Predation is, indeed, an interesting issue in this context, but is very complicated to study. I live directly under Hawk Ridge in Duluth, and a great many accipiters and falcons fly over my yard in fall on the same days that Blue Jays numbers are highest. Many of these jays are migrants, too, and I suspect that migrants don't cache food. Large flocks of jays will line my longer feeders, all feeding together and utterly exposed. My birds have never been color marked or even just banded, so it's impossible for me to keep track of which is which, but I've always believed that those jays that will remain for the winter are the only ones that cache food.
During winters when a Merlin hung around my neighborhood, the jays usually fed from the feeder first thing in the morning and in late afternoon, and cached food at other times. They seemed to check out whether the Merlin was around before they came in, and although they seemed warier all the time than they did in winters without a Merlin hanging around, their visits to feed didn't seem any shorter (except when the Merlin or a shrike or other predator suddenly appeared) than in winters when the predator was nowhere to be seen. This is my judgment, without having sat around timing it. There is so much data I wish I'd collected over the years! I lived with an education Blue Jay for many years, and for several of these years a squirrel I'd raised from a baby would come into my house whenever she wanted to raid my food buckets. When either one took an acorn or peanut, the other would follow and dig it up and hide it somewhere else, and then the other would dig it up and hide it yet somewhere else. This "game" could last for five or six exchanges before bird or squirrel went and took another nut out of the bucket. My kids were always finding peanuts and acorns mixed in with their legos. Best, Laura On Tue, Mar 1, 2011 at 2:36 PM, Jesse Ellis <[email protected]> wrote: > Betsy- > > Another factor to consider is predation, which confounds lots of questions > of behavioral energetics. My first thought is that perhaps your feeding > station now is a little more dangerous - more exposed, or there are more > known predators in the area, something like that, that leads to a higher > cost for the jays to sit and hack nuts. It may be more expeditious to dash > and cache than worry about calories. > > Jesse Ellis > former corvidologist > Madison, WI > > On Tue, Mar 1, 2011 at 10:42 AM, Laura Erickson < > [email protected]> wrote: > >> I think your questions are fascinating and worth examining >> experimentally, but there are a few more points to consider. Blue Jays >> probably started "weighing" food morsels not simply to get the most >> calories per trip but also because in the case of their most preferred >> natural food, acorns, the heavier ones are the ones least likely to >> contain a larval insect eating away at the contents. So selecting the >> heaviest ones is even more advantageous than it seems. >> >> Peanuts start rotting pretty quickly when stashed, and the process is >> quicker when they're not in the shell, so it's possible that over >> time, some jays figure out that it's best when caching peanuts to keep >> them in the shell. But those in your area may also be, as you note, >> simply trying to speed up the time they spend at the feeder. >> >> I doubt if anyone has worked out a definitive answer to your question. >> To start teasing out answers, you might try offering a small number of >> peanuts already shelled to see if the jays eat those on site or also >> carry them away for storing elsewhere. >> >> Best, Laura Erickson >> >> >> On Tue, Mar 1, 2011 at 10:27 AM, Betsy Beneke <[email protected]> >> wrote: >> > I started feeding blue jays peanuts in the shell many years ago, when I >> lived in >> > Detroit Lakes. It was a Saturday morning ritual in the winter. Start a >> pot of >> > coffee, fill the feeders, and throw a couple of handfuls of whole peanuts >> out on >> > the platform feeder. I had two large picture windows in front of the >> kitchen >> > table from which to watch. It was a very relaxing way to start my >> weekend. I >> > LOVE watching behaviors in birds. >> > >> > The blue jays would fly into the yard the moment they heard my storm door >> shut. >> > There were 4-6 birds, I think. Their "mode" was to fly to the feeder, >> pick up a >> > peanut, drop it, pick up another one, drop it - until they found the >> heaviest >> > one - then fly to a nearby branch, where they would hold the peanut >> between >> > their feet, poke a hole in one end of the shell, pull out the kernel, do >> the >> > same to the other side, and then let the shell fall to the ground. This >> process >> > was repeated until they got several kernels in their mouth/throat, and >> then they >> > would fly off to the woods to stash them. They would make repeated trips >> until >> > all the peanuts were gone and there was a pile of shells left in my >> yard. All >> > the birds used this same process. I understand that the heaviest peanuts >> are >> > chosen first because they have more nutrition per trip. The wimpiest >> peanuts >> > were always the last to be chosen. >> > >> > I've been feeding the blue jays at Avon the same way this winter, but >> have >> > noticed that the jays here fly in, grab a peanut and then immediately fly >> off to >> > the woods with the whole thing. They don't stop to pull out the kernels >> the way >> > the Detroit Lakes birds did. I know that there are at least 7 different >> birds >> > who come in for the treats - maybe more. >> > >> > So my question for SOMEONE who knows more about this than me, is...why is >> the >> > feeding pattern different? Is it a learned behavior within the local >> > population? Or could it be that there are more birds here - more >> > competition/grappling for the goodies, so they zip in to grab what they >> can, and >> > then fly off to stash it safely away? >> > >> > I'd love to know the answer! >> > >> > Betsy Beneke >> > Avon, Stearns County >> > >> > >> > >> > >> > ---- >> > Join or Leave mou-net: http://lists.umn.edu/cgi-bin/wa?SUBED1=mou-net >> > Archives: http://lists.umn.edu/archives/mou-net.html >> > >> >> >> >> -- >> Laura Erickson >> >> For the love, understanding, and protection of birds >> >> There is symbolic as well as actual beauty in the migration of birds. >> There is something infinitely healing in the repeated refrains of >> nature--the assurance that dawn comes after night, and spring after >> the winter. >> >> --Rachel Carson >> >> Please consider the environment before printing this e-mail. >> >> ---- >> Join or Leave mou-net: http://lists.umn.edu/cgi-bin/wa?SUBED1=mou-net >> Archives: http://lists.umn.edu/archives/mou-net.html >> > > > > -- > Jesse Ellis > Post-doctoral Researcher > Dept. of Zoology > University of Wisconsin - Madison > Madison, Dane Co, WI > > ---- > Join or Leave mou-net: http://lists.umn.edu/cgi-bin/wa?SUBED1=mou-net > Archives: http://lists.umn.edu/archives/mou-net.html > -- Laura Erickson For the love, understanding, and protection of birds There is symbolic as well as actual beauty in the migration of birds. There is something infinitely healing in the repeated refrains of nature--the assurance that dawn comes after night, and spring after the winter. --Rachel Carson Please consider the environment before printing this e-mail. ---- Join or Leave mou-net: http://lists.umn.edu/cgi-bin/wa?SUBED1=mou-net Archives: http://lists.umn.edu/archives/mou-net.html
