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# Response of Arctic tern (Sterna paradisaea) to American mink (Neogale vison) and its elimination by a hunter

David Pierre Milesi Gaches

► To cite this version:

David Pierre Milesi Gaches. Response of Arctic tern (Sterna paradisaea) to American mink (Neogale vison) and its elimination by a hunter. 2025, pp.3. hal-05224890

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https://hal.science/hal-05224890v1

Submitted on 26 Aug 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

# Response of Arctic tern (*Sterna paradisaea*) to American mink (*Neogale vison*) and its elimination by a hunter

## Context

Arctic terns (*Sterna paradisaea*) nest in coastal colonies exposed to various sources of disturbance, including mammalian predators throughout its range (Nisbet, 2000; Syrová et al., 2020). The fjord Ísafjarðardjúp in the northwest Iceland hosts regular nesting sites. The presence of American mink (*Neogale vison*) is of particular concern, due to their capacity to predate eggs and chicks (Clode and Macdonald, 2002; Craik, 1997). In the municipality of Súðavík, a professional hunter is contracted to remove minks or Arctic foxes when they are observed within bird colonies. The following observation describes the behaviour of terns during such an intervention.

## Methods

Observations were made on the 17th of June 2025 in the Arctic tern colony (circa 500 breeding pairs) located in the Langeyri peninsula in Súðavík. The event was recorded opportunistically during a predator disturbance event. Notes were taken directly in the field and later transcribed. Estimated numbers of birds and their behavioural responses were assessed visually without instruments. No experimental or systematic protocol was followed; the aim was purely descriptive.

## Results & conclusion

When spotted, the terns actively displayed attack behaviours towards the mink, with high participation among colony members (up to 300 birds). Nearby nesting black-headed gulls also joined the defence. While terns engaged in repeated diving displays towards the predator, they did not attempt physical contact. All attack flights stopped about 2 metres above the ground.

The colony's response to the mink was regularly interrupted, with terns returning to their nests, suggesting it was difficult for them to spot and track the predator. However, whenever a tern located the mink again, the colony resumed its coordinated defence.

Meanwhile, three to four people at the colony's edge were observing the situation with binoculars. The hunter entered the nesting area only when necessary and relied on the birds' behaviour to locate the mink (Figure 1). The observers experienced mild attacks from terns, likely due to the proximity of nests. Similarly, the hunter was occasionally targeted by low dives (down to 1 m above his head) without being touched. These minor attacks involved no more than ten terns; the majority remained focused on the mink. When the hunter came within 5 to 10 metres of the predator, the terns no longer attacked him and even shifted slightly away from the area.

<footnote n="1">¹ milesi.david@gmail.com</footnote>
After 40 minutes, the mink moved towards the colony's edge, where only a few remote nests were located. The terns followed closely. From that position, the hunter could move safely without stepping on nests. He fired a single shot and wounded the mink, which fled along the edge before being quickly dispatched by the present people.

At the moment of the shot, all terns and black-headed gulls initiated a coordinated and silent

flight in the opposite direction. No more than 100 metres away, they turned and returned either to their nesting sites or towards the location where the mink was shot. No attack behaviour was displayed towards the dead mink or towards the people after the predator had been neutralised.

Post-mortem examination (Figure 2) confirmed the predator was a female mink (*Neogale vison*), weighing 650 g and measuring 430 mm in total length (320 mm excluding the tail).

<figure><img src="image_5.png" /><figcaption>**Figure 1.** Arctic terns mobbing over the nesting area in response to the presence of an American mink. The hunter (centre) can be seen in the field.</figcaption></figure>
<figure><img src="image_6.png" /><figcaption>**Figure 2.** Carcass of the female American mink.</figcaption></figure>

**Acknowledgements**

I thank Elmar Atli Garðarsson for his assistance in the field and for sharing the mink specimen for documentation.

**References**

Clode, D., and Macdonald, D.W., 2002. Invasive predators and the conservation of island birds: the case of American Mink Mustela vison and terns Sterna spp. in the Western Isles, Scotland. Bird Study 49, 118–123.

https://doi.org/10.1080/00063650209461255

Craik, C., 1997. Long-term effects of North American Mink Mustela vison on seabirds in western Scotland. Bird Study 44, 303–309.

https://doi.org/10.1080/00063659709461065

Nisbet, I.C.T., 2000. Disturbance, Habituation, and Management of Waterbird Colonies. Waterbirds: The International Journal of Waterbird Biology 23, 312–332.

Swift, K., Marzluff, J., 2015. Wild American crows gather around their dead to learn about danger. Animal Behaviour 109, 187–197.

https://doi.org/10.1016/j.anbehav.2015.08.021

Syrová, M., Hromádková, T., Pavel, V., Veselý, P., 2020. Responses of nesting Arctic terns (Sterna paradisaea) to disturbance by humans. Polar Biol 43, 399–407.

https://doi.org/10.1007/s00300-020-02641-2

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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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