After the Churinche's nest is completed, the Bienteveo (_Pitangus bolivianus_) and the Common Cow-bird (_Molothrus bonariensis_) are the troublers of its peace. The first of these sometimes carries off the nest bodily to use it as material in building its own; the female Cow-bird is ever on the look out for a receptacle for her eggs. Seldom, however, does she succeed in gaining admittance to the Churinche's nest, as he is extremely vigilant and violent in repelling intruders. But his vigilance at times avails not; the subtle bird has watched and waited till, seizing a moment when the little Scarlet Tyrant is off his guard, she drops her surreptitious egg into his nest. When this happens, the Churinches immediately leave their nest. The nest is sometimes lined with feathers, but usually with thistle-down; the eggs are four, pointed, and spotted at the broad end with black; usually each egg has also a few large grey spots. The young are at first grey, marked with pale rufous, but soon become entirely grey, like the female. In about a month's time the belly of the males begins to assume a pale mauve-red; this spreads upwards towards the breast and throat; and finally the crest also takes on this colour. The Churinches raise two broods in a season--but if the nest is destroyed, will lay as many as four times. The Scarlet Tyrant is the first of our summer visitors to leave us. As early as the end of January, and so soon as the young of the second brood are able to feed themselves, the adults disappear. Their going is not gradual, but they all vanish at once. The departure of all other migratory species takes place after a very sensible change in the temperature; but at the end of January the heat is unmitigated--it is, in fact, often greater than during December. When the adults have gone, the silent young birds remain. Within a month's time the sexes of these may be distinguished. After another month the males begin to sing, and are frequently seen pursuing one another over the fields. It is only at the end of April, three months after the old birds have disappeared, that the young also take their departure. This is one of the strangest facts I have encountered in the migration of birds. The autumnal cold and wet weather seems to be the immediate cause of the young birds' departure; but in the adults, migration appears to be an instinct quite independent of atmospheric changes. 163. EMPIDONAX BIMACULATUS (Lafr. et d'Orb.). (WING-BANDED TYRANT.) +Empidochanes argentinus+, _Cab. J. f. O._ 1868, p. 196. +Empidonax brunneus+, _Ridgw. N. A. B._ ii. p. 363 (Paraná). +Empidonax bimaculatus+, _Scl. Ibis_, 1887, p. 65.