Table 1(b).

Order of presentation of nest substrate pairs. Four BDUs were placed in each of three pens, and each pen contained four ducks. The ducks rotated through the four pairs over four consecutive nights, then four new pairs were introduced into the pen

Nights	Pen 1		Pen 2		Pen 3
1–4	1	2	5	6	5	6
	4	3	2	1	3	4
5–8	5	6	5	6	1	2
	2	1	3	4	4	3
9–12	5	6	1	2	5	6
	3	4	4	3	2	1
13–16	1	2	5	6	5	6
	4	3	2	1	3	4
17–20	5	6	5	6	1	2
	2	1	3	4	4	3
21–24	5	6	1	2	5	6
	3	4	4	3	2	1
25–28	1	2	5	6	5	6
	6	5	2	1	4	3
29–32	4	3	5	6	1	2
	2	1	3	4	4	3
33–36	5	6	1	2	5	6
	3	4	4	3	2	1