86 



THE GARDENERS' MAGAZINE. 



February 3, 1912. 



THE VALUE OF BIRDS TO 



MAN. 



(Continued from page 58.) 



Value of the 



Insect 



Bird in Checking: 

 Irruptions. 



The marvellous powers of flight and per- 

 ception possessed by birds aibly tits them to 

 perform the office of a swiftly-moving aerial 

 army, large forces of which can be ma&sed 

 at any given point to correct disturbances 

 caused by abnornnal outbreaks of animal or 

 vegetii'ble life. 



When the Mormons first settled in Utah 

 their crops were destroyed utterly by 

 myriads of black crickets that streamed down 

 from the mountains. Promising fields of 

 wheat in the morning Avere by evening as 

 ))are as though the land had not l>een sown. 

 The first year's crop having been destroyed, 

 the Mormons had sowed seed the second 

 year, -and again the crop promised well. 

 Eut again the crickets appeared, devoui'ing 

 every blade of wheat, and the followers ox 

 Joseph Smith were on the verge of starva- 

 tion. At this juncture. Franklin's gull came 

 by hundreds Ol thousands, and, feeding 

 greedily on the crickets, freed the fields of 

 the pest. The settlers at Salt Lake regarded 

 the advent of the gulls as a heaven-sent 

 miracle, and practically canonized the birds. 

 Several times afterwards the crops of the 

 Mormons were attached by the crickets, land 

 "were saved by the gulls. 



In the early days of the colonisation of 

 New Zealand *swarms of caterpillars infested 

 the open tussock-clad country. When the 

 white man began to cultivate the land this 

 caterpillar disappeared from its old haunts 

 and attacked the English grasses and cereal 

 crops, increasing so enormously in numbers 

 fby reason of a more favourable environment, 

 that they quickly became a bla»sting plague. 

 They came not singly, or even in battalions, 

 but in mighty armies, which laid waste the 

 land. I have seen regiments of this invading 

 force cover the pastures in »such numbers as 

 to make the green one brown. I have seen 

 them march out of one cornfield — havinsr 



.stripped every stalk bare — ^cross the road in 

 solid phalanx, and pasis into another. I 

 have seen l)ig mobs of sheep mustered in 

 hot ha.ste and driven ^backwards and for- 

 wards to cruvsh the atoms with their hurry- 

 ing feet. I have seen every available horse- 

 roller in a district 'brought up hurriedly, 

 like engines to a fire, and dragged to and 

 fro over the crawling masses until the huge 

 cylinders stuck fast in a mire of crushed in- 

 sects. I have seen large ditchea dug in an 

 attempt to stop the invaders' progress. The 

 effort was a.s futile as that of a child who 

 builds a bank of sand by the sea, thinking 

 it will stem the oncoming tide. Even rail- 

 way trains were brought to a standstill, 

 the wheels of the engines being unable to 

 grip the rails owing to the countless hordes 

 of caterpillars which were crossing the line. 



In time it l>ecame abundantly clear that 

 if this disastrous condition of affairs con- 

 tinued it would >)e usele.-s to attempt to 

 carry on agricalture in New Zealand. Realis- 

 ing that any attempt wliieli they might 

 make to rid the smitten land of the plague 

 would be but a mockery, the fariiier>, turned 

 their eyes longingly to the natural enemy 

 of the caterpillar — the bird. But the native 

 birds — though they had lived in closest com- 

 panionship with the Maoris — had been 

 taught the treachery of the white man in a 

 school that reeked with blood, and those 

 that had not been killed had retreated from 

 the vicinity of the settlements, visiting the 

 insect-ridden fields occasionally only. 



Wherefore insectivorous; birds from the 

 old country were introduced, and the one 

 that multiplied most rapidly was the spar- 

 row. Aufl the sparrow soon cut short the 

 career of the caterpillars. 



I have said that birds, because o" their 

 unrivalled powers of locomotion, are pecu- 

 liar! v adapled to suppre>sing unusual out- 

 breaks of vegetable as well a^s of animal life. 

 Here is an instance of this, 



llxat formidable imported weed, the varie- 

 gated Scotch thistle, threatened at one time 



to overrun the whole of New Zealand. 

 Where it had once fairly established itself 

 it seemed well-nigh impossible to eradicate 

 it; and it was spreading with the speed of 

 scandal. Much time and money was spent 

 in cutting off the plants close to the ground, 

 and in pouring turpentine upon the stumps. 

 But the wind-driven clouds of thistle-down, 

 which were planting the weed far and wide, 

 grew yearly denser and more frequent. At 

 length the fields became a thickly-packed 

 growth of prickly plants, which nothing 

 could face. 



The sparrows took to eating the seed. In 

 tens of thousands they fed on it, giving it 

 the preference oi" all other hard food, and 

 the weed was conquered. 



To-day, in New Zealand, the sparrow is 

 looked upon as an impudent thief, without 

 a i*edeeming feature in its character. 



No one, of course, can say what would 

 liappen if the sparrow was dismissed from 

 New Zealand, but it 'is as certain as any- 

 thing in this world can be that the Domi- 

 nion would be again overrun with cater- 

 pillars and thistles. 



As it is, the good the sparrows do must 

 far outweigh the mischief which is laid to 

 their charge. This statement receives the 

 amplest confirmation in the bountifiil har- 

 vests with which New Zealand is blessed. 

 Never were the sparrows more numerous, 

 ne^^'er the complaints against them more 

 bitter; yet the yield of grain is without 

 precedent. 



The growling of the New Zealand farmer 

 at the sparrow, again justifies Virgil's com- 

 plaint of the "miserly husbandman.^' 

 Miserly, indeed, and blind. Not a grain 

 will he give the bird which has laboured 

 unceasingly for eleven long months to free 

 the soil from grubs; but whole fields of 

 wheat to the caterpillar ! 



Birds in Woods a,nd Forests. 



Birds attain their greatest usefulness in 

 the woods and forests, because the conditions 

 there closely apjiroach the primeval. 



Forest trees nave their natural insect foes, 

 to which they give food and shelter, and 

 these insects in turn have their natural 

 enemies among the birds, to which the tree 

 also gives food and shelter. Hence it fol- 

 lows that the existence of each one of these 

 forms of life is dependent upon the existence 

 of the other. Birds are not only essential to 

 the well-being of the tree, but the tree is 

 necessary to tUe life of the bird. 



Consider for a moment the life of a tree in 

 connection with the insects that prey upon 

 it. At the very beginning, before the seed or 

 nut has gernimated, it may be entered by a 

 grub which destroys it. Should, however, 

 the seed or not be permitted to grow, the 

 roots of the seedling may be attacked by 

 beetles. Ec^caping this danger, a worm lays 

 its eggs in the cracks of the bark. On hatch- 

 ing, the worm, or borer^ perforates a hole 

 in the stem. This hole, admitting water 

 from every passing shower, causes a decay in 

 the wood to commence, from which the tree 

 may never recover. Other borers feed upon 

 the bark, eating the soft inner layer and the 

 sap. The twigs are affected by the larvae of 

 certain bei'tles, which act as girdiers, some- 

 times destroying linihts over an inch in dia- 

 meter, ee vi 1 s lK>re u n der t he bark and 

 into the ^Mth. 



the cicada makes a 

 often prove's fatal, 

 affected by aphides 

 and feed upon their 



making excavations in which 

 the eggs are laid. For the same purpose 



terrible wound, which 

 The limbs of trees are 

 which puncture them, 

 juices, exhausting the 

 (sap. Many species of plant lice and scale 

 insects infest trees, doing great damage, 

 while over 100 different species of gall flies 

 are parasitic upon them. The buds of trees 

 are entered and destroyed by the larvae of 

 certain moths, while the leaves are devoured 

 by caterpillars. To take the oak as an 

 example, it is known that altogether over 5(X) 

 species of insects prey upon it. Finally, be 

 it remembered that in the bark and in the 

 underlying tLssues lie the vital energies of a 

 tree, 



I spent the formative period of my years 

 in, or in close proximity to, primeval forests. 



and going often to Nature's mighty school to 

 learn her secrets, I was lastingly impressed 

 by the way in which the care of the tree is 

 kept up throughout the changing seasons by 

 bird life, each species exerting its peculiar 

 repressive influence upon the increase of this 

 or that one of the various forms which insects 

 assume. 



How dependent trees are on birds for their 

 existence may be gathered from the following 

 illustration, instances of which I have often 

 seen when the services of one or more of their 

 natural protectors have been withdrawn. An 

 now so generally known, trees breatk- 

 through their leaves. Consequently, if the 

 buds of the leaves are prevented from de- 

 veloping by worms, or are eaten, when de- 

 veloped, by caterpillars, the tree is weakened. 

 Many coniferous trees will die if stripped ot 

 their foliage for one year. Deciduous tree^. 

 if deprived of their respiratory organs for 

 several years in succession will also perisli. 

 though theee trees linger as a rule for two, or 

 even three, years before finally succumbing. 



Nor is injury to its breathing organs the 

 only danger to which a tree, afflicted in thi> 

 way, is subjected. The tree, being in a 

 weakened condition, is at once beset 

 beetles, and other borers, who, multiplying: 

 rapidly under such favourable conditions, 

 tunnel under the bark until all the vital 

 tis.sues of the poor tree are wasted. Thus a 

 tree, which might have recovered from the 

 injury to its lungs, falls a victim to the 

 attacks of an insidious enemy which took 

 advantage of its feeble state. 



Woodpeckers, or other birds of similar 

 feoding habits, would have flown to the 

 rescue of the tree, and possibly saved its life; 

 but, when that corrective influence is miss- 

 ing, the tree must die. 



This illustration of the dependence of the 

 tree on the bird, and of the bird on the tree, 

 is, of course, but one of a long series that 

 could be cited, and it is because of this most 

 delicate adjustment between the tree, the 

 insect, and the bird, that I regard as pro- 

 foundlv true Frank M. Chapman's statement 

 " that it can be clearly demonstrated that if 

 we should lose our birds we should also lofe 

 our forests," 



The Value of the Bird in the 



Orchard. 



For man's purposes the work of the bird in 

 the orchard is not so thorough as that done 

 by them in the forest. Birds are the slaves 

 of Nature, and, in the main. Nature's en- 

 deavours are put forth only to produce such 

 fruits as will ensure the perpetiiity of eaeh 

 species of tree. With man the case is alto- 

 gether different. His main object is not the 

 propagation of trees, but the production of 

 heavy crops. Moreover, by introducing arse- 

 nical sy raying, tarred and greased bandSj 

 and other devices to counteract the evil 

 action of insects, he has, to a certain extent^ 

 taken upon himself the office of the bird. 

 In this he is wise, for it must be admitted 

 that if he wishes a large crop of fruit, he 

 must himself prevent the inroads of those 

 insects which attack the fruit directly. Ij 

 cannot be expected of the bird that it will 

 become an efficient ally of man in protecting 

 the artificially produced fruit from the at- 

 tacks of the numerous insects that are drawn 

 to the orchard by a vastly increased quan- 

 tity of fruit of a vastly better quality than 

 the natural product. 



For all that, fruit-growers are largely i^' 

 debted to the bird for a great part of their 

 annual crop. Tliere are a host of tiny crea- 

 tures that are not affected by spraying. Tliese 

 lilliputian pests are the plant lice and their 

 allies, bark lice and scale insects. Usually 

 their presence is unnoticed on account oi 

 their diminutive size; but they suck out the 

 juices of the tree, and are exceedingly harm- 

 ful. If their multiplication remained un- 

 checked, the ultimate result upon 

 lopment of the fruit, if not upon the Ui^ 

 of the tree, would be very great. 

 nothing, however small, escapes the pryinp 

 eyeis of a bird, and it clears the trunk- 

 branches, and twigs of the tree of theee 

 encumbrances. 



(To be continued.) 



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