Male sticklebacks build a nest by attaching tying together vegetation using secretions from their kidneys. Once the nest is complete it attracts females, who lay their eggs in it. The males then chase the females away and fertilize the eggs. Studies have shown that males build multiple nests, so be sure to keep a look out on your next visit. You might just see a builder at work!
Fourspined stickleback (source: cornell.edu)