In this fifth extract from Birds and The War, author Hugh Gladstone ponders whether the intense hostilities of 1914-18 had any consequence for bird migration.
A FRENCH commentator observed in1916 that ''the war had changed all the habits of migrating birds."
He stated: ''The storks which make their home in Alsace began to leave that country a full fortnight before war was declared."
He attributed this "to the noise of the movement of the German artillery on its way to attack France".
He went on: "In normal times, nearly all the birds of passage used to pass over France on their way north or south, but the thunder of the guns has changed all this.
"The route taken by woodcocks leaving England for warmer climes is across the Channel into Brittany, then by way of the Loire, Charentes and Landes to the Pyrenees.
"As these birds do not have to cross the war zone, they have kept to their old route throughout the hostilities.
"But their brethren from Scandinavia and Holland, who used to fly by way of the Aisne and the mud lakes of Champagne, now make a long round by sea and do not touch land until they arrive off the coast of Brittany.
"Snipe from Russia and Poland wing their way for sunny climes by way of the western coast of the Black Sea to gain the Bosphorus, or else cross Greece and Romania.
"German and Danish snipe go south by way of Italy, and members of the thrush family escape the shrapnel of the front in France by crossing Switzerland and making for Italy.
"The wild ducks of the eastern counties of England, which used to fly over the North Sea, have also a horror of battles, and now fly north, then west, and then south again, skirting the coast of Ireland.
"The calendar of the migrations, which for thousands of generations has been rigorously kept, has, since the war, become more elastic, and some birds, such as martins, have renounced their return journey to the north and remain in Tunis rearing their young "
In 2016, a French zoologist, M. Cunisset-Carnot, maintained that, in places where fighting occurred, the birds became greatly disturbed, screeching and flying about in all directions, unable to settle down any where, day and night.
Among the migratory birds, those which dwell south of the war zone carried out their flight to the warm lands in the customary direction, but began it somewhat earlier than under normal condi-
tions.
As regards migratory birds dwelling north of the war zone, they skirted the line of the front and, instead of flying through France, flew through Switzerland and Italy.
For example, blackbirds, which from Germany and Scandinavia fly southward annually in huge flocks through Burgundy, did not appear there.
Similarly, no larks were seen in October 1915.
In Flanders and Holland, there were neither marsh nor water birds.
According to the observations of Russian naturalists during the first year of the war, jackdaws and rooks disappeared.
Larks no longer sang in the fields, and even sparrows grew very scarce.
The eagle, a constant resident in the Carpathians, migrated to the Balkans, and the wild pigeon disappeared also.
Ordinarily, birds in Central Siberia gravitate during the spring from south to north, in Eastern Siberia from south-west to north-east, and in European Russia from south-west to north-west.
Since military operations were proceeding exactly in the region of these migratory routes, the
flights of birds were powerfully affected, especially those of the stork and snipe.
An extraordinary movement of geese northwards was reported, and this was attributed to the military operations in progress in Mitau and White Russia, which prevented these birds from settling there.
The same explanation was given for the abnormal number of duck which appeared on the River Volkhov.
Individual species of birds which ordinarily carry out their migratory flight through Poland appeared on the island of Qesel.
In the Tauride province, an abundance of every kind of bird was observed in 1915, particularly of those species which migrate through the Carpathians.
Those birds whose nests were usually situated in localities affected by the war were perforce
compelled to abandon their homes and migrate to other places, thus evoking an increased flight of individual kinds of birds to certain spots.
In autumn, 1914, large flocks of gulls were observed off Norfolk, flying in from the North Sea in so wild and erratic a fashion as to suggest that the explosions at sea had disturbed them. Their appearance curiously synchronised with the times of reported sea-fights.
Unusual flocks of starlings were noticed in Norfolk in September 1914, and their premature migration was attributed to the disturbing factors of battle which had driven them from the continental marshes.
It was reported, in summer,1916, that thousands of small birds, apparently took fright many scores of miles from their native homes and sought refuge on American liners.
The presence of a stork near Carnarvon in July elicited the query as to whether this rare visitor had been driven by gunfire from more usual haunts in Flanders.
In 1917, it was publicly stated that, as the result of gunfire, 60 kinds of migratory birds had ceased to visit Britain but this statement was soon disputed.
In 1919, it was suggested that the scarcity of snipe in the British Isles in the past winter was due to the effect of big-gun firing in the North Sea and elsewhere, which had deflected the direction of their migration
In spite of the above assertions, I do not believe that migration was seriously affected.
Incessant gunfire on certain parts of the coast may have frightened away wildfowl from the vicinity, but statistics from Great Britain during the period of the War do not show any marked diminution in our summer visitants.
From such reports as are avail able from the Palestine Front, it would appear that migration went on uninterruptedly, and a similar state of affairs seems to have existed on the Mesopotamian Front and in the zone of our operations in France and Flanders.
In any case, it is a somewhat arbitrary assertion to state that certain migration routes were deserted when these very routes are themselves still only problematical.
Such birds as were migrating during the heavy anti-aircraft barrage of September, 1917, and whose path across the moonlit sky led over London, must have been considerably disturbed by the bursting of shells.
The raid periods in 1917 coincided with the autumnal migration of such birds as the whimbrel, but possibly they ''rose to the occasion" or somewhat diverted their course on seeing the barrage from afar for not a single bird was found whose death could be attributed to a shell splinter.
Small birds, if migrating on those nights, would probably be travelling below the barrage, and September would be too early in the year for many geese or ducks to be on their journey
south.
Their passage over any bombarded area in October or November would probably be diverted in a similar manner if they encountered a barrage on the way.
So far from thinking that the birds forsook their accustomed migration routes, I believe that they continued to use their aerial highways, undeterred by the thunder of guns, the marching of troops, and the din of battles taking place many hundreds of feet below them.
Perhaps the abnormal amount of insect food on the Western Front may have detained a few of the migratory insectivorous birds which habitually visit us, and it is possible that Italy's intervention in the war may have had some effect on the numbers of the migratory visitants to Central Europe.
It has been stated that when the Austrians invaded Italy they destroyed all the "roccolos" so thickly scattered throughout the compartimento of Venetia.
They cut down the groves of hornbeam (skilfully planted and netted in such a way as to give
no chance of escape to any autumnal migrant when once within the high green walls), liberated the decoy-birds, and razed to the ground the towers in which the ''sportsmen'' were wont to conceal themselves from their unsuspecting prey.
Italian ''sportsmen" are apt to kill any bird. Professional bird-catchers, in their ''roccolo" decoys, take thousands of linnets and insectivorous birds as they enter the funnel of Italy on their annual emigration to Africa.
These men being otherwise engaged, Europe may have benefited by having more birds and less insect pests in consequence.
All things considered, I think, however, that I am justified in saying that there is at present no
definite proof that the course of migration was seriously affected by the war.
An airman, who must have been an enthusiastic student of migration, made observations
regarding the height at which he met with birds when in the air.
Swallows, he found, preferred an altitude of 2,000 ft, wild duck 5,000 ft and flocks of plover were encountered at 6,500 ft.
Pilots and men in observation balloons agreed that they rarely saw birds at a height of more than 3,000 ft, but a captain in the RFX., about March 9, 1918, ran into a flock of lapwings at a height of 6,500 ft, over Hulloch, near Lens.
Capt. Collingwood Ingram, in his paper Notes on the Height at which Birds Migrate, gives some interesting figures obtained from airmen on the Western Front .
Lapwings were observed on 14 occasions at between 2,000 and 8,500 ft, the height, in the majority of cases, being between 5,000 and 6,000 ft.
A flock of five hundred duck, or geese, was observed, on November 26, 1915, at about 11,500 feet.
Two large birds, possibly cranes, were met near St. Omer, in August, 1917, at 15,000 feet.
Birds resembling linnets were seen over Bethune, on August 22, 1917, at a height of
10,000 ft.
About 50 rooks, jackdaws, or crows were noted over Lens, in March,1917, at 6,000 ft, and
'' six birds about the size of rooks " over Arras, at 3,000 ft, on July l0, 1918.
Starlings and fieldfares (or redwings) were observed at 3,000 ft in March 1917.
Some species of sandpiper was met with over Arras, towards the end of March,1917, at an elevation of 12,000 ft, and other Limicoline birds at 9,500 and10,000 ft;
Whimbrel were observed at 4,000 feet, and herons at between 2,500 and 3,000ft .
Wartime does not offer the most favourable conditions for the solution of the question at what height birds fly when migrating, but the following advertisement was published on February11,
1919, in The Times newspaper: "Any notes on the flight of migratory birds made in the air would be highly appreciated. Where possible the species, height, and velocity of flight, time of day, and year would add greatly to value. Single or even negative notes would be most acceptable. "
With the return of peace and a more general use of the aeroplane, we may expect many interesting facts and discoveries concerning the question of bird migration, which is, at present, quite unsolved.
Next: Did the war change bird behaviour?
