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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Parts of a Vulture

For those of you who are keen to learn about the different parts of a vulture, we have a series of labelled photos for you, to keep it interesting.  This is of course not every part of a vulture, but gives you a good idea of the different flight feathers etc.

Please feel free to email mandyschroder.uron@gmail.com should you have any queries, or comment on the post and we will get back to you as quickly as possible with answers.

Vulture Head Anatomy
Vulture Head Anatomy

 

Overview of Anatomy of a Vulture
Overview of Anatomy of a Vulture

 

Vulture Foot Anatomy
Vulture Foot Anatomy

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.” (http://www.iaszoology.com/flight-adaptations/)

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.

Wings       

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.” (www.dictionary.com/browse/pneumatization)

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)]

ANATOMICAL ADAPTATIONS

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: http://tabletopwhale.com/2014/10/24/3-different-ways-to-breathe.html)

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.

Metabolism

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.

References:
Sabi Sabi Wild Facts: Vultures
http://www.iaszoology.com/flight-adaptations/ http://themysteriousworld.com/10-highest-flying-birds-in-the-world/ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3140315/ http://jeb.biologists.org/content/214/15/2455 http://www.mnn.com/earth-matters/animals/photos/9-birds-that-set-records-for-their-amazing-flights/highest-flier http://blogs.bu.edu/bioaerial2012/2012/09/26/the-ruppells-griffon-vulture-the-highest-recorded-flying-bird/

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.

 

Sizzle our Electric Fence Vulture

ElectricityWarningSizzle (Tag B432) a Cape Vulture (Gyps coprotheres) was rescued on the 10th of November 2010 in the Damdoryn area of Brits in the North West Province, South Africa.  Sizzle had decided to go through a property’s electric fence and in trying to get through had burnt his neck severely.  Ordinarily an electric fence has up to 6000 volts running through it; this is what is legally acceptable in South Africa.  Kerri has rescued many vultures stuck in electric fences and never before or since seen the kind of burns that Sizzle experienced – leading her to believe that the voltage on that particular fence was much higher.

On initial inspection, Sizzle had a few singed neck feathers as would normally be expected from an experience like this.  Then he started to breathe strangely, making a horrible gargling sound in his throat, not understanding what was causing the problem, he was rushed through to the Exotic Animal Clinic at Onderstepoort.

Sizzle was anaesthetised and the vet checked inside his mouth, normally an endoscope would be used to examine all the tissue in Sizzle’s throat, in this case, his throat was so swollen that the vet couldn’t get the endoscope down his throat.  Using long thin forceps, the vet was able to ascertain that there was necrotic burnt tissue inside Sizzle’s throat, blocking his trachea (air passage).  Not only was this excruciatingly painful, threatened Sizzle’s ability to breathe, the risk of infection from dead and dying tissue all of which would have killed Sizzle without veterinary intervention.

Poor Sizzle had to be anaesthetised and treated every third day for the next few weeks – this meant that the vet had to scrape and remove all of the dead tissue in Sizzle’s trachea and oesophagus.  After that he was treated once a week until he had healthy tissue left in his trachea and oesophagus.

He was kept with Puff Adder (Read Puff Adder’s Story) for few weeks to make sure that he was strong enough to survive after being released and could eat and breathe with no issues.

Electric Fences

South Africa is a country with a high crime rate and electric fences are the go to first line of defence against intruders.  What we often forget about are the wildlife who have to move in and out of our gardens in order to survive.  Snakes, mice, chameleons, hedgehogs, large insects and birds are all at risk of electrocution if the fence is not legally compliant.  Pets are also at risk should a dog get stuck under an electric fence that isn’t legally compliant.

Whilst we all need to remain safe and secure in our houses, please remember that we need to keep our wildlife safe as well.  Sizzle is the perfect ambassador for the implications of illegally designed security measures.  He was released with Puff Adder on the 19th of December 2010.

Release Puff Adder and Sizzle
Release Puff Adder and Sizzle

Electrical Burns

Familiarise yourself with what to do should a person or animal be stuck in your fence:

  • Turn the fence off or move the animal away from the fence using a dry, non-conducting object made of cardboard, rubber or wood.
  • Know how to perform CPR on animals, especially if you really love your dogs and cats
  • Keep the animal warm as shock can cause a significant drop in body temperature.
  • If clean gauze or a sterile dressing is available then cover any external burns. Do not use cotton wool or material with fibres as they will stick in the wounds.
  • Get the animal to a vet immediately, many electrical burns are worse on the inside than you would expect from the external signs on their body.
  • Make sure that your electric fence is legally compliant with current legislation

“Puff Adder” Vulture (Tag B430)– first vulture in the world to be treated with snake anti – venom

Puff Adder starting to swell
Puff Adder starting to swell

Puff Adder a Cape Vulture (Gyps coprotheres) as he became affectionately known arrived at VulPro on the 5th of November 2010.  He was a grounded fledgling that had got himself into trouble due to bad weather.  This happens so often with young fledgling vultures, gardens, swimming pools, dogs and electric fences can all cause huge problems for young, inexperienced vultures.  They end up on the ground without enough space or possibly strength to take off again, left alone they die.

VulPro rushed out and rescued him, taking him back to VulPro to be fattened up a bit and grow stronger, before being tagged and released. “Puff Adder” had been at VulPro a couple of weeks when on the 27th of November 2010, Kerri arrived back at VulPro with an electrocuted vulture (Read Sizzle’s story here) to find Puff Adder screaming in agony and running backwards in his enclosure.

He was quickly caught and inspected, with a single puncture wound being discovered on his neck.  Kerri and her team suspected a snake bite, although the snake was never seen and apart from screaming from shock and / or pain, Puff Adder showed no other symptoms yet.

Kerri rushed Puff Adder to the Exotic Animal Clinic at Onderstepoort to be treated by Dr Francois Le Grange.  By now Puff Adder had started to swell, a huge concern was that his throat would swell so much that he wouldn’t be able to breathe.  Oxygen was administered and Puff Adder was also put on a drip.

Interesting Fact:

The Puff Adder (Bitus arietans) is responsible for causing the most snakebite fatalities in Africa owing to various factors, such as its wide distribution, frequent occurrence in highly populated regions, and aggressive disposition.  It is a sluggish snake that relies on camouflage for protection, most bites occur because the snake is stepped on.  The Puff Adder bite is severely cytotoxic (kills cells) and is responsible for severe pain and swelling leading to tissue necrosis.

Puff Adder
Puff Adder

After a lot of careful thought, it was decided to treat Puff Adder with anti-venom.  This had never before been done with a vulture, and both Kerri and Dr Francois Le Grange had no idea whether it would help or hurt Puff Adder, they just knew that they had to do something or he would die.  His symptoms were worsening and not being able to breathe was a very real problem.

Two vials of anti-venom were administered to Puff Adder and he thrived! There was no tissue necrosis (dead tissue), within a week the swelling started to go down.

Puff Adder on a drip
Puff Adder on a drip

Puff Adder was in the ICU (Intensive Care Unit) at Onderstepoort on a drip for 3 days, to make sure that he was properly hydrated, he then returned to VulPro and was kept in a crate (specialised vulture transport crates) for a few days on a drip to make 100% sure that he was healthy.

One month later, Puff Adder was healthy enough to be tagged and released.  On the 16th of July 2011, Puff adder was resighted feeding on a carcass at Shelanti Game Reserve.  This is the reason that it is so wonderful when people share their resightings of tagged vultures with us.  We add the sightings to our database and it allows us to track these vultures.  We haven’t had any resightings since then, but we are thrilled with the confirmation that Puff Adder was alive a year after his ordeal.

Why is Puff Adder’s story so important?

Living in Africa especially on plots, farm land or in the bush makes sure that wild life becomes a factor in your life – good or bad!  We recommend that you should be aware of and have basic knowledge about the snakes that reside in your area.  We don’t support killing them; rather relocate to a place where human interaction is limited.

It is important for you to know, how poisonous they are, what type of venom they have ie what the symptoms are and how to treat a snake bite.  This is important not only for you and your friends and family but for your pets and livestock as well.  Kerri and Dr Le Grange ensured that Puff Adder experienced minimal damage from the Puff Adder bite because he was treated so quickly.  Left untreated for longer because of the position of the bite it is almost certain that Puff Adder would have died.

Bee Sting our vulture with 9 lives! – Bee Sting’s Story Part Five

The wounds on Bee Sting's wing
The wounds on Bee Sting’s wing

After Bee Sting’s visit at Millstream Primary School and rescue by VulPro, she spent some time at VulPro before being released again.  We all gave a big sigh of relief hoping that Bee Sting would now keep her life a little simpler and give us fewer grey hairs.  Sadly this hasn’t been the case; about 10 days ago we had to fetch Bee Sting from Caribbean Beach in Hartbeespoort, she was brought back to VulPro and initially we didn’t realise what had happened to her.  She was able to fly to the top of the 9m enclosure and was her usual cheeky self, our plans were to let her settle again, make sure that she was well fed and then re-release her.  Bee Sting has an incredibly strong and stubborn personality which had helped save her life when she was stung by over 220 bees Bee Sting’s Story Part One, little did we know that her will to live had been tested again.

On the 26th of June, we noticed some blood on Bee Sting from her right wing, our vultures’ health is always very important, so we caught Bee Sting to find out what the injury is.  Imagine our horror when we discovered a burnt area on her right wing and some singed feathers – the only conclusion is a power line electrocution, which this miracle vulture survived.

When we collected Bee Sting she was on the ground in close proximity to a power line but because she showed no sign of injury and was able to fly, we didn’t realise that she had in fact been electrocuted and without another one of her “extra lives” would have been found dead.   Read about power lines here.

Getting rid of burnt and dead skin
Getting rid of burnt and dead skin

Bee Sting’s electrical burn was treated and healing well, until the itching and irritation of the healing process caused Bee Sting to “help” her healing process a little too much and she caused some new wounds.  This is very similar to when we have a cut or graze that is healing and we end up scratching it until it is sore or bleeding because the itching is driving us crazy.  The difference is we can be told to leave it alone and why, vultures don’t understand that rubbing and scratching their injuries only makes it worse.

Dr Dorianne Elliot treating Bee Sting at the Exotic Bird and Animal Clinic in South Africa
Dr Dorianne Elliot treating Bee Sting at the Exotic Bird and Animal Clinic in South Africa

Bee Sting was rushed to Dr Dorianne Elliot at the Bird and Exotic Animal Hospital at Onderstepoort, North of Pretoria for treatment and to try and save her wing.  Bee Sting has a hole right through the joint of her wing and shows some signs of infection, the tendons and ligaments are exposed and she has torn the follicle capsule on one of her primary wing feathers.  The original burns are healthy and very close to fully healed.  To prevent Bee Sting from “helping” heal her injuries, the innovative Dr Elliot devised a cap of fibreglass cast to stop Bee Sting from picking at the wounds as they continue healing.

Soft bandage padding
Soft bandage padding

The wounds were flushed and treated with an anti-bacterial ointment and then covered with a bandage and the fibreglass cap was placed over the bandage.

Great care has to be taken to protect the blood supply to a vulture’s wings as the blood vessels are very close to the skin with very little protection.  As far as we are aware a “cap” like this has never been used on a vulture before, so our brave, tough and cat-like

Bee Sting with her fibreglass "wing cap"
Bee Sting with her fibreglass “wing cap”

Bee Sting is proving to be a trailblazer all over again.

In spite of Bee Sting appearing to have 9 lives, we can’t risk her life.  This miracle vulture is going to live out her days in our important captive breeding programme run at VulPro.  The wild Cape Vulture numbers are so low, that literally every vulture counts to save the species.  At VulPro, Bee Sting can continue to supplement wild populations with her chicks and her legacy will live on.

If anyone would like to support Bee Sting, they will be able to adopt her by contacting either Kerri Wolter kerri.wolter@gmail.com or Mandy Schroder mandyschroder.uron@gmail.com to arrange this.

Bee Sting Adoption appeal

We would also like to invite you to come and visit Bee Sting and our other vultures at the centre, experience first-hand how important our work is, but most importantly come and see how special, intelligent and what characters our vultures are.