Observational and experimental evidence that rapid mass loss is consistent with the flight efficiency hypothesis and not caused by reproductive effort in three passerine species

Breeding birds often lose mass abruptly around the time that their eggs hatch, but the reasons why and the demographic significance of mass loss are contentious. Energy expenditure during offspring provisioning is one long-standing explanation that fits with life history theory (energetic cost hypothesis). Mass loss may also reflect time constraints that limit foraging and self-maintenance while warming (i.e., brooding) young (time constraint hypothesis). Alternatively, mass loss may be an adaptive strategy to provide benefits through decreased energetic flight costs while foraging and provisioning young (flight efficiency hypothesis). To test these hypotheses, we measured mass loss across the nesting cycle for three passerine species using an automated weighing system and quantified reproductive effort by filming nests. We also experimentally manipulated reproductive effort using a nest heating experiment to test effects on mass loss. Counter to the energetic cost hypothesis, female ma..., , , # Observational and experimental evidence that rapid mass loss is consistent with the flight efficiency hypothesis and not caused by reproductive effort in three passerine species

[https://doi.org/10.5061/dryad.5qfttdzfx](https://doi.org/10.5061/dryad.5qfttdzfx)

## **R Scripts (listed in order of the workflow)**

**1_Mass_loss_estimate_models.R** - This is the code for producing estimates of the change in mass across the nesting cycle for females and males at each nest. 

**2_Reproductive_effort_estimate_models.R** - This is the code for producing estimates of the different reproductive parameters across the nesting cycle for each nest. 

**3_Nestling_growth_estimate_models.R** - This is the code for producing the estimates of nestling mass and wing chord on day 15 for each nest. 

**4_Dataset_building.R** - This is the code for combining the predicted estimates of mass and reproductive effort into one dataset and calculating all the parameters that we need for the analysis. 

**5_Ini...