Birds build nests to provide a safe place to lay their eggs and raise their young. To construct these safe havens, they use items found in nature, like sticks, lichen, spider silk, bark, and mud. However, more birds are finding man-made items in their search for nest materials, and a new study investigated where and how this is happening.
Research recently published in Philosophical Transactions of the Royal Society B looked at more than 35,000 wild bird nests to better understand the use of anthropogenic, or manmade, materials in the nests. The findings show that their use is widespread, with 176 bird species across the world incorporating such items. This included seabirds in Australia using fishing nets, North American ospreys using baling twine, urban birds in South America utilizing cigarette butts, and blackbirds in Europe adding on plastic bags.
Zuzanna Jagiełło, lead author from the Poznań University of Life Sciences in Poland, says, “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”.
The researchers explain that some of the harms include the risk of becoming entangled in baling twine, offspring eating manmade items they thought were prey, and colorful materials attracting predators that eat the eggs or nestlings.
On the other hand, some of the materials were found to provide benefits. Compounds in cigarettes, including nicotine, repel parasites that attach themselves to birds and suck their blood. Harder materials may strengthen nests, and plastic can help with insulation.
The study also investigated the reasons behind the use of manmade materials. They found that sexual dimorphism (different characteristics displayed by male and female birds) may play a role, as may the type of nest being built.
Whatever the reason, the researchers say more research needs to be done to fully grasp litter’s impacts.
Jagiełło explains, “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.”
If you happen to see a nesting bird that has used litter in its nest, remember not to disturb it. You can also help birds by leaving natural nest items out in the spring, including sticks and dry grass.