Specific targeting of host individuals by a kleptoparasitic bird |
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Authors: | A R Ridley M F Child |
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Institution: | (1) Percy Fitzpatrick Institute, DST/NRF Centre of Excellence, University of Cape Town, Rondebosch, 7701, South Africa |
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Abstract: | Kleptoparasitism is a tactic used to acquire food opportunistically and has been shown to provide several benefits, including
greater food intake rate and the acquisition of items not normally available during self-foraging. Host individuals may differ
in their ability to defend themselves against kleptoparasitic attacks and therefore identifying those host individuals that
are particularly vulnerable to attack could both provide energetic benefits and increase the efficiency of kleptoparasitism
as a foraging strategy. Here, we show that the kleptoparasitic fork-tailed drongo (Dicrurus adsimilis) specifically targets juveniles when following groups of cooperatively breeding pied babblers (Turdoides bicolor). Drongos give alarm calls upon sighting a predator, thus providing extra predator vigilance to foraging pied babblers. However,
drongos also use alarm calls to steal food items. During kleptoparasitic attacks, drongos give false alarm calls and then
swoop down to steal food items dropped by alarmed babblers. Juvenile pied babblers are particularly vulnerable to attack because
they (a) spend a longer period handling prey items prior to consumption and (b) respond to alarm calls primarily by immediately
moving to cover, in contrast to adults who respond by looking up and visually scanning the surrounding area. Drongos attack
juvenile babblers significantly more often than adults, with attacks on juveniles more likely to result in the successful
procurement of a food item. This patterns of attack suggests that drongos are able to differentiate between individuals of
different age when targeting pied babblers, thus increasing the efficiency of kleptoparasitism as a foraging strategy. |
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Keywords: | Kleptoparasitism Fork-tailed drongo Pied babbler Targeting behaviour Alarm call response |
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