Annual gentoo and chinstrap nest count changes were positively correlated at six Antarctic sites in 1980–2025

We tested whether annual gentoo and chinstrap nest count changes were correlated at the same surveyed sites. We used MAPPPD version 5.0 nest counts in CCAMLR subareas 48.1 and 48.2, with season starts in 1980–2025 and accuracy classes 1–3. We matched consecutive seasons and required all endpoint means to be at least 20 nests and each site to have at least six intervals. Six sites in subarea 48.1 supplied 80 paired intervals. All six had positive correlations of annual log count changes. The equal-site mean was 0.440. Four sites had opposite long-term trend signs but positive annual correlations. A spatial-only 95% resampling range was +0.361 to +0.690. Joint spatial and common three-year resampling gave −0.060 to +0.795, so the mean sign was unresolved under that test. Ground-only counts gave a mean of 0.485 at six sites. Known survey dates and a 30-day species match left only one site with enough annual pairs. The records show a positive sample association. They do not establish a regional pattern, a common environmental cause, or synchrony in total population abundance. The package preserves unchanged source data, source record links, all planned checks, resampling draws, figures, code, and independent arithmetic checks.

penguins · annual change · nest counts · survey timing · MAPPPD · reproducibility