The first study showing that birds can smell herbivore-induced plant volatiles was published ten years ago. Since then, only 12 studies have been published, showing contradictory results. This review evaluates the role of birds in relation to the crying for help hypothesis and their use of olfactory cues. In accordance with the methodologies used in previous studies, we herein provide a summary of experimental approaches and describe the advantages and disadvantages of experiments conducted in nature versus aviaries. Moreover, we recommend experimental methodologies which lead to a deeper knowledge of the topic, including reflection on the induction of plant defenses and adaptations of birds. Finally, we propose some interesting questions for future research to direct further studies towards a thorough and accurate description of birds' roles in tritrophic interactions.

Biology Centre of the Czech Academy of Sciences Institute of Entomology Branisovska 1160 31 37005 Ceske Budejovice Czech Republic; Faculty of Science University of South Bohemia Branisovska 1760 37005 Ceske Budejovice Czech Republic

Department of Evolutionary Ecology Museo Nacional de Ciencias Naturales C José Gutiérrez Abascal 2 28006 Madrid Spain

References provided by Crossref.org

Exogenous Application of Methyl Jasmonate Increases Emissions of Volatile Organic Compounds in Pyrenean Oak Trees, Quercus pyrenaica

Great tits (Parus major) flexibly learn that herbivore-induced plant volatiles indicate prey location: An experimental evidence with two tree species

Insectivorous birds can see and smell systemically herbivore-induced pines