Читать книгу Birds of Manitoba - Ernest Thompson Seton - Страница 21

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Abundant summer resident; chiefly about the prairie ponds, dead waters; breeding at Pembina; Mouse River at the boundary (Coues). Winnipeg: Summer resident; abundant (Hine). Abundant in Red River and Selkirk Settlements (Brewer). Prairie Portage; plains of the Souris (Hind). Portage la Prairie: Abundant summer resident on all the large prairie sloughs, in which they breed; first seen, May 11, 1884, May 25, 1885; last seen, September 9, 1884 (Nash). Breeding very abundantly in all marshes from Portage la Prairie westward, 1879, and in less numbers in the wooded region, but generally distributed (Macoun). Carberry: Abundant; summer resident; breeding also in all ponds along the trail from Carberry to Port Ellice (Thompson). Brandon: Breeds in great numbers (Wood). Shell River: 1885, first seen, eleven, on May 18; seen every day afterwards; is common all summer, and breeds here; Indian name, “K’ask” (Calcutt). Qu’Appelle: Common summer resident; breeds; arrives May 18 (Guernsey). Severn House (Murray).

On June 11, 1882, went in the morning with two brothers to the lake in the sand hills east of old Dewinton; saw there large numbers of marsh terns. They appeared to be nesting in a weedy expanse far out in the lake, but it was surrounded by deep water, so that I could not come near it to seek for eggs. The birds came flying over my head, in company with numbers of blackbirds, and resented my intrusion by continually crying in their characteristic manner.

August 4. The black terns are beginning to gather in flocks; leave the ponds and skim about over the open prairie.

On July 8, 1883, went southwest to Smith’s Lake; found a number of tern’s nests, just finished, apparently, as they were clean, but empty, and the old birds continued flying above us and screaming their resentment.

On July 5, 1884, at McGee’s Lake, Carberry, I found the terns just beginning to lay. Each nest is a mere handful of floating reeds, slightly moored to others growing in the deep water, where they are found. The whole structure is just on a level with the surface of the water and entirely wet; on this are the eggs, much the same color as the reeds, and as wet as eggs can be.

It is a remarkable fact that, although this species is abundant in all parts of southwestern Manitoba, and I have often searched in various lakes with a flock of terns screaming about my ears, yet I have never before found either nest or eggs. On this occasion I found three eggs in one nest; several nests with two eggs; one or two with one, and one or two empty nests just completed.

On July 9 the terns were numerous everywhere on the prairie. Timed and counted the wing beats of several as a basis for calculating their rate of flight; one made 54 beats in 9 seconds; another, 28 beats in 9 seconds, a third 30 in 10 seconds. July 6, observed one make 27 beats in 10 seconds. July 12, saw another make 15 beats in 5 seconds, showing that about 3 is the average number of beats to the second. July 5 I had an opportunity of measuring the distance a tern covers with 8 beats; it was 24 yards.

August 14: Terns are abundant now on the open prairie; it is a common sight to see this bird zigzagging about in pursuit of the large dragon flies, until, at length, having secured as many as it could conveniently carry, it suddenly ceased the fantastic maneuvering for the swifter beeline, and made straight for its twin nestlings in the reedy expanse of some lake far away.

To-day, I made a calculation of the speed; one bird covered 70 yards with 14 beats, i. e., 5 yards per beat; I find they usually give 3 beats per second; this, therefore, is 15 yards per second or 31 miles per hour; much less than I expected. This black inland member of a white marine family is abundant about all the weedy sloughs and lakes of the Manitoban prairie regions. It seems not to subsist on fish at all, but chiefly on dragon flies and various aquatic insects. It finds both its home and its food in the marshes usually, but its powers of flight are so great that it may also be seen far out on the dry open plains scouring the country for food at a distance of miles from its nesting ground.

The voice of the species is a short, oft-repeated scream, and when any known enemy, be it man or beast, is found intruding on the privacy of their nesting ground the whole flock comes hovering and dashing about his head, screaming and threatening in a most vociferous manner. Under such circumstances it is the easiest thing imaginable to procure as many specimens as may be desired. When one of the flock falls wounded in the water, its fellows will repeatedly dart down and hover low over it, but I have never seen any attempts made to assist it in escaping, after the manner ascribed to some of the family.

Besides aquatic insects the Black Tern feeds largely on dragon flies which it adroitly captures on the wing. The bird may frequently be seen dashing about in a zigzag manner so swiftly the eye can offer no explanation of its motive until, on the resumption of its ordinary flight, a large dragon fly is seen hanging from its bill and sufficiently accounts for the erratic movements of the bird. After having captured its prey in this way I have frequently seen a tern apparently playing with its victim, letting it go and catching it again, or if it is unable to fly, dropping it, and darting under it to seize it again and again before it touches the water. After the young are hatched, a small flock of the old ones may be seen together leaving the pond and winging their way across country to some favorite dragon-fly ground. Their flight at first is uncertain and vacillating, but as soon as one has secured its load it returns with steady flight and in a straight line to its nest.

Under ordinary circumstances I was always impressed with the idea that the tern was very swift and entered into a series of elaborate calculations to ascertain the rate of its flight. A large number of observations resulted in an average of three wing-beats per second, with the greatest of regularity; another series of observations, not so satisfactory, allowed a distance of 5 yards to be traversed at each beat. This gave only the disappointing rate of something over 30 miles per hour, but this was at the uncertain foraging flight. Once the mother tern has secured her load of provender, a great change takes place, as already mentioned; she rises high in air, and I am sure she doubles her former rate of speed, and straight as a ray of light makes for home. It is said that many birds can not fly with the wind; not so the tern; for now, if there be a gale blowing her way, she mounts it like a steed and adds its swiftness to her own, till she seems to glance across the sky, and vanishes in the distance with a speed that would leave far behind even the eagle, so long the symbol of all that was dashing and swift.