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.

References:

http://www.iaszoology.com/flight-adaptations/

http://www.birdchannel.com/bird-health/how-do-pet-bird-lay-eggs.aspx

http://www.pbs.org/lifeofbirds/home/

https://answers.yahoo.com/question/index?qid=20120603163821AAqWKwB

http://lansingwbu.blogspot.co.za/2011/02/how-do-birds-lay-eggs.html

http://www.weldhagen.co.za/eggs/FAQs/Entries/2011/2/10_How_much_does_an_egg_weigh!.html

http://www.fresheggsdaily.com/2015/01/why-should-eggs-be-stored-pointy-end.html

http://fresheggsdaily.com/2012/03/great-eggscape-my-first-hatch-ever.html

http://chickscope.beckman.uiuc.edu/resources/egg_to_chick/development.html

http://www.sciencealert.com/watch-a-chick-develop-and-hatch-outside-of-the-egg

http://www.thepoultrysite.com/publications/1/egg-quality-handbook/2/formation-of-the-egg/

http://science.howstuffworks.com/innovation/science-questions/question231.htm

http://www.enchantedlearning.com/subjects/birds/info/chicken/egg.shtml

Video Link:

https://www.youtube.com/watch?v=l_D1qTNDyJc
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RIP Bee Sting – the end of an era

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

Bee Sting became an unbelievable ambassador for vultures and the work that VulPro conducts when she was first rescued and treated by VulPro and the staff at the Exotic Bird and Animal Clinic at Onderstepoort for over 240 bee stings.  Against all odds she survived and thrived and VulPro was so excited to announce her release back into the wild almost two years ago now.

Sadly for those of you who followed her story, Bee Sting was electrocuted at Caribbean Beach in Hartbeespoort.  On first inspection the injury did not seem to be severe at all, unfortunately as it healed and became itchy, Bee Sting created some really bad damage as she “scratched” at it with her beak.

Sadly in spite of all the amazing work done on Bee Sting and the innovative methods devised to protect her wound, she just wouldn’t leave it alone.  Bee Sting was such a proud and feisty vulture that we didn’t believe that at her age, amputation was an option; sadly the decision was made that euthanasia was the only option.

We would like to thank every person who played a role in working with her and saving her over the years. We would also like to thank each and every one of you, who commented on her story and shared it to raise awareness for the plight of our vultures.  Every single vulture is vital to saving the species, Bee Sting’s loss is tragedy that should never have happened.

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.

 

 

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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.

 

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.

OLYMPUS DIGITAL CAMERA
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

How do vultures learn to fly?

Cape Vulture chick flapping wings on the nest ledge
Cape Vulture chick flapping wings on the nest ledge

Vultures are big heavy birds that can look quite comical with their funny hopping walk on the ground.   Watch them in the air and it is a completely different picture, graceful, powerful and free they can soar and glide for hours as they ride the thermals searching for food.  Vultures are specially built to soar beautifully, their wings are huge and they have short tails.

The Cape Vulture nests on rocky ledges and cliff faces in a nest made of grass and sticks.  Vulture chicks are often seen practicing flapping their wings while they are on their nest ledges, sometimes flapping so hard that they lift off the ledge a little bit.  When the wind picks up they open their wings to feel the wind through them – this may be a way of learning how to feel and use the wind when they do fly.

Watching vultures coming in to land at VulPro’s restaurant, you start to appreciate what skilled flyers they are.  Watching their wing feathers flare on one side while the curve the wing more on the other to change direction, slowing right down to check their specific landing spot or changing their minds and soaring off again.

Dating on the Fly

A vulture’s version of dating is soaring around each other in the sky, with the male behaving like a fighter pilot, showing off his skills by almost touching the female’s wing tip as he flies.  Vultures are very sociable in their colonies, but when it comes to pairing up and breeding, they mate for life.

Fledging

Vulture chicks fledge, or take their first flight, at around 140 days after hatching.  They are the same size as their parents but not quite as heavy and they have their full feathers just their colouring is different showing their youth.

Nature vs Nurture

Birds are born with the instinct to fly; they do still have to learn the mechanics of it though, a little like our parents helping us learn to walk.

It is thought that the vulture chicks build their bravery, strength and muscle development with their wing flapping on the ledge to be able to take the first leap.  Relatively speaking, it appears that the leap and subsequent gliding is easy for them, the difficulty and challenge occurs when they need to get back onto the cliff.  This takes more, skill maneuverability and stamina, and is often the reason that we find so many grounded young fledglings, a bit like us learning to drive, they have the forwards part down pat, but the parking skills are sadly lacking.

There are also reports of parents who” kick” the fledgling out of the nest; this may involve stopping feeding the chick or not allowing the chick to roost on their ledge as well as the literal kick out the nest.  This is nature’s way of making sure that the parents are able to hatch their next egg and raise the next chick. Only with practice do they learn the ropes and develop the muscles necessary to flap their wings to their fullest potential.