7. Swans usually build nests of a few coarse sticks, and a lining of grass or straw. They have a curious habit, however, of raising their nests higher, and of raising the eggs at the same time. 8. At times they seem to know that some danger threatens them, and then they turn their instinct for raising their nests to some purpose. A person who observed all the facts tells this story: 9. For many years an old swan had built her nest on the border of a park, by the river-side. From time to time she had raised her nest, but never more than a few inches. 10. Once, when there had been no rain for a long time, and the river was very low, she began to gather sticks and grasses to raise her nest, and she would scarcely stop long enough to eat. 11. She seemed so anxious to get materials for nest-building that she attracted the attention of the family living near by, and a load of straw was carried to her. This she worked all into her nest, and never stopped until the eggs had been raised two and a half feet. 12. In the night a heavy rain fell, the river flowed over its banks, and the water came over the spot where the eggs had been; but it did not quite come up to the top of the new nest, and so the swan saved them. LESSON XII. _DOVES AND PIGEONS._ [Illustration: The Bath.] 1. Everybody likes the dove; it is such a pretty bird, and is always so clean. It flies all about the yard, the garden, and the street. Even the rudest boys do not often disturb it. 2. It is about the size of a half-grown chicken, and looks more like a chicken than any of the other birds we have studied. 3. The doves about our houses are usually white, or a bluish gray. They live in pairs, each pair having its own nest, or home; but where doves are kept, many pairs live in the same house or dove-cote. 4. They have a short, pointed bill, like a chicken, and strong legs and toes, so that they can walk and scratch easily. [Illustration] 5. The mother dove lays but two eggs before sitting, and then her mate sits on the nest half of the time until the eggs are hatched. The young doves, called squabs, are covered with down like chickens, but, unlike chickens, the old ones must feed them a week or two before they are able to go about by themselves. 6. Both the father and mother dove feed the young ones with a kind of milky curd which comes from their own crops. 7. When the chicken drinks, it sips its bill full, and then raises its head and swallows; but the dove does not raise its head until it has drank enough. 8. The pigeon--which is another name for the dove--has very strong wings, and can fly far and fast without tiring. When taken from their home a great distance, pigeons will fly straight back. 9. Before we had railroads and telegraphs, people would take pigeons away from home, and send them back with a letter tied under their wings. These were called carrier-pigeons.