Category Archives: Uncategorized

It Wouldn’t be Easter without Eggs – Tim Birkhead explains the Science behind a Bird’s Egg

Tim Birkhead, The Most Perfect Thing: Inside (and Outside) a Bird’s Egg

When I started to write about birds’ eggs I wondered whether anyone had established which of the different shapes was most common. Obviously when we talk about something being egg shaped we are usually thinking of a hen’s egg, which is ‘oval’, but with an obvious blunt and pointed end and whose greatest width lies closer to the blunt end. To my surprise nobody seems to have quantified egg shape across all families of birds. Part of the difficulty, of course, is coming up with a simple index of shape. Researchers have devised several complicated ways of describing egg designs but there is no single number that captures the full range of shapes. For this reason most books dealing with egg shape simply show – as I do here – a set of outlines or silhouettes illustrating the different types that exist.

One thing we do know is that as well as being characteristic for a particular species, shape is also fairly characteristic for particular families of birds, too. Owls, for example, typically lay spherical eggs;

egg image1

Different shapes of birds’ eggs. From left to right: Ross’s turaco (spherical), ruff (pyriform), hummingbird (oblong oval or elliptical), crowned sandgrouse (oblong oval or elliptical), African thrush (oval), Slavonian grebe (bi-conical or long subelliptical), alpine swift (ellipitical ovate or long oval). Redrawn from Thomson, 1964.

waders (shorebirds) lay pyriform eggs; sandgrouse produce oval or elliptical eggs; and grebes produce biconical eggs.  As a biologist, two questions come to mind. How are eggs of different shapes made, and why are they the shape they are? The first question is about the mechanics of making an egg; the second concerns the adaptive significance of different egg shapes.

egg image2
Thinking about how a female bird produces eggs of a particular shape, my natural inclination was to imagine that the shape was determined by the shell: shape and shell created together. The truth is more bizarre. The contours of a bird’s egg are governed by its membranes, the parchment-like layer inside the shell – as my eggin- vinegar experiment suggested – rather than by the shell itself. Once you know that the membrane determines the shape it isn’t too difficult to imagine the process.

In an ingenious X-ray study of egg formation conducted in the late 1940s, John Bradfield could see that the shape of the hen’s egg was determined before the shell had even started to form, prior to entering the shell gland. Instead, he could see that the egg’s shape was established in the isthmus, the region of the oviduct immediately anterior to the shell gland, where the shell membrane around the egg is created. He noticed, too, that the part of the isthmus adjacent to the shell gland is ‘more contractile and more like a sphincter’ than the other end adjacent to the magnum, suggesting that: ‘Since the egg greatly distends the narrow isthmus [region of the oviduct], it is to be expected that the caudal [tail] end of the egg, situated in the more contractile part of the isthmus, will become more pointed than the cranial [head] end.’ He adds, however, that this suggestion is far from proved ‘and the problem remains without a clear-cut solution.

At the end of the egg-shape spectrum opposite to the guillemot are certain owls, tinamous and bustards that lay almost spherical eggs. How is that done? Does the isthmus in these birds lack the sphincter that Bradfield saw in the hen? Or does the egg turn continuously as the membrane is laid down so that the sphincter applies a uniform pressure all over the egg? We don’t know.

In humans the maximum size of a baby at birth is determined by the size of the ‘birth canal – that is, the internal diameter of the pelvic girdle. Our present ability to perform caesarian operations removes this constraint, but prior to the twentieth century and the routine use of caesarian section, babies who were too big – or whose heads were too big – failed to be delivered successfully, got stuck and died, usually along with the mother. Strong selection indeed. Because the bones that form the human cranium are still not fused at birth there is some flexibility (literally), permitting the skull to adopt a different shape during birth and allowing some relatively big-headed babies to be born.

Read more in Tim Birkhead’s The Most Perfect Thing: Inside (and Outside) a Bird’s Egg

9781408851258

It Wouldn’t be Easter without Eggs – Tim Birkhead explains the Science behind a Bird’s Egg

Tim Birkehad, The Most Perfect Thing: Inside (and Outside) a Bird’s Egg

When I started to write about birds’ eggs I wondered whether anyone had established which of the different shapes was most common. Obviously when we talk about something being egg shaped we are usually thinking of a hen’s egg, which is ‘oval’, but with an obvious blunt and pointed end and whose greatest width lies closer to the blunt end. To my surprise nobody seems to have quantified egg shape across all families of birds. Part of the difficulty, of course, is coming up with a simple index of shape. Researchers have devised several complicated ways of describing egg designs but there is no single number that captures the full range of shapes. For this reason most books dealing with egg shape simply show – as I do here – a set of outlines or silhouettes illustrating the different types that exist.

One thing we do know is that as well as being characteristic for a particular species, shape is also fairly characteristic for particular families of birds, too. Owls, for example, typically lay spherical eggs;

egg image1

Different shapes of birds’ eggs. From left to right: Ross’s turaco (spherical), ruff (pyriform), hummingbird (oblong oval or elliptical), crowned sandgrouse (oblong oval or elliptical), African thrush (oval), Slavonian grebe (bi-conical or long subelliptical), alpine swift (ellipitical ovate or long oval). Redrawn from Thomson, 1964.

waders (shorebirds) lay pyriform eggs; sandgrouse produce oval or elliptical eggs; and grebes produce biconical eggs.  As a biologist, two questions come to mind. How are eggs of different shapes made, and why are they the shape they are? The first question is about the mechanics of making an egg; the second concerns the adaptive significance of different egg shapes.

egg image2
Thinking about how a female bird produces eggs of a particular shape, my natural inclination was to imagine that the shape was determined by the shell: shape and shell created together. The truth is more bizarre. The contours of a bird’s egg are governed by its membranes, the parchment-like layer inside the shell – as my eggin- vinegar experiment suggested – rather than by the shell itself. Once you know that the membrane determines the shape it isn’t too difficult to imagine the process.

In an ingenious X-ray study of egg formation conducted in the late 1940s, John Bradfield could see that the shape of the hen’s egg was determined before the shell had even started to form, prior to entering the shell gland. Instead, he could see that the egg’s shape was established in the isthmus, the region of the oviduct immediately anterior to the shell gland, where the shell membrane around the egg is created. He noticed, too, that the part of the isthmus adjacent to the shell gland is ‘more contractile and more like a sphincter’ than the other end adjacent to the magnum, suggesting that: ‘Since the egg greatly distends the narrow isthmus [region of the oviduct], it is to be expected that the caudal [tail] end of the egg, situated in the more contractile part of the isthmus, will become more pointed than the cranial [head] end.’ He adds, however, that this suggestion is far from proved ‘and the problem remains without a clear-cut solution.

At the end of the egg-shape spectrum opposite to the guillemot are certain owls, tinamous and bustards that lay almost spherical eggs. How is that done? Does the isthmus in these birds lack the sphincter that Bradfield saw in the hen? Or does the egg turn continuously as the membrane is laid down so that the sphincter applies a uniform pressure all over the egg? We don’t know.

In humans the maximum size of a baby at birth is determined by the size of the ‘birth canal – that is, the internal diameter of the pelvic girdle. Our present ability to perform caesarian operations removes this constraint, but prior to the twentieth century and the routine use of caesarian section, babies who were too big – or whose heads were too big – failed to be delivered successfully, got stuck and died, usually along with the mother. Strong selection indeed. Because the bones that form the human cranium are still not fused at birth there is some flexibility (literally), permitting the skull to adopt a different shape during birth and allowing some relatively big-headed babies to be born.

Read more in Tim Birkehad’s The Most Perfect Thing: Inside (and Outside) a Bird’s Egg

9781408851258

How to get Creative with Herrings

This month, we’re celebrating one of nature’s real unsugn heroes – the Herring.

Scots like to smoke or salt them. The Dutch love them raw. Swedes look on with relish as they open bulging, foul-smelling cans to find them curdling within. Jamaicans prefer them with a dash of chilli pepper. Germans and the English enjoy their taste best when accompanied by pickle’s bite and brine.

Throughout the long centuries men have fished around their coastlines and beyond, the herring has done much to shape both human taste and history. Men have co-operated and come into conflict over its shoals, setting out in boats to catch them, straying, too, from their home ports to bring full nets to shore. Women have also often been at the centre of the industry, gutting and salting the catch when the annual harvest had taken place, knitting, too, the garments fishermen wore to protect them from the ocean’s chill.

In his book, Herring Tales,  Donald S. Murray has stitched together tales of the fish that was of central importance to the lives of our ancestors, noting how both it – and those involved in their capture – were celebrated in the art, literature, craft, music and folklore of life in northern Europe.

Donald contemplates the possibility of restoring the silver darlings of legend to these shores. And to help spark some imagination, he provides some engenious examples of how we can make them live on via the box they arrive in!

A Wheel Barrow

wheel barrow

A Go-Cart

cart

A Baby Cot

cot

A Bike Carrier

Dog Carrier

A Milk Box

milk box

Celebrate the Herring this month with Herring Tales – and join Donald on his campaign to restore this versatile little creature back to former glory!

9781472912169

British Wildlife Blog has a New Home!

We are delighted to announce our new partnership with Bloomsbury Publishing – the UK’s number one publisher of Natural History. Both Bloomsbury and British Wildlife would like to invite you to join our new community hub at the Bloomsbury Wildlife Blog. Stay up to date with the latest Natural History news from our authors and editors here.

You can also join in the conversation on the Bloomsbury Wildlife Twitter feed at @chiffchat. Please do follow us for updates from British Wildlife and Bloomsbury.

British Wildlife Publishing & Bloomsbury – An Announcement

Hello,

A very happy new year to you all. Before returning to normal service with posts about all aspects of British natural history and wildlife, we have a brief announcement to make about the ownership of British Wildlife Publishing.

This is that the company has been acquired, as part of Osprey Publishing, by the very illustrious Bloomsbury Publishing. We can’t tell you very much more than that currently, as all manner of details are still being worked out, but since Bloomsbury is well known for its very estimable natural history publishing you should be confident that we – and the books and magazines – are in safe, knowledgeable and above all careful hands.

Other than that, all that remains is to say please continue to watch this space for more posts about what we’re all REALLY interested in: the wildlife of these beautiful islands.

All the very best for 2015,

British Wildlife Publishing

Dr Nigel Holmes 1949 – 2014

Many of you will already know that Nigel Holmes passed away last month. Nigel was an indispensable pillar of river conservation and restoration, a vital mentor and valued friend to many, a renowned author, and a devoted husband and father. He is sorely missed by all who knew him.

We share with you a lovely picture of Nigel taken by his colleague and friend Dr Paul Raven (with whom he co-authored Rivers), and Peter Marren’s full obituary, which can be read in The Independent at the link below.

60 Poland 2007ii

http://www.independent.co.uk/news/people/news/doctor-nigel-holmes-ecologist-who-led-efforts-to-restore-degraded-rivers-and-formulated-a-scientific-classification-used-across-europe-9836624.html

Welcome to the new British Wildlife blog

Hello,

2014 marks 25 years of British Wildlife magazine. As we approached this milestone, we started to think of ways to celebrate, and to complement the ways in which we already communicate with you, our readership.

Accordingly, this is our new blog, where you will find posts relating to the world of British nature. If you are interested in all or any of the varied wildlife of these islands, and its conservation, do follow us; we will post discerningly and never for the point of posting.

Our first entry, which we will publish tomorrow, is an excerpt from our new contributor Simon Barnes’ first piece for British Wildlife. You will probably know Simon from his books and many years as the treasured sports and nature correspondent for The Times. He will be writing a column every other issue (his will alternate with Mark Avery’s), but this first contribution is a lengthier, searching look at what the next 25 years of conservation in Britain might – and should – bring.

Thanks for joining us here. We hope you enjoy the blog.

Best wishes,
The British Wildlife Publishing Team

PS. If you would like, do follow us on Twitter at @britwildlife as well.