Tracking Radar Station (image) Springer Caption Nilsson et al. measured with a tracking radar over three years the speed by which birds flew over Falsterbo Peninsula, a bird migratory hot spot in south-western Sweden. Passerine birds, also known as perching birds, that migrate by night tend to fly faster in spring than they do in autumn to reach their destinations. Credit Cecilia Nilsson Usage Restrictions The image may only be used with appropriate credit. Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.