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[Plus 2-3“irregularly breeding”Calidris (sp)]

= 27-36 % ofBarrow’s breedingspecies of avifaunabelong to 1 genus !

= 50 - 52 % ofBarrow’s breedingspecies are in a single order ofBirds !

As a recent product of 4 field seasons of tropical studies, I knew to expect that the number of species of plants and animals per unit area drops off as one progresses from the Equator to the North Pole. Clearly, Barrow’s hiccup in that progression of impoverished species numbers—a whole cluster of closely related bird species that breeds in high latitude, treeless, low-temperature conditions—defied biogeographic generalizations. This is the sort of “discrepant observation” that cries out for a rational explanation. (About 1/3 of the entire breeding avifauna at Barrow consists of small-bodied sandpipers assigned to one genus.)

Moreover, Pitelka’s rescue drew me into a rapidly developing synthesis between modern Evolutionary Theory and Quantitative Ecology in the 1960s. That “frontier science” led its participants to “expect” that this cluster of similar-appearing species of sandpipers could only co-exist or breed together anywhere, much less at resource-poor Barrow, if each species had somehow evolved to specialize on food resources so as to minimize competition with all other species present in that biological community.

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Even in my fifth summer of field research, however, my search for adaptive energy-saving, and heat-conserving physiological adaptations was turning up empty: On the contrary, all of Barrow’s breeding sandpiper species seemed physiologically profligate, eating lots, maintaining high metabolic rates, incubating less of the 24-hour cycle than seemed adequate for optimal rates of development of embryos, dumping heat, etc.

One gray morning, just after many of the sandpipers’ eggs had hatched, my very capable field assistant was being…”underfoot”…so I asked him to go forth with our new quick-registering thermometers. He was to act like a statue where very small sandpiper chicks were known to be feeding. Then he was to rush from hiding, pounce on one of these fuzzballs, and quickly determine its deep body temperature with a cloacal probe. This was, as I had expected, a time-consuming operation, during which I could get some overdue paperwork done in the lab. I did not see my field assistant again until suppertime. He produced a clipboard with a list of some 18 deep body temperatures from free-foraging chicks. Wow! Could this be real? The mean body temperature of these undistressed little fast-growing chicks was around 25 degrees C—not the 41 degrees common to adults of the same species. With a few more days of measuring, we confirmed this one small energy-conservative trick:

Insight # 1: With low thermostat settings, Calidris sandpiper chicks can devote a greater share of their intake energy to growth, and less to thermoregulation!

Volcanology, Meteorology, Embryology, Sedimentology, Ontogeny, Thermodynamics, Taphonomy, Hydrography, Geography, Glaciology,Tectonics, Taxonomy, Cartography, Aeronomy, Stratigraphy, Ecology, Phylogeny, Space Physics, Physiology, Biogeography, Immunology,Sociobiology, Political Science, Economy, Pedology, Deuteronomy, History of Science, Evolutionary Theory, Agronomy, Oenology…….

Natvral Philosophy =  HistoireNaturelle

Centrifugal Forces {Darwin’s Era}Geology Biology

Geology

Stratigraphy, Seismology Biogeography, Paleontology

Centripetal Forces {Pitelka’s Era}

Geophysics, Ecology, ClimatologyEarth Science, Ocean Science, Cosmology

Environmental Sciences

That accidental discovery may have made a tiny contribution to…insights emerging all around me among the biologists and others working at Barrow during the International Biological Programme of 1967-74.

Years later, I finally appreciate the bigger picture of where we stood in the late 1960s in terms of the overall development of “frontier science.”

Here is a book in the Norton History Series that covers “Environmental Sciences.” We’ve experienced both the “centrifugal” and the “centripetal” tendencies in scientific specializations over the last few hundred years. Darwin thought of himself as a “Naturalist-Geologist” before Biology split as an academic specialty or discipline from Geology. Subsequently each of these two specialties subdivided again and again.

Beginning in the first half of the 20th century, combinations of specialties became increasingly important to scientists’ arriving at insights. Genetics and Natural History combined to develop the modern synthesis of Darwinian evolutionary theory, for example. Fields combined, then separated, only to recombine elsewhere.

At Barrow in the early 1970s, with the impetus of the International Biological Programme, we found ourselves at the cusp of quantitative ecological studies, in which we could as a team look at quantitative comparisons among different biomes: selva, grassland, deciduous forest, taiga, and tundra.

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These comparisons allowed our whole investigative team—not just any one of us alone—to gain insights on the uniqueness of the coastal tundra biome that we were studying.

The process of decomposition of carbon fixed into larger molecules (as “biomass, B) by primary producers (plants) at 71° N Latitude was shown to be greatly retarded or inhibited by year round limitations on microbial digestion by low soil temperatures. Thus, the “litter” compartment (L) grew faster than its constituents could be recycled. Today, we would salute “carbon sequestration” when describing why peat (dead organic material) accumulates in a shallow, seasonally thawed, or active layer of tundra, then tends to become semi-permanently locked away in permafrost below the living components and the underlying soils of tundra.

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Locked intopermafrost

Active LayerRemains Deep

Tundra Biome studies within the International Biological Programme at Barrow’s NARL showed us that tundra is one of the most out-of-balance biome types. The transfer functions from biomass to litter, and litter to soil, are extremely robust, but because of low soil and litter temperatures, there is little recycling from either component. This imbalance explains why peat builds up as “litter” in cold-dominated soils, like tundra and muskeg, where microbial decomposition is both temperature-and nutrient-limited.

Incidentally, the robust transfer functions (fat arrows) in Selva Biomes show why the litter (L) and soil (S) components are impoverished stockpiles of organic matter and nutrients, while the standing biomass in rainforests is such a large stock of carbon.

For contrast, steppe biomes (such as probably dominated the unglaciated grasslands of Beringia (such as big swaths of Interior Alaska) during much of the Pleistocene) have large standing stocks of nutrients and recycle-able carbon in their soils, analogous to the situation today on the Serengeti Plains of Africa.

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For illustration, the dark brown in this map of Pleistocene or Ice Age maximum glacial extent conditions shows the extensive Mammoth Steppe Biomes thought to have existed up through the time that mammoths and Blue Babe in our University Museum were dominant megafauna from Spain of today to Beringia. Possibly, much of the morphological evolutionary adaptive radiation by calidridine sandpipers really occurred during the 3 million years of the Pleistocene, and on the Mammoth Steppe Biome rather than on Tundra Biome communities.

Prof. Dale Guthrie, of course, is one of the leading experts on Pleistocene Mammoth Steppe ecology.

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The discrepant observations of a rich assemblage of breeding species of sandpipers at Barrow at last begin to make sense from related insights: These birds are living for a few brief weeks each year as carnivores at the apex of a separate trophic system from the one fueled by primary producers (grasses, sedges, mosses, forbs) through dominant herbivores (microtine rodents = lemmings) to their predators (owls, jaegers, foxes).

But wait! The story gets more interesting.

In 1974, Frank Pitelka of UC Berkeley, Steve MacLean of UAF, and Dick Holmes of Dartmouth published a synthesis paper on the evolution of social systems in calidridine sandpipers of the Arctic.

The different species of sandpipers breeding on Arctic coastal tundra have evolved (and are undoubtedly still evolving) behavioral strategies that allow them to partition scarce tundra resources effectively.

By contrast with Darwin’s finches on the Galapagos Islands, there are no big anatomical differences in feeding apparatus that clearly adapt any of the 4-5 species of Calidris sandpipers breeding simultaneously at Barrow to take different-sized food items. Instead, it turns out that there are generally stable behavioral differences among the species. (If their fragile bones preserve poorly for paleontologists, their behavioral patterns preserve not at all!). These behavioral differences take the form of distinct social systems with which the birds undertake their annual migration and breeding activities.

Graphically, the “Conservative Strategy,” with its monogamous breeding system and persistent pair bond is thought to be the ancestral form for this group of diverse experimenters. Strong pair bonds, shared nesting, incubation and parental care duties, long residence on the breeding ground through the breeding season, coupled with site fidelity, philopatry, and renewal of pair bonds in subsequent breeding years—all are variously conspicuous elements of the conservative breeding system. Only a rigorous bird-banding and individual marking effort allowed us to characterize each species’ social system over several years.

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Calidris alpinaDunlin & subspecies

Conservative: Monogamy, Philopatry; Site Fidelity

The Dunlin, Calidris alpina, is a cosmopolitan species, with 5-7 subspecies recognized worldwide. One subspecies breeds in southern Beringia, and winters along the Pacific coast of North America. Another breeds in Eurasia and northern Beringia, but winters entirely in southern coastal Eurasia. The subspecies that breeds in Arctic and subarctic Canada winters on the Gulf of Mexico and Atlantic coasts of North America. So, we have now looked at several populations of one species all characterized by one type of social system: males and females form permanent bonds. They tend to return to their same breeding territories year after year (site fidelity) and birds that hatch and grow in particular parts of the species’ breeding range tend to return there (philopatry) to breed as adults.

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Calidridine Sandpipers with Conservative Social Systems 14 species

The 1974 synthesis paper by Pitelka and his students showed 15 of the 24 species in the Calidris group followed what seemed to be the ancestral or archetypal strategy of conservative social system like that of the Dunlin. That strategy featured monogamous pairing, shared nest incubation between adult males and adult females, often philopatry, and a tendency toward site fidelity.

Preponderance is one reason for regarding Conservative/monogomous strategies to be ancestral. The second reason is because monogomy can be modified in the direction of one or another opportunistic social system, but biologists find it harder to conceive of specialized or derived opportunistic strategies being modified in the direction of conservatism.

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No persistent pair-bond; Female-only incubation;

Males distinctively ornamented; short tundra residency

By contrast with Dunlins, male Pectoral Sandpipers take no part in nesting or incubation, and individual males generally leave territories at Barrow within 7-10 days, and certainly before incubation is complete. Lighter, perhaps less experienced, male Pectorals tend to show up then, and some may mate with females that chance to lose nests to predators, but we’ve had no luck in documenting re-nesting.

Frank Pitelka of UC Berkely, Steve MacLean of UAF, and Dick Holmes of Dartmouth published their paper on the evolution of social systems in caldridine sandpipers of the Arctic. Pectoral Sandpipers, with their fleeting pair bond represent one of the derived, or “Opportunistic Strategies” developed as social systems by calidiridine sandpipers. Nine of 24 species were considered to have “opportunistic” social systems.

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Calidridine Sandpipers with Opportunistic Social Systems:9 10 Species

Too late to be included in that synthesis paper, Dr. Uriel Safriel of the Hebrew University and I conducted a round-the-clock study of individually marked pairs of Baird’s Sandpipers at Barrow in 1973.

We discovered that one or the other member of 3 or 4 of the half dozen pairs we followed during incubation of their eggs deserted, either suddenly or over a day or two, never to be seen again in Barrow.

We hypothesize that we were witnessing facultative divorce, such that one member of the pair was freed to attempt breeding again elsewhere farther north or east in the same season.

Although our sample size was too small to justify trying to publish the results, we became convinced that the Baird’s Sandpiper had evolved a fourth social system within the general strategy of opportunism.

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