Fig. 2

Comparison of migration routes between European nightjars, common cuckoos and common swifts. Circles indicate stopover areas used for at least 5 days. Species are shown in different colors (green = cuckoo, brown = nightjar, blue = swift). Nightjars and swifts were tracked with light-level-based geolocators with considerable uncertainty, especially for latitudes; cuckoos were tracked with high accuracy satellite transmitters [22]. Several of the nightjar locations included here (for illustration purposes) are extrapolated from known longitude and latitude based on an estimated flying speed of 350 km/day (see Fig. 1 for full latitude span). a Complete annual migration. Lines connect stopover locations and do not necessarily reflect route taken (for swift in fall, the easternmost point of the Sahara crossing is included for illustration of the Zugknick here) with darker shading indicating fall and lighter spring migration, b locations month by month. Background layer is vegetation greenness in each 2° latitude × 2° longitude cells averaged for each period 2000–2010 derived from on NOAA-16 Normalized Difference Vegetation Index (NDVI), AVHRR NDVI3 g.v0 [29]