Do Insectivorous Birds use Volatile Organic Compounds from Plants as Olfactory Foraging Cues? Three Experimental Tests

Abstract

Some insectivorous birds orient towards insect‐defoliated trees even when they do not see the foliar damage or the herbivores. There are, however, only a few studies that have examined the mechanisms behind this foraging behaviour. Previous studies suggest that birds can use olfactory foraging cues (e.g. volatile organic compounds (VOCs) emitted by defoliated plants), indirect visual cues or a combination of the two sensory cues. VOCs from insect‐defoliated plants are known to attract natural enemies of herbivores, and researchers have hypothesized that VOCs could also act as olfactory foraging cues for birds. We conducted three experiments across a range of spatial scales to test this hypothesis. In each experiment, birds were presented with olfactory cues and their behavioural responses or foraging outcomes were observed. In the first experiment, two different VOC blends, designed to simulate the volatile emissions of mountain birch (Betula pubescens ssp. czerepanovii) after defoliation by autumnal moth (Epirrita autumnata) larvae, were used in behavioural experiments in aviaries with pied flycatchers (Ficedula hypoleuca). The second experiment was a field‐based trial of bird foraging efficiency; the same VOC blends were applied to mountain birches, silver birches (B. pendula) and European white birches (B. pubescens) with plasticine larvae attached to the trees to serve as artificial prey for birds and provide a means to monitor predation rate. In the third experiment, the attractiveness of silver birch saplings defoliated by autumnal moth larvae versus intact controls was tested with great tits (Parus major) and blue tits (Cyanistes caeruleus) in an aviary. Birds did not orient towards either artificial or real trees with VOC supplements or towards herbivore‐damaged saplings when these saplings and undamaged alternatives were hidden from view. These findings do not support the hypothesis that olfactory foraging cues are necessary in the attraction of birds to herbivore‐damaged trees.

Predatory lizards perceive plant‐derived volatile odorants

“…Error bars reflect one standard error. Both substrate-directed and the total count of chemosensory behaviors were more frequent during the hexanoic acid treatment than during other treatment conditions such as the pied flycatcher, have failed to find evidence of plant VOCs being used during foraging (Koski et al, 2015). Our results…”

“…Recent studies have shown that insectivorous birds use plant VOCs to locate herbivorous prey (Amo et al, ; Mäntylä, Kleier, Kipper, & Hilker, ) and that naïve birds lack this response (Amo, Dicke, & Visser, ). However, studies with other species of bird, such as the pied flycatcher, have failed to find evidence of plant VOCs being used during foraging (Koski et al, ). Our results show that lizards may be behaving in a similar fashion, in which some species use plant VOCs to locate prey while others do not.…”

Disentangling olfactory and visual information used by field foraging birds

“…However, most studies attempting to apply a single compound or an artificially produced blend have failed to attract birds in nature (Koski et al, 2015;Mäntylä et al, 2014), but see (Mrazova & Sam, 2017) who used methyl jasmonate: MeJA; while those using real herbivore infestations have been more successful in demonstrating an effect (Mäntylä et al, 2008(Mäntylä et al, , 2014. We used a single volatile compound, MeSA, which is known to function in plant-plant and plant-insect communication (Dicke et al, 2003;Ninkovic et al, 2003).…”

“…Thus, because these volatiles constitute a reliable signal of herbivore, and thereby predatory arthropod, presence (Kessler & Heil, 2011), it is reasonable to assume that birds could use these signals to direct their foraging behavior. However, even if birds can detect plant volatiles, it is still unclear to what extent birds use these volatiles or other olfactory cues when foraging, as the small number of field studies have produced inconsistent results (Koski et al, 2015;Mäntylä et al, 2008;Mäntylä, Blande, & Klemola, 2014;Mrazova & Sam, 2017).…”

How do predators and scavengers locate resource hotspots within a tropical forest?

“…The mechanisms used by animals to locate feeding sites also vary among species. Many taxa rely primarily on visual (Frings et al 1955;Wells & Lehner 1978), audio (Frings et al1955;Langley 1983) or olfactory (Hershey & Forester 1979;Stoddart 1980;Langley 1983;Koski et al 2015) proximate cues to locate short-term resources. Others invoke all three senses, depending on cues available from the food resource.…”