The Cornell Nest Box Network invites citizen scientists from
across the continent to take part in these exciting experiments.

If a real, honest-to-goodness, Ph.D.-toting scientist were to carry out a continentwide study to determine why Tree Swallows line their nests with feathers, he or she would have to visit nest boxes, peek inside, and estimate the number of feathers in the nest in each box. The problem is, that scientist would need to visit thousands and thousands of nest boxes all over North America to gather enough information. Impossible, if he or she were to do it alone or even with a Jeep full of research assistants.

This is why Lab scientists studying cavity-nesting birds developed the Cornell Nest Box Network (CNBN). Based on the same protocol they themselves use, they've made it easy, even fun, for everyone with a nest box to join them in their scientific endeavor. "There are nest boxes all across the continent, and every one of them has the potential to contribute enormously to science and conservation," says André Dhondt, director of Bird Population Studies at the Lab. "If everybody told us what was going on in just one nest box on his or her property, the overwhelming task of gleaning information from this virtually untapped resource would be as easy for each person as checking his or her mailbox once a week."

There's no doubt that "nest-box landlords" delight at the sight of a swallow or bluebird swooping in and out of a nest box. But Dhondt is convinced that if these people knew that their observations could be used to help answer questions relating to far-reaching topics such as biodiversity, they would promptly join the CNBN team.

In fact, Dhondt wonders if current CNBN participants fully understand the impact they are already having on bird study. To do so, Dhondt says they first need to understand some of the broader questions posed by the scientific community.

Scientists know, for example, that species characteristics vary depending on latitude. House Sparrows, for example, are larger in the North than they are in more southerly locales. Yet, this is a species that was introduced from Europe into New York City in 1865. At that time, those 100 or so individuals. which were brought from the same region at the same time. were roughly the same size. What happened during the last 135 years to cause this latitudinal variation? Are the same influences in motion today, and how do they relate to the fact that biodiversity increases the closer you are to the equator?

Dhondt and his colleagues developed the Cornell Nest Box Network to help answer some of these questions. Participants can join any or all of CNBN's four different studies. For the "clutch size study," participants keep track of the dates "their" birds lay eggs in the nest boxes, the dates the eggs hatch, and so forth. They also record the date the first egg was laid, total number of eggs, and other factors designed to measure the possible effects of latitude on reproduction. "Understanding the influences of latitude will bring us closer to understanding how nature works," says Dhondt. "Unless we know how nature works, we may not know enough to take the right measures to protect the biodiversity that remains."

Since CNBN's inception in 1997, the clutch study has yielded some interesting observations. Here in Ithaca, New York, for instance, Tree Swallows typically begin nesting at one location. a research site featuring several small ponds. one week earlier than at another area just a few miles west. "Imagine what we could learn if thousands of people at every latitude gave us information about the clutches in their nest boxes," says David Winkler, professor of ecology and systematics and a principal investigator with CNBN.

Another of CNBN's studies could yield further insight into the consequences of acid rain. Swallows' primary food source–insects–does not supply the birds with the calcium they need, particularly during egg production. Therefore, they must obtain calcium from their environment in some other way–for example, by eating snail shells. The "calcium study" instructs participants how to place calcium (crushed egg- or oyster shells) on the ground near a nest box and record which birds take the calcium and whether they're using that nest box. "For most songbirds, landing on the ground is routine. But for highly aerial species such as swallows, landing on the ground exposes them to much higher predation risk than usual. They will only come to the ground in extremely poor weather or when they need to obtain two critical resources for breeding: dry grass for their nests and calcium for their eggs," says Winkler. "By studying the use of calcium across the country, we hope to learn how regional variations in soil chemistry and acid rain affect the breeding of wild birds."

The "feather study" is another way Winkler and his colleagues are hoping to gain insights into the risk-benefit relationship of certain behaviors in swallows. Designed to find out just how much risk Tree Swallows will take to acquire feathers for their nests, participants offer feathers at varying distances from themselves. "Participants find out for themselves that Tree Swallows will take unbelievable risks to get feathers," says Winkler. "For all the swallows know, you're a predator who will attempt to eat them, yet they will zoom to distances that, for the birds, are dangerously close. It is thrilling to have a swallow swoop from behind and take a feather right before your eyes."

Why do they do this? The answer lies in the reasons swallows line their nests with feathers in the first place. To keep the young warm? To hide them from predators who've gained access to the nest box? To serve as a deterrent to parasites? Winkler conducted experiments in the Ithaca area and found that feathers help keep the young warm and that young grow faster in nests containing more feathers. But does this also apply in Virginia, Oregon, or other states and provinces? "This is why, in another of our studies, we ask participants to estimate the number of feathers in the nests in their boxes," explains Winkler. "In Ithaca and colder climates, we might know that it would be for warmth, and we therefore might expect there to be lots of feathers in these nests. But if that's true, nests in the South should contain fewer feathers." This is why CNBN needs many participants from all over the continent. Without enough data from geographically different regions, the hypotheses just can't be tested.

Says Dhondt, "I'll admit that the scientist in me wants to know, because scientists hate not finding the answers to their questions. But the truth is, if our questions aren't answered, it's the birds that will ultimately suffer the consequences."