Large citizen science datasets are powerful tools for biodiversity science, but they may have biases. Nice new paper from @louisbackstrom.bsky.social et al. showing that for eBird and Birdtrack lists there is a tendency for rare species to be over-represented
onlinelibrary.wiley.com/doi/epdf/10....

A lot of common species are in that sweet spot. Skylark perhaps closest: 1.001 from the eBird analysis and 0.999 from the BirdTrack analysis. From a quick check through Table S1, other examples inc. Goldeneye, Blue Tit, Goldfinch, Little Egret, Kestrel, Fulmar, Bullfinch, Blackcap.

Brilliant trip to Barra and Colonsay (19th-23rd Sep) with @birdingscot.bsky.social, @louisbackstrom.bsky.social, and James Weeks. Some great birds over the course of the trip, with Stuart Beeby's Swainson's Thrush at Cuithir the undeniable highlight, and a lifer for all of us! 1/4
#BirdingScotland

In spite of these preferences leading to the overrepresentation of certain species in the eBird & BirdTrack datasets, we found that this bias had limited impacts on actual applications of the data (occupancy models). Even so, we urge consideration of observer bias in analyses of #citizenscience.

Rare #birds were significantly more likely to drive survey initiation, with other species-specific factors like novelty and charisma also potentially contributing, especially among more common species.

These observer preferences were most prevalent on short-duration surveys (less than 5 min). ⤵️

Using #citizenscience data from eBird @cornellbirds.bsky.social and BirdTrack @birdtrack.bsky.social @btobirds.bsky.social, we explore what drives birders to initiate semi-structured surveys on these two large-scale citizen science platforms.

The biggest factor: species rarity! ⤵️

Very pleased to share my first PhD paper, out now in @consbiog.bsky.social:

Backstrom, L. J., Drake, R. L., Worthington, H., & Johnston, A. (2025). Detections of Rare Species Lead Citizen Scientists to Initiate Data Recording. Diversity and Distributions, 31(10), e70103. doi.org/10.1111/ddi.... ⤵️