DOI: 10.5061/dryad.s1rn8pkjg
title: Data from: Close encounters: Behavioral responses of migrating songbirds to the perceived risk of predation

description: Migrating birds face competing pressures to travel as quickly and
 efficiently as possible while minimizing the risk of predation en route.
 Despite the potential importance, antipredator behaviors in migrating
 songbirds have been little studied relative to time and energy tradeoffs,
 even as humans have introduced novel predators including free-roaming
 domestic cats (Felis catus) across the globe. Birds confronted with
 predators during stopover can employ antipredator behaviors to reduce
 their immediate mortality risk, but doing so may slow refueling or impose
 other costs that influence migration. We captured migrating Gray Catbirds
 (Dumetella carolinensis) and exposed them to either a live cat, model
 hawk, or non-predator control in an aviary experiment to assess their
 behavioral responses. Birds moved lower after exposure to a model hawk,
 but showed no significant behavioral changes in response to a cat. After
 release, we monitored activity levels of a subset of tagged individuals
 via the Motus Wildlife Telemetry System. Post-release activity level did
 not differ between treatment and control groups, indicating that brief
 predator exposure did not exert a persistent effect on this behavior. The
 lack of detectable responses to the cat may reflect birds navigating the
 tradeoff between antipredator behaviors, which are costly during
 migration, and reduction of predation risk. However, it could also
 indicate naïveté of young birds to this introduced predator, which may
 increase vulnerability to predation during migration. We encourage further
 investigation of the influence of prolonged or repeated exposure to
 domestic cats on songbird behavior and physiology, and ultimately
 migration success.
description: All pre- and post-test behavioral observations were recorded by
 C.E. Nemes using Gray Catbirds captured during fall migration. Methods for
 data collection and processing are described in the associated
 paper. For the activity analysis, a subset of catbirds
 were nano-tagged by C.E. Nemes. Detections of tagged individuals at local
 receivers were downloaded from the Motus Wildlife Telemetry System website
 (www.motus.org) using the Motus R package and de-trended signal strength
 values were calculated as described in the paper. Motus detection data are
 freely accessible but must be cited, which is not compatible with
 Dryad's CC0 policy. Hence, we have archived detection data for the
 activity analysis at Zenodo.
description: # Data from: Close encounters: Behavioral responses of migrating songbirds
 to the perceived risk of predation
 [https://doi.org/10.5061/dryad.s1rn8pkjg](https://doi.org/10.5061/dryad.s1rn8pkjg) ## Description of the data and file structure Behavioral experiment: Spreadsheet containing behaviors of individual Gray Catbirds recorded for 5 minutes pre-exposure and 5 minutes post-exposure to treatment condition. Details of data collection methods are described in the corresponding paper. Activity analysis: Detections of a subset of nano-tagged Gray Catbirds at local receivers were downloaded from the Motus Wildlife Telemetry System website ([www.motus.org](http://www.motus.org)) using the Motus R package and summarized. ### Files and variables #### File: nemes\_et\_al\_close\_encounters\_experiment\_data.csv **Description:** Behaviors of individual Gray Catbirds on stopover recorded for 5 minutes pre-exposure and 5 minutes post-exposure to treatment condition. Details of data collection methods are described in the corresponding paper. ##### Variables * indiv_id: Unique identifier for each individual subject * period: Pre-test or post-test period * treatment: Treatment condition to which subject was exposed - hawk treatment (model hawk), cat treatment (live cat), or aviary control (bird was observed in aviary but not exposed to a predator treatment) * height: Mean height of subject in the aviary (values from 0-4 were recorded at 30 second intervals and averaged for each period) * perch_change: Count of the number of times subject moved from one perch to another * firstmov_time: Number of seconds elapsed before subject made first perch change (0-300) #### File: nemes\_et\_al\_close\_encounters\_motus\_activity\_data.csv **Description:** A subset of catbirds were nano-tagged for the activity analysis. Detections of tagged individuals at a local receiver were downloaded from the Motus Wildlife Telemetry System website using the motus R package. Motus detection data are publicly accessible through [www.motus.org](http://www.motus.org) but must be cited, which is not compatible with Dryad's CC0 policy. Hence, we have archived detection data for the activity analysis through Zenodo.org. ##### Variables * diff*_*abs_mean: De-trended signal strength values from detections of tagged birds for 2 hours following release * treatment: Treatment condition to which subject was exposed - hawk treatment (model hawk), cat treatment (live cat), aviary control (bird was observed in aviary but not exposed to a predator treatment), or tag control (bird was released immediately after tagging and not observed in aviary) * h_after_sun: Number of hours after sunrise (numeric) when the 2-hour tag detection period began ## Code/software Software: R version 4.4.1 R packages used to access and analyze data:  Birds Canada (2022). motus: Fetch and use data from the Motus Wildlife Tracking System. [Online.] Available at [https://motusWTS.github.io/motus](https://motusWTS.github.io/motus). Brooks, M.E., K. Kristensen, K.J. van Benthem J. , A. Magnusson, C.W. Berg, A. Nielsen, Skaug J.H., M. Mächler, and B.M. Bolker. (2017). glmmTMB balances speed and flexibility among packages for zero-inflated generalized linear mixed modeling. The R Journal 9:378. Hartig, F. (2024). DHARMa: Residual Diagnostics for Hierarchical (Multi-Level /Mixed) Regression Models. [Online.] Available at [https://CRAN.R-project.org/package=DHARMa](https://CRAN.R-project.org/package=DHARMa) Henningsen, A. (2024). censReg: Censored Regression (Tobit) Models. [Online.] Available at [https://CRAN.R-project.org/package=censReg](https://CRAN.R-project.org/package=censReg) Lenth, R. V. (2022). emmeans: Estimated Marginal Means, aka Least-Squares Means. R package version 1.7.4-1. [Online.] Available at [https://CRAN.R-project.org/package=emmeans](https://CRAN.R-project.org/package=emmeans). ## Access information Other publicly accessible locations of the data: Motus nanotag detection data are publicly accessible through [www.motus.org](http://www.motus.org).