GA.MAY@forsythe.stanford.edu (mitchell) (05/23/91)
This question came to mind as I was eating breakfast this morning by a patch of grass on campus (UC Berkeley). How do robins hunt? While I was eating breakfast, a pair of red robins was also doing the same. One would take a few steps, stop, and very delibrately stop all motion, with its head erect. If there was no apparent cue or trigger, the robin would jog away to another location a few feet away, again stop, and freeze. If there was a cue, the robin would tilt its head towards the ground, favoring one side of its head or the other. It was not clear to me whether the robin was depending on auditory cues or visual. Once the robin got to the stage of tilting its head towards the ground, it usually got some unlucky bug. It was not clear to me that the robins were favoring visual or auditory cues. I also have a few budgie prisoners. Budgies when they're curious about something will tilt their heads and clearly favor one eye at whatever caught their attention. If they are listening in, it seems that they will stay very still. Maybe a robin uses both. I dunno. thanks, Mitchell ps: if you think they answer might bore other rec.birders, email to ga.may@forsythe.stanford.edu
rsl@cbnewsm.att.com (randolph.little) (05/24/91)
In article <1991May23.165528.3869@morrow.stanford.edu>, GA.MAY@forsythe.stanford.edu (mitchell) writes: > This question came to mind as I was eating breakfast this morning > by a patch of grass on campus (UC Berkeley). How do robins hunt? > > While I was eating breakfast, a pair of red robins was also doing > the same. One would take a few steps, stop, and very delibrately > stop all motion, with its head erect. If there was no apparent > cue or trigger, the robin would jog away to another location > a few feet away, again stop, and freeze. If there was a cue, > the robin would tilt its head towards the ground, favoring > one side of its head or the other. It was not clear to me > whether the robin was depending on auditory cues or visual. > ... Birds such as the American Robin use monocular vision for close-up inspection. Although auditory input may aid detection of prey, monocular vision would be used to pinpoint the target. The deliberate stopping of the head while searching for prey is also a sign of visual sensing, but in the two-eyed (separate views, not binocular) mode. Any animate objects are much more readily detected when there is no relative motion between the bird's eyes and the scene being viewed. Some species, such as the Barn Owl, do have a well-developed sense of binaural hearing which is used for prey location; but most diurnal species rely almost totally on vision. Randolph S. Little <rsl@bonasa.att.com>