Biology subjects

Sargent, A. J.

Publications and source records attributed to Sargent, A. J..

3 recordsLinked to original sources

bioRxiv2025

The daily life of a hummingbird: High-throughput tracking shows a spectrum of feeding and movement strategies

Most pollinators, with their small size and flight ability, are a challenge to study in the wild, yet their behavior is essential for understanding patterns of biodiversity. For example, hummingbirds play a significant role in their ecosystems--their movements from plant to plant across landscapes ultimately determines their potential as pollinators, but these behaviors are poorly understood. Two movement types are most commonly assumed in hummingbirds: territoriality and traplining, the latter strategy involving repeated and predictable visitation to dispersed feeding locations. However, direct evidence for traplining mostly comes from captive birds. In this study, we collected data from white-necked jacobin hummingbirds (Florisuga mellivora) that were implanted with tiny radio-frequency identification (RFID) tags, tracking their movement among a network of 20 tag-detecting feeders spread across the town of Gamboa, Panama, for 99 days. The resulting data cover over 47,000 feeder visits from 97 freely moving birds. Overall, we found scant evidence for traplining as a consistent strategy in this species. Instead, we identify three clusters of daily movement types, two of which are difficult to characterize as either territoriality or traplining. Our findings demonstrate that a diversity of movement strategies can be found within a single hummingbird species and even within individuals, and that many questions remain about the movement of these ecologically key vertebrates. To better understand the ecological role of hummingbirds, the description of a greater diversity of movement types beyond territoriality and traplining is likely to be necessary.

ecology↗

bioRxiv2025

Tiny radio-tag backpacks impact, but do not significantly affect, hummingbird time budgets in captivity

BackgroundGiven that wildlife tags have recently become miniaturized enough to work with some of the worlds smallest vertebrates, there is a newfound urgency for affordable, field-accessible biologging ethics studies. We designed a 3-hour time-budget experiment to investigate how radio-transmitter backpacks affect hummingbirds behavior. Using a large flight arena in Colombia, we individually filmed 25 Black-throated Mangoes (Anthracothorax nigricollis) under two randomized treatments, tagged and untagged, to characterize and quantitatively compare their behavior. We analyzed all videos using the Behavioral Observation Research Interactive Software (BORIS), to create time-budget breakdowns of our key behaviors of interest: flying, feeding, preening, and perching. We also designed an aviary-style "entanglement test" (n = 30) to determine if any individuals would snag on vegetation while equipped with the backpack harness, and tested 6 additional birds in this enclosure overnight for any longer-term negative effects. ResultsAcross duration, number of bouts, and bout length, we found no significant differences in the behavior of individuals (flying, feeding, preening, and perching) when they were or were not tagged. However, the additive effects of treatment number (whether the bird was undergoing its first or second 1.5-hour treatment) and treatment type (tagged or untagged) most accurately predicted time spent flying (birds flew significantly more in their second 1.5-hour treatment). The weight of the bird, meanwhile, best predicted feeding duration (lighter birds fed significantly more). Lastly, the additive effects of time of day and treatment type had the highest predictive accuracy of time spent preening (birds preened significantly more in the afternoon than the morning, and significantly more in the evening than the afternoon); here, the effect of treatment type was highly significant. In our aviary tests, no individuals became entangled in vegetation or exhibited any adverse overnight effects from harness wear. ConclusionsIn our captive study, radio-transmitter backpacks did not significantly affect hummingbird behavior when considered independently; however, additional covariates are essential to account for, and the effects of being in a confined space may also be significant. Nonetheless, our experimental model is relatively straightforward to fine-tune to other small taxa and is suitable for remote conditions, providing a useful basis with which to examine species-specific effects of biologging prior to starting field studies.

animal behavior and cognition↗

bioRxiv2024

Tracking small animals in complex landscapes: a comparison of localisation workflows for automated radio telemetry systems

Automated radio telemetry systems (ARTS) have the potential to revolutionise our understanding of animal movement by providing a near-continuous record of individual locations in the wild. However, localisation error in data generated by ARTS can be very high, especially in natural landscapes with complex vegetation structure and topography. This curtails the ecological questions that may be addressed with this technology. Here, we set up an ARTS grid in a valley with heterogeneous vegetation cover in the Colombian high Andes and applied an analytical pipeline to test the effectiveness of localisation methods. We performed calibration trials to simulate animal movement in high-or low-flight, or walking on the ground, and compared workflows with varying decisions related to signal cleaning, selection, smoothing, and interpretation, along with four multilateration approaches. We also quantified the influence of spatial features on the systems accuracy. We tested the grid by deploying tags on two high-altitude hummingbirds, the Great Sapphirewing (Pterophanes cyanopterus) and Bronze-tailed Thornbill (Chalcostigma heteropogon). Results showed large variation in localisation error, ranging from only 0.4-43.4 m from known locations up to 474-1929 m, depending on the localisation method used. The lowest average median error across calibration tracks was 105 m. In particular, we found that the selection of higher radio signal strengths and data smoothing based on the temporal autocorrelation in movement data are useful tools to improve accuracy. Moreover, the variables that significantly influence localisation error include terrain ruggedness, height of movement, vegetation type, and the location of animals inside or outside the grid area. In the case of our study system, thousands of location points were successfully estimated for two hummingbird species that previously lacked movement ecology data. Our case study on hummingbirds suggests ARTS grids can be used to estimate small animals home ranges, associations with vegetation types, and seasonality in occurrence. We present a comparative localisation pipeline, highlighting the variety of possible decisions while processing radio signal data. Overall, this study provides guidance to improve the resolution of location estimates, broadening the application of this tracking technology in the study of the spatial ecology of wild populations.

ecology↗