It may take more than one night to identify if they are indeed in there, so I recommend leaving the cardboard for up to a week, but to tap it out daily onto a white piece of paper to see if any bugs drop out.
If you positively identify bug life coming from the cardboard tube, make sure that the tube is then either double bagged and placed in the general waste bin, not the compost, or burnt.
Facts About Red Mites
But they are not impossible to see. Check around the base of the feathers on each hen: around the vent and under the wings closest to the body. As you part the feathers, watch patiently.
The poultry Red Mites are often confused with the garden variety of Red Spider and Dust Mites. They are not the same.
They love to live in gaps, joints, nooks and crannies. This includes inside feeders, especially metal ones which have folds.
These mites can migrate to the house and dwell in the soft furnishings, but they prefer to live around the areas of the skirting boards and in the cracks and gaps the most. Regularly sweep and vacuum the floor and furnishings. Soft items can be sealed in a plastic bag and left in direct sunlight for a couple of days in an effort to help kill of any bugs.
Red mites do not live on humans as we regularly wash, but they can leave a raised red lump on the skin from a bite.
They are most active at night, when they like to run along the perches of sleeping hens. If the hens are reluctant to go into their coop in the evening, this could be a sign that mites are in there. They are just as keen as you not to get bitten.
Red mites do not always attack the legs of poultry. Other signs include a drop in egg production, blood streaks on egg shells, pale egg yolks and anemia which shows in a paler wattle and comb.
Look for blood smears along the perches for signs of nocturnal activity of mites. Particularly check UNDER the perches by running a piece of paper towel along to see what you can pick up.
If treating the hens for mites, the coop must be thoroughly cleaned at the same time or the problem will be immediately reintroduced. Pay special attention to the roosting rails, where they are connected and to all small gaps. Sweep and scrub with warm soapy water throughout.
Treat the shed with either Pestene, Diotomaceous Earth or a residual spray such as Coopex (available at Bunnings).
Treat the hens with Pestene throughout their feathers: vent, under wings close to the body and breast area.
If the mites have migrated to the legs (causing a lifting of the leg scales), proceed to treat with washing and applying olive oil and Vaseline as per my earlier tutorial.