Courtship & Parenting Tips from the Male Superb Fairy-Wren (Malurus cyaneus)

Native to the scrubland fringes of Australia’s eucalypt woodlands, superb fairy-wrens spend most of their days hunting grasshoppers or snuggling on low-hanging branches in bundles of 2… 3… sometimes 5. Lavishly-feathered, “rampantly promiscuous,” and a common visitor of children’s parks, they’ve been ballyhooed by The Guardian as Australia’s favorite bird. Despite their cotton-ball size, these flamboyant daredevil passerines pack a suit of evolutionary aces up their tail feathers, especially when it comes to courtship!

1. Keep in mind that your vibrant plumage attracts predators

3 seasons of the year, fairy-wrens don the drab, downy coloration of a miniature koala, but come the next molt, all bets and feathers are off. With dazzling sapphire cheek plumes and a midnight-blue jabbot, the breeding plumage of the male superb fairy-wren is a spectacle of sexual selection. But while gleaming like a crown jewel captivates females, it’s also a flashy candy wrapper to predators. Being sexy is dangerous.

Male fairy-wrens are cognizant and even cautious of this (McQueen, Naimo, Teunissen et. al. 2017). In their 2017 paper, “Bright Birds are Cautious: Seasonally Conspicuous Plumage Prompts Risk Avoidance By Male Superb Fairy-Wrens,” an Australian research team details differences in antipredator responses between superb fairy-wrens of different plumage types. Broadcasting the species’s alarm calls to a population in Lysterfield Park, Australia, they found that blue males were 50% less likely to forage on open ground, took over twice as long to reemerge from cover, and showed a stronger immediate response to predator alarm calls (2017). They propose that breeding fairy-wren males are well aware of their conspicuous plumage and make behavioral adjustments accordingly to avoid predation, and that flock members can benefit from the heightened vigilance of these blue males, either as an early warning system or as a bright decoy (2017).

2. When in doubt, bring her flowers

Because being fabulous ain’t enough to turn up the charm, the superb fairy-wren suitor will bequeath females with a single yellow flower petal, perhaps to accentuate his scintillating blue-black plumage. However, despite the temptingly-anthropomorphic similarities, petal-bearing is no diamond-ring proposal – more like a booty call!

Superb fairy-wrens have the highest rate of “extra-pair fertilization” (AKA cheating) out of any bird species (Double, Cockburn 2000). Though superb fairy-wren flocks are headed by an older, territorial “primary” male that is socially bonded to a single female, cheating is rampant, and a whopping 95% of their broods contain offspring sired by a different father (Mulder, 1997; Mulder, Dunn, Cockburn et. al.  1994). An observation-based study by Raoul A. Mulder, “Extra-group Courtship Displays and Other Reproductive Tactics of Superb Fairy-wrens,” determined that in its 375 observations of fairy-wren courtship displays, petal bearing was performed “exclusively (97%) for extra-group females during excursions into neighbouring territories by lone males, and appears to have evolved specifically for the purpose of soliciting future extra-pair fertilizations” (1997).

3. Evolve Extra-Fancy Sperm

Polygamy’s rough – to maximize reproductive success, individuals of promiscuous species not only have to tirelessly woo as many partners as possible, but also have to deal with sexual selection post-copulation – rife with chemical manipulation, copulatory inhibitors, competitive sperm morphology, hostile pH fluctuations, and intersexual conflict, fertilization is a gametic war zone. Mating multiple times is great, but how does an organism ensure that each of its efforts successfully produced offspring?

Sometimes, it’s a numbers game. Fairy-wrens are known for their copious sperm loads – Malurus splendens, a close cousin to the superb fairy-wren, produces over 8.3 billion sperm per ejaculate (In comparison, a dose of human ejaculate only contains around 280 million) (Tuttle, Pruett-Jones, Webster 1996)!

Alongside gamete quantity, sperm variation and competition becomes especially intense amongst superb fairy-wrens, where the reproductive success of different paternal strategies vary with sperm morphology (Calhim, Double, Margraf et. al. 2011).

In quantifying the relationship between head : flagellum ratio and reproductive success in this species, Calhim, Double, Margraf et. al. mist-netted, banded, and non-invasively sampled sperm from M. cyaneus males from different reproductive stages in their life history. After observing and determining parentage of the offspring, the team calculated intrapair success, measured as the number of offspring the male sired for his social mate, as well as extrapair or “cuckolding” success, “measured as the lifetime number of illegitimate offspring that survived to four weeks after fledgling” (2011). Their study, “Maintenance of Sperm Variation in a Highly Promiscuous Wild Bird,” details that intrapair success was strongly associated with a longer flagellum and relatively shorter head, while a short flagellum and a relatively large head was associated with better extrapair success (2011).

4. Help your mate teach your chicks a song to distinguish them from brood parasites.

Even after their eggs are laid and their brilliant feathers dust over, fairy-wren parents must still be on high alert: both for predators, and for the insidious Horsfield’s bronze cuckoo, who lurks around poorly-guarded nests. Given the opportunity, the female cuckoo will descend, roll one of the wrens’ eggs out of the nest, and replace it with one that looks deceptively similar – pink, with a ring of dark speckles at its base. Securely tucked within the lofty grass walls of the nest, superb fairy-wren parents would hardly be able to tell the difference, so what they do instead is sing a secret passcode to their eggs (Colombelli-Ne´grel, Hauber, Robertson et. al. 2012).

9-10 days before the brood hatches, superb fairy-wren mothers titter a fast, high-frequency trill ranging from 5782.8-11,011,2 ± 250.0 Hz, which her chicks embryonically learn as they develop within their eggs (2012). Within every incubation call is a signature sequence that is unique to each female – the hatchlings who can sing their mother’s fingerprint best are the ones who get fed, and the hatchlings that can’t imitate her calls are abandoned or discarded (2012). The females communicate this to their mates, too, so that they could aid in distinguishing their chicks (2012). The eggs hatch after 15 days, and as the cuckoos start laying 13 days into the fairy-wrens’ incubation period, their foreign chicks get less time to memorize their foster mother’s calls, and thus are most likely to be pushed or starved out of the nest (2012). The joint team of psychology and zoology researchers who reported these findings in their paper, “Embryonic Learning of Vocal Passwords in Superb Fairy-Wrens Reveals Intruder Cuckoo Nestlings,” speculate that this co-evolutionary arms race between superb fairy-wrens and their brood parasites could intensify selective pressures for finer-tuned acoustic learning in both species’s offspring (2012).

All in all, superb fairy-wrens are frickin’ awesome! Ever flitting, singing, and glittering in the Aussie sun, these avian divas are a star 3.4 billion years in the making. Their richly-textured social lives have established new extremes in our study of coevolution, intersexual conflict, postcopulatory selection, and avian social psychology, and that’s barely the beginning of the profound body of research that needs to be done on this species. It just goes to show that even the tiniest species have eons to reveal about the diversity of life on Earth, and our study of evolution will never be complete without them!

SOURCES:

Colombelli-Ne´grel, D. Hauber, M. E. Robertson, J. et. al. (2012).

Embryonic Learning of Vocal Passwords in Superb Fairy-Wrens Reveals Intruder Cuckoo Nestlings. Current Biology, 22: 2155–2160.

Mulder, R. A. Dunn, P. O. Cockburn, A. et. al. (1994). Helpers liberate female fairy-wrens from constraints on extra-pair mate choice. Proceedings of The Royal Society B, 255(1344): 223-229.

Tuttle, E. M. Pruett-Jones, S. Webster, M. S. (1996). Cloacal protuberances and extreme sperm production in Australian fairy-wrens. Proceedings of The Royal Society B, 263(1375): 1359-1364.

Calhim S, Double MC, Margraf N, Birkhead TR, Cockburn A (2011) Maintenance of Sperm Variation in a Highly Promiscuous Wild Bird. PLoS ONE 6(12): e28809. https://doi.org/10.1371/journal.pone.0028809

Mulder, R. A. (1997). Extra-group Courtship Displays and Other Reproductive Tactics of Superb Fairy-wrens. Australian Journal of Zoology, 45(2) 131 - 143.

McQueen, A. Naimo, A. C. Teunissen, N. et. al. (2017). Bright Birds are Cautious: Seasonally Conspicuous Plumage Prompts Risk Avoidance By Male Superb Fairy-Wrens. Proceedings of The Royal Society B, 284(1857).

Double, M. Cockburn, A. (2000). Pre–Dawn Infidelity: Females Control Extra-Pair Mating in Superb Fairy–Wrens. Proceedings of The Royal Society B, 267(1442): 465-470.

Bird Journal - Brown Pelicans

A flock dozing off at Elkhorn Slough – July 23, 2017. Monterey Bay, CA

Brown pelicans are the lumbering Paul Bunyans of the seabird world. The snaking arcs of their necks look almost prehistoric, and indeed, the earliest known pelican, dating back to over 30 million years ago, exhibits little to no change in fundamental morphology (Louchart, Tourment, Carrier 2011)! 

As exclusively-oceanic predators, they have a bunch of cool sea-faring adaptations: specialized glands that allow them to drink salt water (Schmidt-Nielsen, Fange 1958), air sacs under their skin for added buoyancy (US Fish and Wildlife Service 2009), as well as a hunting technique that is novel amongst other Pelecaniids. 

The brown pelican is unique in that it’s the only plunge-diving pelican species in existence (2009). While most others of its clade will scoop at fish while sitting at the water’s surface, brown pelicans dive-bomb the sea like war jets, tucking their wings behind them in one deadly thrust. The timing of this part is crucial. If they don’t corkscrew to the right by just the right amount, they could fatally injure their trachea and esophagus. 

Assuming all goes well underwater, they flap their gums open. Their gular pouch balloons out like a 3-gallon net, ensnaring the hapless fish between their jaws: anchovies, sardines, herring, sheepshead, mullet, pigfish… Occasionally, they’ve even been seen gulping down crustaceans (2009). 

These ambush strategies have proven fruitful in chasing the ever-fast and finicky epipelagic fish, but plummeting from heights of 60 ~ 70 feet is not a skill they are born with (2009). Before maturing into sleek, bow-winged adults, pelican youngsters look something like this: 

It’s like an overcooked marshmallow tried to grow feathers (a 3-5 month old juvenile) – July 3, 2017. San Francisco, CA.

These little ones, while cute, are honestly terrible at fishing. I got the chance to see this particular one attempt a dive, during which it lost balance and smacked against the water in an explosive belly-flop! A 1969 paper, “Age and Hunting Success in the Brown Pelican (Pelicanus occidentalis)” by Gordon H. Orians, attests that plunge-diving is a technique that takes years to develop. Using a paired t-test of nearly 2000 observations off the coast of Playas del Coco, Costa Rica, Orians compared the catch rates amongst different life stages of brown pelicans, and found significant evidence that the learning period for the juvenile birds takes at least 18 months to 2 years (1969). Orians remarks that this phenomenon, if widespread, could in part explain why brown pelicans, as do many sea-faring bird species, exhibit an unusually delayed maturation (1969) – while juvenile brown pelicans fully fledge at about 3-5 months of age, they don’t reach sexual maturity until they’re about 3 years old (US Fish and Wildlife Service 2009). 

Once they hit breeding age, their chocolatey manes melt away. Their lores and bill area flush with color, and their eyes metamorphose from deep brown to salty-pale. 

As social birds, adult pelicans can often be seen soaring together in V-formation over the beaches of North and South America. There are lots of them diving off Santa Barbara and especially IV, so next time you see one of these bombardiering specialists, try and see if you could pick out the steps in its technique! 

SOURCES:

Department of the Interior, U.S. Fish and Wildlife Service (2009). Brown Pelican [Fact sheet]

Retrieved from

https://www.fws.gov/home/feature/2009/pdf/brown_pelicanfactsheet09.pdf

Louchart, A. Tourment, N. Carrier, J. 2011. The earliest known pelican reveals 30 million years of evolutionary stasis in beak morphology. Journal of Ornithology, 152(1): 15-20. 

Orians, G. H. 1969. Age and Hunting Success in the Brown Pelican (Pelecanus occidentalis). Animal Behavior, 17: 316-219. 

Schmidt-Nielsen, K. Fange, R. 1958. The Function of the Salt Gland in the Brown Pelican. The Auk, 75(3): 282-289. 

McShea & Brandon's BIOLOGY’S FIRST LAW – controversial, but worth a read

To anyone searching for a cool theoretical biology/evolutionary mechanisms book, Biology’s First Law by Daniel W. McShea and Robert N. Brandon is a pretty radical read! While its arguments are too complex to summarize in one blog post, its overarching argument proposes genetic drift as the first Zero-Force Evolutionary Law (ZEFL) of biology:

“ZFEL (general formulation): In any evolutionary system in which there is variation and heredity, there is a tendency for diversity and complexity** to increase, one that is always present but may be opposed or augmented by natural selection, other forces, or constraints acting on diversity or complexity” (3).

“ZFEL (special formulation): In any evolutionary system in which there is variation and heredity, in the absence of natural selection, other forces, and constraints acting on diversity or complexity, diversity and complexity will increase on average” (4).

There are some problematic aspects to this argument, however. It’s unclear how much value it holds as a null hypothesis, and it conflicts with the traditional view of drift as a constraint on variation. In addition, a 2012 review, “Puzzles for ZFEL: McShea and Brandon’s zero force evolutionary law,” by Barret et. al, rebutes McShea and Brandon, deeming the special formulation of ZFEL impossible as if it holds true that mutations indicate the presence of a force, and the absence of mutations indicate a constraint of the force, then a force or a constraint must always be present (2012). ZFEL also butts heads with Hardy Weinberg equilibrium, which McShea and Brandon regard as “problematic as a zero-force law because it mixes genuine evolutionary forces … with a non-force, namely drift” (McShea, Brandon 100). But despite the dissent over ZEFL as a viable biological law, I still considered Biology’s First Law a valuable read. ZEFL is elegant, intuitive, and holds a potentially formative perspective on what we consider the “norm” in evolutionary history. I also found its contrast with inertia (the zero-force law of physics) intriguing.

Browsing the literature available about this hypothesis gave me an interesting glimpse into the philosophy of science and how theoretical disputes play out in the academic world. If any of you guys have also happened to have read this book, or have put it on your reading list, let me know what you think!

**defined as the number of part types” or “degree of differentiation among parts” to avoid the anthropocentric connotations of colloquial complexity.

The Tree of Life

Explore Life on Earth
(or if you need phylogeny help)

"The affinities of all the beings of the same class have sometimes been represented by a great tree... As buds give rise by growth to fresh buds, and these if vigorous, branch out and overtop on all sides many a feebler branch, so by generation I believe it has been with the great Tree of Life, which fills with its dead and broken branches the crust of the earth, and covers the surface with its ever branching and beautiful ramifications."

Charles Darwin, 1859

Some recent interviews of interest to biologists

There have been two good interviews on NPR "On Point" in the last week.  The first (here) is with E.O. Wilson (who visited CCS 2 years ago) as he talks about his new book, "Letters to a Young Scientist"

The second (here) about some of the most incredible creatures on the planet.  The interview is with Caspar Henderson, writer and environmental journalist. His new book is “The Book of Barely Imagined Beings: A 21st Century Bestiary.” 

Norwegian sludge

Sometimes the oddest corners of biology research can suddenly hit the headlines (okay, the science headlines).

Mankind's remotest relative is a very rare micro-organism from south-Norway. The discovery may provide an insight into what life looked like on earth almost one thousand million years ago. 

 or, as ScienceDaily put it:  Rare Protozoan from Sludge in Norwegian Lake Does Not Fit On Main Branches of Tree of Life

Rewilding

Re-wilding North America: Nature 436, 913-914 (18 August 2005) North America lost most of its large vertebrate species — its megafauna — some 13,000 years ago at the end of the Pleistocene. And now Africa's large mammals are dying, stranded on a continent where wars are waging over scarce resources. However much we would wish otherwise, humans will continue to cause extinctions, change ecosystems and alter the course of evolution. Here, we outline a bold plan for preserving some of our global megafaunal heritage — one that aims to restore some of the evolutionary and ecological potential that was lost 13,000 years ago, and which offers an alternative vision for twenty-first century conservation biology.

Definitely one of the more controversial Nature papers of recent years. Just Google Pleistocene rewilding for lots of links. Or go to the Wikipedia article for lots of links and this handy guide for who replaces who:

• African Bush Elephant (as a proxy for the extinct Columbian mammoth)
• Sumatran Elephant (as a proxy for the extinct American Mastodon)
• African Forest Elephant (as a proxy for the extinct Pygmy Mammoth of Channel Islands of California)
• Mountain tapir (as a proxy for the extinct California tapir)
  
• Bactrian camel (as a proxy for the extinct camelops)
• Capybara (as a proxy for the extinct species of North American capybara)
  
• Onager (as a proxy for the extinct species of North American horses/asses)
• Grant's Zebra (as a proxy for the extinct Hagerman horse)
• Asiatic Cheetah (as a proxy for the extinct American cheetah)
• Barbary Lion (as a proxy for the extinct American lion)
• Siberian Tiger (occurred in Alaska during the Pleistocene; might also serve as a proxy for the extinct American Lion)

For a contrary view see Pleistocene Park: Does re-wilding North America represent sound conservation for the 21st century? in Biological Conservation

Biodiversity bonanza

Most wildlife photographers strive to capture their subjects in the field in as a natural setting as possible. Joel Sartore has been taking a different approach and has been traveling around the country photographing animals in zoos and wildlife parks against stark black or white backgrounds. The crisp, sharp pictures are more reminiscent of fashion shoots than wildlife photographs and I think he is achieving his aim:
 

This black-and-white background technique gives all species equal weight and importance. A tiny beetle is as interesting as a lion, and a two-toed sloth as cuddly as a panda bear. The clean background, combined with nice light, allows the viewer to look every species in the eye, the window to the soul. I hope these portraits will connect with viewers and get them to understand that all creatures have at least a consciousness as well as a basic right to exist.
For more pictures, and a nice video, check out this National geographic article or visit Joel's website.