Within an hour after reaching Aguilares we had been invited to visit the estate of a wealthy rice-grower named Da Costa, and soon after we were on our way, his son taking us there in a carriage while the luggage went in a cart. At the ranch we found a large, rather dilapidated house occupied by the family of the caretaker. On one side were great rice-fields; on the other, totora marshes, pastures, and woods. The place was most attractive, and the people altogether delightful, so that we spent over two weeks busily engrossed in the abundant work at hand. The marshes covered many acres and were filled with cattails except for a few narrow lanes of open water. Coypu rats had their runways crisscrossing in every direction--sometimes neat, rounded tunnels with the bottom just under water, and again, wide trails where the vegetation had been trampled down. They look like very large musk-rats and their skins, known commercially as _nutria_, are exported by hundreds of thousands each year to be manufactured into felt hats of the better quality. We caught several that gnawed down all the stalks within reach and piled them into neat islands on which to sit. They feigned death until touched with a stick when they attempted to bite and fought viciously. Jumping mice and large, light-brown, woolly rats used the same paths as their bigger relatives. One afternoon a fine individual of the great red wolf we had secured at Corumbá appeared at the edge of the rushes for a moment only to vanish into the dark marsh at our first movement; a few minutes later he was seen loping into the brush several hundreds of yards away. Ducks came to the region daily, mostly teals and rosy-bills, but in small numbers only. They were hard to get, as wading in the waist-deep, ice-cold water and mud was slow work and they invariably took warning and left while still out of range. At night flocks of painted snipe (_Rostratula_) ventured to the open borders to feed. While we were quietly waiting, a dusky form appeared and began to probe the mud frantically, to be joined by others in a short time. They skipped about on the flats adjoining the reed-beds in a most erratic manner, reminding one of the actions of water-beetles, and upon the first sign of danger promptly disappeared in the labyrinth of stems and grasses. They seldom took wing, and then it was but to flutter up above the tallest reeds and immediately drop out of sight in the thick cover. It is to this region of dense totara marshes that the cowbirds revert to spend the winter season, arriving from all directions in comparatively small flocks, but increasing in numbers until there are tens of thousands. As the rice was ripening about this time, the birds did an enormous amount of damage. All day long, men on horseback rode back and forth through the fields, armed with slings and a bag full of pebbles; they hurled stones and shouted themselves hoarse in a vain endeavor to frighten away the marauding hosts.