Beak shape can predict nest material use in the world’s birds, study finds

UNIVERSITY OF BRISTOL

Fig 1 — IMAGE: A ZEBRA FINCH (TAENIOPYGIA GUTTATA) HANDLING NEST MATERIAL view more
CREDIT: SHOKO SUGASAWA

The material a bird selects for its nest depends on the dimensions of its beak, according to researchers.

Using data on nest materials for nearly 6,000 species of birds, a team based at the University of Bristol and the University of St Andrews utilised random forest models, a type of machine learning algorithm, to take data from bird beaks and try to predict what nest materials that species might use.

They found a surprisingly strong correlation. Using only information on beak shape and size, they were able to correctly predict broad nest material use in 60% of species, rising to 97% in some cases.

These findings, published today in Philosophical Transactions of the Royal Society B, include a careful exploration of these models, investigating the ecological and evolutionary context behind these relationships. For example, not every species has the same access to all nest material types, which also affects these results.

The study’s lead author, Dr Catherine Sheard of Bristol’s School of Earth Sciences said: “We know a lot about primate hands, but not as much about how other animals use their limbs and mouths to manipulate objects. We’ve very excited about the potential applications of our findings, to further explore how beak shape may have co-evolved with other aspects of nest building or other functions.”

Dr Shoko Sugasawa, senior author of the study, based at the University of St Andrews, added: “Most animals, including birds, do not have hands like ours, but manipulating objects like nest material and food is such a crucial part of their lives. Our finding is the first step to reveal possible interactions between the evolution of beaks and manipulation like nest building, and helps us better understand how animals evolved to interact with the world with or without hands”.

The team are now working on a project documenting anthropogenic nest material in the world’s birds, trying to understand what type of birds put human-made material (like plastic, wire, or cigarette butts) in their nests. They are in particular looking to see whether this would be linked to urban-dwelling birds.

“I’m also interested in how beak shape relates to other properties of the nest, including overall nest structure,” added Dr Sheard, “such as whether birds build nests with walls, or a roof.”

A Mute Swan (Cygnus olor) building a nest

CREDIT

Shoko Sugasawa

Paper

‘Beak shape and nest material use in birds’ by Catherine Sheard, Sally E. Street, Caitlin Evans, Kevin N. Lala, Susan D. Healy, and Shoko Sugasawa in Philosophical Transactions of the Royal Society B.

JOURNAL

Philosophical Transactions of the Royal Society B Biological Sciences

METHOD OF RESEARCH

Data/statistical analysis

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Beak shape and nest material use in birds

ARTICLE PUBLICATION DATE

10-Jul-2023

PLASTIC POLLUTION

Man-made materials in nests can bring both risks and benefit for birds

Man-made materials are widespread in birds’ nests

Peer-Reviewed Publication

BANGOR UNIVERSITY

Plastic in stork nest 1 — IMAGE: WHITE STORK NEST INCORPORATING PLASTIC view more
CREDIT: ZUZANNA JAGIELLO

We all discard a huge amount of plastic and other man-made materials into the environment, and these are often picked up by birds. New research has shown that 176 bird species around the world are now known to include a wide range of anthropogenic materials in their nests. All over the world, birds are using our left-over or discarded materials. Seabirds in Australia incorporate fishing nets into their nests, ospreys in North America include baler twine, birds living in cities in South America add cigarette butts, and common blackbirds in Europe pick up plastic bags to add to their nests.

This material found in birds’ nests can be beneficial say researchers. For example, cigarette butts retain nicotine and other compounds that repel ectoparasites that attach themselves to nestling bird’s skin and suck blood from them. Meanwhile, there are suggestions that harder man-made materials may help to provide structural support for birds’ nests, while plastic films could help provide insulation and keep offspring warm. Despite such potential benefits, it is important to remember that such anthropogenic material can also be harmful to birds.

This research was published in a special issue of the Philosophical Transactions of the Royal Society B on “The evolutionary ecology of nests: a cross-taxon approach”. The special issue was jointly organised by Mark Mainwaring, a Lecturer in Global Change Biology in the School of Natural Sciences at Bangor University.

Mark Mainwaring said,
“The special issue highlights that the nests of a wide range of taxa – from birds to mammals to fish to reptiles – allow them to adapt to human-induced pressures. Those pressures range from the inclusion of anthropogenic materials into their nests through to providing parents and offspring with a place to protect themselves from increasingly hot temperatures in a changing climate.”

Anthropogenic materials sometimes harm birds. Parents and offspring sometimes become fatally entangled in baler twine. Meanwhile, offspring sometimes ingest anthropogenic material after mistaking it for natural prey items. Finally, the inclusion of colourful anthropogenic materials into nests attracts predators to those nests who then prey upon the eggs or nestlings. This means that we need to reduce the amount of plastic and other anthropogenic material that we discard.

The lead author of the study, Zuzanna Jagiełło who is based at the Poznań University of Life Sciences in Poland, added,
“A wide variety of bird species included anthropogenic materials into their nests. This is worrying because it is becoming increasingly apparent that such materials can harm nestlings and even adult birds”. Zuzanna Jagiełło also went on to say that “more studies are needed to gain a more complete understanding of how many bird species worldwide include such materials into their nests for us to fully comprehend the extent of the problem.”

The second author of the study, Jim Reynolds, a researcher in the Centre for Ornithology at the University of Birmingham in the UK, remarked,

“In a rapidly urbanizing world which we share with many different animal taxa, it is not surprising that birds use our discarded materials in their nests. Although much needs to be understood about how plastics, for example, impact birds, it is exciting that birds, through their high mobility and breeding biology, may prove to be potent biomonitors of environmental anthropogenic material pollution.”

White stork chick entangled in plastic incorporated in its nest.

Plastic incorporated in a white stork nest.