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which flew south at the approach of cold weather and scarcity of food

survived and left descendants ; and what in the ancestor was only a hap¬

hazard flight from a cold and foodless region, became in the offspring, after

many generations, an ingrained habit or tendency, which we call instinct.


It may appear strange that the birds should leave the warm countries

where they winter and come north to breed. The reasons which induced their

ancestors to go north in the spring were probably the pressure of numbers

and the consequent scarcity of food, and the dryness and barrenness of

the warm countries during the summer months.


Migratory birds chiefly belong to the insectivorous class ; birds which

can subsist on grain and berries can generally manage to maintain them¬

selves in their native country all the year round.


One very curious point in connection with the migration of birds is

that those birds which breed farthest to the north generally winter farthest

to the south. Thus, some Arctic birds, which rear their young in those parts

of North America which lie within the Arctic circle, spend the winter in the

more southern portion of South America.


Birds on their migration usually travel by night, and often at a great

elevation in the air. How they know their way is a mystery. There used to

be a notion current that they were possessed of some wonderful instinct,

or sixth sense, which enabled them to direct their course infallibly to their

destination, but this idea is now exploded. They sometimes make strange

mistakes and wander thousands of miles out of their course. More than

once a bird whose home is in Asia has turned up in our own island.

Probably such birds have been confused and turned out of their course by

storms.


The course pursued by birds on their migration is a very ancient one,

sometimes more ancient and permanent than the land over which they fly.

Their three great ways across the Mediterranean are by the Straits of

Gibraltar, by Corsica Sardinia and Tunis, and by Malta and Tripoli ; and

along these routes the land was once continuous. They still follow the

Malta and Tripoli route, although for many thousands of years it has led

them across the sea at a point where it is broader than in many other places

which they could choose. But land once stretched from Italy to Africa,

through Sicily, Malta, and Tripoli ; the birds adopted that route and still

follow it although the land is gone.


It thus appears that though the search for food was what originally

caused the migration of the ancestors of our travelling birds, their

descendants now migrate from habit, which has in their case truly become

second nature, and not generally with any conscious intention of searching

for food. If any individuals show a tendency to abandon the habit by

remaining in their summer home during the winter, they are almost certain

to perish from hunger before the next breeding season, so that they leave

no descendants, and the strength of the hereditary tendency in the race is

unimpaired.


Besides the true migrants there are many birds which travel long

distances in search of food ; these are probably in the same stage as the

ancestors of our migrants. If food be abundant in the neighbourhood of

their breeding place they remain there all the year ; but if scarce they fly

to more bountiful regions. Their course is uncertain in extent and direction,

and totally different from true migration.


note; by dr. butler.


I am very glad to see that Mr. Perkins has brought to light the fadts respecting the

general migration of birds which scientific researcli has revealed.


It must, however, be borne iti mind that the rules laid down are not absolute, for

many seed-eating birds are migratory whilst many insectivorous birds are resident.


Moreover many of our winter visitors are mainly insectivorous birds.


Lastly, in mild winters not a few migratory species delay their departure from our

shores, and stragglers even pass the winter with us.


Mr. Perkins’ paper will form a very good introduction to an article which will, I hope,

shortly appear in our Magazine on the British Migratory Cage Birds.



A. G, Butler.



