Hummingbirds use taste and touch to discriminate against nectar
resources that contain Argentine ants
David T. Rankin
Christopher J. Clark
Erin E. Wilson Rankin
Received: 4 October 2017 /Revised: 25 January 2018 /Accepted: 1 February 2018 /Published online: 24 February 2018
Springer-Verlag GmbH Germany, part of Springer Nature 2018
Hummingbirds compete with other floral visitors for access to floral resources (nectar). Several hummingbird species,
including Anna’s(Calypte anna), Black-chinned (Archilochus alexandri), Allen’s(Selasphorus sasin), and Costa’s
(Calypte costae) hummingbirds, make extensive use of non-native plants of urban areas of Southern California.
Exploitation of urban ornamentals may expose hummingbirds to increased interactions with invasive Argentine ants
(Linepithema humile), which are also frequently found foraging on flowers in such habitats. Here, we investigated the
mechanisms by which hummingbirds interact with invasive ants at nectar resources in a series of aviary and wild exper-
iments. When given a choice, hummingbirds avoided flowers and feeders with ants in or feeding at a sucrose solution. We
identified specific ant-derived cues (visual, tactile, and gustatory) which are sufficient to elicit changes in bird foraging.
Tactile and gustatory cues appeared to play the strongest role in mediating interactions with Argentine ants, with visual
cues alone not enough to deter hummingbirds from feeding at sugar resources with ants. Our experiments provide support
for interference competition at floral resources, where ants limit the birds’ access to flowers and feeders.
Hummingbirds and invasive Argentine ants both visit and exploit floral resources. However, hummingbirds avoid nectar
sources that are occupied by ants. Here, we detail a series of mechanistic experiments to determine the proximate cause
of this avoidance behavior. We found that the touch and taste of ants is strongly aversive to both wild, free-foraging and
aviary hummingbirds. In urban environments and under low water situations, Argentine ants and hummingbirds come
into frequent competition for the same few flowers. This competition leads to changes in foraging behavior and may
have negative effects on hummingbirds.
Keywords Invasive species
Hummingbirds compete intensely for access to flower nec-
tar, both intraspecifically and interspecifically (Stiles and
Wolf 1970; Slauson 2000). Competition for floral re-
sources can be both interference and exploitative (Gill
et al. 1982) and influences territoriality (Thomas et al.
1986), foraging strategy (Carpenter 1979;Gill1988), and
fitness (Temeles and Kress 2010). While the effects of
intra-guild competition among hummingbirds has been rel-
atively well-studied (Stiles and Wolf 1970;Ewaldand
Carpenter 1978; Feinsinger and Colwell 1978), how the
foraging strategies and their pollination services of hum-
mingbird shift in response to non-pollinator floral visitors,
Communicated by D. Rubenstein
Electronic supplementary material The online version of this article
(https://doi.org/10.1007/s00265-018-2456-z) contains supplementary
material, which is available to authorized users.
* David T. Rankin
Department of Evolution, Ecology and Organismal Biology,
University of California, Riverside, CA, USA
Department of Entomology, University of California, Riverside, CA,
Behavioral Ecology and Sociobiology (2018) 72: 44