Ornithologist Nicholas E. Collias spent his career studying the nests of passerines, or song birds. Collias defined a nest as "an external construction that aids in the survival and development of the eggs and young." While nest terminology is not used consistently among ornithologists, in a 1997 paper, Collias defined three types: hole nests in the ground or a tree, open-above nests and dome nests. Open-above and dome nests can hang from small branches.
Pensile and Pendulous
The words "pensile" and "pendulous" both come from Latin. Pensile derives from "pensilis" and means hanging. Pendulous, from "pendulus," means hanging loosely or swinging. The Cornell Lab of Ornithology defines pensile and pendulous nests as "a cup nest whose rim is supported but whose unsupported belly -- the nest chamber -- hangs below" the branches. A pendulous nest hangs lower than a pensile nest. The terms pensile and pendulous can describe both open-above and dome nests.
Open Pensile Builders
Birds sit on an open pensile nest, the depth of which -- by definition -- is less than four inches. Cornell University researchers note: "deep pensile nests grade into pendulous cup nests," so the two descriptors -- pensile and pendulous -- often overlap. Open pensile nests can be found around the world. According to Cornell ornithologists, New World blackbirds, vireos and kinglets build pensile cup nests. The red-eyed vireo, for example, builds an open pensile nest.
Open Pendulous Builders
The Baltimore oriole (Icterus galbula) builds a pendulous nest, often seen in the Midwest and eastern United States. The nest hangs between two branches and looks like a small sack; it opens at the top. Pendulous nest builders weave with plant strips and fibers. Orioles often use horse hair and plastic fibers from feed bags as nesting material. Oropendolas and caciques, as well as some Old World weaver birds, create these types of nests.
Dome nests have a roof and birds access the chamber through a side opening. These nests can be either pensile or pendulous. Some pendulous dome nests can measure in excess of one yard. Many weaver birds are well-known creators of pendulous dome nests.The bushtit (Psaltriparus minimus) found in the western United States, the grey penduline tit of Africa and the caciques of Central and South America build the same type of nests.
- A Guide to the Nests, Eggs, and Nestlings of North American Birds; Paul J. Baicich & J. O. Harrison
- Harvard University Press: Egg and Nest Slide Show
- Nest Building and Bird Behavior; Nicholas E. Collias and Elsie C. Collias