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THE NATIONAL GEOGRAPHIC MAGAZINE 



pair of vigilant eyes, when the flock is 

 immediately notified by a few sharp 

 chirps — warning for every individual to 

 seek safety in flight or to scurry to cover. 



WHAT MYSTERIOUS SENSE GUIDES THEM 

 IN THEIR LONG JOURNEYS? 



In what manner warblers migrate — 

 that is, how they are guided on their long 

 journeys — is a moot question. Little 

 mystery attaches to their ability to find 

 their way north or south in daylight, 

 since the recognizable landmarks are 

 many and prominent. As most birds, es- 

 pecially the warblers, choose starlight and 

 moonlight nights for their trips, perhaps 

 they are similarly guided by night, and 

 natural landmarks, as mountains, rivers, 

 and the coastline may point out much, if 

 not all, of their way. 



However plausible this explanation 

 may sound in the case of birds migrating 

 over land, it utterly fails when applied to 

 migrants whose journeys north and south 

 necessitate flight over long stretches of 

 ocean, in some instances at least 2,000 

 miles, quite out of sight of land and of 

 all landmarks. 



In seeking an explanation of the mys- 

 tery of birds' ability to find their way 

 under such circumstances, many are in- 

 clined to reject the one-time sufficient 

 answer, "instinct," in favor of the more 

 recent theory, the possession by birds of 

 another faculty, the so-called "sense of 

 direction." This added sense enables 

 birds to return to a known locality with 

 no other aid than an ever-present knowl- 

 edge of the right direction. 



But, in the case of our wood warblers, 

 there is little need of appealing to another 

 sense to guide them in migration, or, in- 

 deed, to anything out of the ordinary save 

 excellent memory and good eyesight. The 

 five-hundred-mile flight toward the trop- 

 ics across the Gulf of Mexico is made by 

 preference, and however it originated as 

 a fly line, had it proved to be extra haz- 

 ardous, it might have been abandoned at 

 any time in favor of the apparently safer 

 West Indian route. 



But, after all. the Gulf trip involves few 

 hazards other than those connected with 

 storms, since the flight across the water, 

 even at a slow rate, would necessitate a 



journey of less than 24 hours, and this, 

 no doubt, is quite within the capacity of 

 even the smallest and weakest of the 

 family. Moreover, the South American 

 Continent is too big a mark to be easily 

 missed, and an error of a few hundred 

 miles north or south would make little 

 difference in the safety of the birds. 



WHY WARBEERS MIGRATE 



It may be set down as an axiom that 

 all birds which travel south in fall do so 

 because they must migrate or freeze or 

 starve. Why some of them leave early, 

 when food in their summer home is seem- 

 ingly so abundant, is indeed a puzzle. 

 Once the nestlings are on the wing and 

 ready for the journey, off they go, old 

 and young. 



Nevertheless, by an apparently prema- 

 ture start they only anticipate by a few 

 weeks the time of scarcity when they 

 must go, and perhaps the lesson of bitter 

 experience in the history of the several 

 species has taught them to go when all 

 the conditions are favorable. It is true 

 that every winter a few birds, often a 

 few individuals of a given species, winter 

 far north of the customary winter home. 

 Some of these are evidently stragglers or 

 wanderers which, for some unexplained 

 reason, failed to accompany the rest of 

 their kind on the southward migration. 

 They in no wise affect the general state- 

 ment, being exceptional in every way. 



A few of our warblers in Florida and 

 on other parts of our southern coast do 

 not migrate ; but the almost universal rule 

 in the family is to abandon the summer 

 home when the care of the young ceases 

 and to go far southward ere they stop for 

 the winter. Indeed, the males of many 

 species do not trouble themselves much 

 with the care of the nestlings, but prepare 

 to migrate before the young are well on 

 the wing. 



A still more flagrant case is that of the 

 hummingbirds. The male deserts the 

 female when she is still on her eggs, 

 shifting the responsibility of caring for 

 the family entirely on her devoted head, 

 while he disports himself among the 

 flowers, leaving for the south long before 

 his exemplary mate and the young are 

 ready. 



