How did you do? I had good fun working out the answers.

1.     Lungs in birds are very different to ours, they are more efficient. In mammals we breathe into large dead end sacks of alveoli, use some oxygen then have to get rid of the low oxygen air taking up the space. Birds let air flow continuously through their lungs and get oxygen from fresh air on both in and out breaths. This constant supply of fresh oxygen helps give birds the extra energy needed to fly.

There are two main functional differences to make it happen, extra air sacs and tubes for air exchange rather than little balls like mammals. When a bird breathes in, some of the air goes through the tubes to give it oxygen and some goes into air sacs. When they breathe out, the air sacs are emptied and the air goes out through the tubes as well. It’s easier to see with a diagram:

Modified from Vet. Res. 37 (2006) 311-324

When they breathe in, oxygen rich air splits and goes directly into sacs 3 and 4 or through the lungs then into sacs 1 and 2. When they breathe out all the sacs are emptied. The oxygen rich air stored in sacs 3 and 4 goes out through the lungs and the air they’ve already used in sacs 1 and 2 goes straight out. It’s ingenious and far more efficient than our own breathing.

2.     Birds can’t sweat, so they need to cool down differently to us. One way is though panting, evaporating the water in their mouths uses energy and cools them down.

Hot birds (I have lots in the desert) hold their wings open or drop them to encourage air flow around them. Heat is related to volumes and surface area – warm-blooded animals create heat throughout their volume, but lose it through their surface. So by spreading out their wings birds greatly increase their surface to get rid of the heat.

And some birds like chickens or honeyeaters have fleshy combs and wattles. These look red because they are full of blood and very thin skinned. Apparently if you squeeze them you will actually get drops of blood out, but it isn’t something I’ve tried on my chookens.  The air flow around them cools the blood, that can help cool the rest of the body. They work the same as an elephant’s ears.

3.     Kiwis have the biggest egg of any bird relative to their body size. It’s so enormous female kiwis have trouble walking before laying it and have to fast, they were lucky they could survive that way. Fortunately they had no predators prior to human settlement in New Zealand. Mammals such as cats, rats and possums never made it to New Zealand so the females could afford to be awkward without risking their lives.

Kiwis are ratites, the group of flightless birds that includes ostriches, emus and New Zealand’s extinct moas. Like lots of biological things, there is a fairly predictable relationship between the size of a bird and the size of the egg they lay. However the ratites don’t fit on this nice line very well, their eggs are too big. Then Kiwi eggs are big even for ratites.

But, kiwis only lay one egg. If you look at the relationship of clutch size, rather than egg size, kiwis are in just the right place. Rather than putting energy into lots of chicks and hoping some of them make it, the lack of predators allowed them to put all their energy into just one well-developed chick and give it a better chance.

4.     The Dodo was a large, flightless, ground-dwelling bird in Mauritius, closely related to pigeons. It shared many features with Kiwis not because they are related, but because they fill similar ecological niches. Once again, their island home did not have cats, rats, pigs and humans, which allowed them to stop flying.

We're not even certain what it looked like, there are very different reconstructions.

Humans discovered Mauritius and its Dodos in 1598, and by 1700 they were all gone. This was probably not because of direct human hunting – even though it was easy to catch, no-one seems to have liked the taste very much. But introduced animals and deforestation finished them. It is possible that they were already in trouble as a small, isolated population, however there is no doubt that humans ultimately caused their extinction.

The Dodo is probably the first extinction of the modern era, and it is an important lesson not just of what we can do, but how we do it. Three hundred years later we still aren’t killing most animals ourselves (except for fish), but the pets and hitchhikers we take along and our insatiable appetite for land makes us responsible for their deaths.

5.     The boys up the top are all different types of Birds of Paradise, and they are all showing off for the girls. One of the arguments people used against natural selection was that some animals have features that are detrimental to their survival, like enormous tails or bright colours that make them targets for predators – shouldn’t they be dead? Darwin had a brilliant answer to this and it is its own sub-theory and rather large field – sexual selection.

Basically, natural selection is not about survival, it is about reproduction. In my own words, he who dies with the most grandkids wins. Females have it a bit easier than males because they produce the eggs so generally they are guaranteed to at least be in the race. It might be more difficult and dangerous for them to produce babies, but they will definitely have the chance to do it. Boys have the easy job as far as babies are concerned, but they might not even get to do that much. It’s a simple truth that not every male gets to become a father, a few particularly good ones grab all the girls.

In some animals the competition is between males, in others it’s more dangerous to be male and they have a higher death rate. But some animals pair up through female choice, and that’s when the boys go all out. No-one knows what starts females down a particular path – how did the bright colours or fancy dancing or singing or gifts get started? It’s probably fairly close to random. But once it’s started males tend to get more and more extreme, because if everyone has a little bit you have to have more to stand out.

Then they are stuck in a delicate balancing act – you have to be able to survive until adulthood but then get as many mates as you can. Too extreme and you might die, too boring and you won’t leave any descendants. Pity the poor peacock, carrying an enormous tail to entice the ladies. It almost makes high heels look sensible.

As you know I have budgies and chickens, so I’ve learnt a lot about birds recently. What do you know?

1. How do bird lungs work?
2. How do birds keep cool?
3. Which bird lays the biggest egg relative to body size?
4. How is the dodo special?
5. And what’s with the boys in the picture?

Answers on Friday!

For us, our bodies are familiar and generally predictable. We know what we can do, we are confident in our movements. But this is something that babies and children need to learn. For my little drama princesses, getting a camera out is a sure-fire way to get them to try new things

Can you kiss your elbow?

Can you touch your toes?

Can you stand on one leg?

Can you lick your nose?

Can you be a frog, jumping up and down?

Can you be a crab, crawling sideways on the ground?

Can you walk a wall?

Can you kiss your knee?

Can you bend right over and duck underneath a tree?

Can you climb a stair?

And balance on a chain?

Can you walk a line?

Then crawl back down again?

Can you balance in strange positions, with legs all up and down?

Then stand with feet facing forward and turn yourself around.

What can you get out and do?

When birds first start laying their reproductive system doesn’t always get it together straight away and you can end up with some strange eggs. One of our budgie chicks is starting and she laid an egg without a shell – we’ve had this with a couple of chickens, but you can see how tiny this one is!

We carefully snipped it open to have a look and here is the tiniest breakfast egg you’re ever likely to see. If it was a chicken I would expect a centre with thicker white, I don’t know if it’s different because budgies don’t have that or because she’s still working it out.

And now a closeup of the yolk, showing the germinal disc. This is where the sperm enters the egg and the embryo begins developing. These are on both fertilised and unfertilised eggs, but on unfertilised eggs they are smaller and more compact because there aren’t any developing cells. You can see it as a little white dot on a supermarket egg. If this was a chicken egg I would guess it is fertile, but without the shell it would never develop.

If you stare at a light for about 30 seconds then turn it off or look away you will still see a light in front of your eyes. This is called an afterimage, or technically a positive afterimage.

In the back of your eyes are lots of little cells called cones. When certain types of light hit them they fire and send a signal to your brain. Your brain puts together all the signals to make a picture of what you are seeing. But your brain is very clever – we don’t actually see everything all the time, like a movie. Our eyes are moving around and looking at different pieces at different times, our brain smooths it out and fills in the gaps. Sometimes it can make mistakes or take a little while to catch up.

Positive Afterimages

Positive afterimages like seeing a light when it’s been turned off are a mistake by your brain. One of the things your brain does to make the picture you see look full is assume that things stay the same unless there is a signal that draws its attention that something has changed. A good signal is movement, it attracts our attention right away.

When you flick off a light switch there are no clues to tell the part of your brain putting together what you are seeing that the light isn’t there any more, so it keeps putting it in and you ‘see’ it even though it isn’t there.

Negative Afterimages

Negative afterimages are when you keep seeing something but it is the opposite colour. This is when you walk in from a bright day and everything looks dark, or when you are staring at something red and then have blue splotches. Negative afterimages are caused by your eyes and your brains together.

If you stare at something that is brightly coloured for a long time, the cones at the back of your eye get tired and stop firing as much. But even when the signal from your eyes gets tired and switches off, your brain knows the thing is still there and you keep ‘seeing’ it.

When you turn to look at something else, the tired cones stay switched off for a few seconds. But cones for different coloured light in the same area  that aren’t tired will start to fire because of the new light reaching them. Your brain doesn’t know that some cones aren’t signalling because they switched off, it just knows it isn’t getting a signal from them so it assumes there isn’t supposed to be a signal there.

This means the picture your brain puts together of what you are seeing is wrong, and has a dark hole in the middle of it the same shape as the bright object you were looking at first.

There are lots of illusions you can use to see this happening. Stare at the picture up the top for as long as you can, at least 30 seconds. The longer you look at it, the better afterimage you will get. Don’t try to look at details, pick a spot like the nose or the bridge of his glasses and focus on that as tightly as you can. This works because of your eyes and brain, it doesn’t need you to know what you are looking at.

Then look away at a bright white wall or piece of paper. You will see a very clear image of a man’s face. It is actually Pierre Cardin, the image is by Dimitri Parant.

What flag does the afterimage show you?

1. We see because our eyes pick up light that has bounced off the things around us. It feels a little backwards, but the colour something appears is the colour it reflects rather than absorbs. A green book would absorb every colour except green and bounce the green back to us.

Colour is determined by the wavelengths of the light energy bouncing around and how our brain interprets it. There are three types of cone cells in your retina that are most sensitive to different wavelengths. If the light hitting your retina activates mostly S(hort) cones, your brain will interpret it as dark blue. It is the mix and proportion of the cone cells that are excited that makes up the full spectrum of colours we perceive.

2. Mixing light and paint are quite different, because one is additive and one is subtractive. We are used to paints and pigments, that is subtractive. As above, when we see a colour pigment it is the light that is being reflected to us. Starting with white or mixed light, some of it is absorbed by the pigment and only a fraction is reflected. When you add another pigment it will absorb more and reflect less, subtracting wavelengths from what is reaching our eyes. Eventually when there are many pigments all the wavelengths are being absorbed and none reflected, so we see black.

Mixing coloured light is different because you are starting with limited wavelengths and then adding more. If you shine a red light onto a screen, only red will bounce back to you and it will appear red. However if you shine a green light as well, your eyes are getting both long waves from the red and medium waves from the green. Your brain interprets this mix of wavelengths as yellow. Adding more lights adds to the wavelengths and cone cells being stimulated, when you add them all you eventually get white light.

The video at the bottom demonstrates this and has a fun activity as well.

3. While colours obviously exist, they fall along several continuous spectra. I say several spectra, because the hue, what we label as the actual colour, is only one part of it. There is also tone which describes how dark and light the colour is and intensity for the strength. Then you can get really technical with things like opacity, brilliance and texture.

The way we divide these spectra, where we put the lines and how we describe things, are purely cultural. English speakers focus on hue and tend to divide the spectrum into six colours – or is it seven? It was known that water or a prism could split white light into a spectrum when Isaac Newton experimented with it and wrote Opticks in the 17th century. He divided the spectrum into 7 colours, but this was based on a philosophical belief rather than anything physical – he believed there was a connection between musical notes, the days of the week, the known objects in the solar system and colours, so he needed seven of them. (Thanks to CatWay for putting me on to this.)

Many people find it difficult to distinguish indigo from blue or violet, and in spite of the ROY G BIV mnemonic most of us have learnt we act as if there are six main colours, especially when we are using things like primary and secondary colours. But then there are brown, grey and black and white as well! That’s even more.

Other cultures name and divide the spectrum in different places. In Japan and China blue and green are considered shades of the same colour. There can also be cultural elements such as distinguishing natural and artificial colours or it can depend on what is coloured, such as calling a horse chestnut instead of orange (bright brown?). There has been work done linguistically on colour description that shows languages go through basic stages in how colours are named. The most basic is a division into ‘dark’ and ‘bright’ and colours are added in a set order until there are at least 11 agreed upon basic colours.

4. I’ve often wondered about blue eyes, because I know humans don’t have a blue pigment. Most of our colours of hair and skin are made of eumelanin, or black, and phaeomelanin, or red. It’s a little more complicated than we were taught in school, there are several different genes involved, but making blue itself is a lot simpler than I thought.

It turns out that the melanin that gives our eyes colour is on a thin layer of cells at the back of the iris. In brown eyes there is a lot of melanin and it can be seen through the bundles of tissue in front of it. In blue eyes there is only a little bit of melanin. The tissue in front, which is all those fibres you can see, scatters light in the same way dust and gases in the atmosphere do. And just like the sky, the light that is scattered most is blue, so that’s what you see.

5. As the caption says the wings at the top are wasp wings, but absolutely nothing special has been done to them. Except putting them on a black background. It turns out wasps and flies have wings every bit as colourful as butterflies, and we never noticed because we put them against white backgrounds.

They were actually discovered in the 1800s but basically ignored since then. However Ekaterina Shevtsova has now studied them and discovered that they are not random but unique to each species. They are caused by ‘thin film interference,’ like the rainbow patterns of oil on water. Most light gets through, but some is reflected from the top of the wing and some from the back. The two slightly different reflections interact to make a colour, which depends on how thick the wing is and how far apart they are.

On a white background they are overwhelmed by all the light reflecting from it, but on a black (or green!) background they can be seen. In fact, now that I know they’re there and to look for them I’ve seen them myself when flies are sitting on dark furniture. They’re fun to look out for. As well as helping to identify different species, they could be involved in all sorts of insect puzzles, from fly courtship behaviour to vein patterns.

Does anyone else find the rainbow song frustrating? Red and yellow and pink and green are not the colours of the rainbow! But there are lots of other interesting things about it.

1. If something appears green, what is it doing to light?
2. Is mixing coloured light the same as mixing paint?
3. For StuffWithThing, are colours factual or cultural?
4. Why do some eyes look blue?
5. And what’s happening in the photo?

People who follow me on Facebook might have seen these photos but they bear repeating. While I was away one of our hens went broody, so instead of popping some of our eggs under her my husband got some bantams and Indian Runner Duck eggs. As you would. The bantams hatched a week earlier so the ducks needed to finish off in the incubator and one was having trouble. We thought at the time it was just shrink-wrapped – it had dried out too much while it was hatching and stuck to the shell. However now I think there was something else wrong as well, he’s doing fine but is smaller and weaker than the others.

He’d made a hole on his own but wasn’t moving, after 24 hours I gently chipped off the top of the shell a little like he would have naturally. I had to do a bit at a time because there is still blood in the membrane.

After I got it off I was hoping he would try to push himself out, but he was in an awkward position – when they are hatching they turn around which helps them get ready for the next step.

I freed his head and tipped him out.

Then we turned him all the way over to make sure he wasn’t stuck and to check on the blood vessels going to the membrane.

We popped him back in the incubator to warm up and dry a bit, and up the top you can see all four of them. He’s still smaller than the others, but now he’s doing well.

Do you know about other babies?

1.     Precocial and altricial describe the two opposite types of babies. Precocial babies are large and capable, often they are single or have very small litters. A classic precocial baby is a horse that can get up and run with the herd within hours of birth. They generally require long pregnancies or incubations. Altricial babies are the ones that are born like wiggly pink things and require weeks or months of care.

I have good examples of both precocial and altricial strategies in my birds – chickens and budgies. The chicks hatch together after 21 days, are born with down and stagger around straight away. Within a few days they have feathers and are flying around and out of their enclosure. I have hatched two clutches in an incubator and they are happily feeding and caring for themselves, we just had to get one or two eating and drinking and the rest look after themselves.

The budgies hatch over time and are at all stages of development, they are only in the eggs for 11 days. When they hatch they really are like floppy little embryos and their parents fly back and forth for the next month while their eyes open, they grow down then feathers and generally look more like birds. After a month they are flying clumsily out of the nest.

Humans are very interesting, because our babies are ‘secondarily altricial.’ I made that up myself but it expresses the situation well. If you look at our closest relatives they are precocial but spend a long time teaching their babies. Our minimal litters seem to be pointing towards a precocial strategy, but our pregnancies are far too short and our babies far too helpless. So our large brains and upright walking, which drove early births, mean that our babies are much more like the pink wriggly things than their cousins. Aren’t you glad you don’t have a litter of 8 to look after?

2.     Monotremes are the egg laying mammals – the echidna and platypus. They are not some primitive type of mammal, it’s just that live birth isn’t as cut and dried as ‘we do it and everyone else doesn’t’. There are snakes and fish that give birth to live young and there are even stomach brooding frogs. They swallow their eggs then stop eating and their stomach modifies to become more like a uterus where the tadpoles develop until little froglets are born through their mouths. Live birth is something that is useful in some circumstances and has developed many times.

Monotremes retain their eggs inside for a while and actively transfer nutrients to them, then still spend a lot of time caring for their young in nests. They are distant cousins within the mammal family, like the grandchildren of your Grandmother’s sister – they share recognisable traits and you know they are related to you, but they don’t have other things that are distinctively your family’s and they have some extras that you don’t have. Monotremes have the fur, milk, bones and teeth of mammals, but they have eggs and slightly different brains and they have developed electroreception and poisonous spurs which we don’t have.

Look below for video on a cute baby echidna puggle.

3.     The sex of baby crocodiles is determined by the temperature but it isn’t just high and low. Male crocodiles form in the middle, between 31-32 degrees, and both higher and lower temperatures will produce females. Crocodiles lay their eggs in large nest mounds that they scrape up, which includes a lot of plants from the river bank. This makes compost which heats the mound, but it will vary in temperature in different places so they generally have a mix of males and females in a clutch. There is some concern the narrow range necessary to produce males will make them sensitive to global warming.

4.     Ostriches and pipefish  are both animals where males look after or hatch the babies. It is common in the ratites with ostriches, emus, cassowaries and kiwis all having males on the nest. Sea horses and leafy sea dragons are relatives of the pipefish and they do it too. In fact they don’t just carry the eggs around in their brood pouch, it has definite hormonal and cellular changes and is basically a functioning uterus. For a fun take on it, check out this post by Bec Crew, a prize winning Australian science blogger.

5.     The picture is a Port Jackson Shark egg. Sharks are an ancient and extremely broad group, they use a wide range of breeding strategies ranging from live birth to eggs and also in between. All sharks have internal fertilisation rather then the ‘spread them and let them meet up’ that most fish use.

Most sharks practice ovoviviparity which means they produce eggs where the embryos partially develop, then hatch still inside the mother. They continue developing supported by their yolk and secretions from the mother’s uterus but they aren’t attached the way a placental mammal baby is. Some take it a step further and the first embryo to emerge will eat the other eggs to further support it before it is born. Some types of sharks even have pups that fight and eat each other in the uterus, only the strongest one or two are born.

Some sharks skip the eggs altogether and have a placental connection with their young, their reproduction is more like placental mammals than other fish.

And some sharks lay eggs. But these are not the brief eggs of amphibians, reptiles and birds, Port Jackson shark embryos spend 10-11 months developing. This means they need to be very tough to last that long and most don’t survive. The shells are thick and leathery and the mothers screw them into rock crevices, hence the screw-like thread around them.

And for some extreme cuteness, have a look at this echidna puggle.

Both the girls love being read to, and big girl is reading. Of course this means little girl needs to as well, she’s at the stage where she can identify pictures and follow a pattern to ‘read’ to us and thinks it’s the best thing ever. She’s also starting to draw recognisably and loves making or colouring pictures, so making our own books was an obvious activity.

Our days depend heavily on the weather, especially things like when we can go outside and thinking of things to do in the air conditioning. So I thought I’d combine them and we could make some books about weather.

The Animals Need More Water

Big girl’s book may have started with weather but quickly took off on a tangent. We talked about who the characters could be which got back to us pretty quickly, and some of the things we do every day, she chose looking after our animals. Then we needed a problem to solve, so it was a story not just a recount of our day. At that point she got the hang of it and came up with a nice little story about frogs in the water pipes.

It was build-up, and the animals needed more water. All the chickens, guinea pigs, and budgies were very thirsty.

Mummy turned on the tap but no water came out.

Then we heard a frog croak-croak in the pipe. How were we going to get it out?

It started raining and the frog got washed out. Dad caught it in a box and gave it to the chickens …

And then we had the biggest load of water and we didn’t need to water the animals for a whole week.

She loves writing and working on the computer, she managed to type a surprising amount herself either because she knows the sight words or because she sounded them and worked them out.

Jewel’s Baby Chicks

For the little girl, we used Publisher and the 4-page program template with our own photos. We have the cutest little baby bantams (which may be superseded by ducklings by the time this is published) and she came up with three sentences to match the photos then ‘read’ it back to me.

After the Rain

Back with my original weather idea, I took advantage of a big rain storm to snap lots of photos. We came up with sentences like ‘The guinea pigs were all fluffed up.’

In a very short time we had three simple, appropriate books on the topics they are interested in and knowledgeable about. They got all the fun of making them, tromping around getting photos, using the computer, making up stories and drawing, then get the thrill of reading them back to us. Definitely something to try.

Have you made your own books? What topics did you use?