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This Month in Yellowstone
Nesting Dippers

Last month we showed you an old, empty dipper nest. This month, while checking the bridge more carefully, Tom Cawley (Webmaster) found an active nest with nestlings. He went back three times and shot about two hours of tape to get the few minutes you see here. The video was shot on April 25, 27, and 29.

If you watch carefully, you will notice some interesting nest behaviors. Whenever the nestlings suspect a parent is bringing in food they extend their necks and snap their big mouths open. If one of them is slower than the others it will not be fed as frequently allowing the faster, stronger individuals a better chance to survive. Another common nest behavior is seen a couple of times in the video. Occasionally an adult emerges from the nest carrying a white sac in her beak. This is a fecal sac excreted by one of the nestlings. These fecal sacs are either dropped clear of the nest by the nestling or carried away from the nest by an adult. As a result, the nest is a cleaner, more healthful place to raise youngsters and the feces are not readily obvious to predators looking for clues of an active nest.

Dippers build their nests over rivers and streams. They are the only truly aquatic songbird in the United States. They feed by diving beneath the surface of the river and walking along the bottom, using their wings to hold them down. They locate submerged insects which comprise nearly 100 percent of their diet. A transparent second eyelid, called a nictitating membrane, allows their eyes to be protected while they are looking around underwater. They got their name because of their habit of dipping their bodies up and down when people are nearby.