By Sally Zimmerman, MNA Intern
The cerulean warbler (Dendroica cerulea) is a small, but strikingly beautiful, songbird that has been declining rapidly in the United States over recent decades.
The cerulean warbler has a length of only 4.3 inches and a wingspan of 7.9 inches. Male and female cerulean warblers look rather different from each other. The males are bright blue with a white underbelly. Black streaks line their sides. Females are a dull turquoise color with a yellowish underbelly. The male cerulean warbler has a song that is distinguishable from all other warblers.
These birds spend summers breeding in the United States, ranging from the lower Great Lakes region all the way down to northern Louisiana. It is most prevalent in eastern Ohio and southern Missouri and Wisconsin. They usually arrive to build nests and breed in the United States in late April or early May. Cerulean warblers then leave in August and migrate down to South America where they will stay until the next summer.
Cerulean warblers live in deciduous forests, choosing to build their nests higher up in the canopy than most other warblers. They piece grass stems, hair and bark fibers together in a spider web to create their nest. Here, they will lay between three and five eggs. When their eggs hatch, cerulean warblers will feed their young insects found on tree leaves.
These tiny birds face many threats to their population. Habitat destruction due to land development is a key threat. Climate change is another problem for cerulean warblers, as it may alter forest types. They also face the threat of habitat fragmentation. Brown-headed cowbirds will lay their eggs in cerulean warblers’ nests. When the brown-headed cowbird eggs hatch first, they tend to push all other eggs out of the nest.
Between 1966 and 1999, the cerulean warbler population in the United States declined 70 percent. Its population is dropping faster than any other warbler species.
Luckily, there have been two recent sightings of cerulean warblers in MNA sanctuaries. There was also nesting activity documented in one. This is a positive sign for the cerulean warbler, as there is a guarantee that their habitat will not be destroyed within the land protected by MNA.