Table 1 Mean and SD of δ ¹⁵ N and δ ¹³ C values and range (minimum and maximum) C/N ratio in blood

BRBO

 Incubation

12.17 (0.11)

−16.71 (0.14)

0.29 to 0.32

  Males

10

12.12 (0.07)

−16.72 (0.11)

0.31 to 0.32

  Females

9

12.23 (0.12)

−16.68 (0.18)

0.29 to 0.32

 Chick rearing

12.31 (0.23)

−16.88 (0.22)

0.30 to 0.33

  Males

27

12.25 (0.18)

−16.88 (0.24)

0.31 to 0.32

  Females

27

12.35 (0.28)

−16.84 (0.18)

0.31 to 0.34

RTTB

 Incubation

12.63 (0.23)

−16.96 (0.17)

0.30 to 0.32

  Males

10

12.62 (0.31)

−16.99 (0.18)

0.30 to 0.32

  Females

9

12.63 (0.13)

−16.94 (0.16)

0.31 to 0.32

 Chick rearing

12.68 (0.27)

−16.91 (0.19)

0.29 to 0.32

  Males

14

12.74 (0.27)

−17.09 (0.38)

0.31 to 0.32

  Females

13

12.62 (0.41)

−16.93 (0.27)

0.29 to 0.31