First-Time Migration in Juvenile Common Cuckoos Documented by Satellite Tracking

Abstract

<p>Being an obligate parasite, juvenile common cuckoos Cuculus canorus are thought to reach</p><p>their African wintering grounds from Palearctic breeding grounds without guidance from</p><p>experienced conspecifics but this has not been documented. We used satellite tracking to</p><p>study naïve migrating common cuckoos. Juvenile cuckoos left breeding sites in Finland</p><p>moving slowly and less consistently directed than adult cuckoos. Migration of the juveniles</p><p>(N = 5) was initiated later than adults (N = 20), was directed toward the southwest±significantly</p><p>different from the initial southeast direction of adults±and included strikingly long Baltic</p><p>Sea crossings (N = 3). After initial migration of juvenile cuckoos toward Poland, the</p><p>migration direction changed and proceeded due south, directly toward the winter grounds,</p><p>as revealed by a single tag transmitting until arrival in Northwest Angola where northern</p><p>adult cuckoos regularly winter. Compared to adults, the juvenile travelled straighter and</p><p>faster, potentially correcting for wind drift along the route. That both migration route and timing</p><p>differed from adults indicates that juvenile cuckoos are able to reach proper wintering</p><p>grounds independently, guided only by their innate migration programme.</p>