Kestrels

[Picidae]

Originally Posted by valleyforge

... if you have some experience with one-eyed hawks/falcons I'd be very pleased if you'd share it or point us to a reference, anecdotal or otherwise.

Experience of any surviving in the wild would be helpful. (My understanding is hawks/falcons/owls have a more developed binocular vision to assist with hunting and to magnify the target prey from a distance. For Kestrel spotting small prey from a long distance relies exactly on the specific vision provided by each eye simultaneously - impairment of this ability which relies on two 'good' eyes must surely undermine their ability to hunt in the wild for any prolonged period)

some info here:
Sense of Vision for Birds - Page 1
What is a Raptor

[Kayleigh]

Wow, this is turning out an interesting read you never think of how they cope with one eye..

I have opened a can of worms lol..

[willing to learn]

Originally Posted by valleyforge

I don't doubt that they can cope well enough in care, or where food is being provided by a falconer Colin, but I've not known any bird with unilateral loss of sight become a viable candidate for release.

My experience with casualty BOPs is admittedly restricted to just tawny owls and common buzzards, but if you have some experience with one-eyed hawks/falcons I'd be very pleased if you'd share it or point us to a reference, anecdotal or otherwise.

I would not like to say they could adapt well enough to thrive in the wild.
But there was a well known one eyed goshawk that excelled in the hunting field out performed its fully sighted counterparts on wild quarry. And have flown a one eyed falcon's with sucess. And seen quite a few one eyed performers over the years. Never seen a one eyed buzzard in action, and never come across an owl with eye damage yet thankfully.
Regards
Colin

[Jonathan]

Originally Posted by valleyforge

I don't doubt that they can cope well enough in care, or where food is being provided by a falconer Colin, but I've not known any bird with unilateral loss of sight become a viable candidate for release.

My experience with casualty BOPs is admittedly restricted to just tawny owls and common buzzards, but if you have some experience with one-eyed hawks/falcons I'd be very pleased if you'd share it or point us to a reference, anecdotal or otherwise.

I had a one-eyed female sparrowhawk for several years when I was in my early teens in the '70's. She was handed to me as an eyass, I was never quite sure how she damaged her eye. I was fortunate in that a family friend knew one of the first vets to specialise in raptors in the UK, so the spar got excellent (and cheap!) treatment. I subsequently hacked several spars in later years but was advised not to release this one as it was doubtful she would survive. I never flew her at quarry as I didn't want to risk losing her. In hindsight I think this was a wrong decision, if she'd been allowed to catch quarry she may have learned to compensate for her limited vision, with the advantage of a guaranteed meal at the end of the day whether she succeeded or not - an advantage no wild bird has. She certainly became adept at catching birds off her bow perch on the lawn (I treated her as a falconers birds rather than simply leaving her in an aviary, so she spent the night in a shed and her days on a bow perch). To be honest I used to scatter bread around her perch to entice birds in (not something I'd recommend now, but I was a kid at the time!) and she'd occasionally nail a sparrow (other species were either too wary, too fast, or both). I used to watch her through the window - she'd actually crouch down, using her perch as cover, then rocket out at incredible speed when she judged a bird was close enough - fascinating to watch.

I'd had her about four years when I needed her shed to look after someone's African hawk eagle that had bumblefoot (the bird had to be free-flying so I couldn't keep them both in the same shed!), so I passed her on to a friend who had rehabilitated many raptors (and is still one of the few people I'd trust to rehab birds of prey). Unfortunately, she'd started fitting (a common problem with spars at this time, possibly due to a lack of vitamins in day-old chicks) and died around six months later.

I'm not sure if she would have survived in the wild, but I wish I'd flown her at quarry - it might have given me more of an idea how she might have fared. She was incredibly tame, probably due to all the handling she got due to the problem with her eye. She would actually tuck her head under her wing and go to sleep on my fist on occasion, something I've never seen in a non-imprint spar.

Cheers
Jonathan

[posie]

I can't see anything wrong with her eye, to me it's just the angle.

[evilgrayson]

For one-eyed raptors, I think a lot will depend on how old the raptor was when it lost the eye.

I only recently developed binocular vision; before that, I had no depth perception. Most people never knew - while I occasionally misjudged where something was, I didn't have too much trouble because I compensated. The biggest problem for me was playing tennis and other ball games, but I was an excellent shot with rifle or bow, and good at sports such as fencing.

I judged distance by size - people-shaped targets were much easier than round ones, because I know how big people are and thus how far away they are - and at melee range I never had a problem while on the offensive. Plants, buildings and other known-size things were also easy for me, it was only objects I didn't know well that I'd undershoot or overshoot with the bow. Badminton was easier for me than tennis, and not just because the shuttle moves slower - the shuttle is an object of a known size and flight pattern, rather than something with no distinguishing features.

I can only guess that a raptor can learn to judge these things the way I did, and like every other raptor, will only waste the energy on a kill it thinks it can make. Given the reported miss rates of a two-eyed bird, if a one-eyed raptor takes fewer chances (as I did, I never crossed a road if I wasn't absolutely sure about the cars on it) and doesn't go for the targets it considers marginal, it's not wasting the same amount of energy and thus may survive because while it isn't catching as much, it hasn't worn itself out trying.

[willing to learn]

Originally Posted by evilgrayson

Given the reported miss rates of a two-eyed bird, if a one-eyed raptor takes fewer chances (as I did, I never crossed a road if I wasn't absolutely sure about the cars on it) and doesn't go for the targets it considers marginal, it's not wasting the same amount of energy and thus may survive because while it isn't catching as much, it hasn't worn itself out trying.

I think these miss rates with "experienced" raptors has been some what false. A lot depends if a raptor is prospecting for an easy meal, not really driven with urgency to feed young or hunger its self. On some of the figures quoted it would be impossible for a raptor to maintain its body condition and energy levels or blood sugars, never mind having to catch enough to keep a brooding female going with young chicks. An "experienced" raptor prospecting for a easy meal and taking a half hearted attempt, is not to be mistaken with one that needs.
Regards
Colin