Every day, 100 birds are randomly drawn from a larger pool. Among these birds, only one is the mystery bird. You have 10 tries to find it. I also implemented some rules to ensure that the game is always balanced, but I should not reveal more.

Each guess gives you hints about the mystery bird’s attributes. Using the dice, you randomly pick one bird.

Information on birds is extracted from the AVONET and BIRDBASE databases, with the exception of the beak length index, which I computed myself. These databases are open access and have been the subject of scientific publications (Tobias et al., 2022; Şekercioğlu et al., 2025).

However, I had to simplify some attributes in order to make the game playable (Habitat, Primary Diet, Realm and Nest). When an attribute is heavily segmented, the player becomes less likely to receive meaningful hints with each guess.

For instance, the BIRDBASE database classifies habitat into 15 categories. As a result, a player could use all 10 guesses and still ignore the correct one. I therefore reclassified habitats into five categories: Marine, Wetland, Forest, Grassland, and Dry plains. As an example, the new “Dry plains” category includes the following habitats: plains, shrub and desert.

Tobias, J. A., Sheard, C., Pigot, A. L., Devenish, A. J. M., Yang, J., Sayol, F., Neate-Clegg, M. H. C., Alioravainen, N., Weeks, T. L., Barber, R. A., Walkden, P. A., MacGregor, H. E. A., Jones, S. E. I., Vincent, C., Phillips, A. G., Marples, N. M., Montaño-Centellas, F. A., Leandro-Silva, V., Claramunt, S., … Schleuning, M. (2022). AVONET: morphological, ecological and geographical data for all birds. Ecology Letters, 25(3), 581–597. https://doi.org/10.1111/ele.13898

Şekercioğlu, Ç. H., Kittelberger, K. D., Mota, F. M. M., Buxton, A. N., Orton, N., DeNiro, A., Buechley, E. R., Horns, J. J., Blount, J. D., Socci, J., & Neate-Clegg, M. H. C. (2025). BIRDBASE: A Global Dataset of Avian Biogeography, Conservation, Ecology and Life History Traits. Scientific Data, 12(1), 1558. https://doi.org/10.1038/s41597-025-05615-3

First, only birds for which reliable, published data were available for all relevant attributes were selected.

Second, I tried to ensure that each attribute is as balanced as possible. For example, ~60% of known bird species are Passeriformes, which would result in a very difficult and rather boring game. I therefore ensured that no avian order is over-represented. This logic also applies to other attributes.

The Beak attribute is an index of beak length relative to a bird’s body mass. It correspond to the intuitive perception of its length. The higher the value, the longer the beak. It ranges from 0 to 1.

This index was computed using AVONET data on bird body mass and beak length. Briefly, I used the residuals of a linear regression between body mass and beak length, which I then converted into an index ranging from 0 to 1.

Model used: lm(log(Beak Length) ~ log(Mass)).
R² = 0.61, p-value < 0.001, n = 10.700

Note that I did not use body size but rather body mass here. This is because tarsus length and wing length are the only measures of body size available for most birds. These measure are less intuitive and can be strongly influenced by species-specific biology (e.g., wetland birds have long tarsi, flightless birds have short wings...).

Bird images are imported from the Macaulay Library. For legal reasons, I have to use the embed function provided by the Macaulay Library, which restricts how they can be displayed.

Translating this game in different languages would take an ridiculous amount of time. I therefore only provide a translation for the bird names.

I used the Birds of the World database to extract bird names in as many languages as possible. Unfortunately, I can only include languages for which the dataset is complete and contains no missing entries.

I am a PhD in ecology and physiology. I recently published my PhD thesis and I developped this game as a side project.

This game is not perfect by any means. If you have feedback, suggestions, or encounter any issues, please feel free to contact me at the following email address: birdldaily@gmail.com.