NATURAL ENEMIES. 31 



very slowly and gradually here, only one small colouy the first year, two or three the 

 next, and so on, till in a few years almost all suitable premises had colonies of them. 

 There are none yet, so far as I know, in far northern and western Ontario. No spe- 

 cial protection was given them in our town, save that the general feeling amongst our 

 citizens was to protect them, and they were not molested. (October 11, 1886.) 



CHECKS ON THE INCREASE OF THE SPARROW. 



The checks which have operated in the past to limit the increase and 

 spread of the Sparrow may be roughly classed under two heads, (a) 

 natural, (b) artificial; including under the latter head all those hostile 

 influences due solely to man, and under the former all others. Among 

 the natural checks may be mentioned climate, food, natural enemies 

 (such as cats, hawks, jays, etc.), and disease. 



It is a general rule in the animal kingdom that excessive multiplica- 

 tion tends to disease, and nearly all animals are subject to epidemics 

 and parasites which tend to reduce their numbers when they become 

 extremely abundant. But nothing of this kind is known among Spar- 

 rows, and they seem to be among the hardiest and healthiest of birds. 

 It is true that albinism is quite common, specimens which are more or 

 less white being frequently seen on the streets of most large towns, 

 but this can hardly be considered an indication of weakness or disease 

 in the species, although it probably does result from living under more 

 or less unnatural conditions. 



NATURAL ENEMIES OF THE SPARROW. 



As regards natural enemies the Sparrow is remarkably favored, for, 

 from its constant association with man, it escapes nearly all the perils 

 which restrict the increase of native birds. 



It is generally supposed that cats must catch many Sparrows, but in 

 point of fact it is rare for an adult Sparrow to fall into the clutches of 

 this enemy, and even the young are not often caught. The centuries of 

 experience which have developed this bird into a parasite upon man 

 have taught it how to avoid the other semi-domesticated animals sur- 

 rounding him, and it is safe to say that cats have far better success in 

 catching the wariest of our native birds than in catching the Sparrow. 



A few of our native birds kill Sparrows or eat their eggs and young, 

 but the number of species is very limited, and, except in rare cases, the 

 number destroyed is insignificant. 



Probably the most useful bird in this respect is the northern shrike 

 (Lanius borealis), which visits most of our Northern cities in winter and 

 feeds freely on the Sparrow. At one time this shrike became so abun- 

 dant on the common and public gardens in Boston that it threatened to 

 destroy all the Sparrows, but the shortsighted authorities kept a man 

 busy in shooting the shrikes until several dozen had been killed, and 

 the useless Sparrows were considered safe. 



In many cities and towns of the Mississippi valley the bluejay (Cyano- 

 citta cristata) is said to lessen the number of Sparrows somewhat by 



