Ecologists have developed a way of monitoring the sizes of bird populations by recording their song. Writing in the Journal of Applied Ecology, the team says the new technique gives a more accurate estimate of numbers. Previously, researchers used nets to capture the birds, which can also be stressful for the animals. The research team monitored the chirping of the ovenbird – a small warbler found in North America. According to Dr Deanna Dawson of the US Geological Survey, the ovenbird was the ideal species for testing out the new method.<br/>