To improve the growth environment of wild birds by providing an inlet at the center of a front face inclined forward by a specific angle of a cylindrical hollow block main body, overhanging an upper part of the front face outward to form an eaves part, and banking in the inside of the main body.

As for a block main body of a nesting block 101, an inlet 2 which allows only a wild bird to enter is provided at the center in a front face to prevent the invasion of a snake and a weasel, the front face is inclined forward by 5 to 20 degrees, and an eaves part overhangs toward the outside of an upper part of the front face. Next, at the time of construction, for example, a foundation block 103, a nesting block 201 for fish, and a nesting block 301 for ordinary wild bird are put on a base block 102. Then, the block 101 is put on it through a crest concrete 401, and a banking 7 is provided on a rear face side of the upper part thereof. A wild bird digs a hole in the banking 7 through the inlet 2 to build a nest 8. Consequently, it is possible to exchange the banking for rebuilding a nest hole easily in accordance with the bird's nature that the bird does not utilize the same nest hole again.