How to tell three penguin species apart
Researchers at Palmer Station, Antarctica measured 344 penguins between 2007 and 2009. Body mass and flipper length pick out Gentoo. Bill length separates Adelie from Chinstrap.
| Measurement | Adelie | Chinstrap | Gentoo |
|---|---|---|---|
| Birds measured | 152 | 68 | 124 |
| Body mass (g) | 3,701 | 3,733 | 5,076 |
| Flipper length (mm) | 190.0 | 195.8 | 217.2 |
| Bill length (mm) | 38.8 | 48.8 | 47.5 |
| Bill depth (mm) | 18.3 | 18.4 | 15.0 |
Source: Palmer Penguins data, Gorman, Williams, and Fraser (2014). Means exclude 2 birds with no measurements.
Bill length against flipper length
One dot per bird, 342 birds with both measurements, in millimeters
- Adelie
- Chinstrap
- Gentoo
Source: Palmer Penguins data, CC0.
Read the plot by corner
Adelie birds sit in the lower left: short bills and short flippers. Chinstrap birds have flippers as short as Adelie's but bills about 10 mm longer, so they sit to the right.
Gentoo birds sit apart at the top. Their flippers average 217 mm, more than 20 mm longer than either other species, and they weigh over 1.3 kg more on average.
Two measurements are enough: any bird can be placed by its bill length and its flipper length alone.
Where they were measured
The birds came from three islands. Gentoo were found only on Biscoe and Chinstrap only on Dream. Adelie were found on all three, so island alone does not identify a bird.
| Island | Adelie | Chinstrap | Gentoo |
|---|---|---|---|
| Biscoe | 44 | 0 | 124 |
| Dream | 56 | 68 | 0 |
| Torgersen | 52 | 0 | 0 |
| All islands | 152 | 68 | 124 |
What does not separate them
Body mass does not tell Adelie from Chinstrap. Their averages are 32 g apart, and the heaviest and lightest birds of each species fall in almost the same range.
Bill depth does not either: 18.3 mm against 18.4 mm. Only Gentoo, at 15.0 mm, stand out on depth.
- Adelie body mass
- 2,850 to 4,775 g
- Chinstrap body mass
- 2,700 to 4,800 g
- Gentoo body mass
- 3,950 to 6,300 g
- Missing sex records
- 11 birds
Sources
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.
Horst AM, Hill AP, Gorman KB (2020). palmerpenguins: Palmer Archipelago (Antarctica) penguin data. R package, CC0. Data collected by Dr. Kristen Gorman and the Palmer Station Long Term Ecological Research program.
This page is an Unbranded example. Every figure was computed from the published 344-row file.