Indeed, begging cues increased predation rates for enclosed but not open-cup nests in our playback experiment, and nest predation rates showed greater increases after hatching in enclosed than open-cup nests. Moreover, enclosed nests did not consistently alter nestling begging calls in ways that reduce the likelihood of predation compared to open nests.
We found that enclosed nests are larger than open nests after accounting for adult size, and larger nests had increased predation rates. We also tested whether nest structure was associated with differences in nest predation rates between the incubation (no begging cues) and nestling (begging cues) stages. Specifically, we experimentally broadcast begging calls from open and enclosed nests to determine how auditory cues and nest structure interact to affect predation on plasticine and quail eggs. Finally, we examined how the acoustic properties of different nest structures influence nest predation risk. Second, we assessed how nest structure influences the detectability of nestling begging calls both in field and in laboratory settings. First, we examined how nest size was related to nest structure and nest predation rates across species. We used experiments and 10 years of observational data to examine how nest structure influences nest predation risk in a diverse community of tropical songbirds. Direct tests of the functional bases for nest structure influence on predation risk are lacking. Traditionally, more complex, enclosed nest structures are thought to reduce offspring predation by reducing the visibility of nest contents and muffling offspring sounds compared to open nests. 
Nests are widely used for breeding across taxa and thought to influence offspring mortality risk.
Offspring mortality varies dramatically among species with critical demographic and evolutionary ramifications, yet the causes of this variation remain unclear.
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