We found that the bird existed in numbers; once we had discovered a way of entering its stronghold, it was possible to make the desired studies. Thus our difficult search, covering so many hundreds of miles, came to a pleasant and successful close.
Our work in the Argentine, however, was by no means completed. After a short return trip to our base, we went some distance farther south to Aguilares, a village similar to San Pablo and Acherál. Persimmons and tangerines were in season, and at each station women came to the car-windows offering great bunches of the fruit for sale. The former were most attractive while on the trees; they were as large as a hen’s egg, of a deep-red color, and were evenly distributed among the dense, green foliage. The flavor of both was excellent.
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.
The birds, in bands of a few individuals to several hundred, arrived each morning at daybreak, flying low and swiftly, and making a “swishing” sound as they cut through the air. When immediately over the rice-fields, the band would suddenly swerve as if to circle, but drop almost instantly and eat greedily without a moment’s delay. Upon seeing a flock approach, the men threw stones and shouted, often succeeding in making it pass straight over or leave the vicinity after circling once or twice. Should the birds alight, the hail of stones soon put them to rout, but not until a few grains of the much-coveted rice had been secured by each individual.
As the day advanced the birds spread out over the surrounding country where they were not persecuted, and spent most of the time on the ground near the cattle and horses, often perched on the backs of the grazing animals. At nightfall they returned to the cattails, and in passing over the rice-fields again took toll from the planters. The flocks in the marshes assumed tremendous proportions, and the babble of voices resembled a rushing wind; the roar of wings, if the masses were suddenly startled by the report of a gun, was not unlike the roll of distant thunder. Before finally settling down for the night they spent some time hopping about on the mud-flats and eating minute animal and vegetable matter.
Carlos S. Reed, F. Z. S., Director of the Natural History Museum, Mendoza, Argentine Republic, gives the results of his investigations as to the food of Molothrus bonariensis in a paper in the Revista Chilena de Historia Natural, año XVII, No. 3, 1913. The following is a translation, as literal as possible, of a part of the original paper, which is written in Spanish: