Book Talks, Interviews, Reviews

The Natural History Magazine from the American Museum of Natural History has an excerpt of Bird Love in their June 2020 print issue!

And in Psychology Today

Book Talks

6th March  Harvard Bookstore

7th May  World Migratory Bird Day (a global bird conservation and education campaign)

18th May Princeton Public Library-- replay available

12th September Seattle Town Hall-- replay available

24th September Science On Tap--replay available

30th September San Diego Natural History Museum

20th October Delaware Nature Society

Interviews

4th March  Psychology Today

24th March Bird Calls Radio podcast

8th April Princeton Alumni Weekly

17th April New Books Network podcast with Lukas Rieppel, author of Assembling the Dinosaur (a very good read)

Reviews 

On Amazon

Fatbirder View:

What struck me most from this wonderful book is that nature, even within one family is extraordinary diverse. Mating, pairing and offspring rearing is as varied in the avian world as in the human realm, maybe even more so. The breadth of knowledge of the author is displayed on every page and is really well presented.

Its entirely admirable that someone should know as much as they do with a depth of scientific understanding yet be able to convey that to the lay reader, succinctly, accurately and readably.

I’m still reading and re-reading and have been charmed, captivated and entertained, but mostly greatly educated by this work.

It gets my highest recommendation.

American Birding Association

A review by Joan Roughgarden

Wenfei Tong presents a contemporary overview of diversity in the family life of birds. Other than Darwin’s manifesto of 1874, The Descent of Man and Selection in Relation to Sex, only David Lack’s Ecological Adaptations for Breeding in Birds from 1968 offers comparable coverage. To these might be added Bruce Bagemihl’s Biological Exuberance: Animal Homosexuality and Natural Diversity, published in 1999, which surveys certain additional examples of courtship and family life in birds and mammals.

Weifei Tong was an undergraduate at Princeton University, receiving a degree in ecology and evolution, then receiving a PhD in biology from Harvard University, culminating in postdoctoral research at Cambridge University where she studied avian brood parasites. In addition to her research, she writes popular science articles and serves as a lecturer for Lindblad Expeditions. Also, Mike Webster, a consultant editor and professor of ornithology at Cornell University, contributed a Forward to the book. Chapters cover ecology and mating systems, courtship, nests and eggs, raising chicks, sex role reversal, group breeding, and brood parasitism.

In his Forward, Webster writes:

Our swallows are the very picture of a cooperative, monogamous and loving family. Yet, as a behavioral biologist, I know that lying beneath that cooperation is a lot of complexity, competition, and conflict. The male courts his mate with song and showy plumage, but he also courts and copulates with the mates of other males, and his own mate will likely copulate with `extra-pair’ males herself. (p. 6)

In her Introduction, Tong writes, “Bird family life can look rosy, from the long-term pair-bonds of parrots and albatrosses to the many species in which both sexes, and sometimes an extended family, share parental care duties. However, nature is amoral and a darker side, including sexual conflict, infanticide, and siblicide, is equally common” (p. 8). Thereafter, the chapters deconstruct any possible picture of avian family life that might figure in a Disney production. A movie featuring Tong’s account would be classified as adult-only because of excessive violence. But along the way, Tong brings us wonderful photographs of birds from around the world that illustrate some of the breadth of avian family organization.

Since the time of Darwin and Lack, the popular narrative in behavioral ecology has been to attribute differences in the sex roles of males and females ultimately to a difference in their gamete sizes.  Accordingly, Tong writes in her Introduction that “[t]he female reproductive strategy, with large-investment eggs, is quality over quantity, whereas the male strategy is typically the reverse” because “sperm are individually cheaper than eggs” (p. 10). Continuing, she writes, “The investment asymmetry from the time eggs and sperm are made often leads to larger differences later in birds’ reproductive life” (p. 10).  In particular, “in most bird mating markets, females are the buyers and males must advertise” (p. 10).

Other investigators going back to Darwin have questioned a connection between gamete size and sex role, noting that the cumulative ejaculate size and other mating costs in males is commensurate with egg size in females even though an individual sperm is much smaller than an egg. Darwin wrote “[o]n the whole, the expenditure of matter and force by the two sexes is probably nearly equal” (p. 233). Darwin interpreted differing gamete sizes in terms of different strategies of mobility (p. 230-231)—if the task is for two potential mates (or gametes) to find each other, then one should remain stationary while the other searches, a strategy even we humans should employ when we become separated from our partner in a crowd.

Of relevance then to a possible connection between gamete size and sex role is Tong’s discussion in Chapter 5 of the many avian species with sex-role reversal such as phalaropes, Black Coucals, and jacanas in which the males are the buyer and the females must advertise. Tong concludes that “we still lack a unifying explanation for sex role reversals” (p. 122). Even Lack found the phenomenon puzzling when he wrote: “Why in any species a reversal of the sex roles would be advantageous is not known” (p. 153).

Instead, the conclusion to be drawn is that the premise of gamete size explaining sex role is itself false—it is contradicted by the data. Indeed, the males of phalaropes, Black Coucals, and jacanas all make tiny sperm—that is why they are called males, and yet they still assume what has been considered the female sex role despite their small gametes. As a result, males and females both wind up having approximately the same net investments in their offspring, contrary to the false gamete-size/sex-role premise.

In Chapter 1, Tong offers the central premise guiding her interpretation of various family organizations. She writes, “Within species, mating systems are the passive outcomes of social conflicts between individuals attempting to maximize their own reproduction” (p. 20). From this premise, birds, or their traits, or their behaviors end up being discussed with phrases such as philanders (p. 24), cheaters (p. 25), cuckolds (p. 26), deserters (p. 29), manipulators (p. 30), divorcees (p. 34), between-sex arms races (p. 36), forced copulations (p. 37), inferior males (p. 42), sexy sons (p. 43), ornaments of genetic quality (p. 45), best genes (p. 45), sperm wars (p. 54), sneakers (p. 56), parent-parent conflict (p. 102), infanticide (p. 103), parent-offspring conflict (p. 105), siblicide (p. 111), bondage (p. 133), incest (p. 155), etc. These are the tip of behavioral biology’s iceberg of provocative terms littering their peer-reviewed literature. Explanations in behavioral biology increasingly resemble dime-store crime stories. Although one may reject Disney’s romanticism of nature, perhaps the pendulum has swung too far in the other direction. Is there any more to bird social life than lying, cheating, and stealing?

A way forward is to return to Lack who notes (p. 148) as does Tong (p. 23) that over 90% of nidicolous birds and 80% of nidifugous birds are monogamous. Lack did not know how widespread extra-pair mating is and thought that monogamy implied both social and genetic monogamy. These have different purposes, however. Social monogamy is one possible economic arrangement for how to divide the labor of raising chicks. Genetic monogamy is one possible arrangement for how to distribute paternity.

Departures from genetic monogamy need not indicate cheating or deceit. Indeed, in Razorbills the extra-pair matings occur out in the open witnessed by the pair male. Extra pair matings represent a spreading-the-risk strategy whereby a pair raises a clutch that includes some extra-pair offspring while other pairs raise clutches that include their offspring. Thus, the decoupling of economic and genetic monogamy makes perfect sense without requiring narratives of cheating, deceit, and cuckoldry. In general, family life need not be the passive outcome of conflicts because kin selection, family selection, and other forms of multilevel selection promote cooperation beyond what can be realized by a collection of individual fitness maximizers.

Because of the peacock’s popularity in Darwin’s theory of sexual selection (p. 214-251), a recurring theme in avian biology has been the interpretation of male displays as advertisements of genetic quality. However, Lack notes (p. 148) that “[m]onogamy, in birds and men, tends to be dressed in drab colours, but it is far more frequent than the exotic alternatives.” If colorful plumage, ornaments, and exotic displays in birds really did indicate male genetic quality, then it is puzzling why 10% of avian species have males whose variation in genetic quality requires such exotic advertising whereas the remaining 90% are content with their lack of style. The hierarchy of male genetic quality is a myth. According to what geneticists term the “paradox of the lek,” if, hypothetically, a hierarchy of male genetic quality did exist, and if females did prefer males who had the higher quality, then after a few generations, female choice would select out the bad genes, leaving only males with good genes. To sustain further female choice for male genetic quality, some unknown source of mutation would need to replenish the supply of bad genes in males so that females would have something to continue selecting for.

Instead, Lack (p. 158) endorses Huxley’s 1938 summary of the function of secondary sexual characters as: (i) threat displays to same-sex rivals, (ii) sex recognition prior to mating, (iii) psycho-physiological stimulation for mating, and (iv) mutual and bond-forming displays. These venerable suggestions make more sense than supposing that males possess a hierarchy of genetic quality that females are anxious to discern.

Tong notes (p. 26) that Blue Tit chicks sired by extra-pair males survive better than their half siblings, that extra-pair Bluethroat chicks have stronger immune systems, and that Savannah Sparrows and Reed Bunting chicks sired by extra-pair males are healthier. But Tong also allows that no extra-pair paternity benefits could be detected in Darwin’s finches, Sand Martins, and Coal Tits. Indeed, meta-analysis of extra-pair paternity benefits has shown no consistent genetic benefit, which is consistent with the absence of male hierarchies in genetic quality. Rather, extra-pair matings are best interpreted as representing a distributed system of paternity to avoid a bird’s keeping all its eggs in one nest rather than as attempts by females to solicit genetic upgrades.

The title of the book being reviewed is Bird Love, and a reader might wonder where the love is, given the book’s preoccupation with deceit and cheating. Indeed, is love no more than a mirage, a misnomer for some behavior intended by one party to manipulate the other into furthering its fitness agenda?

Tong offers a photograph of Rockhopper Penguins (p. 33) and of Laysan Albatrosses (p. 92) engaged in “allopreening—using one’s bill to groom and caress another individual.” She adds that “[t]here is evidence from over 500 species that allopreening between mated pairs is more common in species where both parents raise the offspring, and couples that preen each other more have a higher chance of remaining together over the years” (p. 33).

Tong goes on to say that “[r]ates of allopreening have no bearing on the rate of sexual infidelity” (p. 33). That is to be expected because the allopreening relates to the economic function of monogamy—keeping the pair’s teamwork coordinated. What Tong refers to as infidelity relates to implementing the risk-spreading system of distributed paternity which is independent of the coordination needed to successfully provision chicks through teamwork.

The instance Tong gives of allopreening between the rockhoppers is presumed to be heterosexual and that between the albatrosses is labeled as homosexual. Moreover, Bagemihl assembled 177 pages of avian examples of homosexuality (p. 479–656). The element in common between heterosexual and homosexual allopreenings together with vocal duets, nuptial gifts, homosexual copulations, and other forms of social intimacy is the mutual exchange of pleasure. This is the proximal motivation for coordinated teamwork. The sensation, even the gratitude arising from the mutual exchange of pleasure and the shared memory of working successfully together, is what underlies avian teamwork. This is what might be identified as bird love.

Wenfei Tong’s new book, Bird Love: The Family Life of Birds, is important in bringing to popular attention some of the diversity in avian family organization and for placing that diversity in a contemporary explanatory framework. The book can then serve as a starting point for a critical examination of that framework. The book’s extensive and beautiful photographs document the majesty of bird family life, a contribution that will remain valuable long after academic theorists have moved on to other topics of debate.

• BBC Wildlife Magazine
 

by Corina Newsome Biologist, 12 March 2020
Wenfei Tong artfully narrates the complex world of avian reproduction in his newest work. Walking the reader through the many layers of bird family life, Tong describes the intricacies of mating systems and offspring-rearing strategies for bird species around the world, and the suite of social interactions that characterise them. Her use of analogies to the human social experience, such as infidelity and divorce, parental roles, and economic investments, allows us to personally relate to the reproductive decisions made by various species, while simultaneously celebrating the distinctness of avian life.

Understanding that birds have often been misinterpreted by the public as the epitome of romantic commitment, Tong gracefully guides us to the fact that bird mating systems are both more beautiful and more brutal than most people realise.

Bird Love will bring any reader to more deeply appreciate the hidden complexity of birds. 

Birdwatch Magazine

Gardens Illustrated

Wall Street Journal

By Julie Zickefoose April 16, 2020 11 49 am ET 
Brush up on your evolutionary biology and buckle up for Wenfei Tong’s “Bird Love” (Princeton, 192 pages, $29.95), a beautiful book about the world of avian breeding systems. Mountains and years of scientific research are gathered together here in a bare-bones recitation of all that is possible—and much that seems impossible—in bird reproduction. Pelicans lay two eggs but raise only one chick, standing impassively by as Cain and Abel fight it out. To escape predators, female hornbills seal themselves into a tree cavity for weeks, molting all their flight feathers, dependent entirely on their mates for sustenance. Attention is given to the behavioral outliers, with sex-role reversal, cooperative breeders and brood parasites commanding the most ink. Throughout, stunning photographs keep the pages turning. This is an information- dense book best made for dipping in and out. 

—Ms. Zickefoose is the author, most recently, of “Saving Jemima: Life and Love With a Hard-Luck Jay.” 
https://www.wsj.com/articles/spring-books-nature-11587052170?mod=searchresults&page=1&pos=1 3/4 
WHAT TO READ THIS SPRING » 
4/17/2020 Spring Books: Nature - WSJ 
Copyright © 2020 Dow Jones & Company, Inc. All Rights Reserved

Birdwatching Magazine 

May/June 2020
By Matt Mendenhall

The world’s birds have an extraordinary range of mating systems, and this gorgeous and expertly written book explains them all. Author Wenfei Tong covers courtship, nests and eggs, raising chicks, group breeding, and more. She considers why some species, such as the Wattled Jacana, rely on males to do all the childcare, while others, such as cuckoos and honeyguides, dump their eggs in the nests of others to raise. It’s a beautifully designed book on an endlessly fascinating topic.


The Bookbag

by Peter Magee

Summary: An exquisitely-presented and informative look at the family life of birds. Highly recommended.

I was a little perturbed when I looked at the blurb for Bird Love on a couple of on-line booksellers: exploring the sex life of birds it said. I very nearly passed over the book, but a closer examination suggested that the book is about the family life of birds, which is rather different. If the book was confined to the sex life of birds, you would be missing an opportunity to understand how birds live day-to-day, bring up their families and cope in the wild. Not only that, you have missed the treat of so many beautiful illustrations about a wide variety of birds which run through this book from the first page to the last.

Superficially, it might seem that everything to do with birds is harmonious, without any suggestion of conflict but this is far from the truth. For example, if you are unlucky enough to be the second fledgeling in the nest you could find that your older brother or sister could be quite brutal as their aim is to survive rather than nurture. On the other hand, some species collaborate as a group to ensure that as many fledgelings as possible survive. There are even examples of role reversal where the male takes the dominant role in bringing up the chicks: nature discovered house husbands long before humans did so. How many of us knew that female albatrosses can have same-sex partnerships lasting twenty years?

This book is a timely reminder of the damage that humans can cause to the birds' environment. The decline and eradication of species is something which should all be aware of, and do our best to reverse. Wenfei Tong tells us that climate change has affected the migratory patterns of many birds. There are ten thousand species of birds, but the common cuckoo has declined by half in just twenty-five years. It could, of course, be argued that this is good news those birds which have been unwilling hosts in the past.

The coverage of Bird Love is extensive. It looks at ecology and mating systems, courtship, nests and eggs, raising chicks, sex-role reversals, group breeding and brood parasitism (think cuckoos on that one). Once you realise this, it becomes obvious that this is not a 'coffee-table book', as its appearance might suggest, but a serious look at the family life of birds. It is quite technical in places and you will need to work at it to get the most out of it, but I was surprised by how much information was delivered in an accessible fashion.

I found the book fascinating: it's the type of book which can intensely annoy other people because you're constantly telling them about what you're reading: Did you know that house sparrows and house finches use cigarette butts to keep their nests free of lice? I'd like to thank the publishers for giving me this opportunity.

The Well-Read Naturalist

by Johannes E. Riutta

Birds do it.

But if you’ve taken a basic biology course, you likely already knew that.

Dr. Wenfei Tong, however, knows much more about how they do it than just the basics, and in her new book Bird Love; the Family Life of Birds, she explores and explains the extraordinary range of courtship, mating, and brood rearing practices found among the planet’s diverse birdlife.

Covering the essentials of these behavioral categories, as well as delving into some of the more unusual – and frankly, surprising – practices, such as brood parasitism and reciprocal promiscuity, Dr. Tong’s book is clearly a work worthy of attention by ornithologists, birdwatchers, and general naturalists alike.

Avian 101

H.J. Ruiz -Avian101.Wordpress.com – April 9th, 2020

I have enjoyed this book very much. The main reason is the author’s approach, which, I agree 100%. Let’s get to know the bird by knowing how it lives. The points that capture the behaviors and their daily lives are the following:

• Ecology and Mating Systems
• Courtship
• Nests and Eggs
• Raising Chicks
• Sex Role Reversals
• Group Breeding
• Brood Parasitism

You’ll find out and get to know the bird’s way to see life, very much as humans behave and act. This approach will get you closer to your avian friends, and lead you, to understand how they live. 

This book has 192 pages with 220 gorgeous photos and a wonderful foreword by Mike Webster.

I was very pleased when I finished reading this book, which I recommend to my friends, readers, that visit my blog daily.

And on Understanding Bird Behavior

Author Wenfei Tong describes every situation in a comprehensive way, using precise samples of birds that the reader immediately will get the proper information of the chapter in question. All these, accompanied of amazing color illustrations and photos in a total of 150. This guide is a hard cover 224 pages. 

I found this guide to be interesting, since I am always observing and photographing birds, I also pay great attention to their fascinating behavior.

H.J. Ruiz -Avian101.Wordpress.com – August 17th, 2020

First book coming out in March 2020

Published by Ivy Press and Princeton University Press. To pre-order in the US, and in the UK.

Perspective in Science

Threespine stickleback, the protagonists of the research article that we wrote a perspective piece for,
are a model for understanding how repeatable evolution is. This is because populations of these little fish have independently evolved to live in freshwater lakes and streams all over the Northern Hemisphere.

Repeated adaptations to life in freshwater range from anatomical features like losing armoured anti-predator defences, to growing and reproducing faster, to digestive enzymes that compensate for the dearth of fatty acids in freshwater diets.

Life in freshwater does not just involve new predators and new food sources, but also new parasites. Below is an illustration (not to scale) of the life cycle of some of the key tapeworm parasites than infect freshwater stickleback. Eggs and larvae are eaten by little crustaceans such as copepods, as depicted on the bottom of the figure. Stickleback, such as this male guarding his nest, become infected when they eat copepods full of tapeworms. Birds, such as loons and mergansers, distribute tapeworm eggs across different watersheds when they eat infected stickleback and poo out tapeworm eggs. As a result, while the stickleback in each watershed are on isolated evolutionary trajectories, they are constantly coevolving against parasites like tapeworms, with a much more global distribution. This system provides a perfect natural experiment for understanding how host immune systems evolve different ways to combat a single parasite.

The Importance of Being Warm

Field note on great horned owls on Montana Public Radio

Field note on great horned owls on Montana Public Radio

The darker side of pronghorn life: sibling rivalry in the womb

One pronghorn embryo piercing another

On Mother's Day, Montana Public Radio aired my field note on siblicide among pronghorn embryos in utero, and I was on the Rocky Mountain front near Choteau, watching a pronghorn that had just given birth to one fawn.

The umbilical chord was still dangling from both, and we watched for over an hour as the fawn struggled to stand and suckle for the first time.

The mother seemed quite uneasy about all the traffic on Bellview Rd and after lying down and getting back up several times, led her first fawn away from the road, probably to find a more private spot to deliver number two. We left her in peace so didn't watch the second little horror arrive.

The very next day, on the same road, we saw a female pronghorn with two young fawns.

A week later, on the National Bison Range, the pronghorn there are no newborn pronghorn in sight, as their mothers have probably hidden them among the brilliant yellow arrowleaf balsamroot.

Yearling and adult female pronghorn among the arrowleaf balsamroot

Why do races look different?

These are illustrations for a book proposal, showing the differences between European and North American barn swallows. Female European swallows prefer males with longer tail streamers, and have selected for males with streamers that are longer than is aerodynamically optimal. In contrast, North American female swallows don't care much for long tails, but prefer their males bright orange below. As a result, American barn swallow males have shorter tails but brighter bellies than their European counterparts. In the Descent of Man, Darwin first proposed this idea of the arbitrariness of female mating preferences as an explanation for most of the racial variation within humans.

On birds on air: http://mtpr.org/post/singing-snow

A Natural History Note I wrote for Montana Public Radio: http://mtpr.org/post/singing-snow

Some views from cross-country skiing near Missoula this winter:

Top of Crazy Canyon Road between Mt Sentinel and University Mountain

Dog road at Lolo Pass

Ellie at the base of Blue Mountain

Base of Blue Mountain

Reference illustrations for a book on evolution

Cuckoo hosts

 

Primate phylogeny pictures

 

Arms races as analogies

What is progress in evolutionary terms? An absolute increase in complexity, perhaps? Many biologists (myself included) would say that natural selection has no foresight; that organisms don’t evolve adaptations in anticipation of what is to come. This is different from denying that evolution can often take predictable directions, such as increasing the size of weapons, or the complexity of communication. As Dawkins and Krebs proposed in a brilliant paper [1], arms races are situations in which one can predict a kind of evolutionary progress through escalating conflict. Measured purely in terms of evolutionary fitness, the fastest antelope isn’t an improvement on its ancestors, because all its contemporaries are also faster, and so are their predators. Just like the Red Queen in Alice in Wonderland, everyone is effectively running as hard as they can to stay in the same place relative to everyone else in the evolutionary race to survive and reproduce. However in absolute terms, arms races can cause progress in the sense that today’s antelope and cheetah are faster than their ancestors.

  

For historians (including evolutionary biologists), the notion of an arms race is a compelling framework for explaining and predicting the consequences of conflict. In AnimalWeapons: The Evolution of Battle, Doug Emlen makes a very convincing case that evolutionary arms races are often strongly analogous to those in human warfare. Although much of his book addresses the more obvious parallels in weapon evolution – increases in antler or battleship size as conflicts escalate – there is also a fascinating discussion of asymmetric arms races, in which one side is attacking, and the other defending. I particularly enjoyed the parallels between army ants and Assyrians attacking the highly evolved and elaborate fortresses of termites and the city of Lachish respectively.

Just as human history involves arms races of attack and defence, the rest of biological history is rife with asymmetric arms races – most dear to my heart, those between parasites and hosts. Viruses constantly evolve new ways to invade our immune systems, while we both evolve and invent ways to defend ourselves from infection.

Cuckoo:Cheating by Nature, just published by Nick Davies, is all about this kind of arms race, but in this case, both parasites and hosts are birds. As Davies discusses beautifully, brood parasitic birds, which manage to “trick” other birds into bearing the entire burden of childcare, are some of nature’s ultimate cheats. The arms race idea applies because it’s evolutionarily costly to rear someone else’s children at the expense of one’s own, and host birds are under strong selection to detect and deter parasitism, such as recognising and rejecting a foreign egg. This selects for egg forgeries on the side of the parasite, which in turn selects for better discrimination by hosts, and sometimes, to making eggs with more independently varying signatures so that they are harder to forge [2]. The result of this mimicry arms race is eggs with remarkably diverse colour and pattern signatures in two unrelated bird lineages.

Cuckoo is a tale of the finest scientific passion and skilful detection that goes beyond presenting a masterly overview of brood parasite research to painting a personal and highly inspiring account of behavioural ecology at its best.  Nick Davies is one of the giants in this field of biology that tries to explain why animals have evolved to behave the way they do. He is a giant because of the simple elegance of his experiments. Much of science, including evolutionary biology, is tools-driven. Astronomers discover new things with improved telescopes, and biologists are now experiencing a similar revolution with increasingly affordable genomics. Davies has the rare ability to design experiments that require little more than a pair of binoculars, and possibly, a painted balsa wood model, to unearth secrets that would otherwise remain as unanswered questions. I’ll let you read the book to find out how exactly how he does this, because he would make it come alive better than I ever could.

Animal Weapons is just as riveting, but in a very different way. The scope of this book is broader, and Emlen takes more conceptual risks. One of the main ideas Emlen proposes is a novel precondition necessary for weapons arms races to escalate: namely, the importance of duels. If fighters are constrained to a one on one confrontation, the best fighters reliably win, so there is an arms race to evolve bigger, better weapons. In the absence of a duel, say, in a scramble of ardent male horseshoe crabs or in battles with guns instead of swords, this tight correlation between an individual fighter’s abilities and the chances of winning breaks down, so extreme personal weapons are unlikely to evolve. Interestingly, this idea comes from military history, a subject that is skilfully interwoven into the entire book, with illuminating results. Briefly, the reasoning behind this is that large weapons are costly, and thus an honest signal of fighting ability (an idea developed in another fun book, The Handicap Principal) [3]. Once large weapons become honest signals, they act as deterrents to inferior combatants because it is cheaper for both sides to avoid a fight with a known conclusion. This second function would select for extra large weapons because extra large signals would be more daunting than just slightly larger ones, even if the latter would still help you win a fight. So given the existing ingredients for an arms race, with an excess of males duelling for defensible resources, the increasing selection pressure to evolve bigger weapons faster should case the arms race to accelerate. A second novel idea is the prediction that in symmetric arms races that constrain members of the same species and sex to a duel, the race will accelerate towards the end.

While both authors use their passion and personal experience to introduce the broader implications of arms races, the two books are an intriguing contrast in tone and content. Animal Weapons, as the title implies, is largely about escalating conflict between members of the same sex and species. This is consistent with Doug Emlen’s childhood fascination with arrowheads and his brilliant scientific work on how and why male beetles evolve and develop such a diversity of horns (or other ways to gain a mate). Just like the increasingly enormous and elaborate weaponry in the book, American hyperbole may have been subjected to a similar arms race to impress. Emlen’s writing is infectiously engaging in its sincerity, and like the subject matter, it is certainly forceful. In contrast, Cuckoo is full of English understatement, while still managing to bubble with humour and enthusiasm like a pair of twinkling eyes in an otherwise impassive face. The arms races it deals with focus specifically on trickery and detection, sneak invasion and defence, rather than on the broader theme of battle, be it duel or siege, in nature or culture.

Both books are especially worth reading because they bring alive the personalities and passions of their authors in ways that few popular science books succeed in doing. Any aspiring scientist should want a window into how both these top scientists think, and anyone else will simply enjoy biology at its best. By best, I mean a deep love of natural history and an abiding sense of curiosity that fuel the skill and dedication needed generate and test ideas to explain how and why the living world works the way it does. These people love what they do and both books are full of endearingly self-deprecating anecdotes and personal insights. For instance, Davies often writes of identifying with the birds he has watched with fresh joy every year, and observes that like the territorial reed warblers he studies, he prefers to have his own patch when doing fieldwork. This led to an almost sleepless night when a warden told him an old man had been spotted searching for nests in his beloved patch, till he realised with relief the next morning that the “old man” must have been himself. A characteristic Emlen anecdote (some of the funniest are lurking in the footnotes) is all action and adventure, including one about getting covered in hundreds of minuscule ticks while valiantly collecting howler monkey poo miles from camp in a daily struggle to keep some very precious dung beetles fed.

Another very engaging aspect of both books is their constant reference to history and art. Davies writes often of personal sources of inspiration, which include poetry and art that make him see nature in a new light. He pays a special tribute to Eric Ennion, a self-taught and superb bird painter, and his account of how Edgar Chance, a Victorian gentleman, worked out the natural history of cuckoo parasitism is more thrilling than any detective fiction. Emlen writes of unearthing old arrowheads or Mayan with the same deep empathy for how others saw the world, and Animal Weapons is full of interesting military history.

Reading both books made me think about how biologists apply the notion of arms races in evolution, and which arms races they choose to focus on. To borrow the very useful framework from Dawkins and Krebs, evolutionary arms races can come in four broad flavours, each with predictably different outcomes. Cuckoo is largely about asymmetric arms races between species. The asymmetry refers to what Dawkins calls the “life-dinner principal”. A hare that doesn’t run fast enough loses its life, whereas a fox just loses its dinner. Animal Weapons touches on this type of race, but is largely about symmetric arms races within species, such as duelling males fighting for the chance to mate, and escalation results in the evolution of extremes.

Similarly, a cuckoo chick that doesn’t manage to convince hosts to take care of it loses its life, whereas duped host parents lose some children, but live to breed another day. It may not be too surprising to see hosts "lagging" in the arms race against brood parasites.

There are two more categories of arms race that these books don’t focus on. Symmetric arms races within species, essentially what Darwin referred to as his “Principal of Divergence” [4], and causes the phenomenon modern biologists call character displacement. No one really focuses on this category as an arms race, possibly because it encompasses most of ecology, and is too loose and broad to be useful. More interesting, and alluded to in Cuckoo, are asymmetric arms races within a species. Parent-offspring conflict [5], for instance, or conflict between genes inherited from fathers and genes inherited from mothers [6]. A particularly delightful example is a fairly recent paper by David Haig, proposing genomic imprinting for infant sleep as a way for paternally inherited genes to delay inter-birth intervals so that mothers invest more than is optimal for their genes on the current child [7].

I suspect my personal attraction to arms races is due to the irony inherent in a process that produces such beauty, complexity and diversity from conflict. Like anything historical, much of evolution occurs because of chance, such as a meteor colliding with the earth, or a few finches colonising a new island. The really compelling thing about natural selection is that it explains the non-chance side of evolution – the exquisite fit between form and function. And natural selection gets most interesting not when organisms are adapting to the physical environment, but when the environment consists of other organisms, be they siblings, parents, predators or parasites, because they co-evolve. In other words, an arms race ensues. To butcher Darwin’s almost biblical concluding paragraph in the Origin [4], “from the war of nature…endless forms most beautiful and most wonderful have been, and are being, evolved.”

Postscript: I did some experiments in Zambia and found that little bee-eaters, African hosts of another deadly brood parasitic bird, are also remarkably maladapted when it comes to avoiding parasitism.

1.         Dawkins, R. & Krebs, J. 1979 Arms Races Between and Within Species. Proc. R. Soc. B-Biol. Sci. 205, 489–511. (doi:10.1098/rspb.1979.0081)

2.         Spottiswoode, C. N. & Stevens, M. 2010 Visual modeling shows that avian host parents use multiple visual cues in rejecting parasitic eggs. Proc. Natl. Acad. Sci. U. S. A. 107, 8672–8676. (doi:10.1073/pnas.0910486107)

3.         Zahavi, A. & Zahavi, A. 1999 The Handicap Principle: A Missing Piece of Darwin’s Puzzle. OUP USA.

4.         Darwin, C. 1859 On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. 1st edn. London, UK: Murray, John.

5.         Trivers, R. L. 1972 Parental investment and sexual selection. In Sexual selection and the descent of man, 1871–1971 (ed B. Campbell), pp. 136–179. Chicago, IL: Aldine.

6.         Haig, D. 2004 Genomic imprinting and kinship: how good is the evidence? Annu. Rev. Genet. 38, 553–585. (doi:10.1146/annurev.genet.37.110801.142741)

7.         Haig, D. 2014 Troubled sleep Night waking, breastfeeding and parent–offspring conflict. Evol. Med. Public Health 2014, 32–39. (doi:10.1093/emph/eou005)