A few years back I followed a group of chickens for 24 hours checking on their location and activity at 15-minute intervals. Before and since I have watched chickens a lot as well with a lot less rigor. Conclusion is that if you have a slacker forager or two in the mix, they will still keep pace with the more aggressive leaders. Additionally, just because a bird travels a lot does not mean it gets a lot of food. Finally, just because the birds eat a lot does not mean they eats are quality.
If I were to try and do this for real again, then I would put out a feeding station that has only one type of grain, not feed. The volume applied would be limited so all is consumed before end of day. Then I would go out and check crop fill every night and weigh of birds on a roughly weekly basis. Trap nest would be employed to see who is weighing how many eggs and of what size. The birds must be truly free-range for this to work.
When they force me into retirement, then I will be doing this myself.