Getting a bird's eye view

Research biologist Pam Pietz and ecologist Diane Granfors of the Northern Prairie Wildlife Research Center near Jamestown have used tiny night vision video cameras to find that deer, gophers and even mice will eat the newborn birds, and destroy the nest.

They even have tape of a gopher killing a mother songbird that tried to defend its nest.

"The deer were a big surprise, the mice were suspected, but I'm not sure anybody had any real evidence," Granfors said.

The system is a big improvement over the old method of relying on evidence, or signs, at destroyed nests to figure out what happened.

"One of the reasons we wanted to use the camera was to find out what was actually happening at the nest rather than rely on sign," she said.

The researchers turned to tiny night vision cameras because direct observation and other approaches aren't practical in grasslands. The camera has to be close to the nest, otherwise grass blocks the view.

That means it has to be small, or risk causing birds to abandon their nest, risk attracting or repelling predators or causing other changes in natural behavior.

They worked with an electrical engineer to come up with a waterproof 2-inch square infrared camera that sits on a dowel to watch nests.

A cable was then connected to a VCR about 50 yards away. The VCR recorded 24 hours of activity on extremely slow play before it needed a fresh tape.

They tested the camera on nests of 10 grassland species in 1996 and 1997.

"The main goal for us was to just test the system and find out if it worked on grasslands," she said.

This is the camera that local wildlife researchers had developed to find out what kind of predators prey on songbird nests in grasslands and to view nesting behavior. The infared camera can see in the day and night.

They also monitored another 259 nests of 13 species using just periodic nest visits and relying on evidence left at the nest to compare results of the two approaches.

They concluded that evidence at the nest is not a reliable basis predator identification.

For example, holes in nests or no disturbance at all in destroyed nests were often taken as sign of predation by snakes. The camera showed ground squirrels caused these sign.

The cameras also showed two shrub nests that simply tipped over on their own, nestlings knocked out of a nest by a parent that flushed at night, and a red fox scavenging eggs that had already been punctured by a brown-headed cowbird. Those events would have left misleading signs.

"We documented many events that could lead to errors, when nest fates and causes of failures are assigned using information from periodic nest visits," their report on the Internet said.

They would have incorrectly estimated the number of fledglings at some nests, too.

The cameras were also useful for showing behavior of nesting birds that wasn't available before. These include incubation, brooding patterns and parental visitation rates. They also showed cowbird parasitism, parents eating eggshells, interactions between adults, and reactions of nestlings and adults to disturbances.

"It's about the only way you can get detailed information on the behavior of the birds," Granfors said.

They also tested the cameras to ensure they don't influence natural behavior by causing more nest abandonments, or more or less predation.

Abandonments only increased in 1997 when early dry weather created stress on the birds. The camera might have been the extra stress that sparked the abandonment.

Statistically they found no change in predation rates at nests with cameras. Predators seemed to notice the camera - like a curious weasel that stared right into the lens after destroying a nest - but it didn' seem to influence their behavior. Still, nests with cameras tended to have lower daily predation rates.

If that's the case, the cameras might result in underestimation of actual predation rates and biased assessments of the relative importance of some predators, their paper said.

"Nevertheless, the I camera system proved useful for identifying predators and accurately determining nest fates, and for obtaining data on nesting grassland passerines (birds) that were previously unavailable," the report said.

Granfors said the tiny cameras might prove useful for people working with endangered species. They can gather information on predators and behavior that might help increase the numbers of that species.