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PRISMA flowchart of search results and the study selection process. See Dataset S2 for a list of papers excluded from the analysis. The final dataset for begging analyses contained 336 effect sizes from 108 studies on 60 species of birds. The final dataset for structural signal analyses contained 140 effect sizes from 33 studies on 18 species of birds. Overall, we found data in 136 studies on 72 species.
