which has more buffy underparts than the observed individuals but they were also close to Corsican nuthatch in appearance. This record could be indicative of a much wider distribution of the Chinese species, or the bird could be an as yet undescribed species related to S. whiteheadi and S. villosa.
Nomenclature The Corsican nuthatch was described by Sharpe in March 1884, based on the first male specimen collected by Whitehead, after who it was given the specific name. Whitehead sent a second male to Sharpe, who presented it in May to the Zoological Society of London. In June, Sharpe completed the description of the species after Whitehead sent him a female. The Corsican nuthatch is sometimes placed in a subgenus, Sitta subgen. Micrositta, described by the Russian ornithologist Sergei Buturlin in 1916, and has no subspecies.
In 1905 the German ornithologist Ernst Hartert treated the Corsican nuthatch as a subspecies of the red-breasted nuthatch (S. canadensis) and this treatment was then followed until the 1950s. Title page of Vol. 1 has 1903 but published in sections (Heft). See Vol. 1 p. xiii and In 1957, the American ornithologist Charles Vaurie explained that the morphology did not allow one to be sure that the Corsican nuthatch was a distinct species, and that it was probably better to consider it as belonging to the "S. canadensis" group, regrouping the species S. canadensis, S. whiteheadi and S. villosa; The German ornithologist Hans Löhrl, after studying the ecology and behaviour of the birds of Latin America and Corsica, and through the publication of his field notes between 1960 and 1961, disagreed with Vaurie's position. In 1976, the French ornithologist Jacques Vielliard described the Algerian nuthatch (S. ledanti), just discovered in Algeria by Jean-Paul Ledant. He devoted part of his article on the possible relationships of the different species and their evolutionary history. Vielliard suggests that Vaurie stopped at "a superficial morphological similarity" to bring the Corsican nuthatch closer to the red-breasted nuthatch, and that the Corsican species should rather form with Krüper's nuthatch (S. krueperi) a group known as the "Mesogean nuthatches", "where S. ledanti providentially fits in".
Molecular phylogeny and evolution In 1998, Eric Pasquet studied the cytochrome b of the mitochondrial DNA of a dozen nuthatch species, including the various species of the Sitta canadensis group, which he defined as comprising six species, which are also those of what is sometimes treated as the subgenus Sitta subgenus Micrositta: S. canadensis, S. villosa, S. yunnanensis, S. whiteheadi, S. krueperi and S. ledanti. Pasquet concludes that the Corsican nuthatch is phylogenetically related to the Chinese nuthatch and the red-breasted nuthatch, these three species forming the sister group to a clade including Krüper's nuthatch and the Algerian nuthatch. The first three species would even be close enough to constitute subspecies, rejecting Vielliard's "mesogean" theory and thus confirming Vaurie's conclusions. For the sake of taxonomic stability, however, all retain their full species status. In 2014, Eric Pasquet and colleagues published a phylogeny based on nuclear and mitochondrial DNA of 21 nuthatch species and confirmed the relationships of the 1998 study within the "S. canadensis group", adding the Yunnan nuthatch, which was found to be the most basal of the species. The study findings align with the morphology of the species, the red-breasted nuthatch, Corsican nuthatch and Chinese nuthatch sharing as a derived character the entirely black crown only present in males, a unique trait in the Sittidae and related families. The second clade, which includes Krüper's and Algerian nuthatches, has a black front crown only in males, this sexual dimorphism being absent in young individuals.
The phylogeny established, Pasquet concludes that the paleogeographic history of the group would be as follows: the divergence between the two main clades of the "S. canadensis group" appears more than five million years ago, at the end of the Miocene, when the clade of S. krueperi and S. ledanti settles in the Mediterranean basin at the time of the Messinian salinity crisis; the two species constituting it diverge 1.75 million years ago. The other clade split into three with populations leaving Asia from the east, giving rise to the red-breasted nuthatch, and then from the west, about one million years ago, marking the separation between the Corsican and Chinese nuthatches. Current distributions do not necessarily accurately reflect ancestral ones, however, and the Corsican nuthatch may be a paleoendemic that once had a much wider distribution and underwent reductions in distribution; "trapped" in Corsica, it would have evolved by vicariance.
The simplified cladogram below is based on the phylogenetic analysis of Packert and colleagues (2014):
Description
Plumage and measurements The Corsican nuthatch is a small bird, measuring longSvensson, L., Mullarney, K., & Zetterström, D. (2022) Collins Bird Guide, ed. 3. , pages 362-363 with a wingspan of and a weight of . The folded wing measures , the relatively short tail measures , and the tarsus and beak measure . The head is small and the is short for a nuthatch. It is thin and blackish grey, black on its tip. The eyes are black, the legs and toes are light brown.
The are overall bluish grey, the belly pale greyish buff with the throat whiter. The male has a black crown and forehead, and a black eyestripe, separated from the crown by a broad, sharp white supercilium. In females, the crown and eyebrow line are the same grey as the back. In both sexes, the sides of the head as well as the throat are white; the , overall greyish white, are more or less shaded with buff. The outer rectrices are black with white spots and grey tips. The birds undergo a complete moult every year after the breeding season. Sexual dimorphism appears eleven days after hatching, and fledged young have a plumage close to that of adults. As juveniles, they remain duller, with some brown on the large coverts.
Vocalisations
The contact call is a light, whistling pu, which the bird repeats in series of five to six notes, in pupupupu. When agitated, this nuthatch emits a "rough and stretched, slowly repeated" pchèèhr, as might a common starling (Sturnus vulgaris), or a psch-psch-psch that turns into a chay-chay-chay or sch-wer, sch-wer when more agitated. The song, described as a "clear, sonorous, rapid dididididi [and of] variable rhythm", meanwhile, is reminiscent of the alpine swift; the contact call is a similar trill. It "sings fairly regularly in the spring", but is more discreet during the breeding season.
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