This flock of white-winged swallows are taking a break from foraging over the water in search of flying insects. Their iridescent blue head and shoulders plus white belly make them easy to identify. They are small, measuring about 5.5 inches long, and weigh about half an ounce. The birds live near freshwater throughout the upper half of South America. In Brazil, you will only see them from mid-September through mid-April.