Poultry and Eggs

Avian Evolution

This book seeks precision by specifying animals, plants, fungi, bacteria, and protists’ scientific names. These names are part of the International Code of Phylogenic Nomenclature and are meant to standardize biology’s language. The taxonomic rank class includes Aves, whose members are birds. These vertebrates lay eggs with hard shells, have wings and feathers, and are warm blooded.

Like all life, birds are evolutionary products with histories that recede ages into the past. Scientists and journalists have popularized birds’ evolution from dinosaurs, tracing the avian lineage to species that behaved in ways reminiscent of modern birds. For example, these prehistoric creatures made nests for eggs, which mothers guarded, sitting on them to warm the embryos. These species, known as theropods, had hollow, light bones, a feature that would ease liftoff when their descendants evolved wings.

Theropods were carnivores that probably began to diverge from other dinosaurs between 227 and 174 million years ago.1 This theropod class, known as coelurosaurs, included Tyrannosaurus rex, whose reputation for ferocity enthralled generations of children. In Jurassic Park (1993), American filmmaker Steven Allan Spielberg (b. 1946) popularized the genus Velociraptor, another coeluro- saur. Bipedalism freed these animals’ front arms, which their descendants would adapt for flight.

The chief adaptations appear to have evolved between roughly 200 and 150 million years ago and include feathers’ origin and development, reduction in body size, forelimbs’ elongation into wings, enlargement of shoulder bones and sternum to bear arm muscles’ mass and strength, and increase in tail strength and stiffness to improve balance and maneuverability.2 These changes are evident in fossils about 160-150 million years old. For example, a 160-million-year-old specimen of Anchiornis huxleyi in what is today Manchuria, China—Chapter 8 describes its geography—had claws for impaling prey and climbing and descending trees to pursue food or escape predators.3 Feathers likely enabled flight and insulated the bird from cold, heat, and water. Since the 2009 find, scientists have unearthed over 200 kindred fossils. Rarer are the twelve of Archaeopteryx lithographica, which lived about 150 million years ago in what is now Germany.4 The initial 1861 discovery came just two years after British naturalist Charles Robert Darwin (1809-1882) published On the Origin of Species and provided vivid evidence of transitional species by combining reptilian and avian traits.

Diminutive, these animals were not the behemoths whose fossils fill museums and excite children. They occupied faunal interstices and might have remained curiosities but for the mass extinction about 65 million years ago that extirpated around 90 percent of terrestrial species.5 Their competitors gone, birds expanded to over 10,000 species and to every continent.6 Even inhospitable Antarctica has forty-six species.7

Birds and Eggs Entered Diets

Pre-Homo sapiens’ Consumption of Birds and Eggs

This radiation predated humanity’s origins, which Chapter 3 recounted. That chapter and others emphasized humans’ omnivory and eclecticism, characteristics consistent with early consumption of birds, eggs, and much else. This supposition gained credibility with the 1959 discovery of the first specimen of what is now classified Paranthropus boisei (see Chapter 3) amid bones from several animals and eggshells.8 Besides P. boisei, anthropologists discovered ostrich (Struthio camelus) eggshells at Zhoukoudian, China, which Homo erectus occupied about 780,000years ago.9

These finds do not prove pre-tf. sapiens' egg eating because another predator might have been the consumer. Yet eggshells are intriguing because it is difficult to envision what else would have been careful enough to take an egg without prematurely breaking the shell. Moreover, the ostrich shells are charred, intimating cooking, a behavior that appears at be unique to Homo. The P. boisei fossils, roughly 1.8 million years old, may mark egg eating’s origins, though doubts have arisen about the diversity of his diet. If eggs were consumed at the dawn of humanity, birds must likewise have entered diets early because it seems unreasonable to suppose that hungry hominids monitored birds closely enough to find the nest but were too obtuse to identify them as potential food.

H. sapiens’ Early Consumption of Birds and Eggs

Like procurement of any plant or animal before agriculture and animal husbandry, birds had to be captured and eggs collected. The prospect of snaring an animal able to evade predators through flight may have been daunting, though American ornithologist Richard Fourness Johnston (1925— 2014) stated that “Many kinds of birds can be caught readily.”10 Humans long ago appreciated them, especially young adults, as “superior fare” and “highly prized” eggs.11

By observing birds, prehistoric peoples tracked their habits and detected their vulnerability in spring during molting and nesting and in autumn when summer engorgement fattened them.12 During the Mesolithic Period (9000-7000 BCE), humans reconnoitered wetlands for several species. For example, Danes hunted mallards (Anas platyrhynchos), swans (Cygnus species), grebes (species in the family Podicipedidae), Eurasian coots (Fulica atra), cormorants (species in the family Phalacrocoracidae), and gulls (Lams species). Near the North and Baltic Seas, hunters targeted Eurasian cranes (Grus grus), swans, cormorants, and sea eagles (Haliaeetus species). Mesolithic Germans consumed mallards. To the east, Baltic, Polish, and Russian wetlands yielded numerous bird bones as dietary evidence. Eighty-nine percent of bones from a Mesolithic site along Estonia’s Narva River are waterfowl, chiefly mallards.13 Likely wielding slings, Iron Age (800 BCE-42 CE) Britons near what is today Somerset, England, also hunted mallards.

Overconsumption and Extinction

Dodo

The appetite for birds, eggs, or both eradicated the dodo (Raphus cucullatus). Although the bird was too large and heavy to fly, its smaller ancestors flew to the Indian Ocean island Mauritius during the last 8 million years, though the date of arrival has not been pinpointed.14 Absent predators, dodos grew larger and lost or never developed a startle reflex. Enlargement is curious given that many species shrink on islands, a phenomenon known as island dwarfing. African, Arab, and Indian sailors identified but did not settle Mauritius in the tenth century CE.15 The Portuguese arrived in 1507 but never mentioned a flightless bird.16

Dutch colonists, however, encountered it around 1598.17 They must have sampled the bird, else they could not have lamented its toughness and unpalatability.18 These defects may explain why a 2013 investigation found no dodo bones in island middens.19 Even if humans disliked the flesh— excepting tasty breast, stomach, and intestines—they devoured the dodo to satiate hunger and enjoyed its eggs enough to imperil the species.20 Moreover, their tagalongs—dogs, pigs, cats, and rats—also ate the eggs and outcompeted dodos for food.21 Extinction came within eighty years of Dutch settlement.

Passenger Pigeon

Misfortune likewise befell passenger pigeons (Ectopistes migratorius). American journalist Barry Yeoman summarized their appeal, writing that they “were tasty...and their arrival guaranteed an abundance of free protein.”22 An onlooker might have thought their demise improbable given passenger pigeons’ status as the most numerous bird in North America and perhaps the world. American ornithologist Alexander Wilson (1766-1813) estimated a single flock above 2 billion birds.23 These creatures—“the most numerous bird ever to exist on earth”—may have totaled 9 billion at their zenith.24 But their noisiness alerted hunters, and their habits were predictable. In the nineteenth century, American naturalist John James Audubon (1785-1851) warned that overhunting threatened them, though few heeded him.25 In 1900, an Ohioan killed the last wild specimen, and fourteen years later the final captive died in Ohio’s Cincinnati Zoo.

Passenger pigeon eggs. (Photo courtesy of Library of Congress, https://www.loc.gov/pictures/ item/2016872686/.)

FIGURE 6.1 Passenger pigeon eggs. (Photo courtesy of Library of Congress, https://www.loc.gov/pictures/ item/2016872686/.)

Bird and Egg Consumption in the Americas

Earlier in North America, Mississippians ate these pigeons, wild turkeys (Meleagris gallopavo), mourning doves (Zenaida macroura), songbirds (species in the clade Passeri), herons (species in the family Ardeidae), ducks, and geese (Branta canadensis and Anser species).26 Turkeys, ducks, and geese fed natives and Spaniards in Florida. Turkeys were eaten throughout Central America, Mexico, and the American Southwest. Later sections enlarge the discussion of turkeys and their eggs as food, evaluating their nutrition and healthfulness in pre-Columbian times.

Colonizing the Americas, Europeans intensified poultry husbandry and consumption. Into the mid-twentieth century, family farms raised birds, usually chickens, for meat, eggs, and income.27 Farmers and consumers favored poultry because of inexpensiveness and efficient conversion of grains, notably corn (Zea mays), and soybeans (Glycine max) into protein as meat and eggs. The drive toward economy is evident in the fact that about 1940 the average chicken needed roughly 3 kilograms (6.5 pounds) of feed to produce 0.5 kilograms (1 pound) of flesh whereas around 2012 that chicken yielded the same mass on only 0.8 kilograms (1.8 pounds) of feed.28 Moreover, poultry start-up costs have been, and are, low.29 Feed and housing are cheap, and domestic birds tend to be hardy.

Pursuit of economy has made chicken cheaper than beef or pork. In 1960, 0.5 kilograms of chicken breast retailed for 42.7 cents in the United States.30 That year the same mass of pork averaged 55.4 cents and beef fetched 82.1 cents. Chicken has held this advantage, retailing in the United States for $1.90 per 0.5 kilograms compared to $3.70 for the same quantity of pork and $5.95 for beef by a March 2019 estimate. Critics complain that agribusiness exploits chickens, though consumers want bargains at the grocer.31

World Consumption of Birds and Eggs

Around 1995, chicken surpassed beef in global sales.32 Since 1999, the world has produced more chicken than beef.33 Only pork outstrips chicken in world sales and consumption.34 Beyond chicken, turkeys rank fifth in global sales and consumption, ducks seventh, and geese ninth.35 Outside the top ten, pigeons (Columba livia domestica) and unspecified birds are seventeenth. Among livestock, chicken production is growing fastest worldwide at roughly 5 percent annually, a rate that doubled metric tonnage between 1980 and 2003.36 Between 1988 and 2003, countries with the largest income growth tripled chicken production and consumption. By comparison, global pork production is growing 3-4 percent yearly and beef 1-2 percent. World egg supply is increasing over 3 percent per year.37 Turkeys, ducks, geese, and guineafowl (Numididae meleagris) furnish eggs, though most come from chickens.

 
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