Tetrapod Zoology

Mysterious channels of Alca torda

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The mystery skull from the other day is indeed that of a charadriiform: more specifically that of an auk and, most specifically of all, that of a Razorbill Alca torda. Well done Dartian and Kryptos18, and well done everyone else for trying. I admit that I deliberately showed the skull in ‘front view’ (rostral or anterior view) because this made things more difficult. Furthermore, I was hoping that at least some people might make the fairly obvious mistake of identifying the skull as that of a dodo or raptor. Had you not recognised the skull immediately, here’s how you might have identified it…

For starters, this is obviously a bird skull: it has long toothless jaws, rhamphothecae, and an ‘open’ skull morphology with huge orbits and no postorbital bar. You can also see the notches associated with the prokinetic hinge zone, if you know what to look for. As for what sort of bird it is, the biggest clue comes from the obvious bony hollows you can see on the skull roof, over the eyes [see below]. These are the supraorbital fossae: in life, they house the supraorbital salt glands. Seabirds use these organs to excrete excess salt. So, we’re dealing with some sort of marine bird.

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With this in mind, we now have to start thinking about the rhamphothecae (the beak tissue). Which seabirds have deep bills, marked on their lateral sides by vertical grooves? Answer: auks (or alcids). Several auk genera are deep-billed, including razorbills (Alca), puffins (Fratercula and Lunda), and parakeet auklets (Cyclorrhynchus). Several extinct auks were too, most notably the Great auk Pinguinis impennis. We’ll come back to this species a few times in the following discussion.

Among these deep-billed taxa, only puffins, Razorbills and Great auks have obvious vertical grooves. And puffins are out, as their rhamphothecae extend far posteriorly (all the way back to the gape). Similar comments apply to the Great auk: its rhamphothecae were way more extensive posteriorly than what’s shown here. In the Razorbill – the only bird we’re left with – the rhamphothecae are restricted to the rostral half or so of the rostrum (the rest is feathered). So we’re left with the Razorbill, and that’s what it is.

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The Razorbill is a North Atlantic auk, its largest breeding colonies being those around the shores of Britain, Scandinavia, western Greenland, Iceland and north-east Canada. It dislikes ice, avoids brackish water, and prefers rocky islands with broad ledges as nesting areas. It’s a large, stout-bodied auk, and is longer-tailed than other large auks (like guillemots*). Long tails in seabirds typically relate to improved aerial manoeuvrability: I can’t find any comments in the literature on the aerial manoeuvrability of the Razorbill relative to other auks (all of which have much shorter tails), but – as we’ll see – an adaptive reason for the long tail might have been identified.

* As a British person, I associate the name ‘guillemot’ with both Uria and Cepphus. If you’re North American, you’ll know the Uria species as ‘murres’, and will restrict the name ‘guillemot’ to Cepphus. Another thing: I pronounce guillemot ‘ghee-le-mott’, but have learnt that some Europeans say it ‘ghee-le-moh’ [image below, from wikipedia, shows Razorbill and Common guillemot or Common murre Uria aalge].

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Its English common name comes from the superficial resemblance its deep, laterally compressed bill has with an old-fashioned razor (its old name was ‘Razorbilled auk’), and it uses this bill to grab and hold sand-eels, capelin and other mid-water schooling fishes. As many as 20 fish can be held in the bill at any one time. People often wonder how puffins – which manage the same trick – can hold fish while continuing to catch others, yet no-one ever asks this question of Razorbills. I presume Great auks did the same thing, but unfortunately virtually nothing is known of their diet or feeding habits (for data on possible prey species see Olson et al. 1979). Anyway, apparently, the birds use their tongue, the horny papillae on the palate, and the mobile prokinetic hinge zone to retain fish at the back of the bill while continuing to grab new ones at the front. It’s still hard to appreciate how this might work, but it obviously does.

The inside of the mouth is yellow. Incidentally, the Great auk also had a yellow mouth interior according to some reports. However, the inside of its mouth was described as red or orange by others, so we’re really not sure. I tell you, it’s shocking how little we know of the Great auk: a species that only went extinct in 1844 (or thereabouts).

What’s with the lateral grooves on the Razorbill’s bill? We don’t know, but a few suggestions have been made. One idea is that they play a role in sexual display, and this seems likely given that the bill is used extensively for signalling during courtship. Rather more interesting, however, is the hypothesis that the grooves ‘function rather like the sights on a rifle as the bird dives in pursuit of its prey’ (Freethy 1987, p. 58). This seems unlikely to me given data showing that few birds can see the sides of their own bills (e.g., Martin et al. 2004). Again, highly similar structures were present in the Great auk (and presumably in the fossil species intermediate between these two). Debate exists as to whether the grooves of the Great auk were white or not [in the specimen shown below, from wikipedia, the grooves are not obviously white].

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Another interesting feature is the narrow channel that extends backwards from the eye. This is better known in guillemots, where – in so-called bridled individuals of Uria aalge – it is picked out by white feathers. Gaston & Jones (1998) hypothesised that this channel might help ‘aid the flow of water over the eye while the birds are swimming rapidly’ (p. 71), though this intriguing function remains untested so far as I know. Furthermore, if this were true I would expect the Great auk to have such a channel: there’s no mention of it in the Great auk literature (Fuller 1999), but – as just mentioned – our knowledge of the Great auk as a live animal is pitiful and it’s not possible to be confident about such a subtle, easily overlooked feature. The ‘lazy’ hypothesis – that the channel might function in communication – was deemed unlikely as the channel is usually all but invisible (Gaston & Jones 1998). It’s been claimed that prominent supra-orbital ridges in the Razorbill might help resist deformation of the eyeball caused by deep-diving: well, maybe. However, some deep-diving seabirds lack prominent supra-orbital ridges, and I’m not sure that Razorbills – as compared with other seabirds – have prominent supra-orbital ridges anyway.

I was surprised to learn that as much as 42% of the Razorbill diet might be made up of crustaceans and annelids, and 10% by molluscs (W. E. Collinge, cited in Freethy 1987). This is surprising because the Razorbill is almost exclusively a pursuit-diver, swimming underwater with feet and half-open wings, and its short dive time (always less than one minute) and maximum dive depth indicate that it doesn’t spend time foraging at or near the sea-floor. Maybe these benthic prey come from the stomachs of the fish it eats. These data might not be accurate, however, as some sources only discuss fishes (and predominantly mid-water fishes) as forming Razorbill diet (Gaston & Jones 1998). As with so many other seabirds, it turns out that Razorbills dive much more deeply than used to be thought. Older references say that dives are typically of 2-3 m, and that 10 m might be exceptional. More recent work indicates that average dive depth is 25 m, with the range being 11-38 m (Wanless et al. 1988, Barrett & Furness 1990). However, Piatt & Nettleship (1985) reported a maximum dive depth of 120 m for the species and Jury (1986) then reported 140 m, thereby making a mockery of all previous estimates [Razorbill image below from here].

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Equally surprising is the fact that the Razorbill is adept at kleptoparatisism, and it frequently steals from Atlantic puffins Fratercula arctica. Razorbills attack puffins in flight, but more frequently ‘swim beneath the puffin and torpedo it from below or actually pursue the puffin under the water’ (Freethy 1987, p. 71). One might predict that species which indulge in aerial piracy need to be particularly manoeuvrable: is this why the Razorbill has such a long tail?

I was hoping to get away with just a paragraph or two on the Razorbill, but I guess I found a lot of interesting stuff to cover. I’ll stop there. Incidentally, I was playing with the Razorbill skull because of my work on azhdarchoid pterosaurs. I’ll say no more.

Refs – -

Barrett, R. T. & Furness, R. W. 1990. The prey and diving depths of seabirds on Hornoy, North Norway after a decrease in the Barents Sea capelin stocks. Ornis Scandinavica 21, 179-186.

Freethy, R. 1987. Auks: An Ornithologist’s Guide. Facts on File, New York.

Fuller, E. 1999. The Great Auk. Harry Abrams, New York.

Gaston, A. J. & Jones, I. L. 1998. The Auks. Oxford University Press, Oxford.

Jury, J. A. 1986. Razorbill swimming at depth of 140 m. British Birds 79, 339.

Martin, G. R. & Coetzee, H. C. 2004. Visual fields in hornbills: precision-grasping and sunshades. Ibis 146, 18-26.

Olson, S. L., Swift, C. C. & Mokhiber, C. 1979. An attempt to determine the prey of the Great auk (Pinguinus impennis). The Auk 96, 790-792.

Piatt, J. F. & Nettleship, D. N. 1985. Diving depths of four alcids. Auk 102, 293-297.

Wanless, S., Morris, J. A. & Harris, M. P. 1988. Diving behaviour of guillemot Uria aalge, puffin Fratercula arctica and razorbill Alca torda as shown by radio-telemetry. Journal of Zoology 216, 73-81.

Comments

  1. #1 Andreas Johansson
    January 26, 2009

    That’d be northeast Canada, presumably?

  2. #2 Dartian
    January 26, 2009

    Yay, I got the species right! But I must admit that I didn’t look for supraorbital fossae or anything such; my identification was almost wholly based on the skull’s ‘jizz’.

    As for the article, great stuff, as usual (I don’t remember ever hearing of razorbills being kleptoparasites). One small quibble only:

    avoids brackish water

    Not entirely true. The razorbill is a breeding bird along the coasts of the Baltic Sea, which is brackish. Incidentally, so too are two other species of auk, namely common guillemot/murre Uria aalge and black guillemot Cepphus grylle. (The Baltic Sea is a strange place, with a unique mix of freshwater and marine animals.)

  3. #3 Jerzy
    January 26, 2009

    About guillemot – I met a person who pronounced it ga-lee-matt!

    About brackish water – historically, there were breeding colonies of Razorbills and Guillemots on Lake Ladoga in Russia! Its entirely freshwater and perhaps a relict of the same lake which later formed Baltic. Ladoga still has freshwater subspecies of ringed seal, too (most people think that Baikal Seal is the only freshwater seal).

  4. #4 Darren Naish
    January 26, 2009

    Thanks for comments. The Lake Ladoga ringed seals were mentioned back here on Tet Zoo ver 1. As for brackish-water and freshwater (!!!) Razorbills and guillemots, I took that ‘avoids brackish water’ comment from the auk literature (I think from Freethy’s Auks: An Ornithologist’s Guide). Huh, so much for that then.

  5. #5 Andreas Johansson
    January 26, 2009

    Ladoga still has freshwater subspecies of ringed seal, too (most people think that Baikal Seal is the only freshwater seal).

    There’s another ringed seal subspecies in Lake Saimaa, on the other side of the Russo-Finnish border. It’s critically endangered.

  6. #6 David Marjanović
    January 26, 2009

    I was thrown off by the enormous hook on the beak.

    In lateral view, it turns out the hook doesn’t even exist. ~:-|

  7. #7 Dartian
    January 26, 2009

    Jerzy, about those razorbills and (black) guillemots that supposedly used to breed at Lake Ladoga… I have also heard of them, but I don’t know of any primary source that would back up the claim. Do you know? Or anyone else, for that matter?

  8. #8 Edgar
    January 26, 2009

    Doh! well, i learn another new thing…

  9. #9 Dr Vector
    January 26, 2009

    I was hoping to get away with just a paragraph or two on the Razorbill, but I guess I found a lot of interesting stuff to cover.

    See, this is the really irritating thing about your apparently inexhaustible knowledge: you didn’t whip yourself mercilessly grinding out interminable paragraphs on the Razorbill and related species. You tried to be brief but just couldn’t help yourself. I’d be appalled if it wasn’t for your total inability to handle

  10. #10 Raymond Minton
    January 26, 2009

    As you can probably tell, I don’t spend much time examining bird’s skulls. Give me time to bone up on my ornithology before the next quiz.

  11. #11 Jerzy
    January 27, 2009

    @Dartian
    I read it some years ago in Russian literature. I cannot re-find the source now. But it might be eg. in Cramp & Simmons.

    BTW – until last days I believed, that Razorbill is Razorbill because its beak is unusually sharp. And its only about shape…

  12. #12 Dartian
    January 27, 2009

    Jerzy: I became interested enough in the subject of freshwater auks to make a half-serious literature search myself, but I came up with nothing definitive. It is perhaps futile to look for this particular piece of information on the internet; the primary data, if any exist, are most likely buried in some obscure early twentieth-century non-English language publications.

    I did find this, though. Here (on page 25) it is indeed claimed that both razorbill and black guillemot used to nest at this freshwater locality. But it’s not a primary source, so taking this information with the proverbial grain of salt is recommended.

  13. #13 Darren Naish
    January 27, 2009

    After a bit of research I’ve found that Kozlova (1961) specifically referred to the presence of Razorbills on Yalai Island, ‘northwest of Lake Ladoga’ (p. 33). However, this is still not the primary source as Kozlova noted that this information came from ‘Finnish ornithologists’. Better news though: Salomonsen (1944) was cited by Kozlova as a source on Lake Ladoga Razorbills. Salomonsen (1944) is a fairly well known reference on Atlantic auks. I don’t have access to it, unfortunately.

    Refs – -

    Kozlova, E. V. 1961. Fauna of USSR: Birds. Charadriiformes, Suborder Alcae: Suborder Alcae. Israel Program for Scientific Translations, Office of Technical Services, U.S. Dept. of Commerce.

    Salomonsen, F. 1944. The Atlantic Alcidae. The seasonal and geographic variation of auks inhabiting the Atlantic Ocean and the adjacent waters. Göteborgs Kung. Vetenskaps och Vitterhetssamhälles Handl. Följen 6, Ser. B 3, 1–138.

  14. #14 Jerzy
    January 27, 2009

    I cannot help you much. I only remember that the one, but not the only, source was some visiting ornithologist in 19. or 20. century who saw breeding colonies of these alcids.

    You might, however, try to contact some Russian naturalist, who probably has much better access to Russian literature.

  15. #15 Dartian
    January 27, 2009

    Still on those elusive freshwater auks (with apologies to all those who could care less about the subject)…

    I have been able to trace the mention of Lake Ladoga auks back to 1929-1931. The Finnish ornithologist Ivar Hortling wrote that the razorbill breeds at Lake Ladoga; ditto for the black guillemot, although Hortling qualified the latter with a ‘possibly’. Maddeningly, even this publication is still only a secondary source.

    Anyway, it would appear that the Russians are satisfied that at least the records of Lake Ladoga razorbills are legit. Noskov (2002:398) says: ‘Formerly, the Razorbill bred on the north-west coast of Lake Ladoga, on the Jalaja Islands’. And a small map that shows the location of the purported breeding site is included. (The black guillemot is also discussed in this book, but there’s no mention of any freshwater breeding records.)

    References:

    Hortling, I. 1929-1931. Ornitologisk Handbok, J. Simelii Arvingars Boktryckeri, Helsingfors.

    Noskov, G.A. (editor-in-chief) 2002. Red Data Book of Nature of the Leningrad Region, Volume 3. Animals, World & Family, St Petersburg.

  16. #16 DDeden
    January 31, 2009

    There are salt hot springs at Lake Baikal, and evidence of brackish water past and present at Lake Ladoga
    link
    which may be how these seals and seabirds and ancestral humans (barring trade) were sustained in otherwise “freshwater” habitat, I’d guess Lake Saimaa had some similar situation. I’d guess there are no true (in the strict sense) freshwater seals and very few freshwater seabirds

  17. #17 DDeden
    January 31, 2009

    There are salt hot springs at Lake Baikal, and evidence of brackish water past and present at Lake Ladoga
    link

    If the link fails, the title/authors: Shoreline displacement of Lake Ladoga : new data from Kilpolansaari
    Auteur(s) / Author(s)
    SAARNISTO M. (1) ; GRĂ–NLUND T. (1)

    which may be how these seals and seabirds and ancestral humans (barring trade) were sustained in otherwise “freshwater” habitat, I’d guess Lake Saimaa had some similar situation. I’d guess there are no true (in the strict sense) freshwater seals and very few freshwater seabirds

  18. #18 Dartian
    February 4, 2009

    At last! After a bit of detective work, and a little luck, I have been able to track down the original reference to auks breeding at freshwater at Lake Ladoga (btw, thanks Darren and Jerzy for the inspiration and literature suggestions). The source is as obscure as they get: the information is found in the proceedings of a meeting of a Finnish natural history society from 1921, and it’s in Finnish* (it has a summary in German, however).

    * In case someone wonders: until the Second World War, the western half of Lake Ladoga (where the auks bred) was Finnish territory.

    This is the full reference:
    Hildén, I. 1921. Lintutieteellisiä havaintoja Jaakkimasta ja Juuasta. Meddelanden af Societas pro Fauna et Flora Fennica 47, 59-62. [German summary on pp. 218-219.]

    The paper is very brief, and consists mainly of a listing of the more notable birds seen by the author, Ilmari HildĂ©n, during an expedition to SE Finland in May–June 1920. HildĂ©n was allowed to visit some islands that were in the possession of the military; fortification work was going on at the time, and the author suspected that this would lead to the destruction of the islands’ unique breeding bird community (which seems to be exactly what later happened).

    HildĂ©n notes that both razorbills Alca torda and black guillemots Cepphus grylle breed on the Jalaja islands, the razorbill apparently in fairly large numbers. He says that the presence of these birds as well as of some other marine animals (i.e., the ringed seal Phoca hispida and certain fish) at this freshwater lake is probably evidence of Lake Ladoga’s former connection with the Baltic Sea (he speaks of the auks as ‘relict animals’).

    Bottom line: Astonishingly, the rumours of freshwater-breeding razorbills and black guillemots seem to be true. In any case, I myself don’t see any reason to doubt this report’s authenticity. Sadly, the birds are not there anymore…

    Finally, below is the original text of the German summary of HildĂ©n’s paper (‘nistend’ means ‘nesting’):

    Ornithologische beobachtungen aus Jaakkima in Karelia ladogensis und Juuka in Karelia borealis. Neu für Karelia ladogensis sind folgende 9 Arten: Caprimulgus europaeus, Nyctea scandiaca, Haematopus ostralegus, Machetes pugnax, Spatula clypeata, Sterna macrura (nistend), Larus argentatus, Cepphus grylle (nistend) und Alca torda (nistend). Einige von diesen sind typische Meeresvögel, die hier auf den Schären und Klippen des NW-Ufers des Ladoga-Sees leben. Zu dieser gruppe gehört auch die schon früher aus der Gegend als nistend bekannte Phalacrocorax carbo. Eine Erklärung hierfür findet der Verf. darin, dass der Ladoga mit seinen weiten Fjärden und klippigen Inseln an die Ostsee erinnert; vielleicht wären die Vögel hier auch als Relikte aus Zeiten anzusehen, in denen der Ladoga in offener Verbindung mit dem Meere stand. – Neu für Karelia borealis: Picus canus, Dendrocopus leuconotus, Falco aesalon, Scolopax rusticula.

    Note: As you can see, the nomenclature is slightly archaic. ‘Dendrocopus‘ and ‘rusticula‘ are not misspellings. As for the identities of the other species that may not be immediately obvious: Machetes pugnax* = ruff Philomachus pugnax, Sterna macrura = arctic tern Sterna paradisaea, and Falco aesalon = merlin Falco columbarius.

    * Alas, that does not mean ‘he who fights with machetes’. It would be so cool if it did…

  19. #19 Darren Naish
    February 4, 2009

    Wow, well done, Dartian, that’s some excellent detective work. Thanks for finally pinning this down.

  20. #20 Dartian
    February 4, 2009

    beobachtungen

    gruppe

    It should of course be ‘Beobachtungen‘ and ‘Gruppe’, respectively, with capital letters. Those typos are not in the original text…