Hi everyone, Having watched a few winter irruptives over the last couple weeks, both redpolls and Bohemian Waxwings, while in Alberta I've been forming my own opinions about what these birds are doing. It's not just redpolls that are behaving as Laura described but I was watching a flock of a couple thousand Bohemian Waxwings doing the same sort of thing: descending on a feeding site for 10 or 15 minutes and then taking off for no apparent reason only to reappear at the same location several hours later or the next day. It wouldn't surprise me if this sort of behaviour isn't typical of species that both feed in flocks and feed on concentrated food sources like feeders, berry trees (waxwings) or cones of various sorts (redpolls and siskins on alder and birch). I'm not even sure that it's possible to say that redpolls are more mobile than chickadees. When Dave Bonter had colour-banded chickadees at various feeders around Ithaca a few years ago, I was watching "my" flock of colour-banded birds, and while my feeder seemed to be almost continuously used by a small group of chickadees, individually-recognizable chickadees stayed in my yard for very short periods of time...there was just a constant rotation of birds through my yard.
I'm not sure this behaviour is really "skittish" in the sense of the birds being nervous about predators. I'd actually expect the opposite: something that's called a "selfish herd" effect, where the larger the group, the less likely that you'll be depredated because by chance alone you're far less likely to be killed by the small number of predators in the area if you're in a group of 100 than if you're in a group of 2, for example. My own speculation is that this behaviour is some sort of built-in psychological twitch in bird species that flock in winter but also typically feed on food supplies that they can deplete, potentially very quickly, over the course of a few days. These birds need to keep searching for new food supplies over the course of a winter, and I am guessing that their constant movement from one feeding site to the next is part of a general strategy of exploring and finding new food supplies before their current food supplies are exhausted. In other words, I'm not sure that these birds are psychologically hard-wired to know how to deal with an essentially unlimited food source like a bird feeder. I'm also guessing that this sort of behaviour at a local level, of always shifting from one food source to another, is also manifested at the broader scales that Chris mentioned, with redpolls shifting around not just within a local area but from one local area to another over the course of a winter. I think this also happens with Bohemian Waxwings. In the town where I grew up, these birds would arrive en mass at a different date than in a nearby city, swarm around town in huge numbers for a few weeks and seemingly clean out the available berries, before largely disappearing mid-way through the winter. These sorts of broader-scale movements happened every winter. Anyway, that's the extent of my idle speculation. My bet would be on a finite and depletable winter food supply being behind site-level twitchiness of redpolls and other flocking winter invasive bird species. Wesley Hochachka -----Original Message----- From: bounce-72567911-3494...@list.cornell.edu [mailto:bounce-72567911-3494...@list.cornell.edu] On Behalf Of Christopher Wood Sent: Wednesday, January 09, 2013 10:17 AM To: geoklop...@gmail.com Cc: CAYUGABIRDS-L Subject: Re: [cayugabirds-l] 100+ Redpolls-for a minute I also think that many of these redpolls are still actively moving. These birds may have come in, fed briefly and then taken off for some place a hundred miles away. While we often think of migration being in May and September, there probably isn't a single month of the year where at least some individuals of a few species are moving. I've certainly noticed actively migrating redpolls in the last week or so. I've seen flocks of redpolls still moving south along the North Shore of Lake Superior in February, while other species were moving north. Chris Wood eBird & Neotropical Birds Project Leader Cornell Lab of Ornithology, Ithaca, New York http://ebird.org http://neotropical.birds.cornell.edu On Wed, Jan 9, 2013 at 9:52 AM, Geo Kloppel <geoklop...@gmail.com> wrote: > Hi Laura, > > When gathered in large flocks they actually strike me as being _more_ > skittish; perhaps it's a compounding effect. Makes sense in a way. > There may be no predator around at the moment, but they know that by > concentrating at a rich food source in a landscape of scarcity they > create a magnet for any predators in the area. > > -Geo > > On Jan 9, 2013, at 9:14 AM, Laura Stenzler <l...@cornell.edu> wrote: > > Hi, > This morning there was a flock of at least 100 Redpolls in the trees > near our feeders. A few were at the feeders, but after sticking around > for a few minutes they alldisappeared. Here's a question - why would > they leave a rich food source? Our feeders are full, there are 7 to > choose from, and they clearly are happy when they decide to land. I've > seen this happen before, when there is no obvious evidence (to me) of > predators in the area. > Other birds keep happily visiting the feeders - chickadees, > woodpeckers, nuthatches, etc. There are other feeders at neighbors' houses, > close by. > > Any thoughts? > L > > -- > 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/ -- -- 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/ --
