Birds are one of the best known and most
highly valued elements of the natural world,
comprising more than eleven thousand
different species, an extraordinary variety,
ranging from hummingbirds to ostriches,
from penguins to eagles. Each species is
unique, in its appearance, in its habits and
in where it is found. Some occur in huge
numbers and others are represented by only
a handful of remaining individuals; some are
relatively sedentary, with individuals spending
their entire lives in an area of a few hectares,
while others undertake extraordinary annual
migrations, covering literally half the world
Because of the location of Egypt on a major fly-
way, millions of fall Eurasian migratory birds,
exhausted from their long flight over the arid
landscape of the Levant and the Sinai, or from their
journey over the Mediterranean Sea, yearly join in-
digenous species in the wetlands of the Nile Delta.1
Such a spectacle could not fail to leave a lasting im-
pression on the ancient Egyptians, whose survival de-
pended on their observation skills and their under-
standing of the environment. A wealth of evidence, in
the form of iconography, written material, and faunal
remains uncovered near the sites of ancient hunting
camps in the Eastern Sahara and in settlements in the
Nile Valley and Western Desert oases, indicates that
ancient Egyptians capitalized on the providential and
cyclical passage of large flocks of birds. They endeav-
ored to capture them; they reared them in captivity
and incorporated them in varied facets of daily life.
Whether as food for the living or as offerings to the
deceased and to the many gods of the Egyptian pan-
theon, birds remained an intrinsic part of the lives of
all ancient Egyptians.
the capture of birds
As early as the late Palaeolithic period, the inhab-
itants of the Nile Valley were taking full advantage
of the resources provided by the fauna surrounding
them. In particular, the predictable arrival of millions
of birds twice a year during fall and spring migrations
appeared as a reliable source of protein, which was
complemented by the large number of catfish travel-
ing with the Nile flood, as well as the wild cattle and
hartebeests grazing alongside the river (Gautier 1987,
p. 431). Already 15,000 years ago, hunters manifested
their interest in the avifauna by carving depictions
of waterfowl in the company of herds of wild cattle
on the cliffs overlooking the Nile River.
Their flight is direct, with continued flapping and no periods of gliding. House Sparrows aggressively protect a small territory just around their nesting site. This is believed to be strictly a protection of the nest site, and not of any feeding areas. Sparrows have been observed to threaten, and if necessary, attack 70 species of birds that have come into their nesting territory. In these attacks males attack males and females attack only females. House Sparrows are gregarious and active during the day. In North America there may be some local movements in response to weather changes but House Sparrow populations do not migrate extensively.
Fisher’s run-away selection
If Darwin’s contemporaries were sceptical of his theory of sexual selection, his successors ignored it almost completely,for nearly a hundred years. Today, however, sexual selection is one of the most vigorously pursued branches of modern evolutionary biology. Both male–male competition
as well as female choice are widely accepted mechanisms of sexual selection. Much progress has been made in thinking about, and to some extent in understanding,why females might choose particular males—what’s in it for them if the males are not necessarily the best survivors? Ronald Fisher, one of the architects of the genetical theory of evolution was the first to propose a model of female choice. Fisher argued that at first, the slightly exaggerated male character, such as an intermediate sized
train of the peacock might well be correlated with male quality (ability to survive). At this stage females will be selected to prefer peacocks with long trains. Later the very fact that peahens prefer males with elaborate and long trains can drive selection on peacocks to grow trains even longer and more elaborate than is good for their survival. Fisher called this process run-away selection
5. It is ironical that Fisher, who produced precise mathematical models for all his theories, left this one alone unformulated in mathematical language and therefore untested even for its plausibility. But today there exist mathematical models that justify Fisher’s arguments—run-away sexual selection can indeed work in the manner that Fisher thought it might. A crucial aspect of Fisher’s theory, and one that contrasts with other theories (see below), is that peahens continue to be selected to prefer peacocks with
long trains even after such peacocks are no longer the best survivors. They are supposed to do so because they find peacocks with long trains beautiful and are compensated for mating with less than the best survivors because their sons will also have long trains and will be preferred by peahens of the next generation. Will this process of ever increasing length of the trains ever stop? Yes, it will
but Fisher’s prediction was that it will not stop just when peacocks with the longest trains are the best survivors but well after the trains have become much longer than is good for their survival. We may therefore think of Fisher’s theory as one which predicts that the peacock’s long train is preferred by the peahen merely because it is beautiful and not because it is also an honest signal of the peacock’s
ability to survive.
Zahavi’s handicap principle
Of the many theories proposed for sexual selection in
general and female choice in particular, the one most
different from Fishers’ run-away selection theory is the
handicap principle proposed by Amotz Zahavi. Zahavi
made the radical suggestion that the peacock’s long tail is
selected precisely because it is a handicap, not in spite of
being a handicap. By carrying around such a handicap of
a tail and by not yet having succumbed to a predator, the
peacock reliably demonstrates to females that he is indeed
very fit6. Zahavi derived from this idea a far-reaching general
principle that animal signals in general must impose a
differential cost, a handicap, on the signaler in order to be
reliable and thus resistant to faking7. It is the disproportionate
cost to low quality males that is imposed by the
handicap which prevents them from cheating. The scientific
community rejected Zahavi’s ideas outright. Several
distinguished theoretical evolutionary biologists wrote
mathematically sophisticated papers arguing that the handicap
principle cannot work. One paper was actually entitled
‘The handicap mechanism of sexual selection does not
work’8.
Then everything changed in 1990 when Alan Grafen
published two papers showing, with the aid of more economically
inspired mathematical models, that Zahavi’s
handicap principle can indeed work, both in the evolution
of honest signals in general and in the context of sexual
selection9,10. Today, Zahavi’s handicap idea and the more
general, costly, honest signal idea are widely accepted
and have considerably altered the way in which we model
and study animal communication and behavioural evolution.
The well-known evolutionary biologist John Maynard
Smith has graciously admitted publicly that he was
wrong in hastily concluding that Zahavi’s idea was in
error. But of course Maynard Smith said it in his inimitable
style11: ‘I was cynical about the idea when I first
heard it, essentially because it was expressed in words
rather than in a mathematical model. This may seem an
odd reason, but I remain convinced that formal models are
better than verbal ones, because they force the theorist to
say precisely what he means. However, in this case my
cynicism was unjustified. It has proved possible to formulate
mathematical models showing that what Zahavi
called the “handicap principle” can lead to the evolution
of honest signals.’ In contrast to Fisher’s run-away selection
theory, we may think of Zahavi’s theory as one
which predicts that the peacock’s elaborate train is preferred
by the peahen not merely because it is beautiful
but because it is also an honest signal of the peacock’s
ability to survive.