Light‐level geolocator analyses: A user's guide

Lisovski, Simeon; Bauer, Silke; Briedis, Martins; Davidson, Sarah C.; Dhanjal‐Adams, Kiran L.; Hallworth, Michael T.; Karagicheva, Julia; Meier, Christoph M.; Merkel, Benjamin; Ouwehand, Janne; Pedersen, Lykke; Rakhimberdiev, Eldar; Roberto-Charron, Amélie; Seavy, Nathaniel E.; Sumner, Michael; Taylor, Caz M.; Wotherspoon, Simon; Bridge, Eli S.

doi:10.1111/1365-2656.13036

Cited by 140 publications

(164 citation statements)

References 38 publications

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“…Further analyses were then carried within R. We used the ‘LoessFilter’ function in the R library GeoLight v. 2.0.1 (Lisovski & Hahn 2012, Lisovski et al 2019) to validate twilight events and identify those influenced by shading events at dawn and dusk: a polynomial regression of twilight events that identifies residuals that were greater than four times the interquartile range and are therefore likely to be erroneous (Lisovski & Hahn 2012). We used on‐bird in‐habitat calibration during breeding in the deployment year as the method of estimating the sun elevation angle (SEA; Lisovski et al 2012), using all days from the day after deployment until 31 August as the calibration period (mean 69.7 days, range 48–78 days).…”

Section: Methodsmentioning

confidence: 99%

“…We used on‐bird in‐habitat calibration during breeding in the deployment year as the method of estimating the sun elevation angle (SEA; Lisovski et al 2012), using all days from the day after deployment until 31 August as the calibration period (mean 69.7 days, range 48–78 days). We used the ‘getElevation’ function of GeoLight to calculate SEAs, using the zero elevation angle of the twilight error distribution (Lisovski et al 2019). Calculated SEAs ranged from –5.8 to –7.6, with individual SEAs used to estimate locations.…”

Section: Methodsmentioning

confidence: 99%

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Weak migratory connectivity, loop migration and multiple non‐breeding site use in British breeding Whinchats Saxicola rubetra

Burgess

Finch

Border

et al. 2020

Ibis

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Determining the links between breeding populations and the pressures, threats and conditions they experience presents a challenge for the conservation of migratory birds which can use multiple sites separated by hundreds to thousands of kilometres. Furthermore, migratory connectivity – the connections made by migrating individuals between networks of breeding and non‐breeding sites – has important implications for population dynamics. The Whinchat Saxicola rubetra is declining across its range, and tracking data from a single African non‐breeding site implies high migratory spread. We used geolocators to describe the migration routes and non‐breeding areas of 20 Whinchats from three British breeding populations. As expected, migratory spread was high, with birds from the three populations overlapping across a wide area of West Africa. On average, in non‐breeding areas, British breeding Whinchats were located 652 km apart from one another, with some likely to share non‐breeding areas with individuals from breeding populations as far east as Russia. Four males made a direct non‐breeding season movement to a second, more westerly, non‐breeding location in January. Autumn migration was through Iberia and around the western edge of the Sahara Desert, whereas spring migration was more direct, indicating an anticlockwise loop migration. Weak migratory connectivity implies that Whinchat populations are somewhat buffered against local changes in non‐breeding conditions. If non‐breeding season processes have played a role in the species’ decline, then large‐scale drivers are likely to be the cause, although processes operating on migration, or interactions between breeding and non‐breeding processes, cannot be ruled out.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Weak migratory connectivity, loop migration and multiple non‐breeding site use in British breeding Whinchats Saxicola rubetra

Burgess

Finch

Border

et al. 2020

Ibis

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“…Further, we followed standard analysis procedures in 'FLightR' as outlined by Lisovski et al (2020). 'FLightR' uses a template fit method to compute a spatial likelihood surface for each twilight event.…”

Section: Geolocator Trackingmentioning

confidence: 99%

Seasonally specific responses to wind patterns and ocean productivity facilitate the longest animal migration on Earth

Hromádková

Pavel

Flousek³

et al. 2020

Mar. Ecol. Prog. Ser.

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Migratory strategies of animals are broadly defined by species’ eco-evolutionary dynamics, while behavioural plasticity according to the immediate environmental conditions en route is crucial for energy efficiency and survival. The Arctic tern Sterna paradisaea is known for its remarkable migration capacity, as it performs the longest migration known by any animal. Yet, little is known about the ecology of this record-breaking journey. Here, we tested how individual migration strategies of Arctic terns are adapted to wind conditions and fuelling opportunities along the way. To this end, we deployed geolocators on adult birds at their breeding sites in Svalbard, Norway. Our results confirm fundamental predictions of optimal migration theory: Arctic terns tailor their migration routes to profit from (1) tailwind support during the movement phase and (2) food-rich ocean areas during the stopover phase. We also found evidence for seasonally distinct migration strategies: terns prioritize fuelling in areas of high ocean productivity during the southbound autumn migration and rapid movement relying on strong tailwind support during the northbound spring migration. Travel speed in spring was 1.5 times higher compared to autumn, corresponding to an increase in experienced wind support. Furthermore, with their pole-to-pole migration, Arctic terns experience approximately 80% of all annual daylight on Earth (the most by any animal), easing their strictly diurnal foraging behaviour. However, our results indicate that during migration daylight duration is not a limiting factor. These findings provide strong evidence for the importance of interaction between migrants and the environment in facilitating the longest animal migration on Earth.

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“…Rarely are such issues covered in great detail in the ecological literature, and a significant contribution of this Special Feature is in providing guidelines and best practices for would-be users. Here, Lisovski et al (2020) provide a practical "How-To" paper on the effective use of light-based geolocators, and how resulting data should be handled and manipulated for subsequent analyses.…”

Section: Handling and Analysing Biologging Datamentioning

confidence: 99%

“…broad range of biologging technologies used to address a variety of fundamental questions in animal ecology, in aquatic, terrestrial and aerial species. Three papers use light-level geolocator tags-miniature lightweight tags which measure ambient light levels to determine sunrise and sunset times, and hence estimate the approximate location of the animal (Bridge et al, 2011;Wilson, Ducamp, Rees, Culik, & Niekamp, 1992)-to investigate the ontogeny of migratory behaviour in a long-lived seabird species (Campioni, Dias, Granadeiro, & Catry, 2020), quantify effects of biologgers on the survival of tagged birds (Brlík et al, 2020) and provide a practical guide for the effective application of geolocator tags to track animals (Lisovski et al, 2020).…”

Section: Introductionmentioning

confidence: 99%