Before I proceed from birds to fishes, I think proper to subjoin a few
remarks upon common hens and swallows, the latter of which no ways
differ from those of Europe in appearance, voice, and habits. Although
Paraguay is free from snow, yet as the south wind renders the air rather
cold in winter, the swallows migrate like those of Europe to other
places about the beginning of autumn, and pass the winter in some
unknown retreats, but return at the commencement of spring.