Thread by @IBIS_journal

It’s time for another #ORNITHOLODAY! Tweeting today are @hemmingsnicola1, members of her @sheffieldAPS team including @fay_morland, and collaborators @ZSLScience @kikaB8 & @Belfast_Ash9 (we’ll introduce ourselves properly shortly!) #ornithology #teamegg

@HemmingsNicola1 @SheffieldAPS @fay_morland @ZSLScience @KikaB8 @Belfast_Ash9 Today’s #ORNITHOLODAY is all about #eggs! #oology #ornithology #teamegg

We’ll be delivering dozens of amazing egg facts throughout the day (08:00-15:00 UTC) #ORNITHOLODAY #teamegg

We’ll also be talking about our research on why eggs fail - including demos of how to examine unhatched eggs live from our @sheffieldAPS lab! #ORNITHOLODAY #teamegg

All our tweets will have the hashtags #ORNITHOLODAY #teamegg so you can follow us throughout the day for lots of #ornithology & #oology fun!

We’re happy to answer any questions you have throughout the day, & feel free to follow our personal accounts if you want to keep up with our work in the future: @HemmingsNicola1 @fay_morland @kikaB8 @Belfast_Ash9 #ORNITHOLODAY #teamegg

First, some introductions… #ORNITHOLODAY #teamegg

First up it’s me, Dr Nicola Hemmings @HemmingsNicola1. I’m a @royalsociety Dorothy Hodgkin Research Fellow @sheffieldAPS studying bird reproductive behaviour & physiology. I’m particularly interested in the causes of hatching failure in birds #ORNITHOLODAY #teamegg

I’m also mum of two baby girls, who are already starting to develop their ornithological identification skills #ORNITHOLODAY #teamegg

My @sheffieldAPS group includes two PhD students, @fay_morland & Duncan Jackson, @kassersohn who recently completed her Masters & starts her PhD in Sept, research technician Paul Richards, & post-doctoral researcher @JL_Savage #ORNITHOLODAY #teamegg

Find out more about my team & what we all do here nicolahemmings.wordpress.com/people/ #ORNITHOLODAY #teamegg

I also co-supervise PhD student @Belfast_Ash9 in collaboration with @ZSLScience Research Fellow Dr Patricia Brekke @kikaB8, who I’ll hand over to next! #ORNITHOLODAY #teamegg

Hi I’m Dr Patricia Brekke (@KikaB8), I am a research fellow in conservation biology @ZSLScience. Fascinated by the natural world and how to preserve it. @OfficialZSL #ORNITHOLODAY #teamegg

I apply evolutionary genetics concepts and tools to conservation issues. @KikaB8 @OfficialZSL @ZSLScience #ORNITHOLODAY #teamegg #ornithology #conservation

My main model system is an amazing NZ bird called the hihi or stitchbird. I have been studying this little “ray of sunshine” for 15 years. @KikaB8 @OfficialZSL @ZSLScience #ORNITHOLODAY #teamegg

Hihi have high levels of hatching failure ~ third of their eggs fail to hatch. @KikaB8 @OfficialZSL @ZSLScience #ORNITHOLODAY #teamegg

When you have only a few thousand of these incredible birds left in the world EVERY egg counts! @KikaB8 @OfficialZSL @ZSLScience #ORNITHOLODAY #teamegg #conservation

Hihi were once common in NZ but only one natural population left. Seven reintroduced pops have been established as part of its recovery program. @hihinews @KikaB8 @OfficialZSL @ZSLScience #ORNITHOLODAY #teamegg Image credit: ZSL

Also contributing to the #teamegg #ornitholoday today is @fay_morland, @royalsociety funded PhD student @sheffieldAPS #ORNITHOLODAY #teamegg

Hello! I’m Fay @fay_morland and I’m in the 1st year of my @royalsociety funded PhD project with @HemmingsNicola1 & @KikaB8 at @sheffieldAPS & @ZSLscience on hatching failure in the #hihi, a bird endemic to New Zealand. @hihinews #ORNITHOLODAY #teamegg Photo: Eric Wilson

#Hihi are a @IUCN vulnerable species and we hope that studying causes of hatching failure in this bird will help us improve #conservation strategies for the hihi and other threatened and inbred species #ORNITHOLODAY #teamegg

I use genetic, behavioural and environmental data to study causes of hatching failure. My #PhD has been full of learning new field & lab skills such as DNA extractions with @KikaB8, microscopy with @HemmingsNicola1 & bird ringing with @SorbyBreckRG #ORNITHOLODAY #teamegg

I can’t wait for my first field season on #TiritiriMatangi island working with @MhairiMcReady of @docgvtnz to get my head around the problems the #hihi face! But for now, find me in the lab examining formalin preserved hihi eggs #ORNITHOLODAY #teamegg

Finally, @ZSLScience PhD student @Belfast_Ash9 will also be tweeting about her work throughout the day... #ORNITHOLODAY #teamegg

Hi! I’m Ashleigh @Belfast_Ash9, a 1st year @London_NERC_DTP PhD student @ZSLScience and @UCL looking at hatching failure in managed populations. As well as @KikaB8 & @HemmingsNicola1, I am supervised by Prof Francois Balloux (@BallouxFrancois) @UGI_at_UCL #ORNITHOLODAY #teamegg

As part of my research I am examining unhatched eggs from UK populations, including @OfficialZSL, to investigate why some eggs don’t hatch. I'll also be using long-term zoo records as part of an interspecific meta-analysis of hatching failure #ORNITHOLODAY #teamegg

In May I spent time @sheffieldAPS meeting everyone & learning methods I will be using in my #PhD (more on those later!). I spent lots of time in the lab, had a session on bird ringing, & enjoyed exploring Sheffield & the Peak District #ORNITHOLODAY #teamegg Photo: @fay_morland

In Sept I am travelling to New Zealand for fieldwork, visiting some of the fantastic conservation programmes there & collecting data on some of their amazing bird species, including kakī & tuturuatu with @testeeves & the #ConSERTeam, more on this later! #ORNITHOLODAY #teamegg

We’ll also introduce some other colleagues and collaborators later. Some are not on Twitter but have kindly provided information & images for us to share with you today! #ORNITHOLODAY #teamegg

Now a little about where we work, @sheffieldAPS & @ZSLScience - two fantastic places for studying #ornithology & #oology #ORNITHOLODAY #teamegg

The Zoological Society of London (ZSL, @officialZSL) is steeped in ornithological history. Charles Darwin became a Fellow here in 1837, donating most of his bird, nest and egg collections to the then museum of ZSL @ZSLLibrary #ORNITHOLODAY #teamegg

ZSL’s first curator John Gould together with his wife Elizabeth Gould catalogued and classified #Darwin’s Beagle expedition bird specimens @ZSLLibrary #ORNITHOLODAY #teamegg #ornithology #history

The @ZSLlibrary still holds some of the most globally important texts and illustrations of birds and eggs. The oldest egg book in our collection is from 1737 by Giuseppe Zinanni @ZSLLibrary #ORNITHOLODAY #teamegg zsl.org/blogs/artefact… Image credit: @ZSLLibrary

If you want to see more egg literature our library is open to the public @ZSLLibrary (zsl.org/about-us/zsl-l…) #ORNITHOLODAY #teamegg

Here are some beautiful illustrations of the Great Auk from @ZSLlibrary - egg collectors contributed to this species extinction in 1844 and highlights some of the threats birds still face today #ORNITHOLODAY #teamegg Image credit: @ZSLLibrary

At @OfficialZSL and @ZSLScience our emphasis is the #conservation of threatened birds by developing captive breeding programmes and the science behind the conservation and management of wild threatened bird species. #ORNITHOLODAY #teamegg

#teamegg tweeters @kikaB8 & @Belfast_Ash9 are based @ZSLScience, while @HemmingsNicola1 & @fay_morland are at @sheffieldAPS @sheffielduni - another wonderful department for #ornithology research #ORNITHOLODAY

A walk down @sheffieldAPS’s corridors looking at the research posters says it all! #ORNITHOLODAY #teamegg #ornithology

And a few more @sheffieldAPS… #ORNITHOLODAY #teamegg

We also have the fantastic @ADMSheffield with its own beautiful historic egg collections @sheffieldAPS - come visit us! sheffield.ac.uk/alfred-denny-m… #ORNITHOLODAY #teamegg

It’s a fantastic place for an ornithologist to work, which is perhaps why Nicola has stayed for 16+ years, ever since her undergraduate degree! @sheffieldAPS #ORNITHOLODAY #teamegg

Later today, we’ll be showing you 1st-hand how we investigate the causes of hatching failure in our @sheffieldAPS lab. Before that, we want to share just how awesome bird eggs are #ORNITHOLODAY #teamegg

So grab a tea & get ready for some egg-cellent facts coming up at 10:30 BST (09:30 UTC)! #ORNITHOLODAY #teamegg

[ADMIN] Sadly the exaction of the Great Auk pre-dates @IBIS_journal (and we're 160 years old!), but in the early years we published several papers on Great Auks and their eggs onlinelibrary.wiley.com/action/doSearc… | #ORNITHOLODAY #ornithology #oology

[ADMIN] We've got several papers on the Hihi in @IBIS_journal's 160-year archive onlinelibrary.wiley.com/action/doSearc… | #ORNITHOLODAY #ornithology #oology

#Bird #eggs are special. They contain everything the embryo needs to develop from start to finish. Self-contained life-support systems. #ORNITHOLODAY #teamegg Photo: @HemmingsNicola1

#Bird #eggs are also incredibly diverse in shape, size, colour, & pattern. This isn't just random variation (figure from science.sciencemag.org/content/356/63…) #ORNITHOLODAY #teamegg

Eggs can exhibit incredible shape and pattern variation even within species #ORNITHOLODAY #teamegg

Eggs are a huge investment for female birds. Just take a look at this X-ray of a kiwi carrying her complete, shelled egg. This kiwi would laugh at human childbirth. Image source: audubon.org/news/why-kiwis… #ORNITHOLODAY #teamegg

In fact, kiwi eggs represent 20% of the female’s entire body weight. This is the largest ratio in any bird #ORNITHOLODAY #teamegg Video: @Kika_B8

*extinction 😒

The smallest female to egg ratio comes from the largest bird: ostrich eggs are just 2% of the female’s body weight! #ORNITHOLODAY #teamegg

The now extinct elephant-bird eggs dwarf kiwi, ostrich, and even moa eggs at a whopping 33 x 24 cm in size! Want to know more about elephant-birds check out the work of @JamesHansford5 @ZSLScience @OfficialZSL #ORNITHOLODAY #teamegg

Birds only make a single egg at a time, & it usually takes just 1 day from release of the ovum (or yolk) from the ovary to the fully hard-shelled egg being laid #ORNITHOLODAY #teamegg

There are exceptions to this - some #cuckoos for example, produce an egg every 2 days, retaining their eggs inside their reproductive tract for an additional 24h to give the embryo a developmental ‘boost’ royalsocietypublishing.org/doi/full/10.10… #ORNITHOLODAY #teamegg

Do you know how the egg is put together inside a female bird’s reproductive tract? You’re about to find out! #ORNITHOLODAY #teamegg

First, the ovum - or yolk - is released from the ovary. Prior to ovulation, yolk is built up in individual follicles in the ovary, which ends up looking like a big bunch of orange grapes #ORNITHOLODAY #teamegg

Sitting as a tiny target on the relatively massive yolk is the germinal disc. This looks like a white dot, & it contains the female genetic material. Look closely next time you crack open a chicken egg - you'll spot it #ORNITHOLODAY #teamegg Photo: @HemmingsNicola1

The newly ovulated ovum is surrounded by the "inner perivitelline layer", essentially a bag that holds the yolk together. In order to fertilise the egg, sperm must penetrate this layer & enter the ovum #ORNITHOLODAY #teamegg

Lots of sperm usually penetrate & enter a bird's ovum. This is what the inner perivitelline layer looks like under the microscope after sperm have dissolved their entry holes to get in. Entry of multiple sperm into the ovum is called polyspermy #ORNITHOLODAY #teamegg

Polyspermy in birds is different to polyspermy in mammals (including us), where the egg can be destroyed if multiple sperm enter #ORNITHOLODAY #teamegg

In birds, polyspermy is actually NEEDED for normal embryo development - only one sperm is required for fertilisation, but more than one sperm must reach the germinal disc in order for the resulting zygote to survive rspb.royalsocietypublishing.org/content/282/18 #ORNITHOLODAY #teamegg

Just 15 min after ovulation, a second layer begins forming around the yolk. This "outer perivitelline layer" is made up of glycoproteins secreted from the female's reproductive tract #ORNITHOLODAY #teamegg

The glycoprotein layer essentially 'glues' all sperm present at the site of fertilisation onto the yolk. If you take a fertilised egg yolk & remove this layer, you can see all the trapped sperm under the microscope! #ORNITHOLODAY #teamegg

Next time you puncture an egg yolk with your fork, it's this layer you're breaking to allow the yolk to ooze out. If you cut the yolk in half with scissors, pick up 1 half & wash the yolk off with water, the perivitelline layer is what you are left with #ORNITHOLODAY #teamegg

We’ll show you how to do this later when we demo some egg dissections live from the lab! #ORNITHOLODAY #teamegg

Once the outer perivitelline layer is formed, sperm can no longer penetrate the egg. If the ovum isn't fertilised in that 15min window, it will remain unfertilised #ORNITHOLODAY #teamegg

Regardless of whether or not the ovum is fertilised, once there is a yolk in the oviduct, egg formation will proceed. This is why we have tonnes of unfertilised chicken eggs lining our supermarket shelves #ORNITHOLODAY #teamegg

Unfertilised eggs can show embryo development – parthenogenesis occurs frequently in birds and reptiles e.g. komodo dragon at London zoo @ZSLScience @ZSLOfficial & zebra finches @sheffieldAPS onlinelibrary.wiley.com/doi/abs/10.111… #ORNITHOLODAY #teamegg

After the outer pervitelline layer is formed, the egg then begins its journey down the long, winding reproductive tract of the female, gaining albumen, shell membranes, fluids & more, & beginning to acquire its egg-like shape #ORNITHOLODAY #teamegg

The female, via her oviduct, provides all the egg's vital ingredients #ORNITHOLODAY #teamegg

Shell formation begins only once the egg reaches the uterus (which looks like a swollen purple pouch). If you want to know what an egg looks & feels like before the shell forms, pop one in some vinegar & find out! imaginationstationtoledo.org/educator/activ… #ORNITHOLODAY #teamegg

The egg spends around 6 hours in the uterus, as a protective layer of calcium carbonate is built up across the shell membrane surface #ORNITHOLODAY #teamegg

Shell thickness varies markedly across birds. Moa eggs are thin-shelled: even the largest have shells thinner than 2 mm, whereas ostrich eggshell is about 2 mm thick and that of the elephant-bird may exceed 4mm. Photo: @zsllibrary #ORNITHOLODAY #teamegg

Tiny gaps exist between the columns of calcium carbonate that make up the shell. These are not flaws - these pores are crucial for gas exchange. Without them, the embryo wouldn't get enough oxygen #ORNITHOLODAY #teamegg Image: The balancing act - Ostrich egg by Johanna Arenas

The shell is also coated with a layer of proteins & lipids, crucial for strength, waterproofing, & antimicrobial defence #ORNITHOLODAY #teamegg

Some eggs are also pigmented at this point - there are a huge array of colours and patterns, both within & across species #ORNITHOLODAY #teamegg Photos: @HemmingsNicola1

During shell formation, the egg probably turns in the uterus. This isn't 100% verified, but evidence from scans of birds during egg production suggests so. Plus, it's likely the egg enters uterus pointy end first, but eggs are usually laid blunt end first #ORNITHOLODAY #teamegg

Within just a couple of hours of the egg being laid, the next ovum is ovulated, & the whole process starts again. This is repeated until the bird has completed her clutch #ORNITHOLODAY #teamegg

Did you know birds can have twins? It’s rare, but #hihi twins were found in 2004 onlinelibrary.wiley.com/doi/abs/10.111… @informedbird @hihinews @ZSLbirds @ZSLOfficial #ORNITHOLODAY #teamegg Photo: R.Thorogood

Those hihi twins didn’t survive to hatch, but other avian twins have done (albeit rarely) - including one case of genetically identical emu twins! cambridge.org/core/journals/… #ORNITHOLODAY #teamegg

Hopefully we’ve persuaded you that #eggs are amazing (as if you needed persuading)! Now for a bit more of a focus on our own current research #ORNITHOLODAY #teamegg #ornithology #oology

A key aim of our work is to understand the causes of hatching failure in birds #ORNITHOLODAY #teamegg #ornithology #oology #conservation

Hatching failure is a surprisingly common problem for birds #ORNITHOLODAY #teamegg

Hatching failure occurs in ALL bird species - on average, around 10% of all bird eggs fail to hatch (excluding those lost to predation/desertion) #ornitholoday #teamegg

Rates of hatching failures across bird species were first reviewed by Walter Koenig (1982) pdfs.semanticscholar.org/59be/fb3eda0ab… #ORNITHOLODAY #teamegg

There is huge variation in hatching failure rates across species & populations, with hatching failure exceeding 60-70% in some endangered birds #ORNITHOLODAY #teamegg #conservation

Despite the importance of hatching failure for conservation efforts, the mechanisms underlying egg failure are poorly understood #ORNITHOLODAY #teamegg

Here in our lab, we start from a fundamental question - is hatching failure due to fertilisation failure or embryo death? #ORNITHOLODAY #teamegg

Fertilisation failure tells us that there was some problem with sperm reaching or penetrating the egg #ORNITHOLODAY #teamegg

Embryo death tells us that sperm got there fine, fertilisation took place, but then something else caused the zygote/embryo to stop developing #ORNITHOLODAY #teamegg

The factors driving these two causes of hatching failure are likely to be very different, so distinguishing between them is important. But it can also be quite tricky... #ORNITHOLODAY #teamegg

First, the germinal disc of an undeveloped egg often doesn’t look very different to that of an unfertilised egg - you only start seeing obvious signs of embryonic development after ~ 2-3 days of incubation #ORNITHOLODAY #teamegg

Second, unhatched eggs are usually collected from the field several days or even weeks after the other eggs in the nest hatched, which means their contents usually resemble a murky (& smelly) soup! Photo: @HemmingsNicola1 #ORNITHOLODAY #teamegg

However, in our lab we’ve developed & refined methods to allow us to examine even the grottiest of eggs to determine their fertility status onlinelibrary.wiley.com/doi/abs/10.111… #ORNITHOLODAY #teamegg

Want to know how we do it? Join us in the lab at 13:00 for some live egg dissection action! We're heading off for an early lunch break now, but join us back here then to learn more! #ORNITHOLOGY #teamegg

That's 13:00 BST (12:00 UTC) - see you in the lab! #ORNITHOLODAY #teamegg #ornithology #oology

We're back, & @HemmingsNicola1 & @fay_morland are in their @sheffieldAPS @sheffielduni lab assessing fertility status of unhatched eggs #ornithology #oology #ORNITHOLODAY #teamegg

What do you need to examine an unhatched egg? Let us show you! #ORNITHOLODAY #teamegg

First, some basic dissection tools - fine forceps, scissors, dishes for putting egg contents in #ORNITHOLODAY #teamegg

And no egg dissector's kit is complete without one essential homemade tool - the "hair-loop" #ORNITHOLODAY #teamegg

Making these is a right of passage in @HemmingsNicola1's lab. Pluck a hair from your (or an unsuspecting lab mate's) head, form a small loop, & tape it to the end of a pipette tip. Simple! We'll show you what we use it for later #ORNITHOLODAY #teamegg

You'll also need: pipettes (P20 & P200 essential, full set of sizes is desirable)... #ORNITHOLODAY #teamegg

...phosphate buffered saline solution (PBS)... #ORNITHOLODAY #teamegg

...Hoechst 33342 fluorescent DNA stain... #ORNITHOLODAY #teamegg

...& microscope slides, sample tubes, etc #ORNITHOLODAY #teamegg

In terms of lab equipment, you'll need a stereomicroscope ideally with gooseneck lighting - here are ours #ORNITHOLODAY #teamegg

...and a compound microscope with darkfield and fluorescence illumination #ORNITHOLODAY #teamegg

Now we've got our kit ready, let's get cracking (get it?) #ORNITHOLODAY #teamegg

We’ll start simple - let’s take a nice fresh egg (this is a zebra finch egg) #ORNITHOLODAY #teamegg

Open the egg & pop the yolk into a dish with some PBS #ORNITHOLODAY #teamegg

Locate the germinal disc (GD) - as we mentioned earlier, it’s a fairly conspicuous white spot on the yolk (ignore the bright spots either side reflecting from the lights, it’s the disc in the middle we're talking about) #ORNITHOLODAY #teamegg

Now we need to cut through and remove the perivitelline layer (PVL) that surrounds the yolk. The yolk will start to collapse as soon as you cut it, so you have to go fast! #ORNITHOLODAY #teamegg

Technique here depends on egg size - with a large chicken egg you should aim to cut a section of PVL from above the GD. Smaller eggs like this zebra finch one can simply be cut in half #ORNITHOLODAY #teamegg

Once cut, carefully lift the PVL away from the yolk & put it into a clean dish of PBS. It'll be fine in there for a bit while you move onto the GD #ORNITHOLODAY #teamegg

Now for the germinal disc. Time for the first use of our bespoke hair-loop tool. Carefully slide the hair-loop under the GD & lift it away from the yolk #ORNITHOLODAY #teamegg

Under a stereomicroscope, use the hair-loop to gently flick away adhering yolk until you’re left with the isolated white germinal disc #ORNITHOLODAY #teamegg

To check whether the GD contains embryonic cells i.e. was fertilised and started developing, pipette part or all of the GD onto a microscope slide, stain with Hoechst 33342, & view under a fluorescence microscope #ornitholoday #teamegg

The GD of a fertilised egg will contain thousands of cells even when it is freshly laid (cells have been dividing for almost 24 h before laying) #ORNITHOLODAY #teamegg

Stained with Hoechst & viewed under fluorescence, the nuclei of those cells shows up bright blue! You’re looking for numerous regularly shaped nuclei #ORNITHOLODAY #teamegg

You can also use Hoechst stain to check for the presence of sperm on the perivitelline layer #ORNITHOLODAY #teamegg

Clean the PVL in PBS, using the hair-loop to flick away yolk until you’re left with what looks like a piece of clingfilm #ORNITHOLODAY #teamegg

This piece of PVL is actually both the inner and outer PVL stuck together. It can be useful to separate the two layers if you want to accurately count holes made by sperm entering the egg #ORNITHOLODAY #teamegg

For some species, it’s possible to separate the layers manually. Passerine eggs are particularly easy (example in video is zebra finch - apologies for faffing, it's not *that* easy!) #ORNITHOLODAY #teamegg

But it is easier than other (including chicken eggs), which require chemical separation #ORNITHOLODAY #teamegg

Spread the PVL onto a microscope slide - this takes some practice! Try to get the PVL as flat as possible without damaging it too much in the process #ORNITHOLODAY #teamegg

Add Hoechst on top of the PVL, leave to soak in for 5 mins, then view under the microscope - the heads of the sperm are packed with DNA, so they will stain bright blue #ORNITHOLODAY #teamegg

Using darkfield microscopy you can also look for holes made in the inner PVL by sperm that entered the egg #ORNITHOLODAY #teamegg

Darkfield microscopy is a method that excludes unscattered beam from the image, creating a kind of negative of the brightfield image. Since the background is black, the black holes in the whitish PVL are very easy to spot #ORNITHOLODAY #teamegg

What we've described so far is the most straightforward version of how to determine if an egg has been fertilised or not (note you can also use these methods to count how many sperm reached & penetrated eggs), with a nice fresh egg #ORNITHOLODAY #teamegg

Unfortunately, not all unhatched eggs are so straightforward #ORNITHOLODAY #teamegg

Most unhatched eggs we work with have been left in a hot, humid nest for several weeks, and have started to seriously deteriorate! #ORNITHOLODAY #teamegg

In addition, fertilised eggs have often developed for some time before they zygote/embryo died, and the greater the development, the worse the deterioration #ORNITHOLODAY #teamegg

If only we could upload smells with our photos! #ORNITHOLODAY #teamegg

In these cases, you need to become an expert at sifting through the smelly #egg soup to find something that might be useful. Luckily, #teamegg are experts in just that! #ORNITHOLODAY

That’s another reason why @fay_morland needs that gas mask! #ORNITHOLODAY #teamegg

The perivitelline layer rarely degrades completely (unless the embryo is well-developed), but it does split & break up, so finding fragments of PVL is sometimes the best we can do #ORNITHOLODAY #teamegg

However, because the germinal disc usually adheres to the perivitelline layer, this is often all we need to confirm if an egg has been fertilised - & to get an idea of how many sperm reached the egg #ORNITHOLODAY #teamegg

Fragments of PVL can be found by diluting egg contents in PBS &a carefully fishing through with forceps - the PVL readily sticks to the ends for forceps #ORNITHOLODAY #teamegg

It’s also very important to look carefully for small embryos. Even relatively well-formed but tiny embryos are easily missed during standard egg break-out, because they're often wrapped up in a bundle of PVL & just look like a blob! #ORNITHOLODAY #teamegg Photo: @Belfast_Ash9

Indeed, the 'blob' slightly north-west of centre in this image was a tiny embryo wrapped up in a blanket of PVL! #ORNITHOLODAY #teamegg

We hope you've enjoyed learning how to dissect unhatched eggs with @HemmingsNicola1 @fay_morland live from their @sheffieldAPS lab. We're taking a short break to tidy up now but back in approx. 30min to talk about the applications of our work. Stay tuned! #ORNITHOLODAY #teamegg

So how do we apply our techniques to real systems? We work with a number of threatened bird populations, helping to inform conservation teams by identifying the causes of hatching failure #ORNITHOLODAY #teamegg

As mentioned earlier, one of the main systems we work on to try to understand the causes of hatching failure in the wild is the #hihi in #NewZealand hihiconservation.com #ORNITHOLODAY #teamegg #conservation

Egg stage has the lowest survival rate of any stage in the #hihi’s development (nestling, fledging or adult) sciencedirect.com/science/articl… @hihinews @Kikab8 @ZSLScience #ORNITHOLODAY #teamegg Photo: Patricia Brekke

Hihi suffer from around 30% hatching failure royalsocietypublishing.org/doi/full/10.10… Non-threatened species on average have 10% hatching failure @ZSLScience #ORNITHOLODAY #teamegg

#Hihi lay an average of four eggs but some females can lay up to six @hihinews @Kikab8 @ZSLScience #ORNITHOLODAY #teamegg Photo: @MhairiMcCready

#Hihi incubate eggs for approx 14 days, which is similar to other small passerine birds @hihinews @Kikab8 @ZSLScience #ORNITHOLODAY #teamegg Photo: @MhairiMcCready

#Hihi embryo death tends to occur early in development up to five days post-laying besjournals.onlinelibrary.wiley.com/doi/full/10.11… royalsocietypublishing.org/doi/full/10.10… @hihinews @Kikab8 @ZSLScience @HemmingsNicola1 #ORNITHOLODAY #teamegg

Young and old females have higher levels of hatching failure besjournals.onlinelibrary.wiley.com/doi/full/10.11… sciencedirect.com/science/articl…) @hihinews @Kikab8 @ZSLScience #ORNITHOLODAY #teamegg

Second clutches or those laid later in the season are less likely to hatch sciencedirect.com/science/articl… @hihinews @Kikab8 @ZSLScience #ORNITHOLODAY #teamegg

Hihi, unlike other bird species, have not changed their lay dates to keep up with climate change onlinelibrary.wiley.com/doi/full/10.11… @hihinews @Kikab8 @ZSLScience @OfficialZSL #ORNITHOLODAY #teamegg

Clutch size, lay date and hatching success are not heritable – #hihi show little genetic variability in traits important to their survival sciencedirect.com/science/articl… onlinelibrary.wiley.com/doi/full/10.11… @hihinews @Kikab8 @ZSLScience @OfficialZSL #ORNITHOLODAY #teamegg

One contributor to hatching failure in hihi is inbreeding, which depresses embryo survival royalsocietypublishing.org/doi/full/10.10… @InvasionEcology @Pettorelli @hihinews @Kikab8 @ZSLScience #ORNITHOLODAY #teamegg

Male embryo hihi are particularly susceptible to inbreeding royalsocietypublishing.org/doi/full/10.10… @InvasionEcology @Pettorelli @hihinews @KikaB8 @ZSLScience #ORNITHOLODAY #teamegg

Most eggs fail in #hihi due to embryo death and this occurs mostly at early stages of development royalsocietypublishing.org/doi/full/10.10… @HemmingsNicola1 @hihinews @KikaB8 @ZSLScience #ORNITHOLODAY #teamegg

This is consistent with what we've found in another passerine species, the zebra finch, where close parental relatedness leads to more embryo death but does not impact fertilisation success nature.com/articles/ncomm… @HemmingsNicola1 @sheffieldAPS #ORNITHOLODAY #teamegg

#Hihi suffer from inbreeding due to small pop size and isolation, but also the effects of founding bottlenecks onlinelibrary.wiley.com/doi/abs/10.111… @Kikab8 @ZSLScience @OfficialZSL #ORNITHOLODAY #teamegg Image credit: ZSL

Female hihi carrying eggs gain up to 43% in body weight - another example of extreme investment! sciencedirect.com/science/articl… Photo: @kika_B8 #ORNITHOLODAY #teamegg

Egg yolk is yellow because it is full of carotenoids, vital antioxidants. Carotenoids in #hihi eggs are lutein (82%) and zeaxanthin (17%) sciencedirect.com/science/articl… Photo: Luis Lachica @hihinews @Kikab8 @ZSLScience #ORNITHOLODAY #teamegg

If we artificially increase these carotenoids in the environment through supplementary feeding their concentration increases in the egg yolk sciencedirect.com/science/articl… academic.oup.com/beheco/article… @hihinews @informedbirds @kirstyjean @Kikab8 @ZSLScience #ORNITHOLODAY #teamegg

#Hihi egg hatch duration ranges from no delay (all eggs hatched within 2 hrs of each other) to 28 hrs, a mean of 10hrs sciencedirect.com/science/articl… @hihinews @informedbirds @kirstyjean @Kikab8 @ZSLScience Photo: @MhairiMcCready #ORNITHOLODAY #teamegg

Larger #hihi broods take longer to hatch sciencedirect.com/science/articl… @hihinews @informedbirds @kirstyjean @Kikab8 @ZSLScience Photo: @MhairiMcCready #ORNITHOLODAY #teamegg

Female hihi cover the first two eggs of the clutch under a cap of nest-lining to prevent males from knowing their reproductive status sciencedirect.com/science/articl… onlinelibrary.wiley.com/doi/full/10.11… Photo: @MhairiMcCready @hihinews @Kikab8 @ZSLScience #ORNITHOLODAY #teamegg

Males gain info on female fertility status by checking her nest for eggs. #Hihi have very high levels of promiscuity onlinelibrary.wiley.com/doi/full/10.11… Video: Patricia Brekke @hihinews @Kikab8 @ZSLScience #ORNITHOLODAY #teamegg

Female #hihi often have laying gaps during laying associated with male harassment and reductions in weight gain tandfonline.com/doi/abs/10.107… #ORNITHOLODAY #teamegg

This Sept, @sheffieldAPS student @fay_morland is starting her first of 3 field seasons on #TiritiriMatangi island, investigating variation in female fertility in hihi. We’re excited to see what she finds! #ORNITHOLODAY #teamegg

In the meantime, she’s enjoying ploughing through dissections of preserved unhatched #hihi eggs from the last TEN YEARS!!! #ORNITHOLODAY #teamegg

So that’s #hihi - what about the other species and conservation teams we work with? #ORNITHOLODAY #teamegg

When Belfast_Ash9 goes to NZ in Sept she will be collaborating with Dr Tammy Steeves @testeeves, Stephanie Galla @sgalla32, & Ilina Cubrinovska @NamesAreHard89 to examine hatching failure in early stages of development in kakī & tūturuatu #ConSERTeam #ORNITHOLODAY #teamegg

Kakī, also called black stilts, are classified as Critically Endangered on the @IUCNRedList, and Nationally Critical in the New Zealand Threat Classification System @sgalla32 @testeeves #ConSERTeam #ORNITHOLODAY #teamegg Photo: Liz Brown

Kakī are monogamous and can form lifelong pairs, but if they can’t find a kakī mate they sometimes breed with poaka (pied stilt). While such hybridisation was an issue in the past it has been reduced by intensive management @sgalla32 @testeeves #ConSERTeam #ORNITHOLODAY #teamegg

Wild kakī lay a clutch of 3-6 eggs (usually 4) between Aug-Dec, with both parents incubating the eggs during the 24-27 day incubation period and looking after the precocial young until fledging @sgalla32 @testeeves #ConSERTeam #ORNITHOLODAY #teamegg

Some of the main threats to kakī are habitat loss, human disturbance, and predators (especially introduced mammals) @sgalla32 @testeeves #ConSERTeam #ORNITHOLODAY #teamegg

Kakī also experience about 28.4% hatching failure onlinelibrary.wiley.com/doi/full/10.11… @sgalla32 @testeeves #ConSERTeam #ORNITHOLODAY #teamegg

Management, captive-breeding & captive-rearing play key roles in kakī recovery. For example, collecting & artificially incubating wild eggs encourages pairs to lay multiple clutches per year @sgalla32 @testeeves #ConSERTeam #ORNITHOLODAY #teamegg Photo: Liz Brown | DOC

Tūturuatu, also called shore plovers, are classified as Endangered on the @IUCNRedList and Nationally Critical in the New Zealand Threat Classification System @NamesAreHard89 @testeeves #ConSERTeam #ORNITHOLODAY #teamegg Photos: Dave Houston | DOC

Tūturuatu are one of the world’s rarest shorebirds - in April 2019 there were 245 birds in total, of which 220 were wild & with more than half of these living in the Chatham Islands @NamesAreHard89 @testeeves #ConSERTeam #ORNITHOLODAY #teamegg

Tūturuatu are monogamous and lay a 2-3 egg clutch between Oct-Jan. During the 27-28 day incubation period the female mainly incubates the eggs in the daytime, but males take the night shift @NamesAreHard89 @testeeves #ConSERTeam #ORNITHOLODAY #teamegg

Introduced predators, in particular rats, are the main cause of tūturuatu declines, and like kakī they are also vulnerable to habitat loss and disturbance @NamesAreHard89 @testeeves #ConSERTeam #ORNITHOLODAY #teamegg

In addition, tūturuatu suffer from about 12.2% hatching failure onlinelibrary.wiley.com/doi/full/10.11… @NamesAreHard89 @testeeves #ConSERTeam #ORNITHOLODAY #teamegg

Island biosecurity, captive-breeding, & releases of captive-reared juveniles on to predator-free islands are all key parts of the @docgovtnz Shore Plover Recovery Plan @NamesAreHard89 @testeeves #ConSERTeam #ORNITHOLODAY #teamegg Photo: Dave Houston | DOC

To find out more about kakī and tūturuatu and the work of @docgovtnz in the recovery of these amazing birds (and other fantastic NZ species!) check out the Department of Conservation’s website: doc.govt.nz #ORNITHOLODAY #teamegg

Another #NewZealand species we’re excited to be working with this year is the kākāpō, in collaboration with the Kākāpō Recovery Team #kakapo2019 #kakapo @JL_Savage @JMSCrane @takapodigs @Spokesbird #ORNITHOLODAY #teamegg

Kākāpō had a record breeding season this year, with a total of 252 eggs produced & an amazing 72 surviving chicks #kakapo2019 #kakapo @JL_Savage @JMSCrane @takapodigs @Spokesbird #ORNITHOLODAY #teamegg

However, 156 kākāpō eggs failed to hatch & of those, 134 showed no sign of development. Senior ranger @JMS_Crane & post-doc researcher @JL_Savage (both pictured) are in the process of prepping those eggs for examination by @HemmingsNicola1 as we speak! #ORNITHOLODAY #teamegg

By examining these eggs, we hope to identify infertile males to help optimise breeding management decisions for kākāpō in future seasons #kakapo2019 #kakapo @JL_Savage @JMSCrane @takapodigs @Spokesbird #ORNITHOLODAY #teamegg Photo: James Savage

This #ORNITHOLODAY thread continues at