Tag Archives: thrush

A closer look at the wing of Swainson’s Thrush (Catharus ustulatus swainsoni) in First Basic plumage

Like other migratory Catharus species, juvenile Swainson’s Thrushes (Catharus ustulatus swainsoni) molt into a ‘First Basic’ plumage at the end of their first summer, which they wear for one year before attaining their ‘Adult Basic’ plumage. The partial molt that results in First Basic plumage includes some or all of the median coverts (the little olive feathers above the numbered row), and up to five of the (inner) greater coverts, which are numbered 1–9 in the image. In this case, the bird molted only one greater covert: #1, the fresh olive covert without a buffy tip. The retained juvenile coverts (2–9) are paler and more brown, and numbers 2–6 end with a buffy tip. This is called a molt limit, and it helps us to figure out the age of a bird. For all the juicy details of molt limits in North American passerines, check out Peter Pyle’s Identification Guide to North American Birds, Part 1, 1997.

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This bird died in a window collision in Montgomery Co., PA, in late September 2016. After taking the photo, I prepared the specimen for the Ornithology Collection at the Academy of Natural Sciences of Drexel University. Legend: primaries (P1–8); secondaries (S1–9). The 9th and reduced 10th primaries are not visible in the photo.

Alexander Wilson the ornithologist was born 250 years ago today.

Leaning up against the wall next to my office door at the Academy of Natural Sciences (ANSP), is an extremely heavy stone tablet bearing a dedication to Alexander Wilson (1766–1813), the Scottish-born poet and so-called “Father of American Ornithology”. The tablet was donated to ANSP in 1923, on behalf of the St. Andrew’s Society of Philadelphia, an organization promoting Scottish heritage, and dedicated in a ceremony attended by Witmer Stone and other local ornithologists, only later to have an embarrassing error revealed: the date of Wilson’s death (1813) had been accidentally inscribed 1833!

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Stone tablet donated to the ANSP for display, and dedicated in 1923, but bearing the incorrect date of death. It now resides in the hallway of the Ornithology Department.

Wilson was born on this day exactly 250 years ago—July 6, 1766—in Paisley, Scotland. He left that country on May 23, 1794, to seek his fortune in America, and celebrated his 28th birthday at sea, bound for Philadelphia, where he would make a meager living as a schoolmaster, poet, and eventual ornithologist. His life was forever altered in 1803, when he moved to the Kingsessing neighborhood in what is now West Philadelphia, and made the acquaintance of William Bartram (1739–1823) and thereafter became obsessed with the study of American birds. Fun fact: I live in this neighborhood today, just a block from the now-closed Alexander Wilson Public School, and Bartram’s Garden is still a local birding hotspot (eBird).

It was auspicious timing for both men. Bartram was actually the first ornithologist born on American soil, having sent bird specimens and behavioral notes to the English naturalist George Edwards (1694–1773) as early as the 1750s, and his famous Travels… (1792) was chock full of valuable ornithological information. But something changed in 1802, about a year before he met Wilson. Apparently for the first time, Bartram began to keep a (mostly) daily journal documenting the natural history of his family estate Bartram’s Garden. It would become the first multi-year record of arrival dates of migratory birds in the New World, and its entries overlapped Wilson’s entire ornithological career. (Side note: There is no mention of Wilson in the journal, which contains nothing but dated natural history observations.) With Bartram as his tutor, and with access to the library of rare books at Bartram’s Garden, Wilson was able to produce the first scientific work with color plates dedicated to American birds and set a new standard for scientific ornithology: the epic American Ornithology in 8 volumes (and a 9th posthumous volume). Yes, the tale has a sad ending. Wilson died in August 1813, having literally worked himself to death—his last written words were a list of birds he had yet to draw.

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Closeup of the head of the American Robin, in the original copper plate engraved by Alexander Lawson, which begat Wilson’s American Ornithology, Vol. 1, Pl. 2. (Photo by MRH, courtesy of the Archives of the Academy of Natural Sciences of Drexel University).

To celebrate Wilson’s 250th birthday (6/6/2016), I visited the ANSP Archives to see for myself, the first two copper plates from American Ornithology Volume 1 (1808), engraved by Alexander Lawson (1772–1846) from Wilson’s original drawings. On the surface the plates appear old and tarnished, but the engravings are in excellent condition. Lawson’s work was masterful, with incredible detail shown in each feather barb. I had to angle my head to fully appreciate the closely spaced strokes in the face of the American Robin (see pictured). And to think that it was the reverse image that Lawson produced, engraving the opposite of Wilson’s sketch into a copper plate with such precision! For example, look at the number “2” engraved in reverse. But so much of the detail was masked when the color was applied to the final image, especially in the black feathers of the robin’s head. Here, the intricacies of Wilson’s artwork go unnoticed, as does Lawson’s skill with the engraving tool.

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I appreciate Wilson most for the knowledge he gave us. For example, he was the first person to understand that the Veery (Catharus fuscescens) and Hermit Thrush (C. guttatus) were actually two different species! They were lumped as Turdus minor before Wilson corrected things in 1812. My own research on American birds was fundamentally shaped by Wilson—more reason to celebrate this anniversary.

Wilson himself most likely handled these plates, inspecting them for flaws before the first printing of American Ornithology. He must have marveled at Lawson’s handiwork. It is fun to think that he would also have tilted his head in the very same way, trying to catch the light at just the right angle, to reveal just a little more of what birds are.

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One of the original copper plates engraved by Alexander Lawson for Wilson’s American Ornithology. Hand-colored prints made from this plate (#2) were first published in 1808. (Photo by MRH, courtesy of the Archives of the Academy of Natural Sciences of Drexel University)

Many thanks to archivist Jennifer Vess for assisting me with the Lawson plates. Also thanks to Scott McConnell, who discussed the origins of the stone tablet in his excellent book Witmer Stone: Fascination of Nature, solving a mystery for me.

Taxonomic origins of the Veery and Hermit Thrush

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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)

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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.

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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.”

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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.