The Most Perfect Thing by Tim Birkhead
The Most Perfect Thing : Inside (and Outside) a Bird’s Egg
Tim Birkhead
Publisher: Bloomsbury, 2016.
ISBN: 9781632863690
Physical Description: 288 pages, 8 unnumbered pages of plates : illustrations (some color) ; 22 cm.
If you live in the Tropical region of the world, chances are you have never seen a guillemot. At least not in its natural habitat. These sea birds reside in the North Pacific and North Atlantic regions often found in dense colonies on huge limestone cliffs. A common sight in places like Skomer, Wales, and Bempton cliffs in Yorkshire where the author takes us to observe guillemots and their unusual eggs.
Harvesting these eggs of various sizes and colors from cliffsides began around the late 1500s and by the 1920s-1930s, ‘climming’ was a notorious venture for collectors for creating cabinets of curiosities. The eggs were collected for human consumption and were also staples for natural history studies. The guillemot egg has an unusual pyriform shape, pointed at one end. It was falsely believed that since these birds do not form nests, the pointy eggs keep them from rolling off the cliffs since they roll in an arc. A professor at the University of Sheffield, the author has spent decades studying these birds. His publication from 2018 found that the pyriform eggs don’t roll in arcs naturally. The mystery of the shape continues.
The book contains chapters on the various stages of the formation of a bird egg from the creation of shells to coloring, roles of albumen and yolk, warding off microbes via shell pores, laying of the egg, incubation, and finally hatching.
Few things in nature are as flawless as a bird’s egg. Evolution has created ‘a self-contained life support system.’ It is hard enough to protect the embryo inside but weak enough for the chick to break through the shell. It has a shell surface that keeps the microbes out but at the same time allows the embryo inside to breathe. And the thickness of the shell is just right for the parent to incubate sitting atop them. Considering the number of bird species around the planet, natural selection was hard at work.
Consider the eggshell. The soft balloon-like egg inside a bird is actually sprayed with calcium carbonate as it travels through the uterus. As the aerosol sprays deposit calcium, tall pillars of calcite are formed all across the surface. There are spaces where these pillars don’t harden and leave empty spots which become the pores of the shell. How the number and size of the pores are determined in any species is still unknown. But the pores are essential for the survival of the embryo inside. All this happens within 24 hours. And where does all this calcium come from? Well, the birds have to feed on calcium-rich foods. Some birds forage for long hours just to make one egg. Many birds feed on snail shells. The calcium-sensing ability of birds is both innate and acquired. After reading this section, my respect for the batch of eggs in my pantry increased manifold.
How did climate change and industrialization affect birds and the survival of their eggs? Intensive agriculture led to the loss of woodlands, decreased soil quality, leaching of calcium, and reduction in the snail population. Acid rain further reduced the available calcium for foraging resulting in poor eggshell quality for birds like the Dutch great tits. Less calcium, more foraging, more energy expenditure, fewer eggs, tougher survival. On the other hand, intensive poultry is an altogether different ball game and has got me thinking about the overconsumption of eggs by humans.
The most engaging chapters are on the shape and color of eggs. Alfred Russel Wallace puzzled over the conspicuous coloring of bird eggs as an adaptive feature. Something Darwin never pondered over. Wallace surmised that since calcium carbonate is white, reptilian ancestors had white eggs (hello Jurassic Park movie scene.) Later eggs started acquiring colors to ward off predators via natural selection. But does that mean white eggs don’t have advantages of their own? They do. Experiments from the 1970s show that chicken and laughing gull eggs have lower internal temperatures showing that a white eggshell protects eggs from solar radiation. On the other hand, colored eggs are adaptive for camouflage and individual egg identification. Indeed, guillemots can identify their own eggs via their color patterns.
This enjoyable book is teeming with such interesting studies. We meet many naturalists, zoologists, oologists, and ingenious collectors throughout the book. Even though bird eggs have been studied for a long time questions remain. Did dinosaurs lay eggs in the open to be heated by the sun or did they participate in parental care? The debate continues. The book is a perfect case study of investing in bird conservation activities and engages the reader in appreciating the humble commonplace egg as an evolutionary miracle.
