THE RUSTY BLACKBIRD. 
insects is destroyed and very few useful ones are taken. 
blackbirds do not inhabit farms, their economic relations can not be 
said to be very important; but while not preying directly upon nox- 
ious insects or weeds which interfere with the cultivation of crops, 
it is yet possible that they incidentally do considerable good by eating 
insects. 
49 
As rusty 
Although their foraging is done mostly in pastures and 
swamps, yet the insects which they devour count just so much from 
the sum total, and in the long run the destruction of noxious species 
is, perhaps, nearly as great a good to the farmer as though they were 
taken directly from his cultivated fields. 
Grasshoppers and many scarabeid beetles are nuisances, and their 
destruction is a benefit to agriculture, no matter where they may he 
found. The same may be said of caterpillars and many other insects, 
which, though now feeding on useless plants of the marsh or thicket, 
are liable at any time, through an unusual increase in numbers or a 
change in environment, to turn their attention to some crop and 
become a veritable pest. 
crustaceans, which form a considerable percentage of the diet of the 
rusty grackles, are to a great extent carnivorous in their habits, and 
it is difficult to see in what way they can ever become of any great 
economic importance. 
On the other hand, aquatic beetles and small 
The following table shows the percentages of the principal elements 
of the food for each month: 
Food of the rusty blackbird. 
[NUMBER OF STOMACHS EXAMINED: January, 1; February, 6; Mareb,17; April, 49; May, 7: June, none 
collected; July, none collected; August, 4; September, 5; October, 25; November, 15; December, 3; 
total, 182. 
: H ro ay 
a ; 3 4 e 2 a ¥ 
a a) eS lela) ht elels aie 
Be Ve ee Be Be Le ae 
3 2 4 o iS) 2 = as 
5 a ma <a a a n 2 Zz 5 a 
ANIMAL. BON EEG cee (ene ae | Ge | eee | Gee Larne | Gent | oe 
Predaceous beetles ..........|..----|----+- 425 jf 168 ee caeas 1/8!) Ag6 f “288 OLE oswees 1.7 
May-beetle family...........].----- 2.5 |.ceee THe ecvecret (eens SOE Be Olle 2.0 
Other beetles ............2.2-[--2--- 37.3 | 13.4| 13.7] 25.9] 10] 7.0] 16] 1.3]...... 10.1 
VOCE sc icucdenecaaalfieean 420 | va) 2520) | TT | ewees I terctsin D8! | OPA? oseeets D5) 
Grasshoppers ..--..--.---+++-|------ Os 23 lees 973 aes 44.3 | 18.6 | 44.2] 3.9 )...... 12.0 
Other insects.............-..]------ 25.8 | 13.9 | 15.5 | 20.0] 26.0, 16,0] 4.5] 13.2) 1.7] 13.7 
Spiders and myriapods......|.-.--. 0.9] 3.8] 4.9] +1] 23.0 ]...--. OEE |, OES: aeraeer 4.0 
Other animal food _.........)...--- 15 WF | BRP TSB [eee sce 16.2} 5.1] 5.9] 80.0] 7.0 
Total animal food .....|-..--- 72,2 | 44.8 | 68.7 | 63.0 | 96.8 | 59.4 | 65.8 | 27.5 | 81.7 | 53.0 
VEGETABLE. 
<0 | 28:8 [20/8 ocexe,|aescae|esesee 9.0) 26.5 | 5.0] 17.6 
Peres 15:4) BAT] WOT Ne eceal 23: TSH, hide Veccsac! G8 
O84 BA] 44/2818 | ence 6.6] 0.8 | 15.0 |....-. 6.0 
93.5! 7.61 24] 1.6] 3.2 | 20.6 | 17.1 | 26.5 | 63.3 | 16.6 
Total vegetable food ../100.0 | 27.8 55.2 | 31.3 | 37.0] 3.2} 40.6 | 34.2 | 72.5 | 68.3 | 47.0 
8074—No. 183——+ 
