Table 4. Predicted diet compositions of penguin chicks at Cape Shirreff, Livingston Island derived from stable isotope analysis using two variants of a multi-source Bayesian mixing model.
| SIAR δ15N & δ13C multi source models | ||||
| Chinstrap 2008 | Gentoo 2008 | |||
| Prey source | Initial model | Informed model | Initial model | Informed model |
| Krill | ||||
| Euphausia superba | 79.4 (74.4–84.2) | 78.1 (73.5–81.6) | 65.2 (59.6–70.6) | 65.2 (61–69.1) |
| Fish | ||||
| Protomyctophum bolini | 2.6 (0.0–7.0) | 0.6 (0.1–1.4) | - | - |
| Electrona antarctica | 3.0 (0.0–8.0) | 5.0 (2.7–8.3) | - | - |
| Gymnoscopelus nicholsi | 2.2 (0.0–6.1) | 2.9 (1.1–4.6) | 3.5 (0.0–9.6) | 7.8 (3.8–11.8) |
| Notolepis coatsi | 6.7 (0.0–15.3) | 10.3 (5.7–16.5) | - | - |
| Lepidonotothen squamifroms | - | - | 5.5 (0.0–14.8) | 1.4 (0.1–3.6) |
| Pleuragramma antarcticum | 2.5 (0.0–6.9) | 1.2 (0.3–2.4) | 6.1 (0.0–16) | 2.9 (0.8–5.4) |
| Trematomus newnesi | 3.6 (0.0–9.5) | 1.9 (0.7–3.3) | 9.6 (0.0–22.8) | 5.0 (1.9–8.3) |
| Champsocephalus gunnari | - | - | 10 (0.0–23) | 17.6 (10.2–27.7) |
| All Fish | 20.6 (15.8–25.6) | 21.9 (18.4–26.5) | 34.8 (29.4–40.4) | 34.8 (30.9–39) |
Diet compositions were estimated using SIAR [21] and are presented as mean estimates with 95% credibility intervals (in parentheses). The initial model (SIAR Model 3) estimates the relative contribution of individual krill and fish species identified in stomach contents to overall penguin diets. The informed model (SIAR Model 4) restricts posterior draws of diet composition estimates to those agreeing with the relative abundance of each fish species based on reconstituted mass (Tables S1 & S2). All fish represents the sum of the predicted contribution of all fish species.