How do vultures make and lay eggs?

Inside a Cape Vulture's egg
Inside a Cape Vulture’s egg

Have you ever wondered how a vulture makes and lays eggs?  We did and searched to find the answer, so that we can better understand how their bodies work and ensure that our captive breeding programme for population supplementation has the highest success rate possible.  Eggs it turns out are proof of nature’s mastery of engineering.

Reproductive System

It has been noted during post mortems conducted on vultures that have had to be euthanaised, that the female vultures have a very small right ovary.  Like us they do have two ovaries present in their bodies, unlike us the left is larger and fully functional, while the right is smaller and inactive, rather like in chickens.  The theory is that if anything happens to the left ovary then the right ovary could become active to continue the ability to breed.  Sadly there is still a huge amount of information that we just don’t know about vultures, which is why VulPro works so hard not only to conserve them but to research and understand them too.

The video featured below is wonderful and shows clearly how the egg laying process works in chickens.  This gives a very good idea of how it works in vultures too.

All about eggs! – How is the egg formed?

The egg starts its journey as the yolk (oocyte), which is produced by the female vulture in her ovary during ovulation. Each yolk (ovum) is enclosed in a thin-walled sac, or follicle, attached to the ovary. This sac is richly supplied with blood. The mature yolk is released when the sac ruptures, and enters the funnel of the left oviduct.   Fertilised or not the yolk travels through the oviduct which is a long spiralling tube.  It is in the oviduct that the yolk can be fertilised if a mating was successful. As the yolk’s journey progresses down the oviduct into the section called the magnus; it is covered with the vitelline membrane, structural fibres and layers of the albumen (egg white).  The egg continues its journey through the oviduct, spinning as it goes (a bit like a bullet travelling down the barrel of a gun).  This spinning movement twists the structural fibres into the rope like fibres that we call the chalazae. There are two chalazae on opposite ends of the egg that hold the yolk in place.

The shell is not created by the chicken but actually formed by the egg itself, in the lower part of the oviduct just before the egg is laid.  The shell is made of calcite (a form of calcium carbonate).  It is the membrane surrounding the egg that has evenly spaced areas where columns of calcite form as they develop these columns form side by side creating a shell.

Cape Vulture egg being weighed
Cape Vulture egg being weighed

A vulture’s egg weighs in the region of around 260g compared to 33 – 75g for a chicken’s egg.   When you look at an egg you will see that it has a broader rounded end and a narrower pointy end.  As the egg travels down the oviduct, it moves pointy end first.  Just before an egg is laid the egg turns around so that the rounded broader end faces downwards – logic says that this is because the broader rounded end provides a softer landing surface to prevent the egg from cracking or breaking as it lands in the nest.

We also had a very interesting case with an African White-backed Vulture who became egg bound and required assistance to try and save her egg as well as her life.  Her egg was presented narrow pointy side first and ended up jammed, sadly we couldn’t remove the egg without cracking it.

African White-backed Vulture - Egg bound (incorrect presentation of egg)
African White-backed Vulture – Egg bound (incorrect presentation of egg)


Natural Protection

The rounded end of the egg contains the air sac, once an incubating vulture chick’s lungs are developed enough; they use the air in the air sac to breathe prior to hatching.  When eggs are laid they have a natural sheen on them that helps to prevent air and bacteria from entering the egg.  Protecting and preserving the sheen is one of the reasons that eggs should not be washed if they are going to be stored.

Eggshells are porous which means that air and bacteria can enter the egg through the pores in the eggshell.  The albumen or egg white provides a layer of protection for the yolk which is situated more or less in the middle of the egg.   The egg white is very alkaline which slows down bacterial growth unlike the nutrient rich yolk which is a bacteria’s paradise.  This is why when we talk about storing chicken’s eggs for us to eat, they should be stored at a 45°angle, pointy side down, this keeps the air sac at the top of the egg and furthest away from the yolk.

Interesting Facts:

A female vulture can fly when she is carrying an egg.


Video Link:

Khaleesi our vulture Queen (The little Vulture who could!)

Little Khaleesi - captive bred Cape Vulture chick @ VulPro
Little Khaleesi captive bred Cape Vulture chick @ VulPro

Khaleesi got her name from the “Game of Thrones” series, with Khaleesi being the Dothraki name for Queen.   Hatched on the 21st July 2016 in a critical condition, little Khaleesi is already living up to her name proving to be a strong and regal personality.  She didn’t have the easiest start in life, being born very small and underweight and certainly would not have survived if she had been in the wild. Inside her egg was an unusual amount of thick liquid, we suspect all caused by a bacterial infection. She was unable to eat or defecate normally for the first couple of weeks of her life.  Put on an intensive course of antibiotics, fluids and round the clock care, little Khaleesi slowly but surely gained ground.

Khaleesi at 4 days old with surrogate brother PePe
Khaleesi at 4 days old with surrogate brother PePe

A vital part of saving animals, but more especially wildlife, is to ensure that their emotional strength is maintained or boosted.  Preventing depression and stress while still maintaining the will to live is one of the best ways to save any wild animal that is being treated or rehabilitated.  In order to help Khaleesi survive we had to give her extra care and attention. She was put with her surrogate big brother PePe who helped to keep her warm and give her invaluable body contact to keep her fighting spirit strong.  Khaleesi was being fed at this stage, we would place food in her beak which she would swallow.  She was still very quiet at this point probably due to weakness, as she strengthened she became far more vocal.

Khaleesi and friend
Khaleesi and friend

On July the 28th 2016, Khaleesi ate on her own for the first time, which was a huge milestone for her.  We all gave a huge sigh of relief feeling that she might now make it.  You can see how small she still was in the photo where she was lying next to one of our other newly hatched chicks.


Khaleesi exhausted after feeding
Khaleesi exhausted after feeding

By August the 5th Khaleesi was growing and doing very well.  She had really improved, eating on her own and putting on some much needed weight.  An important part of her care was also daily exposure to sunlight; natural vitamin D exposure helps calcium absorption for strong bone development.  Vultures are heavy birds on proportionately short legs, which need to be very strong to support them.

Khaleesi on the 5th August 2016
Khaleesi on the 5th August 2016

Update 10th August 2016

Khaleesi attained another milestone, we put her back on the breeding cliff with her parents, all went well and we will be monitoring her progress closely.

Update 11th September 2016

Khaleesi has been back with her parents for four weeks already and is thriving.  She has grown from a weak, sickly young chick to an incredibly beautiful young vulture.  Today she is just over 7 weeks old, a milestone that fills us with pride, relief and love every time we look at her.

Khaleesi at 7 weeks old, back on the cliffs with her parents
Khaleesi at 7 weeks old, back on the cliffs with her parents

As with all of our chicks, Khaleesi carries with her our hopes for the future of vultures in Africa.  She will be tagged when she is a little older, ultimately she will be fitted with a satellite tracking device and we will release her and monitor her progress in the wild.

Our hopes and dreams are to see her grow, pair up and have chicks of her own a legacy to be continued over the years.

Follow her story as we update you over time, on her life at VulPro and her ultimate release and travels around Africa.

How do vultures fly so high and survive?

Cape Vulture - Vulture Restaurant @ VulPro - Photo Copyright Mandy Schrode
Cape Vulture – Vulture Restaurant @ VulPro – Photo Copyright Mandy Schroder

Vultures are amazing birds that can soar and glide for great distances, they have adapted over time to allow them to fly at great altitudes where oxygen is in short supply.

Mechanics of flight

Whether you are flying in an airplane or a vulture gliding across the sky, flying remains a balance between two sets of forces – “lift and weight” and “thrust and drag”. Lift is created by the flow of air over the wings and weight is created as a result of gravity.  Vulture’s wings are concave on their underside and convex on the upper surface, because of this shape the air that travels over the wing has a greater distance to travel resulting in it speeding up, this causes the pressure to drop (this is because the same amount of air is exerting its pressure over a larger area above the wing than below it.  This creates “lift” or sucks the wing up.

At the same time the exact opposite is happening on the underside of the wing, the air slows down, creates more pressure and “pushes” the wing up. This push and pull effect happens the most along the thin trailing (back) edge of the wing and causes a spiralling vortex (whirling mass) of air disturbance at the wing tip which increases the drag.

Gliding & Soaring

Vultures are masters at soaring and gliding, hanging in the air without having to flap their wings.   Their wings are large, ideal for gliding, but very hard work to flap for flight.  Soaring means that vultures don’t lose height and often climb higher in altitude by using no energy of their own – instead using the thermals (rising masses of warm air), obstruction currents which are produced when wind currents hit mountains or tall buildings cause the air to rise lifting vultures to higher altitudes.  Vultures have large, broad wings and their proportion of bodyweight to wing size is low, making them the perfect gliders and soarers.

Brain straining fact:

 “Aerodynamic properties are measured by aspect ratio, which is the ratio of wing length divided by wing breadth. Long wings are better for gliding but harder to flap quickly and are therefore not much good at quick acceleration.  Wing loading is the relationship between total body-mass measured in grams versus total wing area measured in square centimetres.” (

Feathers for Temperatures

Cape Vulture - back feathers up close
Cape Vulture – back feathers up close

At the higher altitudes, temperatures can drop to -60°C, to survive this high fliers have developed a layer of soft down feathers that act as insulation – exactly why we use down duvets in winter.  Special feathers called “Contour feathers” cover the body, streamlining it and effectively reduce the drag.  “Remiges” are primary feathers, found on the wings they help with flight and provide wing shape.  “Rectrices” are tail feathers which stretch sideways making the tail work like a rudder for turning and balancing.

Bullet shaped bodies

The vulture’s body shape is suited to flight with the centre of gravity being situated slightly below and behind the wings, the placement of the centre of gravity helps with better balance in flight.  Added to the position of the centre of gravity a large number of the organs and large muscles are found near the centre of gravity.


A vulture’s wings are the equivalent of our forelimbs or arms, they attach to the body closer to the vulture’s centre of gravity.  The “hand” bones are small, fused, flattened and are specially adapted to manipulate the flight feathers and “feel” the air for riding thermals.

Bare Bones

Pneumatization means “The development of air cells or cavities, such as those of the mastoid and ethmoidal bones.” (

Evolution has allowed vultures to adapt for flying by reducing their weight by:

  • Fusion of some bones
  • Removal of unnecessary ones
  • Pneumatisation of bones
  • Large bones are often connected to respiratory system air sacs.

To ensure that their bones remain strong they have internal truss like reinforcing.  Fusion of certain bones lightens the skeleton while increasing its strength.   An important adaptation is the fusion of the caudal (tail) bones into what is called a pygostyle(the Pope’s Nose on a chicken).  This pygostyle supports the tail feathers, with the tail working as a rudder it needs to remain strong.

Vultures also have no teeth, having evolved with a beak which is lighter.  Bird’s ribs are stronger than ours as they have hooked boney extensions (uncinate processes) which overlap with the rib behind them providing extra strength and stability.

A vulture’s skull is made up thin hollow bones making it very light

Height Records

  • Andean Condor 15 000feet
  • White Stork 16 000 feet
  • Bar-tailed Godwit – 20000 feet
  • Mallard – 21000 feet
  • Bearded Vulture – 24000 feet
  • Alpine Chough – 26500 feet
  • Whooper Swan – 27000 feet
  • Bar-headed Goose – 29000 feet
  • Common Crane – 33000 feet
  • Ruppell’s Griffon Vulture – 37000 feet [11,274 m when a Ruppell’s griffo collided into a commercial airline over western Africa (Martin, 1987)]


Respiratory System

High Flyers counteract the reduced oxygen levels by having an amazing lung respiratory system, which uses the smallest amount of oxygen available to its full effect.  So why do vultures fly so high… to use the natural jet streams found at higher altitudes, allowing them to cover massive distances with little effort.

A vulture’s respiratory system is proportionately larger than ours is.  Their lungs are smaller and less flexible than ours are as well as being connected with a network of large thin walled air sacs in the body.  The air sacs are also interconnected with the air spaces in the bones.  Vultures like most birds have a unidirectional method of breathing, this means that fully oxygenated air is always entering the lungs unlike us where we breathe into and out of our lungs, resulting in fresh air mixing with old air.

Respiration-bird-mammal-insectAnimated gif used with permission of and created by Eleanor Lutz (Eleanor’s website:

Heart & Blood

A vulture’s heart is large and powerful as well as being similar to ours by having 4 chambers.  The Bird’s heart is large, powerful, four-chambered and of the same basic design as that of a mammal. The vulture’s circulatory system is like its respiratory system in that the blood is separated into oxygenated and de-oxygenated, making them well equipped to handle their high flying.  They also have higher blood pressure and blood glucose levels than ours.


Birds have high metabolism and are able to generate and regulate their body temperature (endothermy) for rapid availability of power and maintenance of high body temp at cold altitudes.

Sabi Sabi Wild Facts: Vultures

Bee Sting’s Story – Part Six

Bee Sting at VulPro wearing her fibreglass cast wing cap.
Bee Sting at VulPro wearing her fibreglass cast wing cap.

For those of you who follow Bee Sting’s story, you will be pleased to know that Dr Dorianne Elliot’s innovative fibreglass cast wing cap, has worked.  Bee Sting is healing well and is now having her dressings changed at VulPro twice a week.  Dr Elliot was able to fit it in such a way that no damage was caused to the fragile blood supply to the wing, Bee Sting will keep her wing, which was one of our biggest concerns.

She is also a lot more comfortable, so is allowing us to work with her more easily.  In true Bee Sting style, she is giving Dr Elliot’s fibreglass cap a good go, and it is starting to show some wear around the edges, hopefully by the time she really damages it, we will be able to take it off her for good.

Bee Sting's wing when we rushed her to Dr Elliot for the first wing treatment.
Bee Sting’s wing when we rushed her to Dr Elliot for the first wing treatment.
Bee Sting's wing showing considerable healing and improvement.
Bee Sting’s wing showing considerable healing and improvement.









The other good news is that Bee Sting has been adopted, Elizabeth and Tertius Bouwer have been welcomed into the VulPro family as Bee Sting’s “family”.

Bee Sting is adopted
Bee Sting is adopted

Cody’s Mazda Advert – “I believe i can fly”

Cody’s Mazda advert was incredibly popular on television, highlighting the then Mazda Wildlife Fund’s work.



The right to Be!!!

VulPro - The right to BE!!!
VulPro – The right to BE!!!

Cody – The Vulture who changed the World

Cody and Kerri adored each other
Cody and Kerri adored each other

Cody was a Cape Vulture (Gyps coprotheres), captive bred at the Pretoria Zoo who came to VulPro at about 2 weeks old to be a vulture ambassador.  No one knew then how impactful this single vulture would become for a species.

Vultures in Africa are declining at a devastating rate – we have to save the species.  Without them we face disease epidemics, vermin population explosions and loss of livestock and wildlife.  Vultures are not generally liked by “Joe Public”, mistakenly seen as dirty and vicious.  Vultures needed a saviour, a vulture so special and so unique that you couldn’t help but fall in love with him.  A vulture who would make people fall for him, so that they learnt to appreciate and empathise with the species.

Cody playing with Kerri

Meet Cody – he became the face of Mazda, the iconic vulture featured in their moving and impactful television and print media adverts. This little vulture put vultures in almost every house in South Africa, in a way that made us proud to be South African and willing to look after our heritage.  Coupled with glorious African sunsets and landscapes he epitomised all that we love and are proud to call South African.

Cody loved to be close to people
Cody loved to be close to people

Normally vultures are quite playful and as they reach sexual maturity can become a bit grumpy about being worked with, so are not best suited to being education birds.  Prone to bite when startled or threatened, they can be their own PR enemy number; one add to that their piercing gaze and they are quite intimidating.


Cody at the Mazda filming waiting out the rain, happy to sit with his human
Cody at the Mazda filming waiting out the rain, happy to sit with his human

Cody was the most unique vulture, gentle to his very core.  In his two years as a vulture ambassador he never bit a person or reacted negatively to one.  He seemed to understand his purpose in life and maintained the gentlest and calmest persona.  A vulture’s gaze is usually highly intelligent and quite piercing; it can be quite intimidating as you feel that they look right into your soul.  Cody’s gaze carried the intelligence of his species but held a highly unusual softness that drew one in.  We can honestly say that he was an old soul with the knowledge and confidence gleaned through the ages; he had the inexplicable charisma that drew whoever met him into wanting to be closer to him and even better he allowed and thrived on the interaction.  He genuinely loved to be around people, as seen in the photo above could be almost human like in his interaction with them.  Whilst we don’t condone the anthropomorphism of animals, it was very difficult to not think in those terms when you were around Cody.

Cody completely unique, loveable and the most gentle vulture we have known
Cody completely unique, loveable and the most gentle vulture we have known

As is so often the case, the best of us often die far too soon.  Sadly he died of unknown causes when he was two years old, his post mortem was inconclusive making his death even harder to accept.

To this day there has never been another vulture with his same gentleness of spirit and age old peace – staff at VulPro still become emotional when the talk about him a true legend and a well-deserved member of the VulPro Vulture Heroes.

Cody’s legacy lives on,

“If you can’t make people love a species, get them to love one special character, because one vulture did make a difference!”

The African Dream
The African Dream