__________I agree - hard to pinpoint whether this was the exact cause - though they do mention the adults abandoning the nests. So unless the fox population jumped up quickly and became more aggressive than usual it would be hard to believe as well. This is a preserve so it's monitored more closely than just any 'ole area.
OC Register Article Re Drone Crash at Bolsa Chica Nesting Area
http://instagr.am/p/CPrbUUUMo6u/
http://instagr.am/p/CPtwNnwNKUt/