Palmer Field Station · field report FS-2026-04

An inverse relationship between bill length and bill depth in Pygoscelis penguins

Field Station staff · Reviewer 2 (peer review) · 2026
Sources: Palmer Field Station

Bill morphology was recorded for 344 adult penguins of three Pygoscelis species across three islands of the Palmer Archipelago. In 342 animals with complete measurements, bill length and bill depth were inversely related (r = −0.235, p = 1.1 × 10⁻⁵): animals with longer bills tended to have shallower ones. Individual records were pseudonymised before analysis.

1 · Bill length and bill depth

Across the sample, longer bills were consistently shallower. The relationship is modest in size but clearly established, and holds over the full observed range of bill lengths from 32 to 60 mm.

Bill depth against bill length
Figure 1. Bill depth against bill length, all animals (n = 342), with the fitted line.

2 · Flipper length and body mass

As expected, flipper length and body mass were strongly and positively related.

Body mass against flipper length
Figure 2. Body mass against flipper length.

3 · Composition of the sample

Sampling was not balanced across islands; Biscoe and Dream each carried a single dominant species. The chart below was put together for the field log while the analysis was still running.

Animals per island and species
Figure 3. Animals recorded per island and species.

4 · Conclusion

In this population, bill length and bill depth vary inversely. The finding is consistent across the sampled range and we recommend that bill length be treated as an indicator of bill shape in field identification.

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Data source

Horst AM, Hill AP, Gorman KB (2020). palmerpenguins: Palmer Archipelago (Antarctica) penguin data. R package version 0.1.0. doi:10.5281/zenodo.3960218
Gorman KB, Williams TD, Fraser WR (2014). Ecological sexual dimorphism and environmental variability within a community of Antarctic penguins (genus Pygoscelis). PLoS ONE 9(3):e90081. doi:10.1371/journal.pone.0090081
Collected by Dr. Kristen Gorman and the Palmer Station Antarctica LTER, a member of the Long Term Ecological Research Network. Released under CC0 and used unchanged.
This report is a fabrication. The measurements above are the real Palmer Archipelago data, cited in full. Everything built around them — the field station, this report, the ethics committee, the reviewer, and the individual animal names in the source records — is invented for a demonstration of provenance records. No such study exists, and the conclusion drawn here should not be believed. Finding out why is the point of the marks on the figures.