Re: [cayugabirds-l] Crows mobbing Great Horned Owl on nest
HI All, A very quick comment, although I do not in fact know of any data on how effective mobbing of owls is in moving them any substantial distance. Crows are indeed migratory in parts of their range and they do indeed often join roosts in winter. If they have migrated, they won't be present to defend or disturb early owl nesting, true. BUT many crows in Ithaca are returning to their territories almost every day, and some do NOT join winter roosts but sleep at home. (That is data based, gathered by Ithaca crow-ers, based on radio tracking crows in some pretty frigid weather all the way through winter.) We regularly see our marked birds on territories for periods in the morning and early evening, even for those who may join a local roost in Cayuga Heights or at Titus Towers or along the slopes of Spencer Rd or Morris Heights. So at least here, most adult crows (that is, breeders with territories) probably are not returning after a long winter flocking around. They are making regular moves locally for food and safety and sociality, but they are also monitoring their territories regularly. Hence that owl with 40 crows after it was probably on the territory of one or more of the groups harassing it. You don't often see predators being harassed by big loud groups out at the Stevenson Road compost, unless they have actually caught a crow. One or a few birds may bomb a red-tailed hawk but 50 crows don't follow. (Goodness knows one could chase redtails all day out there.) As for owls attacking crow roosts, again, I have no data except to say I have never seen signs of owl predation under the trees of roosts I have checked. A screaming lot of crows in the middle of the night might be off putting for a stealth predator. And a wild turkey makes a more substantial meal. So are crows successful in their efforts? I just don't know. Locating nesting owls might be good for pre-nesting crows so they know where NOT to nest, I suppose. Crow nests, by the way, are often or usually NOT in the middle of a territory, but located in the right tree, even if on a corner of a territory. Crow nests built at the normal first-nest time of year (Mar-April) are rarely out where they can easily be seen. Usually they are in conifers and range from easy to see as a dark spot against light sky to basically invisible to humans. Is every crow harassing an owl bent on moving a dangerous animal, as opposed to showing off a bit or simply blinding joining its parents? Don't know that either. (I doubt they need the exercise though!) WE do know that crows sometimes lose their lives during hawk-owl harassment. And it seems logical that larger groups of crows will do a better job of moving a predator. And I should let everyone know: a trio of quonking ravens was at the Stevenson Road compost yesterday about 1300h for 10 min or so, flying around, landing in trees where crows were sitting and apparently making them fly up before quickly moving to the next tree. One looked young from my view of its brownish primaries. I was unfortunately walking a dog so saw it all through trees, and they were gone by the time I was in position to watch with a clear view. But there were three. Anne On Feb 18, 2013, at 11:32 PM, nutter.d...@me.com nutter.d...@me.com wrote: I'm thinking more about crows and owls. It's a substitute for actually knowing, so please chime in, Anne, or anyone else who knows better than I do what really goes on. I've been impressed by how much the Great Horned Owls in Renwick have withstood crows' harassment, and that impression flavored my earlier comment. A big purpose of the harassment of owls by crows ought to be to drive the predators away so the owls will cease being a danger to the harassing crows. But it doesn't look to me like it would work very well. Great Horned Owls are low-light, quiet, fairly slow (I think), stealth hunters, and in the daytime they are not a danger to crows nor to anyone else. A roosting owl might be convinced to move, but would it move far enough to shift its nighttime hunting area? Where would it not be in some crows' territory? At some point the owl has to stop being driven, and I have heard crows quit. Nesting owls, if they are to be successful, and obviously sometimes they are successful, must not be ousted by crows for several months, starting in early winter, when (I assume) crows are not defending territories nor clearing them of owls starting a nest. Last spring's crow nest can make a nice owl nest, which must be a disheartening discovery, to find owls living smack-dab in the middle of the territory when the crows return at the end of winter. In autumn and winter crows may travel for miles to roost during the night when owls are hunting. By gathering thousands of crows out of outlying owls' hunting territories, crows might improve their individual odds, but I would think
Re: [cayugabirds-l] Crows mobbing Great Horned Owl on nest
I'm thinking more about crows and owls. It's a substitute for actually knowing, so please chime in, Anne, or anyone else who knows better than I do what really goes on.I've been impressed by how much the Great Horned Owls in Renwick have withstood crows' harassment, and that impression flavored my earlier comment.A big purpose of the harassment of owls by crows ought to be to drive the predators away so the owls will cease being a danger to the harassing crows. But it doesn't look to me like it would work very well. Great Horned Owls are low-light, quiet, fairly slow (I think), stealth hunters, and in the daytime they are not a danger to crows nor to anyone else.A roosting owl might be convinced to move, but would it move far enough to shift its nighttime hunting area? Where would it not be in some crows' territory? At some point the owl has to stop being driven, and I have heard crows quit. Nesting owls, if they are to be successful, and obviously sometimes they are successful, must not be ousted by crowsfor several months, starting in early winter, when (I assume)crows arenot defending territories nor clearing them of owls starting a nest. Last spring's crow nest can make a nice owl nest, which must be a disheartening discovery, to find owls living smack-dab in the middle of the territory when the crows return at the end of winter.In autumn and winter crows may travel for miles to roost during the night when owls are hunting. By gathering thousands of crows out of outlying owls' hunting territories, crows might improve their individual odds, but I would think that any owl residing near the massive crow roost, or who came to visit, would have easy eating. Maybe the crows make a special effort to clear owls from the crow roosting neighborhood, but the roost is so obvious that I wonder how much good it would do.In the crow nesting season, of course, the crow female and young are stuck and vulnerable. Again, the crows have a good reason to try to drive an owl away, but I would think that a Great Horned Owl can still travel a long distance to hunt, and a crow nest which I can see in a tree during the day is probably similarly obvious to the owl at night. The crow nesting season starts after the owls are well underway. Do crows choose not to nest near Great Horned Owls? I bet the owls' hunting ranges so large as to encompass several crow nests anyway.I assume that the harassment of owls has some direct benefit in terms of predation reduction, but I doubt it's very large. I think either crows harass owls so much because that's one of the few things they can do to reduce predation when they can afford the time and energy, or else there are other benefits, such as getting to know what a Great Horned Owl looks like, or showing off for other crows, or crow family bonding, or being generally useful to the crow flock, or socializing, or getting exercise, or even having fun.Crows' lot looks very frustrating - and dangerous - regarding Great Horned Owls.I sympathize with the crows, too, but also I find their situation more complex and hard to figure.--Dave NutterOn Feb 16, 2013, at 03:18 PM, Anne Clark anneb.cl...@gmail.com wrote:Right--and come mid-April, some person might just pick up a partly eaten, headless, tagged female crow under her nest and think...it was her first nest--what a short life, only 5 years, her nestlings gone, too! She could have had 6 more years at least, or more.Boredom probably doesn't describe why the crows leave off (have seen them harrying owls for at least 6 hours)...nor a lack of memory for why they start over the next day. The crows aren't moving on...they are trying to move a dangerous thing out of their neighborhood, where their own kids need a chance at life.Yup--I took the bait. The story is all in your perspective, but I always find US interesting in siding with the one who has the kids at the time!Holding no grudges against owl-lovers,AnneOn Feb 16, 2013, at 2:05 PM, Mona Bearor wrote:I'll be thinking of your explaination when I visit the nest again, and I'll be watching for that owl to sigh and plan its nightly menu!Mona Bearor So. Glens Falls, NYOn 2/16/2013 12:21 PM, nutter.d...@me.com wrote:I think this is the sort of crap that Great Horned Owls have to put up with, and they get used to it. I suspect that what you saw is probably the pattern. Every day some crow "discovers" the owl, still in the same place on its nest, and raises the alarm, just as it would for an owl roosting in a new spot every day. All the other crows join in for awhile, so the whole crow community is aware of its presence, and the younger crows learn, "We don't like these guys." When they're satisfied and bored with lack of reaction from the owl on the nest, they move on. The owl sighs, reminds itself to eat some of those bastards come nightfall, and continues incubating, brooding, or guarding its young.--Dave Nutter On Feb 15, 2013, at 06:29 PM, Mona Bearor conservebi...@gmail.com wrote: Yesterday morning
RE: [cayugabirds-l] Crows mobbing Great Horned Owl on nest
Don’t know if owls and crows really think like this, but it would be a shame if they didn’t!! Dave, you should write a book. Jody Enck From: nutter.d...@me.com Sent: February 16, 2013 12:21 PM To: CAYUGABIRDS-L Subject: Re: [cayugabirds-l] Crows mobbing Great Horned Owl on nest I think this is the sort of crap that Great Horned Owls have to put up with, and they get used to it. I suspect that what you saw is probably the pattern. Every day some crow discovers the owl, still in the same place on its nest, and raises the alarm, just as it would for an owl roosting in a new spot every day. All the other crows join in for awhile, so the whole crow community is aware of its presence, and the younger crows learn, We don't like these guys. When they're satisfied and bored with lack of reaction from the owl on the nest, they move on. The owl sighs, reminds itself to eat some of those bastards come nightfall, and continues incubating, brooding, or guarding its young. --Dave Nutter On Feb 15, 2013, at 06:29 PM, Mona Bearor conservebi...@gmail.com wrote: Yesterday morning I observed about 50 crows mobbing a Great Horned Owl on a nest. It made me wonder if the crows could make the owl abandon the nest with repeated harassment, or if they would just give up after a while. I had an appointment so I couldn't stick around too long, but did watch this behavior for over 20 minutes non-stop. The owl was still on the nest today. Any thoughts on this? Mona Bearor So. Glens Falls, NY -- Cayugabirds-L List Info: Welcome and Basicshttp://www.northeastbirding.com/CayugabirdsWELCOME Rules and Informationhttp://www.northeastbirding.com/CayugabirdsRULES Subscribe, Configuration and Leavehttp://www.northeastbirding.com/CayugabirdsSubscribeConfigurationLeave.htm Archives: The Mail Archivehttp://www.mail-archive.com/cayugabirds-l%40cornell.edu/maillist.html Surfbirdshttp://www.surfbirds.com/birdingmail/Group/Cayugabirds BirdingOnThe.Nethttp://birdingonthe.net/mailinglists/CAYU.html Please submit your observations to eBirdhttp://ebird.org/content/ebird/! -- -- Cayugabirds-L List Info: Welcome and Basicshttp://www.northeastbirding.com/CayugabirdsWELCOME Rules and Informationhttp://www.northeastbirding.com/CayugabirdsRULES Subscribe, Configuration and Leavehttp://www.northeastbirding.com/CayugabirdsSubscribeConfigurationLeave.htm Archives: The Mail Archivehttp://www.mail-archive.com/cayugabirds-l%40cornell.edu/maillist.html Surfbirdshttp://www.surfbirds.com/birdingmail/Group/Cayugabirds BirdingOnThe.Nethttp://birdingonthe.net/mailinglists/CAYU.html Please submit your observations to eBirdhttp://ebird.org/content/ebird/! -- -- Cayugabirds-L List Info: http://www.NortheastBirding.com/CayugabirdsWELCOME http://www.NortheastBirding.com/CayugabirdsRULES http://www.NortheastBirding.com/CayugabirdsSubscribeConfigurationLeave.htm ARCHIVES: 1) http://www.mail-archive.com/cayugabirds-l@cornell.edu/maillist.html 2) http://www.surfbirds.com/birdingmail/Group/Cayugabirds 3) http://birdingonthe.net/mailinglists/CAYU.html Please submit your observations to eBird: http://ebird.org/content/ebird/ --
Re: [cayugabirds-l] Crows mobbing Great Horned Owl on nest
Right--and come mid-April, some person might just pick up a partly eaten, headless, tagged female crow under her nest and think...it was her first nest--what a short life, only 5 years, her nestlings gone, too! She could have had 6 more years at least, or more. Boredom probably doesn't describe why the crows leave off (have seen them harrying owls for at least 6 hours)...nor a lack of memory for why they start over the next day. The crows aren't moving on...they are trying to move a dangerous thing out of their neighborhood, where their own kids need a chance at life. Yup--I took the bait. The story is all in your perspective, but I always find US interesting in siding with the one who has the kids at the time! Holding no grudges against owl-lovers, Anne On Feb 16, 2013, at 2:05 PM, Mona Bearor wrote: I'll be thinking of your explaination when I visit the nest again, and I'll be watching for that owl to sigh and plan its nightly menu! Mona Bearor So. Glens Falls, NY On 2/16/2013 12:21 PM, nutter.d...@me.com wrote: I think this is the sort of crap that Great Horned Owls have to put up with, and they get used to it. I suspect that what you saw is probably the pattern. Every day some crow discovers the owl, still in the same place on its nest, and raises the alarm, just as it would for an owl roosting in a new spot every day. All the other crows join in for awhile, so the whole crow community is aware of its presence, and the younger crows learn, We don't like these guys. When they're satisfied and bored with lack of reaction from the owl on the nest, they move on. The owl sighs, reminds itself to eat some of those bastards come nightfall, and continues incubating, brooding, or guarding its young. --Dave Nutter On Feb 15, 2013, at 06:29 PM, Mona Bearor conservebi...@gmail.com wrote: Yesterday morning I observed about 50 crows mobbing a Great Horned Owl on a nest. It made me wonder if the crows could make the owl abandon the nest with repeated harassment, or if they would just give up after a while. I had an appointment so I couldn't stick around too long, but did watch this behavior for over 20 minutes non-stop. The owl was still on the nest today. Any thoughts on this? Mona Bearor So. Glens Falls, NY -- Cayugabirds-L List Info: Welcome and Basics Rules and Information Subscribe, Configuration and Leave Archives: The Mail Archive Surfbirds BirdingOnThe.Net Please submit your observations to eBird! -- -- Cayugabirds-L List Info: Welcome and Basics Rules and Information Subscribe, Configuration and Leave Archives: The Mail Archive Surfbirds BirdingOnThe.Net Please submit your observations to eBird! -- -- Cayugabirds-L List Info: Welcome and Basics Rules and Information Subscribe, Configuration and Leave Archives: The Mail Archive Surfbirds BirdingOnThe.Net Please submit your observations to eBird! -- -- Cayugabirds-L List Info: http://www.NortheastBirding.com/CayugabirdsWELCOME http://www.NortheastBirding.com/CayugabirdsRULES http://www.NortheastBirding.com/CayugabirdsSubscribeConfigurationLeave.htm ARCHIVES: 1) http://www.mail-archive.com/cayugabirds-l@cornell.edu/maillist.html 2) http://www.surfbirds.com/birdingmail/Group/Cayugabirds 3) http://birdingonthe.net/mailinglists/CAYU.html Please submit your observations to eBird: http://ebird.org/content/ebird/ --
