Tag Archives: eggs

The (literal) Birds and the Bees

Ok, I’ll give your parents the benefit of the doubt and assume that at one point in your life they sat you down and told you the ins and outs of “the birds and the bees”.  But just in case they failed to raise you properly, here is everything you need to know.

That’s right – The DEFINITIVE guide to bird and bee sex. You’re welcome.

Let’s BEEgin with the bees.

Bee sex happens in mid-air, usually around 10 feet off the ground. In a spectacular display of desperation, agility, and death (I’ll get to that part in a second), hundreds of male drone bees compete for the opportunity to mate with a virgin queen during her once-in-a-lifetime “nuptial flight”.

Drone bees are all male, and are evolved to be good at one thing:  Sex.  They have better eyesight then other bees, no stingers, and large endophalluses (penises).  During the nuptial flight, a dozen drones, on average, will successfully fertilize the queen.

And then things get weird.

Upon ejaculation, the drone’s penis essentially EXPLODES.

It violently ruptures, and is ripped from the drone’s body, remaining inside the queen’s.  The drone falls to the ground, and dies soon after.  The next drone to mount the queen removes the previous drone’s penis, and then proceeds to insert his own.

This kind of expendable-male mating ritual is not unusual in the insect world – female praying mantises, for example, are famous for biting the heads of of males during or following mating.

But that’s enough about insects. On to the birds!

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Our avian friends have evolved some very unique solutions to bringing sperm and eggs together – some of then just as strange as the bees.

Most male birds don’t actually have penises – chickens for example have no protruding sexual appendages.  Instead, they have a hole called a cloaca.  Both male and female chickens have one.  In order to mate, chickens have to press these holes together for a brief time in a behavior described as the “cloacal kiss”.


The cloaca of a bird is multi-puporsed – it is the exit point of a bird’s urinary, digestive, and reproductive tracts. Yes, that means that urine, feces, and eggs all come out THE SAME HOLE.

You can think of it like a water slide with different starts, but the same ending.



Not all birds engage in the cloacal kiss method of copulation; some DO have penis – and not just any penis, ENORMOUS penises.

There are species of duck with some of the largest penises, relative to body size, of any animal alive.  The Argentine Lake Duck for example, has a 16-inch corkscrew-shaped member that exceeds the duck’s own body length when fully extended.

So there you have it! Everything you need to know (and maybe a few things you didn’t).

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My personal take-away from researching this topic is two-fold.  Firstly, my google search-history has gotten significantly more disturbing, as it now includes the search terms “chicken butt hole” and “duck penis”.

Secondly, I’m left with a much greater appreciation for the strange and inventive reproductive strategies found in nature. One thing is certain – mammals don’t have the final say on what defines sex.  Take it from the birds and the bees – there’s more then one way to do it.


Text and graphics by Sam MacKinnon, 2014

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WE ARE THE EGG PEOPLE (Some brief notes on the evolution of live birth)

Here’s a strange thought: You, and all the people you know, were once microscopic bundles of cells, inside of another person’s body (in your case, your mother’s).  You may be all sorts of awesome now, but your life began extremely humbly – an elegant balance of symmetry, simplicity, and chaotic potential.  And it all started inside of an egg. You, like me, are an egg person. Deal with it.

Eggs are beautiful things. They are such an elegant solution to developing new life, that multiple taxa of animals have evolved to produce them, including fish, amphibians, birds, dinosaurs, reptiles and mammals.  For most fish and amphibians, the laying of eggs is the first step in the process of sexual reproduction.  The eggs are then fertilized by the male in water, where they remain until they develop and eventually hatch.

It’s a neat system, but not one that works very well for terrestrial (earth-living) animals like birds, reptiles and mammals. Developing embryos is a delicate business; they need to be kept moist, sheltered, at a relatively stable temperature, and with a steady supply of nutrients. These are all tall orders for any organism to maintain, let alone a defenseless embryo outside of water.

As it so happens, the safest place for many animals to grow their young is inside of their own bodies.

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Humans, as I’m sure you know, don’t lay eggs.  Instead, we retain our eggs, fertilize, and develop them internally; the type of egg we make defines us as Amniotes, along with reptiles and birds.  Amniotic animals have more complex eggs then fish and amphibians, as they have specialized membranes that grow out of the embryo, and preform multiple functions, including providing the growing fetus with nutrients.

Birds grow their eggs internally for a short period of time, then lay them, and then incubate (keep them warm while they develop).  Inside, the  bird embryos are supplied with nutrients from a yolk sac, which supports them as they grow.  Gas exchange also occurs through the membranes and pores of the shell (yes, eggs breathe!).

While many reptiles lay eggs, there are several species of snakes and lizards that give live birth; some snakes even have placentas.  Placentas are something that also define placental mammals – a group to which humans belong.

In placental animals, the membranes of the amniotic egg develop into the placenta and umbilical cord.  Considered in this way, a placenta is essentially a modified egg, and has many analogous features that can be compared to reptile and bird eggs (a couple of which are illustrated below).  Instead of a yolk sac, human fetuses get their nutrients from their mother’s body via the placenta and umbilical cord.

The placenta acts as a bridge between the mother’s body and the growing child’s – allowing the transport of nutrients, but also acting as a barricade against the mother’s immune system (which will naturally want to treat the baby as a hostile “foreign” life-form inside the mother).

There is considerable evidence that live birth has evolved hundreds times, within a diverse spectrum of animal forms – it is certainly not unique to mammals.  The earliest evidence for live birth dates back 380 million years, to the ancient armored fishes the placoderms.

This tells us something interesting about the nature of live birth from an evolutionary perspective – that the difference between live birthing-mammals and egg-laying mammals is not cut and dry (as nothing ever is in evolutionary biology).  Rather, the two methods of developing young have dozens of crossovers and grey areas, and in a more fundamental way, they are really the same thing. For nature, the egg has never truly gone out of style.

Text and illustrations by Sam MacKinnon, 2014



Power, M. L., Schulkin, J., & Project Muse University Press eBooks. (2012). The evolution of the human placenta. Baltimore: Johns Hopkins University Press.

Porous Science: How Does a Developing Chick Breathe Inside Its Egg? 2012 Scientific American.  Retrieved on 02/24/2014 from: http://www.scientificamerican.com/article/bring-science-home-chick-breathe-inside-shell/