One problem that drone package delivery faces that other delivery methods don't face: Hawks and other birds of prey

From Fox News:

. . . a large hawk took offense to the quadcopter drone loudly buzzing in the same airspace. The GoPro camera captured the hawk swooping in from above and slamming into the drone. At this point, Schmidt throttled down the props to avoid doing any serious damage to the hawk and the drone is filmed falling to the ground where it lands upside down on a grassy area of the park. 

According to Schmidt, the hawk zipped away and was apparently unharmed from the encounter. Detailed in the description of the YouTube video, Schmidt states “As far as I could tell, the hawk came out unscathed,…The quadcopter came out unscathed as well.” . . . 

Of course, this isn’t the first time that birds have taken out a drone that was invading nearby airspace. During December 2013, YouTube user Buddhanz1filmed a similar scenario where an entire flock of birds started dive bombing his DJI phantom drone. Also filmed with a GoPro Hero 3+ Black, repeated attacks from the birds ripped the battery connector and control of the drone was slowly lost as it plummeted to the ground below. . . .