by Joanna Reuter

Part two in an occasional series, Birds in Big Numbers

by Joanna Reuter

Blackbirds can congregate in enormous numbers, sometimes in mixed-species flocks with starlings and other birds. In eBird’s current dataset, Red-winged Blackbirds hold the world record for the high count of a single species, with an estimate of 40 million individuals during a Christmas Bird Count in Arkansas in December 1964 (eBird list). Let’s take a look at what’s been seen in the Columbia Audubon Society (CAS) six-county region:

High counts: Dusk on January 5, 2019 in Audrain County:

This was a ‘river of blackbirds’ that contained millions of birds. The river flowed broadly and continuously for over 20 minutes. We described it as looking like a black cloud of smoke being carried out of a smokestack…only it wasn’t smoke. It was all birds…. Any attempt to count the number of blackbirds present is truly a guess.

This is how Jean Leonatti, Susan Hazelwood, Cathy Harris, and Betsy Garrett described their observation. Their rough estimate, at ~10 million “blackbird sp.”, ranks this observation at the top of the high-count list for a single taxa in Missouri as reported on eBird  (full eBird list here).

Another enormous “river of birds” was observed by Ryan Douglas and Vic Bogosian at Eagle Bluffs during the December 17, 2011 Christmas Bird Count (full eBird list here). Here’s a video clip that captures ~2 minutes of a colossal flock that they observed for more than 15 minutes:

They estimated a flock size of 5 million birds, with 75% Common Grackles, 20% Red-winged Blackbirds, and 5% European Starlings.

What: The term “river of blackbirds” is commonly used, but flocks are not always exclusively blackbirds in the taxonomic sense. For example, dark-colored European Starlings often mix with blackbirds, but belong to a different family (Sturnidae) than New World blackbirds (Icteridae); starlings may be black birds, but they aren’t blackbirds. Of the true icterid blackbirds, Red-winged Blackbirds and Common Grackles are the species most likely to be seen in large numbers in Missouri, while Brown-headed Cowbirds can also mix with other blackbirds. Rusty Blackbirds are worth watching and listening for; this declining species winters in Missouri, but eBird reports for the CAS region rarely report more than a few dozen individuals at a time. American Robins (family Turdidae) also flock in the fall and winter, sometimes associating with blackbirds.

The term “murmuration” describes sizeable flocks that fly in tight formation in complex patterns, often related to predator avoidance. The term is used most frequently to describe the acrobatics of European Starling flocks, but true blackbirds can fly in murmuration style, as well (YouTube has some examples). Murmurations are a subject in which the realms of birding, particle physics, and art collide—but the birds don’t. Online videos abound, and live performances over Columbia by flocks composed of at least hundreds of starlings are not uncommon.

When (time of day): The two observations featured at the beginning of this article occurred at dusk, a common time to see large flocks, because blackbirds (and associates) congregate at roosts for the night. During the day, smaller flocks may split off to forage. Thus, observations with the highest counts tend to be near dusk or dawn.

When (dates): Late fall and winter are when the largest flocks of blackbirds have been reported on eBird in central Missouri. During the spring and summer breeding season, blackbirds are reported on a high percentage of eBird lists, but typically not in huge numbers; they tend to be dispersed in favorable habitats, carrying out breeding activities. During late fall and winter, a smaller percentage of eBirds lists report observations of blackbirds, but of those that do, some of the observations are large.

Where: In more southerly states, blackbirds and associated species form winter roosts that are used persistently over a period of time; sometimes the roost territory is reoccupied from year to year (reference). In Missouri, flock use of a given roost location seems to be more temporary, but eBird data are insufficient to provide full details of flock and roost dynamics. Perhaps transient flocks are migrating and/or moving opportunistically to look for food resources (including corn) in the landscape. Some blackbirds that breed in Missouri migrate south; others may arrive in our area from the north. (Wouldn’t it be fun to have some Motus data on this?)

So, where to look? One obvious place is Eagle Bluffs, with its wetland habitat, trees for roosting, food resources, and past history of large flocks (~75% of eBird observations of >1,000 blackbirds/starlings in the CAS region have been from Eagle Bluffs). Keep in mind, however, that hunting season access restrictions do not allow for dawn and dusk observations in the heart of the conservation area. In 2020, most roads and trails will re-open for all-day access on January 13, and the remaining areas will re-open on February 7. Don’t rule out locations other than Eagle Bluffs: stay alert whenever you happen to be outside, especially near dawn and dusk.

Reporting to eBird: Due to a variety of challenges, I suspect more observations are made of large blackbird/starling flocks than are reported on eBird. (Count me guilty.) When millions of birds are sighted on one day with little followup, I wonder where the birds went from there. Did they disperse? Fly to another state? Stay around unobserved? More reporting to eBird would enhance the potential to understand the location and dynamics of these interesting flocks. Here are some challenges and suggested solutions:

Challenge	Suggestion
Estimating numbers.	Consider using photos and video (which can be reviewed later to refine count estimates), and descriptions of flight duration to document your observation. Accept that the number you come up with is a bit of a guess and report anyway (but err conservative). Also, hone your estimation skills by practicing with online photos (see below).
Identifying species in mixed flocks.	Use of “blackbird sp.” can help, but European Starlings are not blackbirds and should not be lumped under this category. Get to know the distinct triangular profile of starlings in flight by watching them in urban Columbia. If unsure, report “passerine sp.” with a note of explanation.
Making observations when you are not otherwise birding.	If driving, find a safe place to pull over. If the flock is interesting but you don’t have time to pay attention to other species, don’t hesitate to report to eBird as an incidental list.

Count quiz: How many birds are in this photo? What is the first value that comes to mind? And after studying the photo a bit longer, have you revised your estimate? Send your estimate(s) to my email, and I’ll reveal the results of the “popular vote” in the February newsletter, along with results from my best attempt to count the birds shown. (Please do email me; it also tells me there’s a reader!)

Implications of large blackbird/starling flocks: As I started to research big blackbird/starling flocks, I thought about them from a bird-watcher’s perspective, as a phenomenon exciting to observe. From a farming perspective, I naively hadn’t thought much about the implications of these flocks, partly because I’ve only encountered large flocks in the winter, when my small-scale crops have long since been harvested. However, blackbirds and starlings are viewed by many as an agricultural menace (sometimes justifiably so; example), and the large flocks are perceived to be vectors of dangerous pathogens (again, sometimes with justification; reference). Even members of the bird-watching community can view these flocks with disdain, particularly when backyard bird feeders are overrun with them. European Starlings, in particular, receive the ire of many due to their non-native status here.

Control measures, including lethal ones, are legal for European Starlings, due to their non-native status. In addition, I was surprised to learn that control measures are also legal for several species of native blackbirds (reference). A bit more online research yielded a window into another world: numerous businesses specializing in bird control (examples, 1,  2, and 3), extension/government advice on how to control these species (examples, 1, 2, and 3), and products, ranging from repellent to lethal, aimed at the control of these species (examples, Methyl Anthranilate, Avitrol, and Starlicide).

Learn more: Here are some additional resources to explore:

• Practice estimating numbers and identifying species. Use these photos, linked from the Macaulay Library, to hone your estimation skills. Do you see any mixed flocks? Click the link for the eBird list; many contain additional photos, as well as a the total list estimate (which may, of course, include individuals not photographed). Many of these are Missouri photos, but I included a few from farther afield for good measure.
  
• Starling murmurations: It’s easy to spend a little too much time watching murmuration videos online. Here are three impressive ones: from the Netherlands, from Rome (with actively hunting peregrines), and from the UK. Noah Strycker’s book, The Thing with Feathers, has an interesting chapter on murmurations.
• Here’s a story about what happened in Jefferson City in 1967 when an intended attempt to control starlings went very wrong.
• Here are a couple of links to help with looking for and identifying Rusty Blackbirds: Sibley and Audubon.
• The MOBIRDS archive contains various postings that describe or mention observations of large flocks (mostly of blackbirds), including: Dec. 2002, another in Dec. 2002, Feb. 2003, Dec. 2003, Nov. 2004, Jan. 2008, Jan. 2011, Feb. 2015 (not a comprehensive list).

Text © Joanna Reuter 2020