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Interesting observation, Edge! In our Bluebird article on the roost (September 2020), we noted the following:

"Blackbirds typically forage within ~25–30 miles of a winter roost (Meanley, 1971), or within about a one-hour flight at a speed of approximately 27 miles per hour (Dunbar, 1952)." We also included a map of likely foraging range based on those assumptions (https://mobirds.org/Bluebird/2020-2029/2020/September_2020.pdf <https://mobirds.org/Bluebird/2020-2029/2020/September_2020.pdf>).

At 30 mph, the Moniteau County birds would have been about 2 hours away from the roost site based on your stated distance. Although this is twice as far as the above citations claim is typical, your flock would have been able to arrive around dusk (sunset is ~5:47 right now). Also, those citations are quite old, and it doesn't seem that modern research has paid much attention to blackbird dynamics, so it'd be really interesting to update those assumptions. We also wonder whether the extreme cold could be driving blackbirds to travel farther than "typical" or otherwise altering their dynamics.

On the other hand, in our article we speculated that there are more blackbird roost sites out there than are documented, since again, nobody really seems to be paying attention to these. After all, the birding/research community was unaware of the huge Boone County roost right in Columbia's backyard. We've seen large streams of winter blackbirds in southwest Missouri, and a non-birder friend reported similar streams north of Sedalia. We would love to get out more and search for such roost sites, possibly by finding large daytime concentrations and then following them (which is how we found the Boone County site in the first place), but we have not been able to do that this winter for personal reasons.

Eric & Joanna Reuter
Boone County, MO

> On Feb 15, 2021, at 8:33 AM, Media.com <[log in to unmask]> wrote:
> 
> Seeing the large numbers at the roost and en route to it causes me to wonder and begin to speculate how far these birds commute between feeding areas and the roost.  Bill Clark and I on Wednesday, February 3 were in Moniteau County along Highway 5 coming north from Manito Lake Conservation Area after 4 p.m. when we observed a heavy stream of blackbirds to our east flying north northeast on a flight path that appeared headed toward north Boone County (and hence, the roost).  I roughly estimated that flight group at 3,500-5,000. 
> 
> From where we sighted the birds to the roost is about 60-65 miles as the crow or blackbird flies, and they were already aloft.  It is not unreasonable to assume some of the roost birds are flying 100 miles or more from daytime feeding areas to the miscanthus fields.  Thinking about it, the radius to provide food for the masses that accumulate north of Hallsville must be very, very great.
> 
> Does anyone have suggestions how we could determine how far these birds commute daily?  Are there studies that might shed some light on this?
> 
> Musing more, how much must they eat to support this daily commute and stay healthy?
> 
> Edge Wade
> Columbia, MO
> [log in to unmask]  
> 
> From: "Eric Reuter" <[log in to unmask]>
> To: "MOBIRDS-L" <[log in to unmask]>
> Sent: Monday, February 15, 2021 7:01:53 AM
> Subject: Large stream of blackbirds following Silver Fork Creek in northern Boone County
> 
> WARNING: This message has originated from an External Source. This may be a phishing expedition that can result in unauthorized access to our IT System. Please use proper judgment and caution when opening attachments, clicking links, or responding to this email.
> On Saturday evening, Joanna and I walked ~2/3 mile out to the Silver Fork Creek valley from our nearby property to get a better view of the large streams of blackbirds seen passing nearby or overhead on a recent evening (and periodically through the fall/winter); this location has a much broader sky view than our narrow side valley. We were rewarded by a constant linear flow of blackbirds from SW to NE for ~40 minutes, following the Silver Fork Creek valley. We presume these were headed for the massive roost location at the miscanthus fields farther up Silver Fork, as we've previously reported noticing that bird streams heading for that roost seem to follow drainage patterns when navigating. We started observing just as the first birds in the flow appeared from the SW and stayed until the flow ended as the sun was sinking below the hills, at which point we were freezing as the temperature was in the single digits (and still had a ~2/3 mile walk back). However, it was an amazing experience to watch a constant flow of birds for so long a time. The essentially unbroken stream meandered back and forth across the ~1 mile wide valley like the movement of a snake, sometimes over the southern hills, sometimes over the northern, crossing back and forth directly over us. Red-Winged Blackbirds were dominant, though we saw a few grackles mixed in. At times two equal streams seemed to either parallel each other or join from the south, but the quantity per time (i.e. size of the stream) was reasonably consistent. We estimated a conservative 200,000 based on an estimated 1000 birds passing a given location in 10 seconds (see eBird list for details). We might be able to do a more precise estimate on a day when note taking isn't precluded by fear of frostbite. It was neat to be able to get a decent count of one such flow, as we're certain that far more birds are accessing the roost site from the north based on general observations of arrival direction there. If we could count a lowball 200,000 just in one stream from the SW, it supports previous conclusions that the roost itself hosts several million at its peak.
> 
> eBird list: https://ebird.org/checklist/S81469254 <https://ebird.org/checklist/S81469254> 
> 
> Eric & Joanna Reuter
> Boone County, MO
> 
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