Data from: Close encounters: Behavioral responses of migrating songbirds to the perceived risk of predation
Data files
Feb 19, 2025 version files 10.38 KB
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nemes_et_al_close_encounters_experiment_data.csv
6.29 KB
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README.md
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Abstract
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.
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) 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 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.
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
Henningsen, A. (2024). censReg: Censored Regression (Tobit) Models. [Online.] Available at 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.
Access information
Other publicly accessible locations of the data:
Motus nanotag detection data are publicly accessible through www.motus.org.
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.