Fork-Tailed Drongos (Dicrurus adsimilis) use different types of mimicked alarm calls in response to different alarm threats
Bachelor Thesis
2014
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University of Cape Town
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Abstract
Vocal mimicry is a fascinating phenomenon in the animal kingdom, noted in scientific research as early as the 18th century. Approximately 20% of bird species use vocal mimicry, yet very little is understood regarding why species use vocal mimicry, whether it provides functional benefits and in which contexts vocal mimicry is produced. I propose that some of these species produce alarm mimicry in the appropriate alarm contexts, matching the context of call production by the model species whose calls are mimicked. Previous research suggests that alarm mimicry in the appropriate context could provide heterospecifics with information regarding predators that are in the area. Aerial alarm call mimicry could indicate that an aerial predator is present and may cause individuals to flee, while terrestrial mob call mimicry could indicate the presence of a terrestrial predator and could prompt heterospecifics to aid in the mobbing of the predator. I investigate this possibility in the Fork-Tailed Drongo (Dicrurus adsimilis), a species renowned for its use of mimicry of other species alarm calls. Natural alarm responses to predators show that drongos produce alarm mimicry in alarms and never in non-alarm contexts. Overall drongos were more likely to mimic alarms in response to terrestrial predators. I then explored whether drongos use mimicked aerial and terrestrial ‘mobbing’ alarm calls in appropriate aerial or terrestrial predator alarm contexts using recordings of responses by drongos both to natural predators, and to experimental presentations of aerial and terrestrial predator and control models . Drongos were more likely to mimic aerial than ‘mob’ terrestrial alarm calls in response to natural and experimentally presented aerial predators. Conversely, they were more likely to mimic ‘mob’ terrestrial than aerial alarm calls in response to natural and experimentally presented terrestrial predators. Comparison of aerial and mob alarm call mimicry with the drongos production of their own equivalent aerial and terrestrial ‘drongo-specific’ alarm calls, revealed that mimicked and drongo-specific alarm calls were produced in similar contexts. These results support research showing that some bird species produce context-dependent alarm mimicry and the implications for the possible function of alarm call mimicry are discussed.
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Reference:
Adams, I. 2014. Fork-Tailed Drongos (Dicrurus adsimilis) use different types of mimicked alarm calls in response to different alarm threats. University of Cape Town.