Alternative title: Blue Jay brutally feeder mogs Tufted Titmouse
From the Cornell Lab of Ornithology, a pretty neat article about dominance hierarchies at the bird feeder using over 7,600 observations collected by citizen scientists contributing to Project Feeder Watch. Essentially, bird watchers reported instances when one bird species successfully displaced another at the bird feeder, and used this network of comparisons to build a dominance hierarchy. By using information contained within the network, you can even compare birds that are rarely observed together. Not all dominance patterns are linear, however, as the article reports:
A separate analysis uncovered some dominance triangles in which three birds had one-to-one relationships independent of each other, like a game of birdy rock-paper-scissors. For example, the House Finch dominates the Purple Finch, and the Purple Finch dominates the Dark-eyed Junco, but the junco dominates House Finch.
The full paper is here: Fighting over food unites the birds of North America in a continental dominance hierarchy.
This work is reminiscent of network meta-analysis, in which three or more interventions (e.g., drugs) are compared using both direct and indirect evidence. For example, if there are studies comparing drug A versus drug B and drug B versus drug C, we can infer the comparison between drug A and drug C, even if no study has ever directly compared them.