Nesting Ecology of Black-Chinned Hummingbirds in an Urban Environment

There are more than 300 species of hummingbirds that reside in the Western Hemisphere. Their habitats are incredibly diverse, ranging from rainforests and deserts to swamps and snowlines of high elevation mountain ranges such as the Andes.  The Trans-Pecos region of west Texas is a hummingbird hotspot. Through a statewide project conducted by Texas Parks and Wildlife with the help of citizen scientists, biologists have been able to identify 19 species of hummingbirds across the state, 8 of which breed in the Trans-Pecos. Though these hummingbirds are known in the region, very little about their ecology has been studied.

We examined the nesting ecology of black-chinned hummingbirds at the courtyard of Sul Ross State University in Alpine, Texas. Observations included identifying and monitoring site selection characteristics, nesting architecture, and nesting chronology. We also estimated nesting success and determined mortality factors in nesting black-chinned hummingbirds.

Seven of the 20 nests found were placed in deodar trees and the average nest height was 3.5 meters.  It appeared that the hummingbirds placed nests based on windbreaks of buildings, surrounding canopies, and thick overhanging leaves and limbs for protection. The majority of nests seemed to be mostly shaded throughout the day and had dappled sunlight throughout parts of the day.  Only two nests were placed in the outer canopy of trees that hung directly over sidewalks and were highly exposed to weather conditions, human traffic, and possible predation.  Both of these nests were unsuccessful due to what appeared to be predation. The mortality rate for individual eggs laid was 44%. Breaking down the 44% by cause, the factors leading to mortalities were weather (6%), non-viable eggs (9%), predation (23%), and unknown (6%). Of 17 active nests that were monitored, 11 nests were successful.

It appears that the courtyard area of Sul Ross State University is an attractive nesting site for black-chinned hummingbirds. We speculate that the nests at Sul Ross were successful due to a controlled environment. In a campus setting, there may be fewer predators and more food sources from native landscape plants around campus, as well as a continuous supply of water in the mall fountain that may create more favorable conditions than remote locations.

nest

Hummingbirds nesting on the Sul Ross State University campus showed a preference for locating their nests in deodar trees.

 

map

Location (gray circle) of black-chinned hummingbird nests found during nesting season. Nests are numbered based on the order in which they were found. The darkened nests represent mortalities of the eggs or the nestlings.