The head movement of a walking pigeon Columba livia is characterized by two alternating phases, a thrust phase and a hold phase. While the head is rapidly thrust forward during the thrust phase, it has been shown repeatedly that it remains virtually motionless with respect to translation along a horizontal axis (roll axis) during the hold phase. It has been shown that the stabilization during the hold phase is under visual control. This has led to the view that the pigeon's head-bobbing is an optokinetic response to stabilize the retinal image during the hold phase. However, it has never been shown explicitly that the head is really held stable in space with respect to other translatory or rotatory dimensions. Using videography, we show here that this is in fact the case: except for a small but systematic slip that presumably serves as an error signal for retinal image stabilization, the head of the pigeon remains locked in space not only with respect to the horizontal (roll) axis but also with respect to vertical translation (along the yaw axis) and with respect to rotation around the pitch and yaw axes.

Daanje
A.
(
1951
).
On locomotory movements in birds and the intention movements derived from them
.
Behaviour
3
,
48
–.
Davies
M. N. O.
,
Green
P. R.
(
1988
).
Head-bobbing during walking, running and flying: relative motion perception in the pigeon
.
J. Exp. Biol
138
,
71
–.
Dunlap
K.
,
Mowrer
O. H.
(
1930
).
Head movements and eye functions of birds
.
J. Comp. Psychol
11
,
99
–.
Friedman
M. B.
(
1975
).
Visual control of head movements during avian locomotion
.
Nature
255
,
67
–.
Frost
B. J.
(
1978
).
The optokinetic basis of head-bobbing in the pigeon
.
J. Exp. Biol
74
,
187
–.
Galubitski
M.
,
Stewart
I.
,
Buono
P.-L.
,
Collins
J. J.
(
1999
).
Symmetry in locomotor central pattern generators and animal gaits
.
Nature
401
,
693
–.
Goodale
M. A.
(
1983
).
Visually guided pecking in the pigeon (Columba livia)
.
Brain Behav. Evol
22
,
22
–.
Green
P. R.
,
Davies
M. N. O.
,
Thorpe
P. H.
(
1994
).
Head-940bobbing and head orientation during landing flights of pigeons
.
J. Comp. Physiol
174
,
249
–.
Lemeignan
M.
,
Sansonetti
A.
,
Gioanni
H.
(
1992
).
Spontanous saccades under different visual conditions in the pigion
.
NeuroReport
3
,
17
–.
Morgan
B.
,
Frost
B. J.
(
1981
).
Visual response characteristics of neurons in nucleus of basal optic root in pigeons
.
Exp. Brain Res
42
,
181
–.
Ostheim
J.
(
1997
).
Visual sensation during pecking in pigeons
.
Eur. J. Morph
35
,
269
–.
Pratt
D. W.
(
1982
).
Saccadic eye movements are coordinated with head movements in walking chickens
.
J. Exp. Biol
97
,
217
–.
Simpson
J. I.
(
1984
).
The accessory optic system
.
Annu. Rev. Neurosci
7
,
13
–.
Westheimer
G.
,
Blair
S. M.
(
1974
).
Unit activity in the accessory optic system in alert monkeys
.
Invest. Ophthalmol
13
,
533
–.
Wylie
D. R.
,
Frost
B. J.
(
1990
).
Binocular neurons in the nucleus of the basal optic root (nBOR) of the pigeon are selective for either translational or rotational visual flow
.
Visual Neurosci
5
,
489
–.
Wylie
D. R.
,
Frost
B. J.
(
1990
).
Visual response properties of neurons in the nucleus of the basal optic root of the pigeon: a quantitative analysis
.
Exp. Brain Res
82
,
327
–.
This content is only available via PDF.