But according to another study, some migratory birds rest for only seconds at a time during their flights:
http://www.livescience.com/1045-migrating-birds-hundreds-dai...
At 4-minute intervals over 200 days, you have 72,000 datapoints. There are 1,920,000 9-second intervals (avg nap period from other article) over 200 days, so given their data collection spans only 3.75% of this time there's a chance they missed one of these naps.
Nevertheless, this is still very interesting.