Please choose the correct ending to complete the given sentence: Pets and Animals: [header] How to prevent premature fledging [title] Purchase a top opening nesting box. [step] Although they are harder to clean out, and more difficult for shorter people to monitor, premature fledging is less likely to occur if you have a top opening nesting box. This type of nesting box is especially effective at preventing premature fledging if the entrance is covered with a sock or piece of cloth while checking the box.

Ending1: [title] Decrease pressure on your baby with your feet. [step] During the first step, make sure that the area above your baby's head is completely closed. Ending2: [substeps] To make cleaning more easy, make your nesting box open multiple ways, for example from the sides, front, and top. However, only use the top opening to monitor the box. Ending3: [title] Avoid nesting boxes with back-to-back ventilation to prevent premature fledging. [step] During breeding season, sealed nesting boxes are more than usually covered in all sorts of board insulation. Ending4: [substeps] This type of box is called " barrier nesting box, " and will not need to be fully emptied because it is made with a cover. [title] Use a scoop to check inside the box.

Answer format: ending1/ending2/ending3/ending4