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| Discussion of other Raptor species; their anatomy, biology, ecology, etc. | |
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| Tweet Topic Started: Sep 16 2007, 11:04 AM (18,111 Views) | |
| ostrich2 | Dec 26 2007, 04:08 PM Post #466 |
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Hi Patti - I also got reminded of an osprey when I looked at that photo too. The things that reminded me of an osprey are the sharp bend in the wings at the wrist and the general black and white sort of plumage. However, one reason I didn't think this could be an osprey is that ospreys are supposed to be fish eaters only, and the prey looks like some kind of shorebird or small waterfowl to me. It kind of looks a bit like a mallard duck, although I think it is not in fact a mallard and is some other species. Some other features I noticed were the odd looking grayish mottled "necklace" and the dark top of the head and neck. |
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| Patti | Dec 26 2007, 04:15 PM Post #467 |
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Yep, Ostrich, got to thinking about that duck type prey and thought, would they do this...the fish diet? On the other hand, bald eagles are linked to fish-eating in some reference books, but they eat other creatures, for sure. Like you, that duck fellow has thrown me. I'll keep looking, but.... Edit: This is from Eagles, Hawks & Falcons of the World, Brown & Amadon, Wellfleet Press, 1989, page 81: "Sometimes birds of prey have very wide tastes in food, so that they are able to vary their diet according to what is locally abundant. Specialised feeders include, for instance, Snake Eagles, which live almost entirely on snakes, the Snail Kite which lives entirely on snails, the Osprey which lives entirely on fish, and the Bat Hawk which lives entirely on bats, swallows and swifts. In areas where snakes, snails, fish, or bats are not abundant these birds do not occur. But many other birds of prey have far more generalised feeding habits." Food for thought--page 198 of the same book under Osprey information: "Food: Almost entirely fish, usually taken alive, and up to four pounds in weight; fish that bask on the surface, e.g., pike , are favorites. Unusual items include some birds, possibly wounded, such as a storm petrel, sandpipers and duck, very occasionally land birds like the jackdaw, frogs, and crustacea (probably by unskilled young.)" |
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| Raptorman | Dec 26 2007, 05:42 PM Post #468 |
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| Patti | Dec 26 2007, 05:51 PM Post #469 |
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Thank you for picking an easier raptor to I.D., even if the prey was not typical! :lol: |
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| ostrich2 | Dec 26 2007, 06:54 PM Post #470 |
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I have also been doing some research on that other bird I posted - my initial impression has changed, but I'm not ready myself yet to decide whether the id of a Cooper's is correct or not. My initial thought when I saw it was that the prey was quite large (blue jay) compared to Bea's backyard juvenile Coopers that had the starling. For that reason I wanted to check whether the bird's size was consistent with a Coopers as well as whether the Coopers would be likely to take prey that large. For a close comparison here they are: This was Bea's Coopers: ![]() Candidate Coopers: ![]() I'm assuming the new bird is also an accipiter (as it seems to be). I think it can be tricky judging the perspective from different pictures, but the prey does kind of give a frame of reference, and you certainly get the impression the latter bird is much larger. Unfortunately we don't really have a good viewh of the tail for distinguishing the three possibilities. The id bird I'm interpreting to be roughly the same length as the prey blue jay. Because of this size difference I initially considered whether this could be a goshawk, since that's the largest accipiter. However the references say the adult goshawk has a slate grey plumage on top so for goshawk to be a possibility at all, it would have to be a juvenile. The normal length for a blue jay is listed as 30cm. However, the normal size listed for the goshawk in my guide is 46-62cm. By contrast the Coopers comes in at 37-47cm, which is a bit long relative to a 30cm benchmark. Now actually the sharp-shinned is listed as ranging from 24-34cm, but the bird still seems rather large to be a sharp-shinned. It does seem to have the more roundish head as opposed to the squarish one of the Coopers, but Bill mentioned earlier that is not always a sure indicator. So right now I'm tending to lean away from goshawk (although I haven't eliminated it completely) but I'm not sure if there's still an argument for sharp-shinned. I'm going to do some more research
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| Naturegal | Dec 27 2007, 08:17 AM Post #471 |
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Ian/Ostrich - On occasion you have inquired about raptor sightings in Florida but I am such a novice at identifying them and even photographing them as they are usually soaring very high up. This is the best I could do today, there were about 10 of them but I am using a new camera and zoomed in as far as I could. Any idea as to what they are..............I apologize for the poor shots but hope to improve Raptorman - would appreciate your comments too ![]() ![]()
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| Raptorman | Dec 27 2007, 08:17 AM Post #472 |
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| ostrich2 | Dec 27 2007, 01:09 PM Post #473 |
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One thing that I notice looking at the comparison pictures, and I can't recall if the field guide mentions this, is that the goshawk seems to be much more heavily feathered on the legs than either the Coopers or sharp-shinned. The goshawk has very thick feathers almost looking like "pants", and the feathering extends well down closer to the feet than it seems to on the others. Unfortunately you can't see the legs and feet of the id bird. It's interesting that Bea's bird has virtually no feathering on the legs at all (even less than some of the other comparison photos of Coopers) - I remember thinking when I first saw it how tiny its legs seemed compared to other types of hawks. My field guide specified the adult goshawk as having more grayish plumage and you can see that somewhat on the left picture, but the right one is much more brownish overall, closer to some of the Coopers plumage. Both of those seem to have much more prominent streaking on the breast than the id bird does though. Where was the shot of the goshawk on the right taken Bill? That prey looks like it's been hit by a missile
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| Raptorman | Dec 27 2007, 01:59 PM Post #474 |
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| ostrich2 | Dec 27 2007, 02:10 PM Post #475 |
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Okay I think then the explanation is just that I hadn't taken into account the difference between adult and immature plumage for the goshawk. The id bird does have a bit of an "eyebrow" although to my eye it isn't that prominent compared to some of the other goshawk pictures. How about the feathering on the legs? Is that a consistent difference? (Although it doesn't help us here). In general I'm still kind of curious what would explain why Bea's bird had so little feathering on the legs, and seemingly such tiny legs as well. |
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| Patti | Dec 27 2007, 02:34 PM Post #476 |
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Bill, the physical trait that seems to help me the most is the finer barring/streaking on the Goshawk chest, but I don't think I'd know one from another--the Sharp's, Coopers or Goshawks--except by size. Those are nice photos you've posted. I don't think we HAVE Gosharks down here? Unless they migrate? Sibley's doesn't show them here, exactly...but that can be vague. Carole, I wish I could take photos as nice as yours are, even if we can't see markings. I can't even see to zoom in like you have & only get a glare on my screen--cannot focus to video. My few videos are...awful. |
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| Raptorman | Dec 27 2007, 03:02 PM Post #477 |
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| ostrich2 | Dec 27 2007, 06:00 PM Post #478 |
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What is the opinion on the id Patti? I'm still not sure Based on the "book" size of the prey you'd think it would match the sharp-shinned most closely, but this conflicts with the visual size which certainly appears at least as large as Bea's Coopers. The plumage doesn't seem to match the goshawk in the fine details as far as I can tell. None of the options seem to quite fit all the criteria, so I don't know which ones to base an id on.
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| Raptorman | Dec 27 2007, 07:24 PM Post #479 |
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| ostrich2 | Dec 27 2007, 09:11 PM Post #480 |
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The other reasonable thing to do is when a definite identification cannot be made is just to make the most probable one. When I was at the Hawk Hill raptor watches many of the raptors were identified by the official recorders from quite a distance and I'm sure there is a certain amount of error in them. When you're tracking overall numbers some amount of error is probably tolerable as long as it is reasonably small. Of course it's worse if the errors do not average out, i.e. there are systematic biases such as you could get if some species are consistently easier to recognize/identify than others. In this case, at least to me I can't tell anything that definitely indicates either Coopers or sharp-shinned. But I think I would tend to say sharp-shinned is more likely, if you go by the size. Taking a 13" size for the prey, that certainly falls more strongly into the typical range for the sharp-shinned than the Coopers. Since I gather these are only averages, this isn't definitive, as it could be possible that an individual Coopers falls into a smaller range. Bill, for the accipiters, are the juveniles at basically full size by the time they fledge, as with the bald? If the juveniles could be smaller than their full adult size that would make the issue more complicated. The head and beak to me also seems a bit closer to the sharp-shinned - but since we already know that is not always a sure indicator, this is only suggestive. |
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