Taxonomic origins of the Veery and Hermit Thrush


Cateby_LittleThrush

Catesby (1731), pl. 31.

The publication history of the songbird genus now known as Catharus began, as did so many other American birds, with the English naturalist Mark Catesby (1683–1749), whose seminal work Natural History of Carolina, Florida and the Bahama Islands (1729–1747) was the first illustrated publication to be dedicated to the American flora and fauna. Catesby lived for seven years in Virginia (1712–1719), during which time he collected and sent plant specimens and seeds to England. In 1722, he returned to North America on behalf of the Royal Society of London to collect more plants, and along the way he also collected a number of animal specimens. It was during this latter trip that he prospered as an ornithologist, and when he encountered a species that he called the Little Thrush (Turdus minimus; Catesby 1731, pl. 31):

“In shape and colour it agrees with the Description of the European Mavis, or Song-Thrush, differing only in Bigness ; this weighing no more than one Ounce and a quarter. It never sings, having only a single Note, like the Winter-Note of our Mavis. It abides all the Year in Carolina. They are seldom seen, being but few, and those abiding only in dark Recesses of the thickest Woods and Swamps. Their Food is the Berries of Holly, Haws, &c.”

Today, we know that Hermit Thrushes (Catharus guttatus) occur during the winter in coastal South Carolina and Georgia, and during the spring and summer they are replaced by Wood Thrushes (Hylocichla mustelina). Thus, there is little doubt from Catesby’s (1731) description that his Little Thrush refers to the Hermit Thrush, which, corroborating his account, is frugivorous and does not typically sing on the wintering grounds (see Bent 1949). Further, the weight of the bird provided by Catesby (“no more than one Ounce and a quarter” [i.e., < 35 g]) is too light to be a Wood Thrush, which weigh on average 38.8 g with no fat, and 45.2 g with fat (n = 35; Yong and Moore 1993, Condor 95, 934–943), but just right for a Hermit Thrush that has been gorging on berries; and this is comparable to the slightly larger European “Song-Thrush” to which Catesby refers (Turdus philomelos). There is no member of Catharus with a breeding distribution that includes the South Carolina and Georgia coastal region, so Catesby’s assertion that the bird “abides all the year” is speculative and probably reflects his ignorance of bird migration (see Bartram’s Travels 1790:284).Bartram_PealePortrait

In June of 1756, the Philadelphia-born naturalist William Bartram (1739–1823), then a young man of seventeen, sent a collection of bird specimens from Philadelphia to London, to be examined by the English naturalist George Edwards (1694–1773) for inclusion in his forthcoming Gleanings of Natural History (2 vols., 1758, 1760). There were fourteen species represented in the collection, including a small spotted thrush that had been collected near Philadelphia:

“The head, upper side of the neck, back, wings, and tail, are all of a reddish-brown or clay-colour, not at all varying in the shades of the feathers, as they do in our English thrushes. . .the breast yellowish, with dusky spots.” (Edwards 1760:183; pl. 296)

Edwards_1760_PL296_ProbableVeery

Little Thrush (Turdus parvus) — Edwards 1760, pl. 296

There is only one thrush species in eastern North America that can be said to have a uniform reddish-brown dorsum, and in which the ventral spots are restricted to the upper breast as in Edwards’s (1760) painting — the Veery (Catharus fuscescens). However, with just one specimen to compare to Catesby’s (1731) poorly rendered drawing, Edwards (1760) found no reason to classify them differently. Therefore, Edwards’s (1760) account included (1) the first painting and physical description of a Veery, with some limited notes on its life history provided by Bartram, and (2) the life history information from the account of the Hermit Thrush, copied from Catesby (1731). In this way, Edwards’s Little Thrush, Turdus parvus, came to be an amalgamation of two species. In the same year, Brisson (1760:212) described “Le Mauvis de la Caroline,” which was basically just a copy of Catesby’s description with no illustration. Buffon (1775), Latham (1783:20–21), and Gmelin (1789:809; T. minor) continued the tradition, copying details about the Little Thrush from previous authors.

VEERY_002

Veery (C. fuscescens), at White Clay Creek SP, Delaware. Photo by MRH.

[Taxonomic sidebar: Edwards’s and Catesby’s inconsistent and variable use of Latin descriptors is generally thought to be proto-Linnean, i.e., they do not supercede the authority of Linneaus (1758) or later authors. Bartram’s Latin names in Travels. . . (1792) were suppressed by the International Commission on Zoological Nomenclature (ICZN) for the same reason (Opinion 447, 1957). Thus, both T. parvus (Edwards) and T. minor (Bartram) are taxonomically invalid.]

Bartram (1792:300–301) corrected Catesby’s assertion that the Little Thrush does not sing, and pointed out that the pioneer naturalist had only observed it in winter (i.e., it was a Hermit Thrush). However, it is clear from this passage that even Bartram himself thought that the Veery and Hermit Thrush were one species:

“CATESBY is chargeable with the like mistake with respect to the little thrush (t. minor), [an eminent singer]. . .for his shrill, sonorous and elevated strains in the high, shady forests. . .BUT yet Catesby has some right of claim to our excuse and justification, for his detraction of the fame due to these eminent musicians of the groves and forests, when we consider that he resided and made his collections and observations, in the regions which are the winter retreats and residence of these birds, where they rarely sing, as it is observable and most true, that it is only at the time of incubation, that birds sing in their wild state of nature.”

To make things even more confusing, Bartram used the name ‘wood thrush’ interchangeably to mean the Wood Thrush (Hylocichla mustelina) and the bird he called T. minor, following Gmelin (1789): “The high forests are filled with the symphony of the song or wood-thrush (turdus minor.)” (1792:xxxii). Bartram refers to ‘Song Thrush’ and ‘T. minor‘ in his personal diary, but Stone (1913, Auk 30) combined them with references to ‘Wood Thrush’ and ‘Wood Robbin.’ — a more detailed analysis of the original diary is needed to distinguish these records.

Portrait of Alexander Wilson, created by Paquet after American engraving of unidentified author. Published on Magasin Pittoresque, Paris, 1850

Portrait of Alexander Wilson, created by Paquet after American engraving of unidentified author. Published on Magasin Pittoresque, Paris, 1850

That Bartram distinguished between the Wood Thrush and T. minor is clear from a passage in the first volume of Alexander Wilson‘s American Ornithology. Wilson (1808:33–34) encountered a bird in Carolina that he considered to be the one called Little Thrush by Edwards (1760), and he asked Bartram, who had transmitted the original specimen, for his opinion:

“But Mr. Edwards has also described and delineated the Little Thrush, and has referred to Catesby as having drawn and engraved it before. Now this Thrush of Edwards I know to be really a different species; one not resident in Pennsylvania, but passing to the north in May, and returning the same way in October, and may be distinguished from the true Song Thrush (Turdus Melodus) by the spots being much broader, brown, and not descending below the breast. It is also an inch shorter, with the cheeks of a bright tawny color. Mr. William Bartram, who transmitted this bird, more than 50 years ago, to Mr. Edwards, by whom it was drawn and engraved, examined the two species in my presence; and on comparing them with the one in Edwards, was satisfied that the bird there figured and described is not the Wood Thrush (Turdus Melodus), but the tawny cheeked species above mentioned. This species I have never seen in Pennsylvania but in spring and fall. It is still more solitary than the former, and utters, at rare times, a single cry, similar to that of a chicken which has lost its mother. This very bird I found numerous in the Myrtle swamps of Carolina in the depth of winter, and I have not a doubt of its being the same which is described by Edwards and Catesby. . .A figure and description of this passenger Thrush will appear in an early part of the present work.”

_095, 8/9/04, 11:53 AM, 8C, 4302x5598 (63+195), 75%, Default Settin, 1/80 s, R75.6, G57.2, B73.1

Wilson (1812), plate featuring both the Hermit Thrush and Tawny Thrush (Veery)

Four years later, Wilson (1812:95) included the Hermit Thrush Turdus solitarius in the fifth volume of American Ornithology, which he considered to be synonymous with the Little Thrush of Catesby (1731) and Edwards (1760). Wilson (1812:98) also described another species that he considered to be completely new to science, which he called the Tawny Thrush Turdus mustelinus. This species would later be renamed fuscescens by Stephens (1817), and would come to be known as the Veery. Thus, Alexander Wilson was the first ornithologist to realize that there were multiple species of spotted forest-dwelling thrush in North America, other than the well-known Wood Thrush, and William Bartram can rightly be credited as the ‘discoverer’ of the Veery.

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Categories: History of Science, OrnithologyTags: , , , , , , , ,

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