The grim cycle of life: our blue tit nest failed

June 7, 2015 • 1:05 pm

by Matthew Cobb

This post is most definitely not for the faint-hearted, so you may wish to turn away now, or at least after you’ve looked at this very weird cat gif (pronounced…)

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About six weeks back I posted about the blue tit nest box we had set up in our garden in Manchester. Over the few weeks the parents have been flying back and forth, taking prey items (mainly caterpillars) into the nest. We could hear the chicks cheeping away, and although the parents looked a bit scrotty, they seemed to be doing their job. They were very worried about the cats, and would not fly into the box if the cats were around.

Last week the chirping ceased. We assumed they had fledged, and even announced it on Tw*tter. Later on, we heard one chick cheeping, the parents carried on going in. Then eventually there was silence, but the parents carried on bringing food, chirping and looking confused when they received no response from their offspring. Once it was clear that there was nothing going on inside the nest, we decided to take it down. What we found was not nice.

I managed to extract the nest intact:


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The chicks were all dead, including the one on top, which looks like it might be alive, or sleeping. I fished them out to try and see what had gone wrong. There were five in total – one is still on the nest on this pic:

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The one in the middle on the bottom was basically mummified – you can see on the top pic that it had been pushed to the edge of the nest. It was the smallest, so presumably was the first to die…

As if that wasn’t bad enough, a really grim discovery awaited when I got out the fifth chick from the nest:

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It was heaving with blowfly maggots… The cycle of life – or, more strictly, the cycle of carbon – had taken on an unexpected form. The chicks had all died, and their carbon was about to be converted into flies, which would in turn be turned into birds or spiders or whatever. Nature is pitiless, and natural selection even more so.

So why did they die? Disease seems unlikely – it would have hit them all at the same time. It seems most likely that they simply starved to death. Spring has not been particularly early or warm this year, and although the parents seemed to be attentive, they appear not to have been able to find enough food for their brood.

We hope – but we don’t know – that the brood was bigger than the five dead nestlings we found, and that some of the chicks successfully fledged. On the other hand, we haven’t seen the parents around feeding babies in the trees, which we have done in previous years. I fear these five were all there were.

This is not an uncommon occurrence, but it is sad. I’ll clean out the box in the winter and then put it up again, ready for another attempt next year.

Apologies to those of you who found that too grim – you were warned.

 

42 thoughts on “The grim cycle of life: our blue tit nest failed

  1. this has happened to broods in my boxes many times. I used to blame insecticides sprayed by gardeners on green and blackfly but I think its mainly just that the food source dries up due to cold snaps or perhaps one of the parents bites the dust and a single parent cant deliver enough food.

  2. This is the downside to waiting until the clutch is complete to begin sitting. Food drops below some level and they’re all dead.

    I suppose someone has looked into the relative advantages of the “full clutch” system vs. the owl system of sitting from the first and then having very unequally sized young. When food is short the larger/older owlets grab all of it, while the younger siblings get little or none. I’d guess owls tend to lose some every year to nestling competition, while blue tits more often bring off the whole clutch, if they don’t lose them all. An “owl system” blue tit might have saved one or two out of this clutch.

  3. It could be disease. Disease can take them all at once or a few at a time.

    I’ve read that avian flu is going around North America and has killed (or required to be destroyed) so many chickens that some stores in Texas have started restricting the number of cartons sold to a person.

    Canada is also experiencing a bad year. I don’t know if this kind of bird gets avian flu, but if they do, that could be it, or something similar. I would think young chicks would be more susceptible to flu than the parents would, young usually are.

    1. I live in Texas, and our big chain store, HEB, restricts egg sales to three cartons at a time, so restaurants and such won’t take so many that regular customers are left without. Prices are up roughly 50% there and at Costco, which is a national chain. We’re not that close to Iowa and South Dakota, where I understand the greatest impact on egg production has been, but we’re sure seeing the effect.

      FYI, eggs keep outside the fridge even in Texas, even if they’ve previously been refrigerated. I proved it to myself, the past two summers. I stocked up.

      1. Not that I would recommend anyone treat their eggs like this, but we once forgot a carton of eggs in an under-floor compartment in the back of our vehicle after grocery shopping. The kids found it a couple of weeks later. I asked them to dispose of them in an abandoned grove near us.

        Being kids they, of course, did not listen to me. Instead the carton sat in our garage for at least two more weeks before I noticed it. I called the kids to attention, put the eggs in their hands and told them to go directly to the old grove and leave the eggs for the critters. Out of curiosty I asked them to check and see if they were spoiled or not. They appeared to be perfectly fine. They looked and smelled fine. After at least a month enduring constant temperature changes from 90 – 100 F (possibly a good deal higher stuck in the back of the car) down to 70 F.

        1. I have heard that commercially washed eggs are more likely to be contaminated by bacteria (salmonella) than eggs from the back yard coop. Something to do with the wash damaging the natural barrier found in the shell.
          I suspect that eggs generally contain antibacterial substances to ensure development.

          1. I suspect the biologic membrane, just inside the shell, is the microbial shield. The fetus must require oxygen and carbon dioxide exchange, which could be permitted through the membrane while blocking anything larger. Osmotic pressure might hold the water inside. And the shell, then, is for structural support and safety while being, itself, permeable to small gaseous molecules. This is all conjecture. Anyone out there who actually knows?

    2. There is a pretty strict monitoring regime for avian flu in UK (as elsewhere) because of its human health implications and I am not aware of any reported outbreaks recently. So, although I believe blue tits could be affected by avian flu I doubt this is the case here.
      I would suspect starvation and cold to be the likely cause of this nest failure. We have had poor weather in May in the UK with low temperatures and high winds and these conditions would make it difficult for the parent birds to forage successfully. Low temperatures would increase the energetic demands of the chicks giving a double whammy effect. I don’t think that the chicks would necessarily need to look particularly stunted for this to have happened: I suspect that they live on a bit of a knife edge and a relatively short period of energy imbalance would be enough to kill them off.
      I expect that 2015 will prove to be a poor year for blue tits in the UK because of the widespread bad weather but fortunately they are towards the ‘r-selected’ side of the spectrum and high levels of breeding output can ensure that population levels bounce back quickly from one year to the next.
      That doesn’t make it any less sad to see the fate of an individual brood like this, of course.

  4. Very sad. It could be starvation (but they did not all look stunted). It could be disease, or it could be pesticide exposure.
    I have a robin family nesting on our porch this summer. They started with 4 but now there are 3 as the 4th could not get enough food. But the 3 remaining seem to be doing well.

  5. Nature can be a bastard in many ways. I should report that one nest of young birds I have been watching were invaded sometime in the night because this morning they were all gone and the nest was torn up. It almost had to be another bird where this nest was as nothing like snakes or coons could have gotten to it.

    1. There are birds like crows and I think jays that would do this. A year or so ago I saw a crow being chased very frantically by sparrows. The crow was definitely carrying something pink and wiggly in its beak.

      1. I did not know that Jays would do this. And we have lots of them here as well. I knew they would take eggs and were just generally nasty but eating baby birds…

        1. A few years back there was a blue tit nest in the house over the way; we watched in horror as the chicks fledged, flying onto a telephone wire whence they were each picked off and eaten by a gang of magpies. What a waste.

          1. Why a waste? Magpies have to eat too and blue tits themselves are voracious predators specializing in immature prey items (ok, so caterpillars are not quite so cute as baby birds but they are babies!).

      2. Last year a pair of the delightful pied wagtails (Motacilla alba) nested within arms length of my front door. (They are fairly friendly and tolerant of human beings.) The chicks were getting quite large when the nest was discovered by jackdaws (Corvus monedula), which destroyed the nest and ate the chicks.

  6. Don’t worry about me, the only time I have ever gagged was a podcast re-tellimg of a bout of feculent emissions.

    Plus, the neighbor’s cat used to bring my mom dead things all the time. She was the food monster for when the neighbors were out.

  7. Maybe mosquito-vectored parasites, bacteria, or viruses could have caused this? The parents, constantly in flight, would have been harder for the mosquitoes target.

    (After all the rain Texas got, I definitely have mosquitoes to remind me of their presence.)

  8. A few years ago our barn swallow nest presented the same tableau. Always disappointing, esp. when the chicks have already developed so far.

    Sad to think of the parents trying to bring food to dead chicks…

  9. The chances of all five babies surviving to adulthood are almost zero, and if you think about it, just as well, because in a few years bluetits would be the dominant species in the avian world and eventually evolve into huge carvivorous man-eating monsters.

    1. “evolve into huge carnivorous man-eating monsters.”

      As opposed to what? Huge vegetarian man eating monsters? I would think huge blue tits would be pretty deadly either way. 😎

      1. Tits are not vegetarians, they eat insects which creationists will tell you don’t class as animals if you try to tell them that before the Fall of Man, insects were eating each other and insectivorous plants were eating insects .

        1. I may be wrong but I rather suspect that Rickflick never thought that blue tits are vegetarians!

          1. Right. You’re not wrong.
            Huge blue tit fear runs across all persuasions. I’m certain eating lettuce and asparagus will simply not deter a huge blue tit.

  10. Matthew, sorry to snag on a less-than-relevant aspect of this but I’m wondering why you so pointedly correct yourself in your use of “the cycle of life”. “The cycle of life – or, more strictly, the cycle of carbon …”, you say.

    I don’t get it. If anything “cycle of carbon” is the figure of speech there, not “life”. Carbon is black, gritty stuff. You don’t have carbon there any more than you have water. What’s to stop you saying “… or, more strictly, the cycle of water.”? Or what about all the other minerals and molecules there?

    Honestly, I’m interested in the conceptual background to that.

      1. Okay, thanks. Stupid question. Sorry. I see he means the carbon cycle as opposed to the biological life cycle, as in that of an insect. I was thinking of the cycle of life in the broader, Life-with-a-capital-L sense and in that sense, of course, the carbon cycle is only one part of the cycle of Life, as is the nitrogen cycle. It seemed strange to me to so pointedly reduce the part to the whole.

  11. In the south-east it has been a very dry sping – about 90mm over the last three months. That the UK average is ‘normal’ is because of more rain in Scotland & the north-west. I wonder if that has more affect than cold?

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