Readers’ wildlife photos

July 26, 2018 • 8:00 am
Reader Jacques Hausser from Switzerland continues the bird photos from his vacation to the north. His notes are indented and there’s some good science here.  
Holidays in Shetland, continuation: today is dedicated to the common guillemot (or thin-billed murre), Uria aalge, family Alcidae. As before, photos taken by my daughter are labelled with (Jo).
This one shows an very elegant monocle, complete with its lace. In the Shetland, about 10% of the guillemots bear this ornamentation; they are called “bridled”. Polymorphism is always interesting for biologists; below the photo are some results of their studies (some references at the bottom of the post):
  1. The frequency of bridled guillemots follows a cline, from 0 % in the most southern part of its distribution (Portugal) to about 50 % in the northern part (Bjørnøya, an island halfway between continental Norway and Spitzbergen). 
  2. This polymorphism is apparently due to a single gene, the bridled allele being recessive (that is, b/b guillemots are bridled, NB/b and NB/NB ones are not). 
  3. The probability of mating with a bridled partner (both for a bridled and a non-bridled bird) is proportional to the number of bridled birds in the colony: neither sexual selection nor assortative mating seem to occur.
  4. Mixed pairs (bridled x not bridled partner) produce stronger and larger chicks than either bridled x bridled or not bridled x not bridled pairs. It’s a case of selection for heterozygotes, which would insure the maintenance of a stable polymorphism in a given colony. [JAC: this “heterosis” is also seen in sickle-cell anemia, where heterozygotes don’t have the sickle-cell disease but are more resistant to malaria than “normal” homozygotes and of course far healthier than individuals homozygous for the allele causing the disease.]
  5. In northern Norway, the winter survival of bridled individuals is better during cold winters (cold sea surface temperature), the survival of non bridled individuals better in mild winters. The differences are very slight, but significant. That would be expected if the “bridled” mutation first appeared in the northern part of the species’ distribution and is partly linked to genes dealing with climatic conditions. 
  6. In northern Norway and in Bjørnøya, the northern tip of their distribution, common guillemots live in huge mixed colonies together with the arctic Brünich’s guillemot (Uria lomvia), which has a thin white “moustache” (Clark Gable style) but is never bridled. These species occasionally hybridize; it is suggested that Brünnich would-be partners more efficiently avoid pairing with bridled common guillemots, which would save the latter from losing genes in sterile (or at least poorly fit) hybrids and therefore would favour the bridled form. From these northern mixed colonies, the “bridled” mutation would have slowly diffused to the south during cold periods like the little ice age.
(Jo) In this partial photo of a colony , showing about 120 individuals, I counted 12 bridled ones. Can you spot the (probably abandoned) eggs ? Guillemots lay their eggs directly on the rock and incubate them on their feet. The eggs are pear-shaped, which prevents them from rolling too far away and falling down the cliff. They are very variable in coloration and pattern, improving individual recognition.
Three non-bridled individuals:
For comparison: the arctic species,  the thick-billed murre or Brünnich’s Guillemot, Uria lomvia (Spitzbergen 2014):
Looking underwater in search of fish.
(Jo) Diving: the guillemots use their wings to “fly” underwater and actually open them before going under with a little jump. Their very efficient underwater flight can be seen here [JAC: I’ve embedded the video below].  Aerial flight is straight and fast (up to 80 kmh, between 300 and 400 wingbeats per minute); the delicate moment is the landing on the colony, however crash landings are strongly over-shown on the web.
Flying underwater:
(Jo) Thin-billed murre indeed!
Some references on polymorphism:
Jeffries,D.J. and J.L.F. Parslow (1976): The genetics of bridling in guillemots from a study of hand-reared birds. J. Zool., Lond. 179,411-420.

Kristensen D.L., Erikstad K.E. et al. (2014): Differential breeding investment in bridled and non-bridled common guillemots (Uria aalge): morph of the partner matters. Behav Ecol Sociobiol 68: 1851.


Taylor, S.A., Patirana, A. et al. (2012): Cryptic introgression 

18 thoughts on “Readers’ wildlife photos

  1. Good pics!

    It seems guillemot chicks leave their rocky nests only three weeks after hatching & live by floating on the sea from then – with the male adult supervising kiddo in the ways of fishing. More info & explanation HERE. I also read the eggs are particularly waterproof & conically shaped to reduce rolling off the nest!

      1. Oh, yes. Back in the lilypad pond the 5th turtle was in the lilypads, at ~ 11:00, near the edge of the lilypads. Its head was sticking out.

  2. Off topic question: I understand that theistic evolution is inconsistent with mainstream evolutionary theory, which says that the processes of mutation and natural selection are unguided. However, I would not be able to argue for that claim if I came across a theistic evolutionist. Is there any literature aimed specifically at theistic evolution that I could read for ammunition?

    1. …theistic evolution is inconsistent with mainstream evolutionary theory, which says that the processes of mutation & natural selection are unguided. […] Is there any literature aimed specifically at theistic evolution that I could read for ammunition?

      The best arguments against “theistic evolution” avoid the bible/Qur’an & illustrate how cruel, wasteful & poorly engineered** darwinian evolution is. Why Evolution Is True, Chapter 3. Remnants: Vestiges, Embryos & Bad Design is a good start! Chapter 9 too.

      “Theistic evolution” could be indistinguishable from darwinian evolution – you can’t disprove that god sent an asteroid 67 million years ago to shift the balance in favour of us mammals. The range of arguments from ID proponents to “theistic evolutionists” is so extensive & poor that I don’t think there’s a book that arms you directly as such.

      ** human oesophagus, human back, Laryngeal nerve in giraffes

      1. I should point out that using scientific arguments on theistic evolutionists is a waste of your time – though you may sway the undecideds. Generally your audience of naysayers are semi-literate & they’ve absorbed only the bits of distorted science that they think disprove evolution by natural selection.

        Pointing out errors in understanding of carbon isotope ratios is going nowhere & is ‘wooosh’ over their heads.

        Pointing out evolutionary poor design evokes Garden of Eden, The Fall defence. A science discussion becomes a Biblical one & ears close.

        And so on.

  3. Good report! I never thought guillemots could be so interesting. My view, without having read the original reports, is that point #5 seems adequate by itself to explain the latitudinal frequency cline by itself: Brindled birds survive better where it is cooler (Norway) whereas non-brindled ones where it is warmer (Portugal). The next thing is to explain why birds with different markings do better at different temperatures, or whatever they are responding to. Point #4 seems inconclusive: “Stronger and larger chicks” are not an automatic ticket to greater fitness. Point #6, selection against birds genetically predisposed to interspecific mating, needs to be demonstrated. Hats off the hardy biologists who undertook these fine studies.

  4. “The frequency of bridled guillemots follows a cline”

    Aged 46. This is my first encounter with the word ‘cline’. Guess it’s connected to decline and incline. Now I’ve just got to manufacture circumstances where I can casually drop it into conversation.

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