Lessons from the Banded Stilts

One of the less accessible set of key ideas underpinning evolution (and, hence, optimal human fitness and diet strategies as well as environmental change) relates to uncertainty, irregularity, instability and their manifestation in power laws.  Understanding these ideas is a hurdle for many of us; internalizing that understanding so we can apply it to problems with the same fluency we apply to the use of our first language is even more difficult.  An illustration of the importance of uncertainty is given in the article by Libby Robin of the ANU published in the Canberra Times of 24 September 2002.

Her article describes how naturalists and, later, scientists, came to understand the breeding and migration cycles of the Banded Stilt, a long-legged, medium-sized Australian wading bird with a needle-like beak.

19th century naturalists and egg collectors were of European origin and intellectual and cultural formation.  They thought in terms of four standard seasons (spring, summer, autumn and winter) and how (European) birds’ breeding and migration cycles could be mapped reliably to those seasons.  For them, the seasons were not only distinct; they were also regular and reliable.  But arid Australia, with its extremes dominated by the irregular El Nino phenomenon, followed no annual cycle.  The European Australians explained environmental fluctuations in terms of ‘failure’ of rainfall or the ‘tragedies’ of bushfires and floods as they unconsciously struggled to squeeze their observations of nature into the Procrustean bed of their European preconceptions.

The Banded Stilts are relatively common along the southern and south-western coasts of Australia.  But little was known of their breeding, nor why entire colonies disappeared in their tens of thousands at irregular intervals.  It was only in 1930 that an isolated farmer contacted a Perth museum about the influx of the birds onto freshly flooded land that the mystery was solved: the Stilts were ‘winter breeders’.  But further floods just six months later produced evidence of identical weight that the Stilts were ‘summer breeders’.  The naturalists thought the birds had been confused by the irregular weather extremes of that year; in fact the birds probably had no concept of our ‘calendar years’ and, instead, were responding with ease finely tuned over millions of generations to optimize their survival in the Australian environment.

Immediately after heavy rain they migrate to the flooded flats and saltpans of the distant inland to breed in anticipation of the brine shrimps and other feed which proliferates in freshly flooded arid lands.

Robin says: ‘Banded Stilts’ nests were hard [for European humans] to find because they defied expectations shaped elsewhere.  Nesting is not annual, not seasonal or affected by day length, not in regular locations or even tied to flowering or seeding of particular plants … Cultural preconceptions shape the understanding of fauna and place in subtle ways. …’

Then Robin proceeds to draw out the lessons of her story.  ‘If, however, we try to think like a Banded Stilt, we might revisit some of our cultural preconceptions … Banded Stilts are a species that can teach us much about living with uncertainty, how to take opportunities as they arise, but not to expect regularity.  Lack of regularity challenges all fiscal models built around annual cycles.  The global economy is annual, based on seasonal agricultural regularity [Robin could have added reporting requirements and consumer demand] … it is much easier to make international treaties to protect migratory birds on regular annual flights along international “flyways” than to manage rangelands … for unpredictable, non-annual seasons.’

What lessons can we draw from Robin’s article?

Humans evolved in lands without our traditional four seasons.  Until the predominance of agriculture over the hunter-gatherer and big game hunting lifestyles, our ancestors evolved to be opportunistic within the constraints of the natural environment.  They ate the foods that gave them the greatest chances of survival and pleasure for the least effort: tubers, nuts, fruit, vegetables and carrion (and their associated activities: walking, digging, harvesting and carrying) and fresh meat when it was relatively easy to obtain or otherwise preferable (and their associated activities: cooperation and planning followed by sprinting, grappling, carrying and butchering).

Has the regularity of the European seasons, which is actually rare on the planet as a whole, directed our cultural preference toward order, regularity, predictability and routines?  And has this preference often blinded us to the possibility that other, more subtle, patterns may be more appropriate responses to environmental phenomena?

Today we feel obliged to keep even our wilderness areas tidy, safe, fire resistant and visually appealing to meet the expectations of visitors and public liability insurance obligations.  Our approaches to diet and exercise are based on structure, patterns (generally linear) and, importantly in the affluent West, the expectation of consumer choice which meets our expectations of comfort, ‘balance’ and other unexamined cultural determinants which generally serve to separate us from our environmental heritage.


Unfortunately, the Canberra Times article is not available on the internet.


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