# Behavioural response of Arctic terns (Sterna paradisaea) to a single drone flight on Æðey, Iceland

David Pierre Milesi-Gaches

► To cite this version:

David Pierre Milesi-Gaches. Behavioural response of Arctic terns (Sterna paradisaea) to a single drone flight on Æðey, Iceland. 2025, pp.3. hal-05131931

HAL Id: hal-05131931

https://hal.science/hal-05131931v1

Submitted on 26 Jun 2025

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Distributed under a Creative Commons Attribution 4.0 International License
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David Pierre Milesi-Gaches<fnref n="1" /> | Department of zoology, University of South Bohemia in České Budějovice

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https://orcid.org/0000-0002-0605-7038

# Behavioural response of Arctic terns (*Sterna paradisaea*) to a single drone flight on Æðey, Iceland

## Context

Drones are increasingly used in ornithological research as they can reduce disturbance compared to direct human presence, which is known to negatively affect nesting birds (Borrelle & Fletcher, 2017; Nisbet, 2000). However, bird responses to drones vary by species, context, and flight parameters such as altitude and angle of approach (Vas et al., 2015; Weston et al., 2020). Arctic terns (*Sterna paradisaea*), despite their aggressive defence of nests, remain poorly studied in this context. Here, I report a single drone flight near a breeding colony on Æðey, a small island in the Ísafjarðardjúp fjord, Iceland.

## Methods

The observation was conducted on Æðey Island in the Ísafjarðardjúp fjord, where an Arctic tern colony of approximately 804 breeding adults nests around the island's farm (Gallo et al., 2023). In recent years, the colony has expanded into areas closer to buildings, indicating some tolerance to human activity. The location of the drone flight is shown in Figure 1.
On 4 July 2023, a DJI Mini 4 Pro drone (249 g; max. 61 dB at 10 m) was flown from a lawn near the colony edge (GPS: 66.099179, -22.660008), at the boundary between old and newly occupied zones.
The launch location was regularly frequented by humans and chosen in agreement with the

landowners. The drone ascended vertically at a controlled speed of 2 m/s to 100 m altitude and then moved away from the site (Edney et al., 2023; Vas et al., 2015).

## Results & conclusion

The flight began at 14:36:52. Prior to take-off, Arctic terns in the vicinity were already active, flying in circles above the colony. The drone ascended vertically from 0 to 100 m in 48 seconds, maintaining a constant speed of 2 m/s and a fixed GPS position. Throughout the ascent and brief hovering period, the terns showed no observable reaction. Their activity remained consistent with pre-flight behaviour, and no signs of agitation, alertness, or defensive responses were noted.

This observation suggests that a controlled vertical drone flight reaching 100 m may not disturb breeding Arctic terns under similar conditions. However, this result is based on a single event, and individual or contextual variability may lead to different responses. Further observations under varied conditions are needed to better assess the potential of drones as a low-impact monitoring tool for this species (Leija et al., 2023; Weston et al., 2020; Vas et al., 2015). Figure 2 illustrates the type of aerial image that can be obtained under such conditions, with no visible disturbance to the colony.

<footnote n="1">¹ milesi.david@gmail.com</footnote>
<figure><img src="image_4.png" /><figcaption>**Figure 1.** Map of Æðey showing the location of the drone flight near the Arctic tern colony (Basemap: Loftmyndir ehf).</figcaption></figure>

<figure><img src="image_5.png" /><figcaption>**Figure 2.** Photograph taken by the drone at an altitude of 100 m, illustrating its potential use for population monitoring and counting sections of Arctic tern colonies.</figcaption></figure>

**Acknowledgements**

We thank the owners of Æðey for their permission and hospitality. We are also grateful to the Arctic Lab

expedition for logistical support aboard the Peter Pan, and to Vincent Grison, Jean Guérin, Guillaume Roissard, Clément Pichard and Gérard Lambert for their warm welcome.
## References

Borrelle, S.B., Fletcher, A.T., 2017. Will drones reduce investigator disturbance to surface-nesting seabirds? Marine Ornithology 45, 89–94.
http://doi.org/10.5038/2074-1235.45.1.1205

Edney, A., Hart, T., Jessopp, M., Banks, A., Clarke, L., Cugniere, L., Elliot, K., Juarez Martinez, I., Kilcoyne, A., Murphy, M., Nager, R., Ratcliffe, N., Thompson, D., Ward, R., Wood, M., 2023. Best practices for using drones in seabird monitoring and research. Marine Ornithology 51.

Gallo, C., Bobeková, I., Árnason, S.H., 2023. Distribution, breeding success, and survey methods of Arctic terns in the Westfjords, 2022-2023 (No. 32–23). Náttúrustofa Vestfjarða, Bolungarvík.

Leija, A.C. de, Mirzadi, R.E., Randall, J.M., Portmann, M.D., Mueller, E.J., Gawlik, D.E., 2023. A meta-analysis of disturbance caused by drones on nesting birds. Journal of Field Ornithology 94.
https://doi.org/10.5751/JFO-00259-940203

Nisbet, I.C.T., 2000. Disturbance, habituation, and management of waterbird colonies. Waterbirds 23, 312–332.

Vas, E., Lescroël, A., Duriez, O., Boguszewski, G., Grémillet, D., 2015. Approaching birds with drones: first experiments and ethical guidelines. Biology Letters 11, 20140754.
https://doi.org/10.1098/rsbl.2014.0754

Weston, M.A., O'Brien, C., Kostoglou, K.N., Symonds, M.R.E., 2020. Escape responses of terrestrial and aquatic birds to drones: Towards a code of practice to minimize disturbance. Journal of Applied Ecology 57, 777–785.
https://doi.org/10.1111/1365-2664.13575

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This field note is part of the *Commentarii de Natura series*, a collection of descriptive field observations, shared in support of open and reproducible naturalist documentation.

© 2025 David Pierre Milesi-Gaches

This field note is licensed under a [Creative Commons Attribution 4.0 International License (CC BY 4.0)](https://creativecommons.org/licenses/by/4.0/).

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