Scare Tactics in a Neotropical Warbler: White Tail Feathers Enhance Flush–Pursuit Foraging Performance in the Slate-Throated Redstart (Myioborus Miniatus)

Abstract

AbstractFlush–pursuit foragers use exaggerated and animated foraging movements to flush potential prey that are then pursued and captured in flight. The Myioborus redstarts comprise 12 species of flush–pursuit warblers found in montane forests of the American tropics and subtropics. All members of the genus have contrasting black-and-white tail feathers that are exposed by spreading the tail during animated foraging displays. Plumage pattern and tail-spreading behavior were examined to see how they affected flush–pursuit foraging performance of the Slate-throated Redstart (Myioborus miniatus) in Monteverde, Costa Rica. Although flycatching was the most common foraging tactic used by Slate-throated Redstarts, flush–pursuit foraging increased in both frequency and intensity when birds were feeding nestlings. Flush–pursuit prey attacks occurred more frequently following hops in the spread-tail foraging posture than hops in more typical warbler-like posture, suggesting that tail-spreading behavior assists in startling and flushing potential prey. The hypothesis that the white tail feathers enhance flush–pursuit foraging was tested by means of a plumage-dyeing experiment. After locating nests containing young 5–7 days old, I captured the male and female at the nest and assigned one member of each pair to the experimental treatment group; its mate served as a control. For experimental birds, a permanent marker was used to blacken the white tips of the three outer retrices. For sham-darkened controls, the naturally black tips of the three inner retrices were also “blackened”. Experimental birds with darkened tail feathers were significantly less successful in flush–pursuit foraging, showed a significantly lower overall rate of prey attack, and fed their nestlings at a significantly lower rate than did their sham-darkened mates. For experimental birds, only 7.6% of hops in the spread-tail posture were followed by an attack on a prey item, compared to 20.9% of hops for controls. These experimental results, similar to those obtained recently by Jabłoński (1999) for the congeneric Painted Redstart (Myioborus pictus), indicate that white tail feathers are critically important in startling potential prey and raise questions about interspecific and intraspecific geographic variation in plumage pattern in the genus.