So my son is now motivated for the upcoming safari into Saskatchewan, such that ordered the GO-PRO movie camera ( the one you can attach it to the gun butt or helmet it also works straps to a dog. It films in HD and has the wide angle option. I can only guess that it will only show half decent when the bird are really close in. He will strap it up to the Browning A-5 as it aligns up with the barrel better plus he will be going rapid fire versus the 870.
Of course, myself I will be bring the 400mm f5.6 lens along with 75-300mm f4-5.6 and the 35-70mm f4 for the group shots .