YELLOW-BILLED CUCKOO. 
219 
imen. I do not know of any reason for this peculiarity unless it be caused by the temper¬ 
ature of particular seasons. These Cuckoos arrive about the same time as the other species 
and occasionally associate with them. They have much the same habits and notes but I 
have fancied that I could distinguish the song of the present species as it appeared harsher. 
As a rule, the notes of the Yellow-billed are more broken, thus they appear to utter cow- 
co-cow-co , giving the four syllables together, as it were, and therefore, they do not glide 
forth as smoothly as those produced by the Black-billed. There are, however, some sounds 
which are made by both which are so nearly alike that I have never been able to detect 
any difference. 
This species in company with the former are the terror of other small birds during the 
nesting season for they will constantly rob their nests. I have frequently seen a Cuckoo 
enter a thicket in which a Robin or Cat Bird had built a home and in a moment the air 
would resound with the shrill cries of distress given by the parents, causing all the small 
birds in the immediate vicinity to rush to the spot and as each joins in the outcry, the 
noise produced is apparently enough to frighten away a bolder bird than a Cuckoo. But 
in spite of all this din, the glossy thief nearly always succeeds in accomplishing his pur¬ 
pose and emerges from the thicket, carrying an egg impaled on his beak. He does not 
always escape unscathed, however, for he is pursued by a motley crowd consisting of Rob¬ 
ins, Cat Birds, Thrushes, Warblers, etc. that follow him closely, harassing him on all sides, 
and some of the more courageous will even assault him with blows from their beaks so that 
he frequently leaves some of his feathers floating in the wind behind him. As the long 
and broad tail of the Cuckoo is a prominent object and as it is also a portion of the bird 
which its enemies can seize with comparative safety to themselves, this member often suf¬ 
fers in these forays, insomuch, that by the middle of summer, it is quite difficult to find a 
Cuckoo of either species which has a full complement of tail feathers. 
In spite of this propensity to rob the nests of other birds, the Cuckoos are quite use¬ 
ful as they destroy quantities of insects. I have mentioned under generic characters that 
the lining of the stomachs of our northern species were thickly covered with hairs that 
resembled those from caterpillars. This internal membrane or stomach lining is soft and 
the hairs which under the microscope are seen to be furnished with barbs, are fastened 
into it just as they grow on the larvae of insects. The hairs which I have examined ap¬ 
pear to come from one species, viz:- the tent caterpillar. I have noticed that the Cuckoos 
are very fond of these destructive insects and apparently do much toward checking their 
ravages. During the passed summer, I had an opportunity of observing how beneficial the 
Cuckoos were in this respect for a pair of Black-bills which had a nest near, would visit a 
small apple tree on which these caterpillars had established a colony, several times every 
day and thus devoured so many of the destructive pests that their ravages were so com¬ 
pletely checked that the foliage of the tree which would have been entirely eaten had the 
insects remained unmolested, showed but few traces of their devastation; in fact, I do not 
think that one out of the large number of caterpillars that were hatched in the spring, ever 
came to maturity. This good was accomplished, be it noticed, through the exertions of a 
single pair of birds which, without doubt, also ate quantities of other insects. 
