26 BIRDS OF CALIFORNIA AFFECTING FRUIT INDUSTRY. 
of insects, many of them harmful, the tanager has a fair claim to con- 
sideration at the hands of the farmer and even of the orchardist. 
It is probable that means may be found to prevent, at least in part, 
the occasional ravages of the tanager on the cherry crop. The tan- 
ager, like the robin, prefers to swallow fruit whole, and as the latter 
takes small wild cherries in preference to the larger, cultivated kinds 
when both are equally accessible, it is probable that the tanager would 
do the same; and it is suggested that a number of wild cherry trees 
planted around California orchards might prove an economical in- 
vestment for the orchardist. 
SWALLOWS. 
Swallows are the light cavalry of the avian army—always on the 
move, always on the skirmish line, ever gathering stragglers from 
the insect camps. They furnish another instance, and perhaps the 
most remarkable one, of change of habit induced by civilization. In 
eastern United States the bank swallow and the rough-wing are the 
only species that adhere persistently to their original nesting sites. 
In the West a third species may be added to these, the violet-green 
swallow: but there all the swallows are somewhat less domestic than 
in the East. It is probable, also, that some species, notably the barn 
swallow, are more abundant than when the country was unsettled, 
owing to the increased number of nesting sites. Supposing for a 
moment that the country was swept bare of buildings, where could all 
the barn swallows find suitable places to nest? The cliff swallows 
might discover enough overhanging cliffs upon which to attach their 
mud domiciles; the white-bellied and the martin, as formerly, might 
nest in the hollows of trees, but there are not caves enough east of 
the Mississippi River to afford nesting places for one-tenth of the 
barn swallows. In the far West they would fare better. When the 
country was first settled, barn swallows must have been confined to a 
few rocky cliffs and caves here and there along the seashore or in 
mountains. Now they live wherever man has erected a structure of 
anv kind. 
As is to be inferred from the movements of these birds, their food, 
with some curious exceptions, consists principally of insects caught 
in mid-air, For this reason all the species are migratory, except i 
the Tropies, for the food supply fails in regions where frosts prevail. 
As many insects that usually do not fly, periodically ‘ swarm,’ they 
are often captured by swallows at such times in great numbers. Such 
is the case with ants and ‘white ants’ (Termitide), which most of 
the time are concealed in the earth or in logs, but at certain times 
‘swarm? in immense numbers. Many species of beetles that live in 
offal and ordinarily are not accessible to birds, in case of failure of 
