White Plastic Made Magpies Hesitate Before Raiding Artificial Nests

January 19, 2026

Eurasian magpie holding an egg in its beak

Research · Behaviour

White plastic made Eurasian magpies (Pica pica) hesitate before taking eggs from artificial nests in a field experiment in central Norway. When a plastic-decorated nest and an undecorated nest were placed side by side, the magpies generally attacked the undecorated nest first.

The researchers worked in farmland gardens in Stjørdal, Frosta and Levanger. Inside established magpie territories they placed artificial ground nests containing two quail eggs. In the main experiment, a nest decorated with pieces of white plastic was placed one metre from an otherwise similar control nest.

Plastic delayed the start of nest raiding

During the first trials on 62 territories, egg removal began later from the plastic-decorated nests. Where the order could be determined, an egg from the plastic nest was taken first in only 32% of trials.

The effect was a delay rather than lasting protection. Once the magpies had begun taking eggs, birds that started later did not take longer to remove the remaining eggs.

The birds learned the experiment, but still hesitated at the plastic

When the researchers repeated the paired experiment later in the season on 60 territories, magpies approached the experimental nests sooner overall. The authors interpret this as habituation to the cameras and artificial nests. Even then, eggs from the plastic-decorated nests still tended to be taken later in the sequence than eggs from the control nests.

Plastic already present around a territory did not make the birds attack the decorated nests sooner, and experience with a similar experiment the previous year produced no detectable effect the following spring. Together, the results support neophobia — reluctance to approach something novel — as an explanation for the delay.

The advantage disappeared when there was no nearby control nest

When the magpies were offered only a single artificial nest, time to the first egg removal did not clearly differ between nests with and without plastic. The authors suggest that conspicuous white plastic may make a nest easier to find, offsetting the hesitation caused by the unfamiliar material.

The experiment does not show that plastic generally protects real bird nests. It does suggest a trade-off: conspicuous anthropogenic material can make a nest easier to detect while also making a neophobic predator hesitate after discovery. In colonies or other situations where nest owners can return quickly, even a short delay could potentially matter.

Sources and image credit

Slagsvold, T., & Husby, M. (2026). Birds decorating their nests with plastic may suffer less egg depredation by corvids. Ecology and Evolution, 16(1), e72966. https://doi.org/10.1002/ece3.72966Primary peer-reviewed open-access field experiment, first published 19 January 2026; CC BY 4.0.

Image: Magne Husby — Eurasian magpie (Pica pica) holding an egg. Photograph published with the University of Oslo's account of research on nest decoration and egg predation, via forskning.no. Representative image for this story; not presented as an animal or scene from the reported study or event. · © Magne Husby · Source