Data from: Context-dependent survival effects of tracking devices in small songbirds: implications for ecological studies
Data files
Nov 04, 2026 version files 234.05 KB
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Behaviour_data.txt
5.77 KB
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Condition_data.txt
41.56 KB
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README.md
6.68 KB
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Survival_data.txt
180.04 KB
Abstract
Tracking and biologging devices are now commonly deployed in ecological and behavioural research. To what extent data reflects natural patterns, however, depends on the impact of those devices on the individuals bearing them. Devices often have a negative effect on bird survival, but underlying mechanisms are largely unknown. To provide early indicators of survival impact and identify potential biases in data, mechanistic studies into the immediate and delayed effects of devices are required.
Here we present such a detailed analysis by leveraging an individual-based study of a small passerine, the purple-crowned fairy-wren, Malurus coronatus. Intensive fieldwork enabled us to quantify tracking device effects over time and across ecological contexts. We deployed radio-transmitter tags (~4.4% of body mass) and conducted focal behavioural observations on tagged and control birds across ~6 months, to quantify time budget, habitat use, and flight behaviour. Secondly, we recaptured individuals up to four times to measure condition (mass, pectoral muscle size, haematocrit, ectoparasite load). Thirdly, we compared survival of tagged and untagged control birds.
Device attachment briefly increased preening, partly due to capture effects, but device presence did not clearly affect any condition indices, flight behaviour or time spent foraging. In the longer term, tagged individuals spent more time in dense mid-storey vegetation, where predation risk is likely lower. Devices reduced survival, but only in poor-quality habitat, and only when a long antenna was affixed.
Our results indicate that neither physiology nor behaviour were clearly impacted by tracking devices. Instead, increased mortality of tagged birds is likely due to stochastic events such as long antennas causing entanglement or, given higher mortality only in open low-quality habitat and altered habitat use indicating strategic risk reduction, impaired ability to escape predators. Importantly, our findings highlight that tracking device effects can depend on ecological context, which may generate biased results if unidentified. We recommend researchers (1) assess device effects longer-term, (2) are cognisant of potential biases that device design (specifically antenna length) can introduce to results, and (3) explicitly factor in potentially stressful environmental conditions when deploying devices or interpreting tracking data.
Dataset DOI: 10.5061/dryad.gmsbcc365
Description of the data and file structure
We quantified impacts of radio-transmitter devices on purple-crowned fairy-wren individuals over time and across ecological context. We conducted focal behavioural observations on tagged and control birds to quantify time budget, habitat use, and flight behaviour. We captured individuals to measure condition (mass, pectoral muscle size, haematocrit, ectoparasite load). Lastly, we compared survival of tagged and untagged control birds.
Files and variables
File: Survival_data.txt
Description:
This file contains the data used to analyse the effect of tracking devices on purple-crowned fairy-wren survival.
Variables
- BirdID: Identifier of the purple-crowned fairy-wren individual
- Sex: Sex of individual (male, female)
- Social_status: Whether the individual was dominant or subordinate during the survival period
- TerritoryID: Identifier of the purple-crowned fairy-wren territory (i.e. social group) corresponding to the survival period
- Watercourse: Watercourse that the territory is located at (Annie Creek, Adcock River)
- Year: Year corresponding to the survival period
- Season: Season corresponding to the survival period (wet, dry)
- Survived: Whether the focal bird survived (1) in the given season, or disappeared (0)
- Age: Age of focal bird at the end of the survival period (in years)
- Tagging_status: Whether the focal bird was tagged or untagged during the survival period
- Tagging_status_antenna: Whether the focal bird was untagged, tagged with antenna attached, or tagged without antenna at the start of the survival period
- Habitat_quality: Riparian habitat quality of focal bird's territory (index reflecting Pandanus volume; for details see Hoppe et al. 2025 Good habitat and group living mitigate nest failure from predation and flooding in a riparian bird. J Appl Ecol 62:3016-3025)
File: Condition_data.txt
Description:
This file contains the data used to analyse the effect of tracking devices on purple-crowned fairy-wren condition (body mass, pectoral muscle size, ectoparasite presence, haematocrit).
Variables
- Date: Date of capture
- Season: Season of capture (late dry 2022, early dry 2024, late dry 2024, wet 2025, early dry 2025)
- TerritoryID: Identifier of the purple-crowned fairy-wren territory (i.e. social group)
- Habitat_quality: Riparian habitat quality of focal bird's territory (index reflecting Pandanus volume; for details see Hoppe et al. 2025 Good habitat and group living mitigate nest failure from predation and flooding in a riparian bird. J Appl Ecol 62:3016-3025)
- Watercourse: Watercourse that the territory is located at (Annie Creek, Adcock River)
- Capture_time: Time of capture
- Capture_time_hr: Time of capture, as numerical value
- BirdID: Identifier of the purple-crowned fairy-wren individual captured
- Tagging_status: Whether the individual was tagged or untagged
- Body_mass: Body mass (in g) of individual (excluding tag device mass)
- Haematocrit: Packed cell volume (in %). NA indicates not available because no blood sample was taken (a blood sample was only collected if it had been ≥4 weeks since the bird's last capture).
- Tarsus_length: The individual's tarsus length (in mm), controlled for observer effects
- Sex: Sex of individual (male, female)
- Age: Age of individual at time of capture (in years)
- Social_status: Whether the individual was dominant or subordinate at time of capture
- No_ectoparasites: The number of ectoparasites visible on the bird. NA indicates not available (not recorded in the field).
- Pectoral_muscle_size: Visual pectoral muscle score (range 1-6; higher scores indicate greater pectoral muscle mass, reflecting better body condition). NA indicates not available (not recorded in the field).
File: Behaviour_data.txt
Description:
This file contains the data used to analyse the effect of tracking devices on purple-crowned fairy-wren behaviour (time budget, habitat use, flight behaviour).
Variables
- Observer: Identifier of the person who conducted the focal observation
- Date: Date of focal observation
- Time_period: Period in which observations were conducted relative to tag deployment (immediate, short-term, long-term)
- Observation_time_start: Time at which observation was conducted (start time)
- Observation_time_start_hr: Time at which observation was conducted (start time), as numerical value
- TerritoryID: Identifier of the purple-crowned fairy-wren territory (i.e. social group)
- Habitat_quality: Riparian habitat quality of focal bird's territory (index reflecting Pandanus volume; for details see Hoppe et al. 2025 Good habitat and group living mitigate nest failure from predation and flooding in a riparian bird. J Appl Ecol 62:3016-3025)
- Dependent_young: Whether dependent young (nestlings or fledglings up to 9 weeks post-hatching) were present in the social group
- BirdID: Identifier of the focal purple-crowned fairy-wren individual
- Tagging_status: Whether the focal individual was tagged or untagged at the time of observation
- Sampled_in_week_prior: Whether the focal individual was captured and sampled in the week prior to observation
- Preening_count: Number of times (every 30s) during the observation where the focal bird was recorded preening
- Foraging_count: Number of times (every 30s) during the observation where the focal bird was recorded foraging
- Flying_count: Number of times (every 30s) during the observation where the focal bird was recorded flying
- Seen_count: Number of times (every 30s) that the individual's behaviour was recorded during the focal observation
- No_short_flights: Number of short (1-2m) flights by the focal individual during the focal observation. NA indicates flight behaviour was not recorded (applicable to immediate and short-term time periods).
- No_long_flights: Number of long (>2m) flights by the focal individual during the focal observation. NA indicates flight behaviour was not recorded (applicable to immediate and short-term time periods).
- Avg_distance_long_flights: Average distance (in m) of long (>2m) flights by the focal individual during the focal observation. NA indicates flight behaviour was not recorded (applicable to immediate and short-term time periods).
- Substrate_Pandanus_count: Number of times (every 30s) that the individual was recorded to be in Pandanus during the focal observation