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title: "eBird checklists from citizen scientists used to study seabird distribution in the Southern Ocean"
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# eBird checklists from citizen scientists used to study seabird distribution in the Southern Ocean

*![Flock Paper](https://acap.aq/images/Flock_Paper.jpg)  
Observation effort and environmental context during the Flock to Marion 2025 expedition. (Top) Overview of eBird contributions, including total sightings, number of checklists, number of taxa after harmonisation, number of observers, proportion of complete checklists, median checklist duration (with 10th and 90th quantiles) and proportion of checklists with counts. (Middle) Ship track overlaid on concurrent oceanographic conditions: Sea-surface temperature, surface current speed and chlorophyll-a concentration averaged over the period 24–30 January 2025. The grey line shows the full ship track, while overlapping yellow segments indicate periods of active observation. (Bottom) Temporal pattern of checklist submission effort (number of active checklists per 5-min interval) showing a strong diurnal pattern (from the publication)*

 Raphaël Nussbaumer ([Swiss Ornithological Institute](https://www.vogelwarte.ch/en/), Sempach, Switzerland) and colleagues have published in the open access journal *[Diversity and Distributions](https://onlinelibrary.wiley.com/journal/14724642)* on using seabird lists from the mass-participation [Flock to Marion AGAIN! 2025](https://www.birdlife.org.za/flock-to-marion-again-2025/) voyage in the southern Indian Ocean to infer species distributions at sea.

 The paper’s abstract follows:

 “**Aim**

 Citizen-science observations are increasingly used to infer species distributions at sea, yet the extent to which observer behaviour and heterogeneous detectability may bias inferences from such pelagic seabird observations, and how explicitly accounting for these processes affects inferred distributional patterns, remains poorly understood.

 **Location**

 Southwest Indian Ocean, from mainland South Africa to the Prince Edward Islands.

 **Methods**

 We analysed 2563 eBird checklists submitted by 212 observers during a seven-day oceanic cruise (24–31 January 2025) traversing a broad latitudinal gradient (~30° S to ~47° S) spanning warm subtropical waters to sub-Antarctic conditions. This unusually dense, transect-based dataset allowed us to quantify selective reporting, effort-driven temporal bias, and observer- and species-specific detection bias associated with checklist type and observer engagement. We then applied a novel multispecies, transect-based occupancy model to estimate seabird occurrence for 39 species while explicitly accounting for species-, observer- and effort-dependent detection probability. Bias-corrected occupancy patterns were compared with independent tracking-based space-use estimates for 10 species.

 **Results**

 Incomplete and short-duration checklists inflated the apparent importance of rare, charismatic species. Observer effort was structured in time, peaking at dawn and during days of high species novelty. Detection probability varied markedly among species and observers, increased with species prevalence and body mass, and rose non-linearly with observation duration, reaching a plateau after approximately 1 h. Bias-corrected occupancy estimates revealed clear community turnover along the transect. Inferred spatial occurrence patterns were strongly correlated with independent tracking-based space-use estimates.

 **Main Conclusions**

 Pelagic citizen-science data can yield ecologically realistic distributional inferences when observer bias and detectability are explicitly modelled. Large cruise-based birding events, combined with occupancy modelling, represent a powerful and scalable complement to tracking and structured surveys for studying seabird biogeography across oceanic gradients.”

 **Reference:**

 Nussbaumer, R., Kéry, M., Schrimpf, M. & Lee, A.T.K. 2026.  Quantifying bias and detectability in pelagic seabird citizen science: insights from a mass-participation cruise-based dataset.  *[Diversity and Distributions](https://onlinelibrary.wiley.com/doi/10.1111/ddi.70243)*[32, No. 7: e70243.](https://onlinelibrary.wiley.com/doi/10.1111/ddi.70243)

 *John Cooper, Emeritus Information Officer, Agreement on the Conservation of Albatrosses and Petrels 03 August 2026*