Migrant bird

“ The relation of the world's land masses to each other and the distribution and association of biotypes within these land masses influence the direction birds migrate. Topography may aid, hinder, or prevent the progress of a migrant depending on the bird's particular requirements. Old World migrants must contend with east-west tending mountain ranges and deserts, whereas New World travelers can proceed north and south across a landscape with its major mountain ranges and river systems oriented in the same direction as the birds migrate. ”

“ This altered nature of the migrant is a fact of some importance in relation to our present subject, but it does not stand alone—the same characteristic is observable in other phases of bird life. Some of the residents, the Buntings and the Finches for example, occupy their breeding ground very early in the year, and it often happens that the situations which they select are not capable of supplying them with food so early in the season, though at a later date food will be there in abundance ”

“ The male resident deserts its territory at intervals, even in the morning; the male migrant betrays no inclination to do so. Thus there is a very close correspondence between the behaviour of the two, and what difference there is—slight after all—cannot be said to affect the main biological end of securing territory. One is apt to think of the problem of migration in terms of the species instead of in terms of the individual. ”

“ Before attempting to explain the difference in the times of arrival of the male and female migrant, let us examine the behaviour of some resident species at a corresponding period. My investigations have been made principally amongst the smaller species—the Finches and the Buntings—which often pass the winter in or near the localities wherein they brought up offspring or were reared. It is true that they wander from one field to another according to the abundance or scarcity of food ”

“ But the fact that a bird has established a territory is not in itself sufficient to render its hostile nature susceptible; it must be actually in occupation if a response is to be elicited. We reach this conclusion step by step: the242 behaviour of the migrant, that lacks the "will to fight" when on migration but is pugnacious when it has secured a territory, shows it; the behaviour of the resident, which temporarily joins the flock and is there sociable, shows it ”

“ What dangers do they face on their round-trip flight and in their winter homes? These and other questions on the migratory habits of birds puzzle the minds of many who are interested in the feathered species, whether it be the farmer who profits by their tireless warfare against the weed and insect pests of his crops, the bird student who enjoys an abundance and variety of feathered inhabitants about him, or the hunter who wants a continuation from year to year of the sport of wild-fowling. ”

“ It is an observed fact that some birds in a migratory movement alter their course to travel along a leading line, but whether this feature in the landscape caused the migrants to change their course is only theory (Thomson 1960) . Besides topography, many other factors can influence this type of flight behavior including weather, wind speed and direction, time of day, species, age, and experience of the bird (Murray 1964) .
Large bodies of water constitute real barriers to soaring birds dependent on thermals and air currents. ”

“ From Lapland, then, to the Cape of Good Hope, and from Portugal to Palestine is a pretty extensive range for so small and weak a bird as our Common Flycatcher. I should not be surprised to hear that it is found even still further to the eastward, for so many of our summer migratory birds spend their winter in India and China, and after all the greater part of their journey would be by overland route, which admits of their travelling by stages, to rest and feed by the way. ”

“ The great majority of birds are killed striking on foggy, misty, or dark nights, and it is perhaps not impossible for a great migration to take place, and pass almost unrecorded if the night -83- be fine and bright. Whenever a bird has been killed striking, it is so stated, and not left to be understood.
The bulk of the migrants appear to arrive on our south eastern coast, except such birds as the Barnacle Goose and Snow Bunting, which are mainly recorded from the north western stations, being rarely entered in the schedules from the east or south coasts. ”

“ During the whole period of migration there is a general northward movement of all the migratory species, but under the influence of warm spells of weather this more or less uniform movement rises into a vast wavelike sweep of birds. These bird waves, as already noted, follow the rise of temperature appearing at any given locality about a day or two after the first day of the warm spell. Many species of land birds migrate at night—such, for example, as the orioles, tanagers, warblers, vireos, wrens, the majority of the finches, the woodpeckers, and the thrushes, excepting the robin. ”

“ In addition, if daylength influences when birds are stimulated to migrate, why should they not all leave the same locality at the same time? Or, if weather controls the departure of birds from a given area, should not all the migrants leave when conditions are optimal and refrain from departing when conditions are not so? Actually, the conditions that place a bird in a disposition to migrate are probably the result of a combination of factors affecting different species - 16 - differently. ”

“ It has been put forward as a serious objection to many arguments that migration, instead of being advantageous to birds, is a danger to the race; that the perils of the journey are greater than those occasioned by more sedentary habits. It has even been suggested that migration is a, habit specially created to thin down the surplus bird population. ”

“ It is one of the latest of our summer migrants to arrive, seldom appearing before the second week in May, and generally taking its departure during the first week of September. It is found throughout the British Islands, but is much less common in Scotland. It has, however, been found breeding as far north as Sutherland and Caithness. The situation selected by this bird for its abode during its stay with us is generally in the neighbourhood of gardens and orchards, where it takes up its quarters on a wall or fruit tree, and sallies forth into the air after passing insects. ”

“ All species have been of ever-increasing recreational and esthetic value for untold numbers of people who enjoy watching birds. We began to realize our migratory bird resource was an international legacy (that cannot be managed alone by one state or country) and all nations were responsible for its well-being. The need for laws protecting game and nongame birds, as well as the necessity to regulate the hunting of diminishing game species, followed as a natural course. ”

“ Why should a bird subject itself to the rigors of a long migratory journey twice a year if it can find all the requirements suitable for existence in one locality? It seems well to consider briefly the ends that are served by this annual round trip between breeding grounds and winter quarters. Obviously, the migratory habit enables a species to enjoy the summer of northern latitudes and to avoid the severity of winter. In other words, migration makes it possible for some species to inhabit two different areas during the seasons when each presents favorable conditions. ”

“ It is to be remembered, however, that while homing may involve flight from a point that the bird has never before visited, the flight is always to a known point — that is, the bird's nest— while, on the other hand, the first migratory flight is always from the region of the bird's birth to a region it has never before visited. The spring migration might, of course, be more nearly considered as true "homing." ”

“ The few or many birds we meet with, either on the coast or inland, resting on passage, may represent a lost or wandering party of stragglers or weaklings from a vast army which has passed over; they may or may not be on the route or course normally followed by the majority. The cartography of bird migration is a study in itself. Mr Abel Chapman, describing his experiences in the Mediterranean, says—"For forty hours we were passing across (or beneath) the lines of an army of migrants—say 500 miles in width ”

“ It affects different birds in different ways. In North America, migratory movements are continent wide, and no evidence has indicated any particular part of the landscape influences all birds in the same manner. Certain bird populations may use general areas in migration, but they are usually not rigidly restricted to them because of topography. ”

“ There probably is no single aspect of the entire subject of bird migration that challenges our admiration so much as the unerring certainty with which birds cover thousands of miles of land and water to come to rest in exactly the same spot where they spent the previous summer or winter. The records from birds marked with numbered bands offer abundant proof that the same individuals of many species will return again and again to their identical nesting sites. ”

“ Thus, if all birds were to remain constantly either in tropical or in temperate regions, there might be intolerable overcrowding during the breeding season. By the spring withdrawal to regions uninhabitable earlier - 5 - in the year, the migrants are assured of adequate space and ample food upon their arrival in the winter-freed North, and it may be assumed that nonmigrant species resident in the South are benefited by the withdrawal of the migrants. ”

“ The migration season is full of peril for birds. Untold thousands of smaller migrants are destroyed each year by storms and attacks by predatory animals. These mortality factors, and others, help keep bird populations in check. Perils of migration are among these causes. ”

“ So cruelly and relentlessly have the shore birds been pursued by men who call themselves "sportsmen;" that many species are nearly extinct. We hope that the Migratory Bird Law will be enforced and that with the protection this gives them they will again increase and fill their old haunts. But we must ever be on the watch, for there will still be greedy hunters trying to evade the law until all our boys grow up with love and appreciation for the birds. ”

“ As bird populations become more and more migratory, we might expect their flight capabilities to be enhanced accordingly. These changes in morphology are readily seen in wing shape. Several groups of birds have closely related species or populations some of which are migratory and others sedentary. The sedentary species or populations have more rounded wings because of the relative length of the wing quills. On the other hand, populations that migrate great distances, such as albatrosses, falcons, swifts, various shorebirds, and terns, have more pointed wings. ”

“ While some migrants are still traveling south, some early spring migrants can be observed returning north through the same locality. For example, many shorebirds start south in the early part of July, while the goshawks, snowy owls, redpolls, and Bohemian waxwings do not leave the North until forced to do so by the advent of severe winter weather or a lack of customary food. Thus an observer in the northern part of the United States may record an almost unbroken southward procession of birds from midsummer to winter and note some of the returning migrants as early as the middle of February. ”

“ The migratory birds are actuated by such a strong desire to regain their nesting places and summer homes that they embrace every opportunity to journey towards them, and not infrequently suffer severely for the risks they take. In some instances species which have begun their northward flight too soon are killed by thousands owing to a return of severely cold weather or die for lack of food. ”

“ As they are full of nervous activity, and are “eminently migratory birds,” they seem to flit rather than fly through the United States as they pass northward in the spring to their breeding places, and southward in the fall to their winter homes among the luxuriant forests and plantations of the tropics. All the species are purely American, and as they fly from one extreme to the other of their migratory range they remain but a few days in any intermediate locality. Time seems to be an important matter with them. ”

“ This has occasionally been the case in Ireland, and the fact that these birds were caught by frost and snow on one side, and by the Atlantic on the other, shows that migration is not always salvation to the migrant. Just why the birds became so weak as not to be able to go forward to Spain or Africa, it is difficult to say. But possibly those that get starved in this way are the late arrivals that find themselves weakened by much flying when they first arrive on the Irish coast, and without food can go no farther. ”

“ What is the cause which operates to restrain one species from migrating, when a closely allied bird of similar habits is impelled to take a long and perilous journey? Truly it is a curious question.
Before taking leave of our British flycatchers, it may be observed that a third species, the Red-breasted Flycatcher (Muscicapa parva) , a native of South-eastern Europe and Western Asia, has been met with and procured on three separate occasions in Cornwall. ”

“ To increase such support, information must be more generally available on that little understood but universally fascinating subject of bird migration. A brief presentation of facts on the migratory habits of the birds, scientifically gathered by the Bureau of Biological Survey over many years, will be helpful to bird-study classes, to conservation organizations, and to farmers and others individually interested in the welfare of the birds. ”