Migration of Northern Birds: Encyclopedia Arctica 4: Zoology (Birds)

Author Stefansson, Vilhjalmur, 1879-1962

Migration of Northern Birds

EA-Zoology (William Rowan)


The spring and fall migration of birds in the northern hemisphere are schoolboy knowledge. One does not have to be ornithologist to know that robins, swallows, and many other species are here during the summer months and absent in winter; their journeying back and forth from place to place are called migrations. Hans Gadow’s definition of the word (3) is perhaps the best extant and runs as follows: “Migration is the wandering of living creatures into another, usually distant, locality in order to breed there: this implies a return, and the double phenomenon is annual. All other changes of the abode are either sporadic, epidemic or fluctuating within lesser limits.”
Typically, migration routes extend north and south, for many birds must vacate the Far North during the winter months in order to avoid starvation and death. Since food of great variety is available the year round in the more equable climates of lower latitudes, the fall migration is, generally speaking, southward. Yet there are many exceptions, some of which will be noted.
Many of our common northbound migrants of spring do not remain with us through the summer months at the latitudes of, say, the northern United States or Canada, but travel through and beyond them to make a transitory reappearance in the fall on their return journey. Certain species, such as knot

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( Calidris canutus ) and sanderling ( Crocethia alba ) go so far north for the summer as to breed wholly within the Arctic Circle. Numerous other species, including the snow goose ( Chen hyperborea ), Canada goose ( Branta canadensis ), and snow bunting ( Plectrophenax nivalis ), breed both within the without the Circle. Since the total arctic bird populations of the summer run into mil– lions of individuals, the inference is that there is no limit to the food supply at this season, a supposition amply supported by explorers, and afford– ing an important contrast between the Arctic and Antharctic. The point war– rants brief consideration.
The map on page 52 of Rowan’s Riddle of migration (16) conveys at a glance one of the two outstanding aspects of the case, which is this: whereas the land masses of the Southern Hemisphere (Australia, Africa, and South America) extend only to latitudes 40°, 35°, and 55° S., respectively, and are compara– tively restricted, much larger land masses spread continuously in the Northern Hemisphere to beyond latitude 80° N. the southern end of Australia, for in– stance, if that island were inverted and placed in the Northern Hemisphere, would just reach to New York, w ^ h ^ ile the extreme tip of South America under the same circumstances would barely stretch to Edmonton, Alberta. Except for ice– bound Antarctica, and remainder of the Southern Hemisphere (save only for cer– tain islands) is open ocean.
The second significant point is one of temperature. While the winter of of the Antarctic is on the average less severe than that of the Arctic, summer temperatures are lower and remain consistently below the minimum tolerated by most plants; from the whole of Antarctica only two flowering species and a mere handful of mosses and algae are known (4). In contrast, over 760 species of flowering plants have been recorded from the Arctic, 120 of them, including

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chickweed and dandelion, as far as 600 miles north of the Circle. In addition there are some 600 nonflowering species (17). At latitude 64° S. the mean temperature of the warmest summer month (January) is −0.9°C., resulting in an in ^ e ^ vitably flowerless world. In contrast, latitude 64° N. (about the level of Trondheim in Norway) is a mass of bloom during its warmest month, July. Insect life presents an analogous picture of extreme paucity in the Antarctic and un– limited plenty in the Arctic. The only insects known to be abundant in the Antarctic are parasites on seals (1), while the only birds of numerical note are the penguins and various petrels — including the so-called cape pigeon ( Daption capense ) — which depend on the sea, not the land, for their food sup– ply, and the skuas ( Catharacta skua ), which parasitize the penguins.
The Arctic thus affords a bounteous summer haven for a surprising variety of birds and offers certain advantages over conditions at lower latitudes, length of day possibly being the t ^ g ^ reatest. Most species summering in the Arctic take full advantage of continuous daylight in rearing their families and feed them throughout the 24 hours, thus probably abbreviating the nestling period. In the case of the larger species this may be a factor of importance in en– abling them to make the best use of the brief period of optimum conditions. Larger clutches of eggs are also characteristic of numerous northern species. Many of the arctic-breeding shore birds passing northward through central Al– berta reach the local height of their migration in the latter half of May, with the first adults already returning in July, barely two months later. Even at Edmonton (lat. 54° N.), where only a faint glow is visible in the northern sky in June, slate-colored juncos ( Junco hyemalis ), Leconte’s spar– rows ( Passerherbulus lecontei ), and certain other species may be heard sing– ing at midnight. Many birds which breed in the Arctic are said not to sleep

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at all, or merely to snatch sleep at irregular intervals, mainly between the hours of 8. P.M. and 2 A.M. (2).
The Arctic thus offers a limitless breeding ground to those species of birds of sufficient migratory ability to reach it, that do not require trees for nesting or woodlands for feeding, and that find the northern summer en– vironment suitable in other respect. Several questions of interest immediately pose themselves. When and how did birds first discover the Far North? How do they annually find their way there and back? What is the timing mechanism that enables them to pick their traveling dates with the extraordinary pre– cision that most of them show? Why do so few species winter in the North?
To consider the last question first, it is quite evident that numerous species would starve to death if they attempted to remain in the North through the winter months. Birds which feed on mature insects would stand no chance whatever of survival, for such food is available for only a few weeks in summer. Seed-eating birds would not survive because for eight months of the year or more seeds would be covered by snow. Most aquatic birds could not survive because of the freezing of the water. Such species as the black guillemot ( Cepphus grylle ) and ivory gull ( Pagophila alba ) do find food in open tide rips, however, and the Greenland mallard ( Anas platyrhynchos conboschas ) is said to be resident on Greenland coasts, north to Upernivik on the west and to Angmags– salik on the east. Certain predatory birds, notably the snowy owl ( Nyctea scandiaca ) and gyrfalcon ( Falco rusticolus ) would starve but for lemmings, and these small mammals spend so much of their time under the snow that they are not readily available. Those beautiful northern grouse, the ptarmigan ( Lagopus ), manage to live on willow buds and twigs, but even Lagopus is migratory. Of all far northern birds the ravan ( Corvus corax ) is best equipped for strictly

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nonmigratory existence. It can live on lemmings, if they happen to be abun– dant; it can steal bait from traps; or it can share a whale or walrus carcass with the foxes and bears. Since birds are homiothermic animals with a normal temperature of over 100°F. this level must be maintained, and its maintenance depends on ready availability of food supply. Where food is unfailingly available, as in captivity, most species, including even domestic canaries (13), can tolerate temperatures of −50°F. and doubtless lower. In the Ant– arctic, the emperor penguin ( Aptenodytes forsteri ) may incubate its eggs at −78°F. while exposed to gales of 70 miles per hour. Availability of food thus appears to be a decisive factor. There is also total darkness within the Arctic Circle to contend with, and excessively long nights and short days hundreds of miles below the Circle. Even a brief period of starvation at low temperatures is fatal to birds; to survive they must be able to meet the severest known conditions of the arctic winter.
About wintering species in the Arctic much more information is needed than is at present available. Birds have been seen within the zone of total winter darkness, but such records are few and scattered. How far north individuals actually survive the entire winter is open to question; it ap– pears that the vast majority of species and individuals move varying dis– tances southward from the extreme north with the coming of winter. Such movements should probably be considered in the nature of true, if limited, migrations, although they are difficult to disentangle from purely local movements, which cannot be strictly classed as migrations since they vary from year to year according to circumstances. These are well developed in the Arctic (as also at much lower latitudes under stress of exceptional weather conditions). Ptarmigan, for instance, may require snow to burrow into during extreme weather and may collect in suitable areas by moving out

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of others. The willow ptarmigan ( L. lagopus ) shifts annually from its breed– ing place on the barrens into wooded country along their southern edge, al– though the rock ptarmigan ( L. mutus ) appears to remain on the tundra. Spruce partridges ( Canachites canadensis ) concentrate in the best feeding areas. Sharptails ( Pedioecetes phasianellus ) move southward regularly, though , ac– cording to McDonald, the winter in fair numbers just south of Great Bear Lake at latitude 65° N. The snowy owl ( Nyctea scandiaca ) moves south in certain years in large numbers, presumably when the supply of lemmings and hares is deficient. On these occasions the owls straggle into the United States and become abundant in central Alberta, where the species is normally represented every winter by only occasional individuals.
Certain northern birds such as the Bohemian waxwing ( Bombycilla garrulus ), white-winged [: ]^ cro ^ ssbill ( Loxia leucoptera ), and evening grosbeak ( Hesperi phona vespertina ) are inexplicably nomadic. The first two of these range north to the limit of trees, and south, sporadically, to the southern United States. The grossbill has been noted every month of the year and the waxwing all months but February and March at Yellowknife, according to McDonald. The grosbeak certainly ranges north to central Alberta but beyond that nothing seems to be known of it. The waxwing and crossbill may occur at Edmonton in large num– bers through the entire winter, and the grosbeak from January on. The fact that this species is practically never seen until January suggests that it may have more regular habits than its congeners. Both the waxwing and crossbill, however, undertake extensive wanderings and may be present in thousands one year and totally absent the next, this applying to both breeding and winter– ing grounds. The assumption is that they follow the food supply regardless of points of the compass and so, in some years, may actually go south to

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breed, a reversal of the regular trend of migration.
The opinion is held by some authors that bird migrations into the Far North have developed since the cessation of the ice age which began and ter– minated during the past million years (the Pleistocene period), but modern birds go back in the fossil record for some millions of years, and it seems unlikely that the migratory habit should be as recent as this. There are generally believed to have been four periods of glaciations with intervening s ^ p ^ ells warmer than our present climate, but even at the maximum development of the ice sheets which covered most of this continent, there remained an open north-south flight way both east and west of the Rockies, while much of Alaska and the arctic coast were never glaciated at all. It thus seems probable that the habit is older than the ice age rather than newer. One can logically picture the origin of migrations as the outcome of an early increase in numbers both as to species and individuals of birds and a constant pushing outward from the center of evolution ever since the days of Hesperornis , Ichthyornis , and other toothed precursors of modern forms, taking us back perhaps 30,000,000 years. The Far North was then comparatively warm, but slowly cooling. As conditions became more difficult, individuals that re– mained at high latitudes over winter paid the penalty of death, while those retreating southward survived. Thus a seasonal oscillation ultimately evolved, resulting in the annual migrations with which we are now familiar. The abler migrants tended to exaggerate the performance, producing such extravagant flights as those of the knot, which breeds as far north as latitude 81°77′ N. and winters south to southern Australia and New Zealand; and of the arctic tern ( Sterna paradisaea ) which performs a 22,000-mile round trip annually from the Arctic to the Antarctic.

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Not all migrations are as spectacular as this, however, nor are all of them strictly north and south. The breeding crows ( Corvus brachyrhynchos ) of Alberta habitually travel southeast in the fall when they leave that province. The Ross’s snow goose ( Chen rossii ) nests in the Queen Maud Gulf region and travels southwestward to its winter home in California. Many red– head ducks ( Aythya americana ) which ne x ^ s ^ t in Utah winter in the Finger Lakes region of New York. The yellow-billed loon ( Gavia adamsii ^ Gavia adamsii ^ ) is said to reach its breeding grounds on the barrens by turning south in the spring from the arctic coast. Virtually all the adult American golden plovers ( Pluvialis dominica ) breeding in continental North America and the Arctic Archipelago travel southeastward in the fall to Labrador and Newfoundland before heading for South America over the open Atlantic.
Some migrations are largely altitudinal. The Attu rock ptarmigan ( Lagopus mutus evermanni ) descends from the rough, high interior of the island to the valleys and coasts in winter. The blue or dusky grouse ( Dendragapus obscurus ), a bird of the Rocky Mountain system, breeds in Alberta in the foothills east of the Rockies and moves westward across the mountains into the milder valleys of British Columbia in winter. In the tropics, some migrations are definitely correlated with wet and dry seasons, their extent and direction apparently being determined by the availability of fruits or insect food.
Migration in progress is an impressive spectacle, not merely by virtue of the vast numbers of birds that may be seen together in passage, but perhaps more so on the ground of the biological mechanism that underlies the regularity and infallibility of migration. The problems that remain to be solved in this connection are among the outstanding questions in biology.

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Apart from the notable antarctic migrations of penguins, which are achieved by swimming since the birds are flightless, and which have been described by various authors, spectacular migratory movements are character– istic principally of the Northern Hemisphere. In southern Manitoba, for ex– ample, in the Whitewater Lake district, snow geese and blue geese ( Chen caerulescens ) have been recorded in aggregations of several millions in the spring before the final dispersal to the breeding grounds takes place in what may be a single flight of a thousand to fifteen hundred miles. Such banking up of individuals at suitable resting grounds en route for the North possibly occurs with more species than is yet known. It is usual among shore birds (15) and is found even in some passerines. On April 20, 1945, for instance, on the shores of Beaverhill Lake in central Alberta, the author encountered a single flock of snow buntings that covered several acres of ground; a million birds would probably be a conservative estimate.
Some vivid accounts of migration in progress have been published, as in Thomson’s Problems of Bird Migration (18), Low’s report of rock ptarmigan crossing Chesterfield Inlet (7), Manniche’s discussion of ravens in Greenland (6), and Rowan’s report on waterfowl in Alberta (14). It is more or less an accident that large-scale movements should ever be witnessed, frequently as they must occur, since the necessary combination of time, place, and qualified observer is inevitably a rare event. With the larger and numerically abundant species, however, diurnal migratory movements may be conspicuous. Such is the case with the little brown or lesser sandhill crane ( Grus canadensis canadensis ), for instance, which passes through Alberta in scores of thousands in mid– September. Particularly with a high barometer, dozens of clear-cut, V-shaped flocks may be seen almost anywhere during the day winging their way southwestward,

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often at great altitudes. Because, like geese, they are seldom silent, they are particularly easy to spot. Under these circumstances the author has counted as many as 30,000 cranes in a single day. When one considers that this represents the number seen from one point only, and that there may be a spread of two weeks in time and a great spread in space, one may imagine the impressive proportions of the movement as a whole.
To some authors [: ] migration appears a hazardous habit, but there seems no good reason for this assumption under normal conditions. When, however, an ice storm or analogous weather phenomenon happens to hit migrating hordes of small birds such as Lapland longspurs ( Calcarius lapponicus ) scores of thousands may be wiped out (see Roberts, 9). Yet this can also happen to them when they are not migrating, and such catastrophes have overtaken small species on their usual wintering grounds on an enormous scale from time to time (see Witherby and Jourdain, 19).
Migratory flights at night are familiar to most northerners, for the nocturnal passage north or south of large flights of geese, shore birds, coots ( Fulica _mericans ), and numerous passerine species are constantly heard and are well recognized. Many species are then traveling relatively fast, but the speeds of both flight and migration of birds [: ] have in the past tended to be exaggerated. Few birds exceed 60 miles per hour. Many fly no faster than 20, while the average cruising speed of ducks is in the neighborhood of 40. Altitudes are also lower than generally supposed and various diurnal species effect large parts of their migrations at heights only a few feet above ground or water level. Exceptional heights are occasionally attained by long-distance specialists such as cranes; in crossing mountain ranges, altitudes of 10,000 feet and over are not uncommon. With regular air services now becoming a

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commonplace in the Far North and bush pilots still plying their trade in remoter areas, more precise observations on bird altitudes and speeds during migration are gradually accumulating.
How birds find their way north and south, especially at night, still remains essentially a mystery. Topographical memory is known to play an important part with many diurnal species, but that there is more to it than that is made clear by the performances of many young birds undertaking their initial migrations. The parents of numerous shore birds, for instance, desert their young as soon as they are able to feed themselves, and return south. Weeks later, the juveniles themselves set out, but although they have no parental guidance, they nevertheless reach the habitual wintering grounds of their own species. Young crows, released in Alberta in November under experimental conditions without any adults, and long after all wild crows have gone south, ha ^ v ^ e adopted the standard flight lines to Oklahoma without error (12). (Oklahoma and Kansas are the wintering grounds of probably 90% of Alberta Crows.) Nothing tangible is yet known of the mechanism on which such achievements depend.
Finally, there is the question of timing. Most species arrive in the North as though by the calendar and, among the stronger fliers least affected by weather conditions, with truly astonishing precision. The experimental method has been applied up to a point to this aspect of migration (10; 11) but the answer is still far from clear. Length of day, however, appears to be one of the important factors, at least with birds of the Northern Hem– isphere, the increase in the amount of daylight in spring conditioning the physiological mechanism in such manner as to instigate the onset of the

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northern passage. An internal rhythm, kept in phase by the annual sum total of the bird’s environmental experiences may, among transequatorial migrants wintering in the Southern Hemisphere, be responsible for the impulse to move northward.

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1. Enderlein, . Erg., D. Sűdpol. Exped . vol.10, no.2, 1909.

2. Fisher, J. Birds as Animals . London, Heinemann (1939?)

3. Gadow, H.F. “Migration (under Zoology),” Encyclopaedia Britannica , 11th ed., vol.18.

4. Hesse, R., Allee, W.C., and Schmidt, K.P. Ecological Animal Geography . N. Y., Wiley, 1937.

5. Levick, G.M. Antarctic Penguins . London, Heinemann, 1914.

6. Low, A.P. Cruise Of The Neptune. Report on the Dominion Government Ex–pedition to Hudson Bay and the Arctic Islands . Ottawa, Govern–[]ment Printing Bureau, 1903-1904.

7. Manniche, A.L.V. “The terrestrial mammals and birds of North-East Greenland,” Medd. Grønland , vol.45, pt. 1, pp.93-200, 1912.

8. Phillips, J.C. A Natural History Of The Ducks . Boston, Houghton Mifflin, 1922-26.

9. Roberts, T.S. The Birds of Minnesota . Minneapolis, University of Minnesota Press, 1932, vol.2.

10. Rowan, W. “Experiment in bird migration, III. Effects of artificial light, castration and certain extracts on the autumn movements of the American crow,” Nat. Acc. Sci., Wash. Proc . 1932, pp.639-54.

11. ----. “Experiments in bird-migration. 1. Manipulation of the reproduc– tive cycle: Seasonal and histological changes in the Gonads,” Boston Soc. Nat. Hist. Proc . vol.39, pp.151-208, 1929.

12. ----. “Homing,migration and instinct,” Science , vol.102, pp.210-11, 1945.

13. ----. “Light and seasonal reproduction in animals,” Cambridge Phil. Soc. Biological Reviews , vol.13, pp.374-402, 1938.

14. ----. “Migration in relation to barometric and temperature changes,” Northeast Bird-Banding Ass. Bull . vol.5, pp.85-92, 1929.

15. ----. “Notes on Alberta Waders included in the British list,” British Birds , vol.20, p.41, 1926.

16. ----. The Riddle of Migration . Baltimore, Williams & Wilkins, 1931.

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17. Stefansson, Vilhjalmur The Friendly Arctic . N. Y., Macmillan, 1944.

18. Thomson, A.L. Problems of Bird-Migration . London, Witherby, 1926.

19. Witherby, H.F., and Jourdain, F.C.R. “Report on the effect of severe weather in 1929 on bird-life,” British Birds , vol.23, 1929.

Williams Rowan