The immense aggregations of flamingoes which, in wet seasons, throng the middle marismas can scarce be described. Our bird-islets lay so remote from the low-lying shores that no land whatever was in sight; but the desolate horizon that surrounded them was adorned by an almost unbroken line of pink and white that separated sea and sky over the greater part of the circle. On examining the different herds narrowly through binoculars, an obvious dissimilarity was discovered in the appearance of certain groups. One or two in particular seemed so much denser than the others; the narrow white line looked three times as thick, and in the centre gave the idea that the birds were literally piled upon each other. Felipe suggested that these flamingoes must be at their _pajeréra_, or breeding-place, and after a long wet ride we found that this was the case. The water was very deep, the bottom clinging mud; at intervals the laboured plunging of the mule was exchanged for an easier, gliding motion--he was swimming. The change was a welcome relief to man and beast; but the labours undergone during these aquatic rides eventuated in the loss of one fine mule, a powerful beast worth £60. [Illustration: FLAMINGOES AND THEIR NESTS] On approach, the cause of the peculiar appearance of the flamingo city from a distance became clearly discernible. Hundreds of birds were sitting down on a low mud-island, hundreds more were standing erect thereon, while others stood in the water alongside. Thus the different elevations of their bodies formed what had appeared a triple or quadruple line. On reaching the spot, we found a perfect mass of nests. The low, flat mud-plateau was crowded with them as thickly as its space permitted. The nests had little or no height above the dead-level mud--some were raised an inch or two, a few might reach four or five inches in height, but the majority were merely circular bulwarks of mud barely raised above the general level, and bearing the impression of the bird's legs distinctly marked upon the periphery. The general aspect of the plateau might be likened to a large table covered with plates. In the centre was a deep hole full of muddy water, which, from the gouged appearance of its sides, had probably supplied the birds with building material. [Illustration]