Killifish manage to endure a variety of environments. The wee freshwater fish survive in isolated desert pools, lakes made by flood water, even seasonal ponds that are little more than puddles.

One place scientists didn’t expect to find them was in swan poop. But an international team of researchers reported last week in the journal Ecology that whole killifish eggs make it through the digestive tract of water birds intact, with one egg in the study even hatching more than a month after its transit through a swan. The findings suggest that bird feces may be capable of carrying fish eggs far from their original locations.

Giliandro Silva, a graduate student at Unisinos University in Brazil, and colleagues found last year that small flowering water plants in bird feces were still alive and able to grow. While they were completing that study, they found a killifish egg in a frozen fecal sample from a wild coscoroba swan. They realized that what was true for plants might also be true for fish eggs.

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To test this hypothesis, they mixed eggs of two killifish species found in Brazil into the feed of swans living in a zoo. Over the next two days, they collected what the swans excreted and looked for intact eggs. They found five, about one percent of the 650 eggs they’d mixed in.