The idea of a bird feasting on fried wings might sound somewhat cannibalistic, but new research indicates that certain wetland birds living close to urban areas are able to thrive during periods of low natural food availability by switching to junk food. In light of this finding, researchers now believe that urbanization may in fact help some species to survive by providing them with an alternative source of nourishment when their natural environments can’t support them.
Describing their observations in the journal Scientific Reports, the study authors tracked wood storks living in South Florida during the 2015-2017 nesting seasons. A total of 160 nests were monitored, of which 106 were located in urban areas and 54 were in the more natural surroundings of the Everglades.
During periods of natural food abundance, both the urban and non-urban birds stuck to pretty similar diets – consisting predominantly of native marsh fish – and produced high numbers of chicks. However, whenever natural marshes went through lean spells and fish became less abundant, urban birds began rummaging through trash cans in search of extra grub and were observed supplementing their diets with chicken wings and hot dogs, amongst other things.
As a result, storks living in urban areas were able to maintain their high rate of reproduction during these periods. In contrast, the number of chicks born to storks living in natural colonies declined when food on the marshes was scarce.
"The ability of urban birds to switch their diet to include different prey types such as human-provided food that included chicken wings and hot dogs likely allowed them to produce more chicks during poor natural wetland prey availability conditions than their non-urban counterparts,” explained study author Betsy Evans, a natural resources specialist with the United States Army Corps of Engineers and graduate student at Florida Atlantic University, in a statement.
Aside from junk food, urban storks also feasted on crayfish, frogs, and other amphibians living in unnatural water sources such as ponds, canals, and swales when marsh species were less available.
Based on these findings, the study authors insist that not all species suffer when urban sprawls encroach on natural habitats. In the case of the wood stork, they say, proximity to a city provides essential opportunities to survive and thrive when natural conditions are suboptimal.
That said, they do concede that many species do not fare so well in the face of urbanization and that the experience of wetland birds may be an exception rather than the rule. This is because wetland species generally have much larger home ranges than other types of birds and are therefore able to seek out alternative food sources when those in the vicinity of their nest are depleted.