I assisted with the Round Square Junior Conference this year, and was humbled to be asked to be a keynote speaker. I chose to talk on the wonder of eggs, using a turtle dove (live) that one of my students had given me for "show and tell" as well as twelve ostrich eggs which the student blew, painted and then ate as an interactive ending.
The natural world is full of different species that tell incredible stories. It is one of the reasons why we have chosen your baraza group names – each one tells a story of the origin of a name. To quote Dr Ian McCallum, a South African environmentalist who pioneered the idea of what is called ecological consciences, Have we forgotten That every creature is within us carried by tides of earthly blood and that we named them? We named the different creatures of the earth because we were inspired by them. Understanding the natural world created a sense of wonder. I want you to do me a favour to before I start this talk. Close your eyes. I want you to try and think back to when you were the youngest version of yourself. Now with that picture of you in your head, I want you to try and place yourself into the earliest memory you can conjure up of being inspired by nature. Maybe it was seeing a butterfly land on a flower in your garden. Maybe it was the feeling of freshly cut grass under your toes. Maybe it was the flapping of a bird that made you squint into the sky. You can open your eyes. For me, the furthest back that I can remember involved one of these little birds. I was fascinated by how something so small, could travel so far just to avoid a cold winter. I would trace my finger on an old globe that we had at home, marvelling at the endurance a bird weighing about 20 grams (that’s the same as about 4 grapes). Now it is common knowledge that Swallows are migratory birds, but even up until the 1900s, people were not entirely sure where they went. It was only in 1911 when a British doctor put a ring on the leg of a swallow that had for years frequented his barn in Staffordshire, England that the answer became apparent. He wrote on the ring “England: Aug 1911”. Happily, a South African farmer noticed the unusual ring on the swallow’s leg once it had completed its almost 9000 km migration for our summer and fashioned a similar ring: “South Africa March ‘12”. And why all that effort – for this: (show an egg) When David Attenborough was asked what is the most incredible of nature’s creations, he responded that “the egg is perhaps Life’s most perfect creation.” Which brings me to the title of this talk: The Wonder of Eggs. They come in all shapes, sizes and textures. The largest is the Ostrich egg weighing 1.5 kg, while the smallest in South Africa is he Cape Penduline Tit with an egg that weighs between 1 and 2 grams. The Emu egg is beautifully textured and or an egg that is simply beautiful from a bird as common as a crowned lapwing. Most of us take eggs for granted, they are something that we have alongside our breakfast, fried in a pan, folded into an omelette or scrambled into a yellow deliciousness on toast. Crack egg But eggs are far more complicated than just a shell, yolk and white. I mentioned David Attenborough earlier, and since he is simply a legend, let me play you a clip that gives you an idea of just how complicated the process of making an egg really is: So which end emerges first? I’m going to give you four clues which might provide the answer (it is not just a matter of physics). To understand this, you need to know a little more about why I think that eggs are a miracle creation: Let’s take a look at one of my favourite birds and an egg that I feel is simply a work of art. You have been watching it in the bottom corner of this presentation. African Jacanas (or lily-trotters as they are colloquially known) have these huge, long toes that help to spread their weight across the lily pads where they find their home. They nest among these pads as well, raising a clutch of chicks which they transport rather awkwardly under their wings as you can see here. Like many other water birds, Jacanas build nests which are flooded with water at least a few times during their incubation. So, the eggshell has a waterproof cover that protects the egg from water, but still allows it to breathe. However, there is bacteria that travels in the water, and this can be a real hazard for the young embryos as they do not have the immune system that the adults possess. The first takeaway from this is that yes, eggs breathe. The second is that eggs have a substance called SAM (shell accessory material) in their shells. This is an obvious protection to the outside world. There is another line of defence, and this is the albumen. The albumen is the clear white stuff that surrounds the yolk. It works as a physical and biological barrier. Think of it this way: if bacteria were to penetrate the shell, the albumen would be like a vast desert that prevents the microbe from getting to the yolk. There is nothing to sustain life. It does, however, have more than 100 microbial proteins (well those identified so far). And some of these are the building blocks for modern medicine. So, then, the albumen provides protection. The inside of an egg, therefore, looks something like this. And then we get to the third take-away: the yolk. This is essentially the food for the embryo. Large yolks provide more food, so the chicks that hatch from these are fully feathered and able to search for food themselves shortly after hatching (like chickens). Eggs with smaller yolks produce chicks that are weak and defenceless, their parents needing to spend a lot of energy to feed their offspring, like doves. And so here comes your fourth take-away. So then, which side is laid first? Well, it is the blunt end. This is because the embryo needs to have its head at the blunt end of the egg. And all of the processes in the embryo’s development ultimately led to that singular positioning. But how can an egg that is strong enough to protect a chick from the outside world, also be weak enough for the chick to break it? Although the egg looks the same from the outside, it actually gets thinner as the chick absorbs calcium from the inner shell to build its bones. The calcium also creates an egg tooth that allows the chick to break through the shell. As they some birds break out of their shell, they communicate with each other in order to motivate the clutch to break out of their own individual shells. I think that is all pretty miraculous. And there is more to it than that. I am sure that most of you have heard about cuckoos. These are birds that don’t raise their own chicks, but rather sneakily lay their egg in another birds nest, getting them to do the parenting for the cuckoo. Cuckoos are not the only ones who are these brood parasites – coucals, whydahs and indigobirds to the same thing. What is incredible, though, is that these dodgy birds are able to lay eggs that are incredibly similar to those of their host. And somehow, once the persistent chirping for food from their surrogate chick as forced them to experience a near “death by exhaustion” feeding regime, the adults don’t seem to notice that there is something amiss in their offspring. And then there is the shape of eggs. There are a whole range of different factors as to why some eggs are rounder than others, but the most fascinating story must come from the North American Murre. This bird roosts on the edge of cliffs - a very perilous place to try and incubate eggs into chicks. So, they have adapted to lay the most conical shaped eggs of all the birds, which means that instead of rolling off the nest, the eggs tend to rotate back to the centre of the nest. Ingenious. And then there is the timing of birds and when they lay their eggs. And this is where our eggs begin to tie into the theme of the conference. Many birds are to schedule the laying of their eggs with the arrival of their food supply. Many insectivorous birds, for instance, will ensure that their eggs hatch at the same time as caterpillars in their ecosystem also hatch so that there is an abundance of food available. I wonder how climate change will influence that sense of timing. Reptile eggs are equally susceptible to changes in temperatures. Warm unlike the chromosomic differences that determine male and female in in mammal offspring, the sex of turtle and crocodile egg are determined by temperature. For reptiles that bury their eggs into the sand, a difference in depth means a difference in temperature. If this crocodile egg was buried at a depth of a comfortable 32-33 degrees Celsius, it would hatch as a male. Anything more would create a female. The same is true for sea turtles. So, the increase in global temperature as a result of climate change can cause increased temperature in eggs. A 2022 study on American Green Turtle hatchlings of the same year concluded and ultra-biased towards female population. 99% of the most recent green turtle hatchlings were female. So, eggs are amazing. They seem to be like us humans, incredibly complicated. They are resilient, but fragile. Sensitive but tough. And to see what one of the most impressive eggs is like first hand, we are giving each baraza group an ostrich egg. You need to work out how to get it open, and you will be able to decorate the shell as an award for something in your group who has been simply amazing. Perhaps it will make you and them remember how, just like our planet, eggs have a hardcore fragility, but if we understand them, just like we understand how to look after our planet, they can bring life (or at the very least give us a good meal).
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