treasure

Turquoise blue with brown speckles, four blackbird eggs in a nest made from grass stems, moss and leaves. A structure made without  tools, or hands or a written plan, with care and attention to detail  and skill. A place, briefly a “Home” for this bird. A small miracle, treasure in the garden. And Max has a very interesting rumination on the subject of “home” here.

I cannot get pictures of the bluetits’ nest-it is in a box above the back door, but would love to see any nests-bird, bee, dragon, whatever, if you come across them. Send me a note or leave a comment and I will link to them.

Another tiny miracle-the nest entrance made by a mining bee, about 5 mms or 1/4  inch across. When I enlarged this picture I could see part of the occupant’s little face. It made me smile. I have found a bumble bee nest entrance too-but cannot stretch you patience by posting  another picture of a hole in the ground. You will just have to imagine that one.

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7 thoughts on “treasure

  1. That’s amazing! I’ve been doing my darnedest to find a nest and get a photo, gently peering around all our shrubbery. But for all the birds I can see around, I guess they have declined to actually take up residence in our backyard (perhaps something to do with our two puppies…). 😦

    1. Maybe the puppies-and they are SO adorable-have put the birds off this year, but there’s still time for nest building. I’ll keep my fingers crossed for you.

  2. Great question-I have no idea why they should be that colour, but blue seems to occur commonly in birds eggs. Can’t find anything from a quick Google either.

  3. Thanks! We have much of the yard fenced off now, so maybe the birds will still come and build nests if there is still time as you say!

    For the coloring…from wikipedia below (long sorry):
    So perhaps it does serve an evolutionary purpose – but sounds like that is still a hypothesis! (http://en.wikipedia.org/wiki/Egg_%28biology%29)

    The default color of vertebrate eggs is the white of the calcium carbonate from which the shells are made, but some birds, mainly passerines, produce colored eggs. The pigments biliverdin and its zinc chelate give a green or blue ground color, and protoporphyrin produces reds and browns as a ground color or as spotting.

    Non-passerines typically have white eggs, except in some ground-nesting groups such as the Charadriiformes, sandgrouse and nightjars, where camouflage is necessary, and some parasitic cuckoos which have to match the passerine host’s egg. Most passerines, in contrast, lay colored eggs, even if there is no need of cryptic colors.

    However some have suggested that the protoporphyrin markings on passerine eggs actually act to reduce brittleness by acting as a solid state lubricant.[1] If there is insufficient calcium available in the local soil, the egg shell may be thin, especially in a circle around the broad end. Protoporphyrin speckling compensates for this, and increases inversely to the amount of calcium in the soil.[2]

    For the same reason, later eggs in a clutch are more spotted than early ones as the female’s store of calcium is depleted.

    The color of individual eggs is also genetically influenced, and appears to be inherited through the mother only, suggesting that the gene responsible for pigmentation is on the sex determining W chromosome (female birds are WZ, males ZZ).

    It used to be thought that color was applied to the shell immediately before laying, but this research shows that coloration is an integral part of the development of the shell, with the same protein responsible for depositing calcium carbonate, or protoporphyrins when there is a lack of that mineral.

    Biliverdin is an important component of avian egg shells. There is a significantly higher concentration of biliverdin in blue egg shells than in brown egg shells. Research has shown that the biliverdin of egg shells is produced from the shell gland, rather than from the breakdown of erythrocytes in the blood stream. The presence of biliverdin in egg shells may be an indicator of female fitness, and therefore is likely evolutionarily important [7].

  4. That’s amazing Laura-thank you for taking the trouble to research it. The whole process of egg shell production and deposition is fascinating and that hypothesis certainly helps to explain the blue/green colouring that is common in birds eggs and the speckling. 🙂

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