We found that much of the jungle was almost impenetrable, and on one of our first excursions we were fortunate enough to find a means of making the birds come to us from the deeper recesses of the forest. As we left the doorway, a silent little shadow fitted into the pommerosa tree in front of us, and soon among the glossy leaves came a sound which we had heard day and night, but the author of which had thus far evaded us. It is impossible to put into words, but it may be imitated by a monotone whistle, of about four notes to the second, of A above middle C. The glasses showed a mite of a Pygmy Owl[60] glaring at us with wide yellow eyes, and firmly clutching a dead bird, half as large as himself. Later, when standing at the edge of an impenetrable tangle of thorny vines and vainly trying to discover what bird was singing in loud, ringing tones within it, we thought of the fierce little owl, and concealing ourselves, gave the call of _Glaucidium_. The effect was instantaneous; the song near us ceased, and with angry cries a pair of beautiful Black-capped Mocking-thrushes[126] flew almost overhead. Black-tailed Euphonias[139] and Grassfinches followed, Bananaquits[137] whirred about us, and within a few minutes thirty or forty birds had testified to the hatred in which the little Owl is held. A great surprise to our northern eyes was the Yellow Woodpecker,[90] not uncommon here, and clad in bright yellow plumage from crest to tail. It was very conspicuous in flight, but when it alighted, merged with the lichened bark and spots of sunlight. One bird was very tame and frequented a tree close by our window. One of our first walks led us through a narrow valley or gorge to the westward, shaded by ranks of tall palms and with isolated banana and cocoa plants, hinting of native Indian clearings long since overwhelmed by the luxuriant jungle growth. Wasps and other Hymenoptera outnumbered other insects at this season, and one could have collected scores of different species in a few hours. A few Heliconia butterflies drifted across our path, and now and then a giant morpho shot past like a meteor of iridescent blue. Other great butterflies (_Caligo ilioneus_) were iridescent blue and brown above, while the under sides of their wings were mottled and with a great eye-spot on each of the hind wings, which gives them the name of the owl butterfly. But however much, in an insect cabinet, the expanded reverse of the wings suggests the face of an owl, the spot, as we observed it in the forest, seemed rather to render the insect invisible. These great fellows would shoot up to a lichen-covered trunk and drop lightly upon it, and unless one’s eyes had followed closely, the butterfly vanished like magic. Creeping up to one we secured its picture, the mottlings on its wings merging it with the lichens, and its owl-eyes becoming the painted facsimiles of darkened knotholes, or of little atoll-like fungus rings. [Illustration: FIG. 20. YELLOW WOODPECKER.]