Posted by: Rob Viens | June 22, 2013

Birding on the Rio del la Plata

Without a whole lot to do while the Beagle carried on its business, Darwin spent the better part of the next month furthering his collection of animals from Uruguay.  In late May, it was birds that caught his eye – or at least birds that caught the pen of his diary:

“Took a long walk to the Laguna del Potrero; my principal object at present is birds, of which there are a great number of very beautiful ones. — The weather is most delightful. Temp. in room about 60°.” (May 25/26)

As I mentioned earlier this month, Darwin really started to take up birding in Maldonado – recording somewhere between 50 and 100 different birds in this Zoological Notebook. I shared a few earlier (see Colorful Birds of a Feather), and thought I’d add to that list today. All three of the birds below are “perching birds” – members of the Order Passeriformes. With over 5000 species, they make up more than half of all species of birds, and are what most of us are most familiar with on a daily basis.

(1) Rufous-browed Peppershrike (Cyclarhis gujanensis)

“Lanius (?). Legs pale blueish; iris reddish: I have never seen but this one specimen: Coleoptera in stomach.”

Rufous-browed Peppershrike (from Wikipedia Commons)

Rufous-browed Peppershrike

Reports on the peppershrike say that it eats insects and spiders – of course, Darwin already cleared that up for us with a little dissection.  I can picture him, sitting in his apartment (or, when at sea, in the poop cabin) dutifully describing his specimen (probably collected/shot the day before).  Then dissecting it and examining the insides, before carefully preserving it to send back to England in a jar of “spirits”.

(2) Rufous-capped Spinetail (Synallaxis ruficapilla)

It is interesting to see how Darwin describes a couple separate specimens here. Note the interest in determining if the differences represent different species or not, and his reference to intermediate characteristics. Even in these brief descriptions are illustrations of Darwin’s attention to the details of different individuals – a skill that allowed him to see the subtile difference resulting from natural selection. The numbers are Darwin’s specimen numbering system:

“(1252) Certhia: legs pale colour, iris rusty red; exceedingly like to (1226), differs in that depth of lower mandible & curvature of upper; I scarcely believe it to be a different species, more especially as I found one specimen which was intermediate in character between them both.—

(1255) Certhia. only differs from (1248) in shape of bill. Upper mandible in the latter is longer, & the symphysis of the lower one is of a different shape in the two specimens: Are they varieties or species?

(1256) Certhia: iris yellow reddish; legs pale with touch of blue”

Certhia is a genus that today contains a number of different treecreeping birds in the family Certhiidae. Darwin is probably referring to the family, or at the very least to the similarity with European treecreepers. The spinetail noted here actually bellows to a different family altogether (Furnariidae – the oven birds)

Rufous-capped Spinetail (from Wikipedia Commons)

Rufous-capped Spinetail

(3) Barred Antshrike (Thamnophilus doliatus)

“Lanius; not common; cry rather loud, plaintive, agreeable.— |Iris reddish orange, bill blue especially lower mandible; there are specimens in which the narrow black & white bands on breast are scarcely visible, & what is more remarkable the under feathers of the tail are only most obscurely barred.— as this absence varied in extent, I imagine it to be the effect of age not sex.”

Again, note that Darwin is looking for subtleties that distinguish males from females (as they can often look like entirely different species).

Barred Antshrike – male (above), female (below) (from Wikipedia Commons)

Barred Antshrike

Meanwhile, Darwin also reported that the schooners , which had been surveying the coastline to the south, had returned.  This was the first time Darwin had a chance to see some of his friends, including Lieutenant John Wickham, since they separated 6 months ago (for a refresher on Wickham see John Clements Wickham – Tortoise Herder from almost exactly one year ago).  It appears to have been a happy reunion:

“Captain FitzRoy hired a small Schooner to go to the Rio Negro to bring Mr Wickham in order that he might take command of our Schooner. She arrived yesterday, & to day Mr King, who came with Mr Wickham paid me a visit. — They are heartily tired of their little vessels & are again as glad to see the Beagle as every one in her is to see them. — The weather has generally been very fine; but the gale of the 12th of Jany reached them. — It appears however to have been miserable work & more than sufficiently dangerous: from the smallness of the vessels, it was scarcely possible to keep anything dry. — to possess a dry shirt or bed was an unusual luxury. — In addition to these discomforts, Mr Wickham & some of the others constantly suffered from sea-sickness. Mr Stokes & Mr Usborne (who has taken Mr Wickhams place) will continue to work in the neighbourhead of the Rio Negro.” (May 28/29)

I am particularly taken by the notion that ” to possess a dry shirt or bed was an unusual luxury.” Again, it brings be back to the my time working in the temperate rainforests of southeast Alaska. It was nice on days when you had a wilderness cabin to stay in at the end of the day – where you could dry out overnight.  But more often than not, after a long wet day, all you could do is crawl in your tent and hope that your cloths were less wet the next day.  Getting the chance to dry out was a blessing.  Now, I only experienced this degree of wetness for days or a couple of weeks at a time.  I can’t imagine how being damp for 6 months would feel!

The month of May ended for Darwin with the opportunity to do one of the things he enjoyed the most – collecting and cataloging more specimens:

“Usual quiet occupations; one days collecting & the next arranging.” (May 30/31)

The entire month of June would bring a lot more of the same – exploring the biodiversity of Uruguay… (RJV)

PS – I realize that I am some weeks behind Darwin, but am hopeful (given that he only has a few diary entries in the entire month of June) of being back on track by the end of the month!

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