Birds use different materials for different reasons to build their nests. Some of these reasons including mating, camouflage, security, and reproduction. This article is about how debris and plastic could affect marine organisms and birds. In human-modified landscapes, effects of terrestrial plastic tend to be more pronounced. The article presents a study that focuses on examining landscapes, types, and sources of anthropogenic nest materials in the American crow, which is a species that breeds in both agricultural and urban landscapes. Out of the 195 nestlings monitored in 106 nests, 85.2% of the nests contained anthropogenic material. Additionally, nestlings are entangled, which means that the material is not safe.
Impacts of debris and their effects on terrestrial organisms have poorly been documented or even sensitized because of lack of proper examination. Unlike other aspects that affect living organisms, terrestrial debris has not been that conspicuous. However, this has recently changed since urban landscapes have rapidly spread across the surface of the earth. For lack of other materials among other reasons, birds end up adapting hence utilizing anthropogenic resources. With an increase in urbanization, anthropogenic materials in nests keep increasing. However, potential consequences and adaptation to such adjustments are not examined. Such consequences include entanglement.
Three methods are used in the research. They include nest analysis, entanglement, and fledging success. The approaches involved monitoring 106 crow nests in an urban agricultural gradient. Nests were placed on tree branches, and nestlings were checked for entanglement once or twice a day. Some nestlings died from entanglement, and the survivors were marked with colorful bands after hatching. These were checked daily to monitor failure or success, and a minimum entanglement represented the encounter rate because either the parents or predators could remove dead nestlings.
Results from the study show that 85.2% of anthropogenic materials were detected in the nests. Only 36 nests placed in the primary agricultural territories lacked anthropogenic material. The material present in a nest ranged with the landscape which means that birds have different reasons for making nests with materials like plastic. In this case, the reason is convenience. Mainly, the birds take advantage of the availability of the readily available anthropogenic material to make their nests. Moreover, birds in urban and agricultural settings use plastic as their nest material because it resembles their natural nest material. Suggestions are put across regarding modified environments that are viewed as ecological traps. In this case, animals would be attracted to settling because of historical adaptive cues that cannot sustain a population due to the low quality of habitats. Entanglement is, therefore, one of the habitat stressors that cause low quality in habitats.
In urban landscapes, anthropogenic nest materials are readily available hence a beneficial resource for the birds. They help birds to construct their nests in places where natural materials are not available or are limited. Such benefits balance hazards that cause entanglement among other dangers. Urban areas provide different nesting anthropogenic materials, including plastic, unlike agricultural landscapes, which provide readily available twines and cloth wire. Birds, therefore, use plastic materials to build their nests mostly because of opportunity more than other reasons, which include the use of cigarette butts to repel some predators. In the end, these materials tend to be hazardous to the birds, which means there is both a positive and negative impact of using plastic material to build nests.
Townsend AK, Barker CM (2014) Plastic and the Nest Entanglement of Urban and Agricultural Crows. PLoS ONE 9(1): e88006. https://doi.org/10.1371/journal.pone.0088006