[azernik]

That got me curious, so I ran the numbers on the chances they'd miss all of the naps; assuming these birds take only one 9-second nap a week (28 naps total over 200 days) there's a 35% chance the researchers would have missed all of them ((1 - (28 / 1920000)) ^ 72,000), which is pretty reasonable. But that chance goes down to 8% for one nap every 3 days, and to 0.055% for one nap a day. I'd say maybe one 9-second nap every few days is the lower limit of what I'd find plausible (assuming this was run for only one bird).

EDIT: Ah, missed this in the article - they were three birds. So the chances they'd miss all naps for all three birds goes down to 0.055% for one nap every three days, and 4% for once a week. So 9 seconds once a week is barely believable, but if they can reproduce this with another couple of birds that becomes really unlikely.