Ground nesting by arboreal American robins (Turdus migratorius)

Area of Science:

• Ornithology
• Behavioral Ecology
• Animal Behavior

Background:

• Nest site selection is crucial for offspring survival, influencing exposure to environmental factors, predation, and competition.
• Bird species are often categorized by typical nesting locations, such as ground or arboreal sites.
• American robins (Turdus migratorius) typically nest in trees or on human-made structures.

Purpose of the Study:

• To document and investigate the phenomenon of American robins nesting on the ground.
• To explore potential reasons behind this atypical nesting behavior in a specific environment.

Main Methods:

• Field observation of American robin nests over three breeding seasons (2018-2020).
• Nest site locations were recorded at a commercial tree farm in Illinois, USA.
• Nest survival rates and timing of nesting were analyzed in relation to environmental conditions.

Main Results:

• Twenty-four American robin nests were found on the ground, deviating from typical arboreal nesting sites.
• This ground-nesting behavior was observed exclusively in the first half of the breeding season.
• The study found no evidence that this behavior was a response to competition or that it affected daily nest survival rates.

Conclusions:

• Ground nesting in American robins during the early breeding season might be an adaptive strategy to mitigate cold temperatures or avoid exposure.
• Alternatively, this behavior could represent a previously undocumented flexibility in robin nest-placement strategies.
• Further research is needed to fully understand the drivers and consequences of this atypical nesting behavior.