I am planning to take about 17 roosters to auction on Tuesday. I plan to put them in cardboard boxes with holes and putting them in the bed of my truck. My question is, is it better for them if I put the cover on the bed, or leave it open air? It's not a truck cap, just a flat tonneau cover. I'm worried about air circulation. I will be traveling about 40 min in approx 70 degree weather. I will tie down the boxes either way just can't decide what to do about the cover. I've never transported this many birds before and I usually just put them in the back of my SUV. Thanks!