Pigeon homing: Early experience determines what factors are used for navigation

et al. 2008

SUMMARYAnatomical evidence and conditioning experiments have recently suggested that magnetoreceptors are located in the upper beak of homing pigeons, where they are innervated by the ophthalmic branch of the trigeminal nerve. These findings have raised the issue of whether the trigeminally mediated magnetoreception is involved in the navigational mechanisms of homing pigeons. Recent data have shown that, in inexperienced pigeons, section of the ophthalmic branch of the trigeminal nerve does not impair navigational abilities, whereas the navigational performance of inexperienced pigeons is disrupted after section of the olfactory nerve. Nevertheless, the issue of whether the stimuli available during development of the navigational mechanism can influence the types of cues used in determining the direction of displacement remains unresolved. To address this issue, we surgically deprived young pigeons of either olfactory or trigeminally mediated magnetic information, and then later tested their navigational abilities subsequent to an intensive training flight program of up to 10 km in different directions. The birds deprived of trigeminally mediated magnetic information when young developed navigational abilities at the same level as intact control pigeons, whereas the olfactory deprived pigeons displayed randomly scattered initial orientation and poor homing performance. Our data show that olfactory cues are needed for the development of navigational abilities from unfamiliar locations and that the lack of magnetic information does not affect the development of homing abilities.

Section: Training Proceduressupporting

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Navigational abilities of homing pigeons deprived of olfactory or trigeminally mediated magnetic information when young

et al. 2008

“…But even if true, such geographical or environmental differences should not be regarded as some form of confounding variable; rather, the task is to determine which particular cues, or combination of cues, are operative in each particular location, as well as to determine the mechanisms that mediate perception of those cues. Some authors have proposed that when environmental conditions provide insufficient olfactory cues, pigeons develop the ability to rely on magnetic cues for navigation (Wiltschko et al, 1987;Walcott, 2005), but this still remains to be fully demonstrated. In fact, Benvenuti et al (Benvenuti et al, 1990) were not able to confirm the results reported by Wiltschko et al (Wiltschko et al, 1987) and a large body of evidence has shown that the lack of exposure of young pigeons to the winds carrying olfactory information impairs the development of navigational abilities (Wallraff, 1966;Gagliardo et al, 2001;Odetti et al, 2003).…”

Section: Resultsmentioning

confidence: 99%

Having the nerve to home: trigeminal magnetoreceptor versusolfactory mediation of homing in pigeons

et al. 2006

SUMMARY The ability of pigeons to find their way home from unfamiliar sites located up to hundreds of kilometers away is well known, but the mechanisms underlying this ability remain controversial. One proposed mechanism is based on the suggestion that pigeons are equipped with magnetoreceptors that can enable the detection of either the earth's magnetic field and/or magnetic field anomalies in the local terrain over which the pigeons fly. Recent reports have suggested that these magnetoreceptors are located in the upper beak where they are innervated by the ophthalmic branch of the trigeminal nerve. Moreover, this nerve has been shown to mediate pigeons' ability to discriminate the presence versus the absence of a magnetic field anomaly in a conditioning situation. In the present study, however, we show that an intact ophthalmic branch of the trigeminal nerve is neither necessary nor sufficient for good homing performance from unfamiliar locations, but that an intact olfactory nerve is necessary.

“…One such kind of study proposed the presence of magnetite particles innervated by the ophthalmic branch of the trigeminal nerve in the upper beak of the pigeons (Fleissner et al, 2003;Williams and Wild, 2001); another was a laboratory demonstration that putative upper beak magnetoreceptors are functionally involved in sensing differences in magnetic field intensity (Mora et al, 2004); and yet another found an effect of magnetic pulse treatments on the initial orientation of pigeons and migratory passerines (Beason 2005;Wiltschko et al, 2006). The characteristic of the proposed magnetic map is that it should be learned during previous homing or migratory flights by allowing the birds to experience the magnetic gradient(s) of a region (Walker, 1998;Wiltschko et al, 1987;Wiltschko et al, 2006) and the magnetic intensity values of the area flown over are thought to be sensed through a putative trigeminally mediated magnetoreceptor.…”

Section: Introductionmentioning

confidence: 99%

Navigational abilities of adult and experienced homing pigeons deprived of olfactory or trigeminally mediated magnetic information

et al. 2009

SUMMARYAnatomical evidence and conditioning experiments have suggested that magnetoreceptors innervated by the ophthalmic branch of the trigeminal nerve are located in the upper beak of homing pigeons. Following these findings it has been proposed that the trigeminally-mediated magnetorececeptors are able to detect magnetic field intensity, which might be useful for a position finding mechanism for pigeons homing from unfamiliar locations. Recent data have shown that, in inexperienced pigeons, section of the ophthalmic branch of the trigeminal nerve does not impair navigational abilities. Similarly, no impairment was observed if the trigeminal section was performed on young pigeons, before they have had the opportunity to learn a navigational map. By contrast, section of the olfactory nerve either in adult inexperienced pigeons or in young birds before map learning, disrupted their homing performance. Nevertheless, because a magnetic map mechanism requires training flights for learning the magnetic gradient of the territory around the loft, the question remains as to whether the navigational performance of adult experienced pigeons can be affected by lack of magnetic information. To answer this question we extensively group-trained adult pigeons and then surgically deprived them of either olfactory or trigeminally mediated magnetic information, prior to testing their navigational abilities. The birds deprived of trigeminally mediated magnetic information displayed similar navigational abilities as intact control pigeons, whereas the olfactory-deprived pigeons were dramatically impaired in homing. Our data show that even in trained adult pigeons, olfactory cues are needed for homing from unfamiliar locations and that the lack of magnetic information does not affect navigational abilities of experienced adult homing pigeons.