Hawaiian Forest Birds Steal Nest Materials From Each Other

Forest life can seem calm and well balanced. Year after year, birds nest, forage and rear their young in the same places. Yet even in such apparently steady habitats, competition can emerge in unexpected ways.

In Hawaii’s high-elevation forests, certain birds do more than collect nesting supplies. They take them from one another.

A recent study highlights this little-noticed behaviour and indicates that it may subtly influence survival.

Birds steal nest materials

Researchers at the University of California, Riverside wanted to gain a clearer picture of the everyday lives of native Hawaiian birds.

Rather than examining predators or disease, they followed a much less conspicuous activity: birds taking twigs, moss and fibres from neighbouring nests.

Scientists track nest theft

“People working in the field have seen this behavior for years, but it’s never been documented at this level,” said Erin E.Wilson Rankin, the study’s first author.

“Now we can say who’s doing it, who they’re stealing from, and what happens to the nests afterward.”

Across six months, the researchers intensively observed more than 200 nests throughout the forest canopy.

Their detailed monitoring let them go beyond informal observations and quantify how frequently this behaviour takes place.

Who steals the most?

The results exposed an unexpected trend. The Apapane, a widespread native species, featured on both sides of these encounters. It was commonly seen removing materials, while also being a frequent target.

This crossover probably relates to how regularly these birds encounter each other. Bigger populations create more opportunities for contact and, in this instance, more opportunities for theft.

“What’s fascinating is that this behavior is happening within species as well,” Wilson Rankin said. “Apapane were stealing from other Apapane.”

Theft occurs at the same height

The research further found that position is important. Birds generally removed materials from nests constructed at comparable heights.

This implies that they do not deliberately look for nests to plunder. Rather, they exploit nests they come across while moving routinely through the forest.

Active nests sometimes fail

Nest theft does not always cause damage. Numerous nests involved were no longer occupied. However, the study showed that some remained active, containing eggs or chicks, or were still being built.

Such incidents had genuine effects. “We saw instances where nests failed, either because the nest structure was compromised or because the parents were disturbed and left,” Wilson Rankin said.

Roughly 5% of the nests under observation failed following these incidents. This percentage underlines how seemingly small disturbances can influence breeding success.

Birds face survival pressure

Hawaiian forest birds already face difficult survival conditions. Habitat loss has limited the nesting space available to them.

Changing climatic conditions are altering their surroundings, while mosquito-borne diseases have pushed many species into increasingly restricted high-elevation areas.

Against this backdrop, even modest losses can be significant. Having part of a nest taken, or leaving it altogether, can lower the likelihood of successfully rearing young.

For birds that steal, the practice may bring immediate advantages by reducing the time and energy needed. It could, however, bring fresh dangers, including contact with parasites in the stolen materials.

Nest theft may increase

This behaviour may become more widespread as circumstances shift. Competition could intensify if suitable nest locations or materials become more difficult to obtain.

“This kind of behavior could be more common if nesting materials or safe nesting sites become scarce,” Wilson Rankin said. “It’s something we should measure.”

Recognising these patterns may help inform conservation efforts. Although the behaviour itself may not be preventable, knowing when it is most likely can enable more effective planning.

Findings guide conservation

“If we can predict when and where this behavior happens, we might not be able to stop it, but we can intervene in other ways to support at-risk species,” Wilson Rankin said. “That’s a benefit of this work.”

The research also changes the way threats in the natural world are considered. Risks do not always originate from external forces.

“Sometimes threats to animal species don’t come from predators or people,” Wilson Rankin said. “They can come from similar animals.”

Implications of the study

In a densely populated forest, survival involves more than avoiding predators and severe conditions.

Animals must also manage ongoing competition from the creatures around them. When many birds occupy the same restricted area, even minor actions can become important.

Taking only a few twigs from another nest can alter that bird’s prospects of rearing its young.

These minor encounters may disrupt nests, consume energy or compel birds to build again. As they recur, they can place further pressure on species that are already struggling.

Survival, then, means more than evading clear and immediate dangers. It also relies on how effectively animals cope with daily competition, including actions that initially appear insignificant.