If nothing occurs to disturb the repose of the pair, the male, perched upon a neighbouring branch, pours out a song expressive of his felicity. The little ones are finally hatched. Helpless and incapable, without feathers and with closed eyes, they are utterly dependent on the parent birds, by which they are fed until the time when they are covered with feathers. They now begin to try their wings, and find their own food. The mother directs their first efforts, uttering a peculiar cry to attract them when she discovers a favourite morsel; defending them courageously, and, with a total abnegation of self, meeting the most formidable enemies; sometimes going so far for their protection as to offer herself a victim. How pitiful are the cries of a Swallow whose nest is built under the roof of a house on fire! Fearlessly she rushes on the flames, flying to the assistance of her young, as if she would rescue them or perish under the fatal roof. Or mark the unhappy Partridge which the sportsman has surprised on the nest. She hesitates not to offer herself a sacrifice, throwing herself almost under the intruder's feet, in order to attract his attention from her progeny. When the young are strong enough to take wing, they abandon the family tie, and soon lose themselves in the great world of nature, forgetful of their parents' unselfish care. The ingratitude of their first-born does not, however, discourage the forsaken couple. With the returning season they renew their labours, exhibit the same solicitude, the same affection, to meet with the same return. Nature is an unfailing source--an eternal focus of tenderness and love. Most families of birds are migratory; that is, they abandon their summer quarters and undertake long journeys at certain seasons. These migrations occur with the greatest regularity. By their departure from temperate or cold climates they prognosticate the approach of winter, as their return heralds spring. Among the ancient Greeks, as we learn from a passage of Aristophanes on birds, the arrival of the CRANE pointed out the time of sowing; the arrival of the KITE the sheep-shearing season; and the arrival of the SWALLOW in Greece was the date for putting off summer clothing. The impulse which causes birds to depart is an instinctive desire to find climatic conditions appropriate to their wants of life. At the approach of winter they desert the regions of the north in search of southern countries with a warmer climate, while others migrate northwards to escape the heat.