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Electric fields in terrestrial environments are used by caterpillars to detect their predators, as foraging cues by pollinators, and facilitate ballooning by spiders. This study shows that electric fields facilitate transportation and detection of hummingbirds in a guild of tropical phoretic mites. Hummingbird flower mites feed on nectar and pollen and complete their life cycle inside flowers. Mites colonize new flowers by hitching rides on hummingbird beaks. Flower mites emerge from hummingbird nostrils and disembark when the beak touches a flower. We tested whether flower mites are attracted to unmodulated electrostatic, or to modulated electric fields with amplitudes and frequencies in the range of those previously reported for hummingbirds. In a laboratory setup, mites were only attracted to modulated electric fields. In a choice experiment between positive or negative polarities, mites almost instantaneously chose positive charges, but only when the field was modulated. Mites display questing behavior, moving their front legs toward an electrostatic source. In experiments where we removed one or both front leg tarsi, we show that modulated fields are detected by sensory structures present in the front legs. We also show that flower mites use electrostatic attraction to bridge the gap to the beaks of hummingbirds, for a few milliseconds becoming one of the fastest terrestrial organisms. Our results confirm that hummingbird flower mites evolved an additional sensory modality — electroreception — to quickly detect hummingbirds and use electrostatics to facilitate transportation onto their hosts.
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Pairing automated mark–recapture and social network models to explore the effects of landscape configuration on hummingbird foraging patterns
Landscape changes can alter pollinator movement and foraging patterns which can in turn influence the demographic processes of plant populations. We leveraged social network models and four fixed arrays of five hummingbird feeders equipped with radio frequency identification (RFID) data loggers to study rufous hummingbird ( Selasphorus rufus ) foraging patterns in a heterogeneous landscape. Using a space-for-time approach, we asked whether forest encroachment on alpine meadows could restrict hummingbird foraging movements and impede resource discovery. We fit social network models to data on 2221 movements between feeders made by 29 hummingbirds. Movements were made primarily by females, likely due to male territoriality and early migration dates. Distance was the driving factor in determining the rate of movements among feeders. The posterior mean effects of forest landscape variables (local canopy cover and intervening forest cover) were negative, but with considerable uncertainty. Finally, we found strong reciprocity in hummingbird movements, indicative of frequent out and back movements between resources. Together, these findings suggest that reciprocal movements by female hummingbirds could help maintain bidirectional gene flow among nearby subpopulations of ornithophilous plants; however, if the distance among meadows increases with further forest encroachment, this may limit foraging among progressively isolated meadows.
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- Award ID(s):
- 2025755
- PAR ID:
- 10299671
- Date Published:
- Journal Name:
- Biology Letters
- Volume:
- 17
- Issue:
- 8
- ISSN:
- 1744-957X
- Page Range / eLocation ID:
- 20210188
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1098/rsbl.2021.0188
