Bird experts examining the video have discovered the eight-week-old chick was forced from its perch by a young rival eagle that invaded the nest.
They say this kind of behaviour has never before been recorded in Scotland.
Live footage of the nest has been beamed around the world by satellite since the new webcam was set up at a secret location on the Isle of Mull last month.
The camera is trained on the eyrie where white-tailed sea eagles Sula and Cuin have chosen to raise their brood.
Worried viewers raise alarm
The chick had been spotted on camera over the weekend, but worried viewers raised the alarm on Sunday night when they could detect nothing moving in the nest.
Experts from Forestry Commission Scotland (FCS) and RSPB Scotland were called in to climb the tree and search for the missing bird.
Rescuers soon heard the hungry youngster calling for food and were able to find it hidden in undergrowth below.
A health check showed the chick was unharmed by its ordeal and it was hoisted back to its treetop home.
In the wake of the incident, reports on social media had claimed an intruder eagle may have been near the nest and caused the chick to fall.
Now examinations of the recording show they were correct.
The footage shows the immature invader gradually sidling up to the chick, who is screeching for its parents.
Eventually, after much wing-flapping and a short retaliation by the chick, the marauding adolescent forces the eight-week-old chick off the nest, causing it to plummet 30ft to the ground.
The video then shows parents Sula and Cuin landing back at the roost and swiftly chasing the interloper away.
FCS conservation ranger John Taylor said: “This whole episode has been a real drama from start to finish.
“Immature sea eagles are often attracted to active nests as they think there may be food to scavenge. This was just a step too far.
“We’re pleased the chick was returned safely and the opportunistic invader got short shrift from the parents.”
‘I have never witnessed this kind of astonishing behaviour before’
RSPB Scotland’s Mull Officer, Dave Sexton, added: “This unique Forestry Commission Scotland webcam not only alerted us to the missing chick in the first place but it then revealed the quite remarkable and dramatic turn of events at the nest with the intruding immature sea eagle pushing the chick off the nest.
“I have never witnessed this kind of astonishing behaviour before in 30-plus years of observing them.”
White-tailed sea eagles are found near large bodies of water and coastlines across Europe and parts of Asia. Standing 3ft tall and with a 8ft wingspan, they are the largest eagles in Europe and the fourth-largest in the world.
They became extinct in Britain during the early 1900s but were reintroduced to Scotland in 1975.
Live footage of the chick can be viewed on the webcam, believed to be a UK first, at http://scotland.forestry.gov.uk/visit/mull/mull-eagle-watch