Seasonal and circadian biases in bird tracking with solar GPS-tags

Silva, Rafa; Afán, Isabel; Gil, Juan Antonio; Bustamante, Javier

doi:10.1371/journal.pone.0185344

Cited by 25 publications

(28 citation statements)

References 32 publications

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“…As expected (Silva et al . ), there were substantially fewer tag records in winter but there were no major seasonal differences between the training and first test data proportions (Table ). Season had little effect on model predictions and there were no major differences between the training and first test records with respect to the distribution of tag records between the predicted use‐classes with season (Table ).…”

Section: Resultsmentioning

confidence: 89%

A simple topographical model to predict Golden Eagle Aquila chrysaetos space use during dispersal

Fielding¹,

Haworth²,

Anderson

et al. 2019

Ibis

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Many large raptors exploit or rely on anabatic and orographic winds which provide vertical lift, to supplement or provide the energy fuelling flight. Airspace is therefore a critical habitat for such large raptors and its use is subject to the underlying terrestrial topography, because particular topographical features are more likely to provide wind‐energetic lift. Accordingly, ridges and/or ‘rugged topography’ are common preferred features in habitat use by large raptors. Our study aimed to provide a simple model of space use for a large raptor, the Golden Eagle Aquila chrysaetos, based on thousands of GPS telemetry records during juvenile dispersal of 92 birds tagged as nestlings between 2007 and 2016 across upland Scotland. Model development was based on the hypothesis that four topographical variables would be influential: slope, aspect, altitude and distance from ridge. The telemetry dataset was divided into training and two testing components. The first testing set was derived by a temporal split resulting in approximately equal sample size on records and some temporal overlap in individuals’ records with training data. The second testing set involved no individuals from the training set. Aspect was removed early in training model development because it was not influential. The model found that young Golden Eagles preferred, or used according to availability, space above slopes greater than 10°, at an altitude of ≥ 300 m, and within 300 m of a ridge. The test data were highly correlated with those from the training data in the model variables, and performance as regard to expected preferences from the model was improved in both test datasets, indicating the model was robust. Given the apparent universal nature of large raptor dependence on topography, that topography is relatively immutable according to time and use, and that topographical data are readily available, we commend our approach to other habitat preference studies of Golden Eagles and other large raptors elsewhere.

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Section: Resultsmentioning

confidence: 89%

A simple topographical model to predict Golden Eagle Aquila chrysaetos space use during dispersal

Fielding¹,

Haworth²,

Anderson

et al. 2019

Ibis

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“…7 ). In addition, the flying fixes ratio registered in winter (37%) was higher than all of the other seasons (the lowest was logged in summer (32.5%), considering flying fixes > 1.39 m/s following Silva et al [ 51 ]). This supports our aforementioned hypothesis that the energetic requirements of Bearded Vultures rise during the breeding period (winter and spring) combined with the decrease in of food availability in this time of year [ 17 ] which forces them to fly for longer periods and over longer distances.…”

Section: Discussionmentioning

confidence: 94%

“…The influence of season has been generally evident in other studies of the circadian rhythm of birds [ 24 , 47 , 48 ], because variations in the quantity and intensity of solar radiation throughout the year determinate the timing of a bird’s circadian behaviour [ 49 ], and conditioning intrinsic factors such as the speed of migration [ 50 ]. Seasonal effects can also influence external factors such as variation in carrion food availability due to seasonal transhumance of livestock [ 17 ], thus shaping vultures’ daily activity patterns, and biasing the performance of solar powered GPS transmitters [ 51 ]. We detected a seasonal influence on the values of the distance covered estimators, the longest distances being recorded in spring.…”

Section: Discussionmentioning

confidence: 99%

Drivers of daily movement patterns affecting an endangered vulture flight activity

2018

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BackgroundThe development of satellite tracking technology enables the gathering of huge amounts of accurate data on animal movements over measured time intervals, to reveal essential information about species’ patterns of spatial use. This information is especially important in optimizing the design of conservation and management strategies for endangered species. In this study, we analysed the main drivers of daily patterns in the flight activity of the threatened Bearded Vulture Gypaetus barbatus. We studied 19 Bearded Vultures tagged with solar-powered GPS transmitters from 2006 to 2016 in the Pyrenees (Spain). We assessed the relative influence of external factors (season and daylight time) and internal factors (sex, breeding season and territorial status) on their daily activity behaviour by computing mean hourly distance travelled, maximum displacement and cumulative distance travelled per hour.ResultsOur findings showed a clear difference in all the estimators between territorial and non-territorial (floating) members of the population, showing that non-territorial individuals spent much longer in flight and travelled larger distances per day. We detected an important influence of daylight time and season on the daily rhythms of Bearded Vultures; flight activity increased during the last three quarters of daylight and was greatest in the spring. Breeding period and sex had also an effect on the maximum displacement and cumulative distance travelled. Individuals flew more during the breeding period and females tended to exhibit greater cumulative and maximum distances per hour than males regardless of breeding season.ConclusionsPyrenean Bearded Vultures flight daily activity was strongly influenced by daylight time, season, and territorial status, while individual sex and breeding season showed a milder effect on the birds’ movement behaviour. This study gives a novel insight into how external factors act as main drivers of the daily flight activity pattern of a long-lived avian scavenger.Electronic supplementary materialThe online version of this article (10.1186/s12898-018-0195-7) contains supplementary material, which is available to authorized users.

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“…The use of tracking devices has significantly improved the way we approach the movement of opportunistic species in response to both natural and human-induced environmental variability [19,26,27]. Tracking devices typically provide relevant information on the main foraging grounds of a particular organism, but can also inform on individuals' decision-making on a near realtime basis over larger periods of time [19,28]. This spatio-temporal data collection on individuals' behavior, therefore, greatly benefits the study of activity patterns in relation to human activities [9,23,29].…”

Section: Introductionmentioning

confidence: 99%

Behavioral rhythms of an opportunistic predator living in anthropogenic landscapes

et al. 2020

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Background: Human activities have profoundly altered the spatio-temporal availability of food resources. Yet, there is a clear lack of knowledge on how opportunistic species adapt to these new circumstances by scheduling their daily rhythms and adjust their foraging decisions to predicable patterns of anthropic food subsidies. Here, we used nearly continuous GPS tracking data to investigate the adaptability of daily foraging activity in an opportunistic predator, the yellow-legged gull (Larus michahellis), in response to human schedules. Methods: By using waveform analysis, we compared timing and magnitude of peaks in daily activity of different GPS-tracked individuals in eleven different habitat types, in relation to type of day (i.e., weekday vs. weekend). Results: Daily activity rhythms varied greatly depending on whether it was a weekday or weekend, thus suggesting that gulls' activity peaks matched the routines of human activity in each habitat type. We observed for the first time two types of activity as modelled by waveforms analysis: marine habitats showed unimodal patterns with prolonged activity and terrestrial habitats showed bimodal patterns with two shorter and variable activity peaks. Conclusions: Our results suggest that gulls are able to fine-tune their daily activity rhythms to habitat-specific human schedules, since these likely provide feeding opportunities. Behavioral plasticity may thus be an important driver of expansive population dynamics. Information on predictable relationships between daily activity patterns of gulls and human activities is therefore relevant to their population management.

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Seasonal and circadian biases in bird tracking with solar GPS-tags

Cited by 25 publications

References 32 publications

A simple topographical model to predict Golden Eagle Aquila chrysaetos space use during dispersal

A simple topographical model to predict Golden Eagle Aquila chrysaetos space use during dispersal

Drivers of daily movement patterns affecting an endangered vulture flight activity

Behavioral rhythms of an opportunistic predator living in anthropogenic landscapes

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