Cerulean Warbler

Dendroica cerulea
Warbler family (Parulidae)

Habitat:
Large tracts of mature deciduous forest

Description:
Small warbler, 4” long.  Male (shown in image) – “cerulean” blue upperparts with black streaks, white wing bars, white below, blue-black “necklace” across throat, blue-black streaking on sides.  Female (not shown) – greenish-blue upperparts; yellowish-white eyebrow, throat, and upper breast.

Nesting:
Nests in tall trees, usually 20 to 90 feet above the ground.  Builds nest well away from the trunk on a horizontal branch.  Eggs are green with variable brown marks.  Clutch size – 3 to 5 eggs.

Voice:
Song is a series of rapid buzzy notes on one pitch ending with a higher note, “zray zray zray zree”. 

Name Origin:
Dendroica:  dendron, Greek for “tree”; oicos, Greek for “inhabit”; cerulea, Latin for “sky blue”

In the Nature Park:
Neotropical migrant, arrives in early May.  Difficult to see because they usually stay high in the canopy.  There is an established breeding population in one forested site ("Quarry South") at the Nature Park (see table below).

Other Notes:
Cerulean Warblers are uncommon over most of their range, and their populations have declined significantly over the last few decades due to habitat loss on their breeding and wintering grounds.  The Cerulean Warbler is listed as a species of special concern in Indiana.

Cerulean Warbler nests are almost impossible to find or monitor, given that they are usually placed high above the ground in the tops of the trees, but we could learn more about their population structure and dynamics within this habitat. For example, we assume that singing males are indicative of the presence of nesting females, but this is an untested assumption. We can look for females early during the nesting season, when they first arrive from migration and begin pairing with males. This type of monitoring is logistically feasible but would require focused effort during the breeding season.

Cerulean Warbler territories tend to be clustered or grouped together in suitable habitat, but reasons for this clustering are unknown. Thus it is not surprising that Cerulean Warblers occur in only one location at the Nature Park. What is surprising, however, is that Cerulean Warblers occur in the park, given their rarity and the fragmentary nature of the forest. Cerulean Warblers tend to occur only in large tracts of unfragmented forest, although they have been observed in other small forested tracts in other regions of North America. The presence of Cerulean Warblers in the forest at the Nature Park appears to be unrelated to differences in vegetation composition or cover but attests to the importance of maintaining the forest within its existing condition to provide habitat for this rare bird. In addition, this isolated population at the nature park is deserving of more research attention. We recommend that the forest habitat at the Nature Park where Cerulean Warblers occur should be protected indefinitely.

Cerulean Warbler population levels at the Nature Park, measured as number of bird pairs per 10 hectares
Location 2004 2005
Arboretum 0 0
Quarry Hillside 0 0
Quarry South 3.7 5.6

 

 

 

 

 

 

 

 

 

More information about the Cerulean Warbler, from the USGS Patuxent Wildlife Research Lab

Identification and life history characteristics of the Cerulean Warbler
Distribution map of the Cerulean Warbler
Map illustrating population declines of the Cerulean Warbler in North America

References

Hamel, P. B. 2000. Cerulean Warbler. In The Birds of North American, No. 511. A. Poole and F. Gill, editors. The Birds of North America, Inc., Philadelphia, PA