The computers at the two facilities were linked by microwave, but printing the drawings at the test base would have required a printer that was very expensive at the time. The team therefore drew the pictures at the main plant, photographed them, and sent 35mm film to the test station by carrier pigeon, where it was enlarged and printed photographically. The pigeon's 45-minute flight took half the time of the car, and cost only a few dollars per day. During the 16 months of the project the pigeons transmitted several hundred rolls of film, and only two were lost (hawks inhabit the area; no classified data was carried). Because of the low price of modern printers, a current solution to the problem would probably use the microwave link.Hawks have a habit of attacking small things we send through the skies. There is this great piece on the effect of Amazon drones on ecology. The Dark Extropian Report: The Evolution of Amazon’s “Prime Air” Drone Delivery Service
Hawks and other birds of prey taking issue with these noisy (for now) airborne intruders into their territory. Everyone was worried about people below shooting them down, but it turns out there may be another threat that can’t be so easily policed; outlaw avians....A delivery drone that takes its shape and forms that outline in the sky will not be attacked by a lesser predator, even if it’s not already wired into their genetic memory
The article suggests creating drones that look like very big hawks to discourage natural hawks from attacking them.
This effect doe not just apply to birds of prey though. Prey species hide when they see the outline of a bird of prey. And doing this increases their anxiety enough to reduce feeding and decrease numbers drastically over time. The drones that look like birds of prey will not have to prey. Just being in the sky with the right silhouette will drastically reduce the number of vermin.
According to this article
Changes to ecology have unpredictable effect on the environment. Less pigeons would seem an improvement to the urban environment but they do eat bread and other foodstuffs. If numbers are reduced enough to prevent this bad things could happen.
tldr: 1. there will be lots of drones 2. They will look like birds of prey 3. They will have a big effect on rats, pigeons and other prey species.