I think hackberries play a role. I don't know when the cities began planting hackberry trees on boulevards, but I think it was not many decades ago. Most of the trees do not look very old. Did large crops of hackberries begin to appear within the last 10 or 15 years?
On the 2008 St. Paul (North) CBC, my team had the area west of Cleveland Avenue and south of Marshall Avenue/Lake Street, extending south to the Ford Dam and west past the Hiawatha grain elevators in Minneapolis. We counted 808 American Robins. As I recall, about 650 of them were feeding on Hackberries on the Summit Avenue median in the two blocks between Cretin and Cleveland Avenues. It seems to me that robins become scarcer in late December, as the hackberry supply is depleted. Julian ________________________________ From: Minnesota Birds <[email protected]> on behalf of Rebecca Field <[email protected]> Sent: Thursday, December 6, 2018 6:21 PM To: [email protected] Subject: Re: [mou-net] Northern Raven/Number Winter Robins I just heard this evening that Robins eat Buckthorn berries. Of course, we are trying to eradicate that invasive. I hope that isn’t causing less food for the robins. Becky Field Sent from my iPhone > On Dec 6, 2018, at 5:36 PM, Jason Frank <[email protected]> wrote: > > It would be interesting to compare the data of outstate CBCs as well. > I haven't lived in Minneapolis during winter since 1997, and it seemed > noteworthy to me to see large numbers of robins in the winter. A few > years ago I visited Minnehaha Falls around Christmas and couldn't > believe how many there were, though I just figured they were local > birds who stayed for the open water along the creek and had reliable > food sources nearby. Those numbers from Val show a pretty stark > increase, which to my eyes fits the trend of climate change. > > But... having lived in the Lac qui Parle area since 09, I can't say > I've seen many impressive winter flocks except during the mildest > winters of the last decade, and those birds were usually seen in town > or at parks, and not out in the countryside for the most part. > > Since the Twin Cities urban heat island effect means the temperature > averages there would be trending warmer than elsewhere in the state, I > wonder if outstate robins have gotten into the habit of migrating into > cities and towns, rather than further south? Collating banding data > with rural CBCs might shed some more light on the case. > >> On 12/6/18, GREG ELIZABETH CLOSMORE <[email protected]> wrote: >> Buckthorn! >> >>> On Dec 6, 2018, at 4:32 PM, Val Landwehr >>> <[email protected]> wrote: >>> >>> I was intrigued by the discussion of whether in recent years >>> more robins are being seen during winter in the Twin Cities(Charles Neil, >>> Mary White and J. Baumann). I think that I >>> have seen more robins, particularly in large flocks, in >>> recent years. To put this hypothesis to the test I looked at the >>> results from four Christmas Bird Counts over the years that are >>> online at the Minnesota Ornithologists' Union website. The >>> Christmas Bird Counts I checked were Bloomington CBC, St. Paul >>> (North) CBC, Excelsior CBC and the Minneapolis (North) CBC. >>> I found a distinct trend of more robins being counted during >>> the counts since the winter of 1996 than were in prior years. >>> The numbers vary widely each year, but there is a distinct >>> inflection point around 1996 for a larger number of robinssince that date >>> than prior to it. Since 1996, the number ofrobins counted varies greatly >>> from year to year, but I don't >>> see any clear evidence that the numbers are continuing to >>> increase. >>> Average number of robins counted at Twin Cities CBCs: >>> Bloomington St. Paul (North) Minneapolis (North) Excelsior >>> Pre 21.2 17.1 2.5 >>> 5.3 >>> 1996 >>> 1996- 367.4 420.5 114.6 >>> 181.2 >>> 2017 >>> >>> Median number of robins counted at Twin Cities CBCs: >>> Bloomington St. Paul (North) Minneapolis (North) Excelsior >>> Pre 5 6 0 >>> 1 >>> 1996 >>> 1996- 278 255 26 >>> 132 >>> 2017 >>> I considered that the increased number of robins might reflect >>> more birders participating in these Christmas counts as well >>> as an increase in birding skills. If there are more skillful >>> birders involved in these counts I would expect a similar >>> increase in the counts of other species. So I looked at the >>> counts reported by the Bloomington CBC for the black-capped >>> chickadee, blue jay and dark-eyed junco. I didn't find any >>> trends or long term changes in the number of these species. >>> Therefore, I'm convinced that the increased number of winter >>> robins is real. >>> I didn't attempt to see if there is a link between the increasein the >>> number of robins counted and weather/climate. >>> That leaves a question in my mind. Are the larger counts just >>> a reflection that the Twin Cities population of robins has >>> increased but the same proportion of that population is >>> overwintering as in the past or have the overwintering habits >>> of the robins changed? >>> The CBC data speaks only to the presence of robins in December. >>> Maybe the only change is when the robins migrate to warmer >>> regions. Maybe if we had many years of counts for January and >>> early February we would find that the number of robins in >>> those months hasn't changed much over the years. As Manley >>> Olson pointed out, once the robins exhaust the availability of >>> crab apples, perhaps they head south and are now just as >>> uncommon in January and February as they were back in the >>> 1950s through 1980s. >>> Val Landwehr >>> Minneapolis >>> >>> ---- >>> Join or Leave mou-net: http://lists.umn.edu/cgi-bin/wa?SUBED1=mou-net >>> Archives: http://lists.umn.edu/archives/mou-net.html >> >> ---- >> Join or Leave mou-net: http://lists.umn.edu/cgi-bin/wa?SUBED1=mou-net >> Archives: http://lists.umn.edu/archives/mou-net.html >> > > > -- > Jason M. Frank > Ortonville Public Library > Founder & Vice President > Luddite Ornithologists League (LOL) > Big Stone County, Minnesota > > ---- > Join or Leave mou-net: http://lists.umn.edu/cgi-bin/wa?SUBED1=mou-net > Archives: http://lists.umn.edu/archives/mou-net.html ---- Join or Leave mou-net: http://lists.umn.edu/cgi-bin/wa?SUBED1=mou-net Archives: http://lists.umn.edu/archives/mou-net.html ---- Join or Leave mou-net: http://lists.umn.edu/cgi-bin/wa?SUBED1=mou-net Archives: http://lists.umn.edu/archives/mou-net.html
