Birds can smell
Despite the fact that songbirds have for a long time been thought to be anosmic, i.e. unable to perceive smells, more and more evidence accumulates that songbirds do not only have a sense of smell and use extrinsic odour cues for orientation, foraging and nest construction, but also make use of intrinsic cues for social communication.
Zebra finches are able to perceive and react to olfactory cues. Adult females prefer the odour of their own nest during the nestling phase of their chicks but do not show a preference once their juveniles have fledged. Zebra finch fledglings are able to distinguish their own nest from a foreign nest using olfactory cues alone and are also able to recognise the nest of their genetic origin.
- Zebra Finch chicks can recognise their parents by smell. This is the outcome of our latest study on the function of body odours in Zebra Finches. We presented one day old chicks the odour of the parents and the odour of unfamiliar adults and measured the duration of their begging response. Chicks begged significantly longer in response to the odour of their mother and to the odour of their father than to the odour of an unfamiliar adult. In a second experiment we fostered single eggs into other nests and presented chicks from fostered eggs the odour of their foster parents (either mother or father) and the odour of their genetic parents (either mother or father). Chicks did not show any difference in begging behaviour in repsonse to the male odours, but showed a clear preference for the scent of their biological mother. This is very interesting as the chicks have never seen their mother before. Thus maternal kin cues can be learned in the absence of direct association.
- In a recent study we have tested whether blue tit nestlings can discriminate between the odours of conspecifics and nestmates. We found that nestlings beg longer as a repsonse to the odour originating from unfamiliar and unrelated conspecifics from a different nest (Rossi et al. 2017).
- Olfactory kin recognition in Zebra Finches
Furthermore the ability to perceive the odour from kin has an dramatic impact on reproduction in zebra finch females. In the presence of a brother, females being able to smell lay fewer eggs and raise fewer chicks compared to females in the same situation that were not able to smell (Caspers, Gagliardo, Krause 2015)
In addition, we recently elucidated the mechanism by which such olfactory kin recognition can come about. Fledglings which had been cross-fostered shortly after hatching preferred the nest of their genetic family, despite not having encountered it for three weeks. In contrast, individuals that had been cross-fostered as eggs preferred the nest odour of their host nest, indicating that information about the natal nest, and probably kin, is learned early in life, i.e. familial imprinting (Caspers et al. 2013).
- Female zebra finches can smell their eggs
At the end of the incubation period female zebra finches are able to smell their eggs Golueke et al 2016. In a binary choice experiment, we gave female zebra finches the choice between the scent of their own and a conspecific egg. After the onset of incubation, females chose randomly and showed no sign of discrimination. However, shortly before hatching, females spent significantly more time in the vicinity of the odour of their own egg. We are currently running more experiments to investigate whether olfactory egg recognition may be used to recognize infraspecific brood parasitism and to understand where the differences in egg odours come from.
- A method to test odour recognition in hatchlings
In a recent study we developed a method to test odour recognition in one day old zebra finch hatchlings (Caspers et al. 2015). Zebra finch hatchlings begged significantly longer in repsonse to a familiar odour compared to an unfamiliar odour. This way our simple testing procedure allows to test odour recognition or odour preferences in altricial songbirds at a very early developmental stage.
Media Coverage (selected)
Cage & Aviary Birds 2017
our project is part of this wonderful graphik novel pp10-11.
Bild der Wissenschaft 10. 2013, “Immer der Nase nach” p. 13
National Wildlife Magazin, 29.7.2013 “By a Nose: Birds’ Surprising Sense of Smell”
New York Times, 10.Jan 2012 “In a Surprise, a Songbird Displays a Sense of Smell”
WDR Wissen, 30.Sept 2010 “Singvögel können riechen”
Caspers BA, Hagelin JC, Paul M, Bock S, Willeke S, Krause ET (2017): Zebra Finch chicks recognise parental scent, and retain chemosensory knowledge of their genetic mother, even after egg cross-fostering. Scientific reports, 7(1), 12859. link
Rossi M, Marfull R, Golüke S, Komdeur J, Korsten P, Caspers BA (in press): Begging blue tit nestlings discriminate between the odour of familiar and unfamiliar conspecifics. Functional Ecology
Golüke S, Dörrenberg S, Krause ET, Caspers BA (2016) female zebra finches smell their eggs. PLOS ONE
Kohlwey S, Krause ET, Baier MC, Müller C, Caspers BA (2016) Chemical Analyses Reveal Family Specific Nest Odor Profiles in Zebra Finches (Taeniopygia guttata): A Pilot Study. In: Chemical Signals in Vertebrates 13
Krause ET, Kabbert J, Caspers BA (2016) Exploring the use of olfactory cues in non-social context in zebra finches (Taeniopygia guttata). In: Chemical Signals in Vertebrates 13
Caspers BA, Gagliardo A, Krause ET (2015) Impact of kin odour on reproduction in zebra finches. Behavioral Ecology and Sociobiology 69:1827-1833, DOI 10.1007/s00265-015-1995-9
Caspers BA, Hagelin J, Bock S, Krause ET (2015) An easy method to test odour recognition in songbird hatchlings. Ethology
Krause ET, Brummel C, Kohlwey S, Baier MC, Müller C, Bonadonna F, Caspers BA (2014) Differences in olfactory species recognition in the females of two Australian songbird species. Behavioral Ecology and Sociobiology 68:1819-1827
Caspers BA, Hoffmann JI, Kohlmeier P, Krüger O & Krause ET (2013) Olfactory imprinting as a mechanism for nest recognition in zebra finches. Animal Behaviour 86: 85-90
Caspers, BA. & Krause, E.T. (2013): Intraspecific olfactory communication in Zebra Finches (Taeniopygia guttata) – Potential information apart from visual and acoustic cues. In Chemical Signals of Vertebrates XII. (Marioan East & Martin Dehnhard eds.). Springer Verlag, Berlin, Germany
Krause, E.T., Caspers, BA (2012): Are olfactory cues involved in nest recognition in two species of social estrildid finches? PloS One 7(5): e36615 doi:10.1371/journal.pone.0036615
Krause, ET, Krüger O, Kohlmeier, P, & Caspers, BA (2012): Olfactory kin recognition in a songbird. Biology letters 8: 327-329 doi:10.1098/rsbl.2011.1093
Top ten cited article 2012 of Biol Lett
Caspers, BA & Krause ET (2011): “Odour-based natal nest recognition in the zebra finch (Taeniopygia guttata), a colony-breeding songbird”. Biology letters 7:184-186
Top ten cited article 2011 of Biol Lett & evaluated by F1000