CAN METHODOLOGICAL DECISIONS RELATED TO NEST LOCATION AND EGG TYPE AFFECT ARTIFICIAL EXPERIMENTS OF BIRD EGG PREDATION?

Nest predation is the primary factor responsible for the reproductive failure of birds. Through an experimental study, we investigated how methodological decisions related to nest location and egg type affect the predation of artificial nests. The experiment was conducted in 30 cocoa agroforests located in the southern Bahia state, in northeastern Brazil. We used 40 artificial nests in each agroforest, evenly distributed on the ground and in the understory, with 10 nests containing synthetic eggs and 10 nests containing quail eggs in each stratum. We observed that predation was significantly higher in ground nests (54.63%) than in the upper stratum (45.36%; p < 0.001). We also found that nests containing synthetic eggs had a 1.5 times greater chance of being preyed upon than nests with quail eggs (p = 0.04). These results may be directly linked to the predator’s ability to access different vegetation layers and prey on eggs with varying textures. Therefore, we recommend that future studies consider these methodological factors in their sampling designs to avoid undesirable effects on the results.