y 2 Recent Literature. Ll" n - 



instance where some or all of the individuals of a species quit their 

 breeding-grounds unless compelled to do so by severity of climate, failure 

 of food, or both" (p. 24). "Amongst birds in which the habit of migra- 

 tion is dominant, the impulse to migration is unquestionably instinctive, 

 in the sense of being transmitted from parent to offspring, which has 

 become so deeply rooted in the uninterrupted course of countless ages of 

 passage to and fro. that in many species nothing but death can eradicate 

 it. . . . This desire to migrate gradually becomes an overwhelming 

 desire, before which all other inclinations bow, and at last the great flight 

 is commenced. But here instinct, hereditary desire, ceases its sway; 

 reason, memory, knowledge of locality and perception take its place" (p. 

 26). Again he says (p. 70) : "It must not be supposed, however, that 

 because the impulse to migrate is inherited from their parents, the ability 

 to do so is equally hereditary. That has to be acquired; the road has to 

 be pointed out by the more experienced guiding birds, and the long, often 

 circuitous, route has to be lear?it by the experience of not one but many 

 annual journeys to and fro." 



How this is brought about, Mr. Dixon proceeds to explain. The pio- 

 neers, the "avant-courieres of the migrating army," he tells us, are the 

 barren or unmated birds which have no home ties, or else those that have 

 lost their eggs or young broods, and are thus free from any restraining 

 influence due to parental instinct, in which "the desire to migrate often 

 becomes so prematurely strong that they begin to leave their summer 

 quarters in some cases even before their moult is absolutely completed." 

 The young birds of the year are next to follow, as, since "they travel in 

 their first plumage," "they are the first to be in position to migrate," and 

 "consequently are ready to go as soon as they can fly." ( !) "A week or so 

 after the young birds have left, the adult males begin their migration, 

 having got over the moult a little earlier than the females, the latter 

 being delayed somewhat by maternal duties, so that their departure is a 

 little later still. The rear of the great migrating army" is brought up by 

 the halt and the lame, or by birds delayed "from various causes," either 

 in starting or on the way. In the spring migration the order of return is 

 somewhat reversed, the adult males going first, followed soon by the 

 females, later by the young of the previous year, and last of all by "the 

 weakly and the wounded." "Unquestionably the one grand dominating 

 impulse of migration in spring is reproduction" (p. 202). 



We have thus the complete history of the migratory movement, including 

 its causes, manner of inception, and the methods of its execution, down to 

 even minute details. Unfortunately, however, many of his statements are 

 purely assumptions, impossible of verification, and often improbable, 

 though given with the positiveness of observed facts; and he fails to note 

 their occasional lack of harmony, amounting in some instances to complete 

 contradiction. 



He states that "we can only make the wildest guesses at the time occu- 

 pied by individual birds in reaching their summer or winter quarters. . . 



. . Probably migrating birds do not average more than 300 miles per 



