Species Spotlight: Cerulean Warbler

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. Photo courtesy of Wikimedia Commons

The cerulean warbler. Photo courtesy of Wikimedia Commons

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.

Rare Birds Call MNA Sanctuaries Home

A cerulean warbler.

A cerulean warbler.

This year, MNA’s stewardship team made an effort to determine the status of numerous rare species at MNA sanctuaries around the state.

They uncovered several interesting findings related to birds listed as rare, threatened or endangered in the state of Michigan.

A peregrine falcon high in a tree at an MNA sanctuary. Photo by Nancy  Leonard.

A peregrine falcon high in a tree at an MNA sanctuary. Photo by Nancy Leonard.

This year’s findings included:

  • Multiple bald eagle nests in the Upper Peninsula were verified as active, including one nest that was active again for the first time in several years.
  • A peregrine falcon nest in the Upper Peninsula fledged chicks again in 2013, the third successful nesting season for this pair.
  • Two black tern colonies which had not been confirmed as active in five to 15 years were found to still be active. Black tern colonies have been faring poorly across Michigan over the past decade and many have crashed during this timeframe.
  • Two black-crowned night heron colonies were confirmed to still be active.
  • Two sanctuaries had cerulean warbler sightings confirmed in June and nesting activity was documented at one sanctuary. These sightings were recorded along Michigan’s southern tier of counties in the Lower Peninsula.
  • A new nesting grasshopper sparrow record was recorded in one of MNA’s prairie sanctuaries in the Lower Peninsula.
  • Multiple sanctuaries had nesting season records for other listed species including the American bittern, marsh wren, and the black-backed woodpecker.

Keep an eye on the MNA blog for more updates about rare, threatened and endangered species at MNA sanctuaries across the state. To learn more, visit the MNA website.