Towheeblog

There has been some discussion of a robin population slump in Willamette Valley. Right now it is likely that many of breeding robins have headed south. In this mild autumn (so far) it is equally likely that robins from Alaska, bigger and darker than “ours”, have not yet arrived. They stopped off to party on Vancouver Island–as you or I would do if we could.

Still, there are many factors to consider when looking at breeding robins hereabouts (I write from Salem).

Likely multiple factors as nature does not often opt for simplicity:

1) Isn’t our area similar to coastal California in that robins came down from the mountains to nest as our forefathers changed the environment putting in lawns, pastures, shrubbery? Self-introduced like collared-doves or Black Phoebe?  First nesting robin in San Francisco was found in 1913, first Mocker in 1932.

In 1902 Florence Merriam Bailey published the first-ever field guide for western birds. She says this of the western robin; “Breeds in Transition and Boreal zones in the western United States…*” That would indicate the robun, pre-agriculture and cities, was a montane forest bird.

2) Pesticides, hard on all ground-feeding species—main reason kingbirds, burrowing owl, meadowlark, lark sparrow, bluebirds and shrike are so scarce in Willamette Valley that superficially looks ideal for them

Hazelnut poisons:  https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/em8328.pdf

Nearly every profitable agricultural business has an equally horrific list of killing chemicals. If the scarcity of earthworms is a factor in robin scarcity, should we not assume we have poisoned them? We can’t even blame the hated housecat, or picture windows or windmills or high rise lights for killing earthworms.

3) Cats–enough said.

4) Jays & crows—but these have always co-existed with breeding robins; robins long ago evolved to get rid of cowbird eggs and I cannot believe they don’t know best how to hide from corvids who’ve always been a threat. Robins long ago evolved ability to avoid cowbird eggs, surely they kniow well how to hide nests from corvids that have always threatened their nestlings and eggs.

5) Squirrels—eastern species that are invasive with only one natural enemy (great horned owl).

Then another birder wrote this about her robins back in Virginia:

“I don’t know if my experience in the 1990s in Virginia would mean anything, comparing it to your area in the 2020s, but here goes.  I lived in Vienna, VA for 19 years.  Vienna is a suburb of Washington, DC, a very developed urban/suburban area.  At that time the population of the DC area was about 5.5 million people.  We chose our house because it backed up to a strip of woods with a small creek running through it.  The woods was pretty good habitat for wildlife, including many Eastern Gray Squirrels.  There were 10-20 in my yard most of the time.  My high count for squirrels (all in view at one time) was 44! 

Being a wildlife gardener, over about 10 years I transformed that typical suburban yard into good wildlife habitat, so the birds and critters felt comfortable in my yard.  I also fed birds, so that attracted the critters as well.  The result was, plenty of birds and squirrels, and also deer, foxes, raccoons, opossums, and rats, of course.  Occasionally a roaming cat or dog would show up, but not that many, surprisingly, given that coyotes were rare there.  The Town of Vienna had an ordinance against letting cats and dogs run loose, so perhaps that helped a bit.  There were nesting birds in my yard and/or the woods, including Robin, Cardinal, Sparrow/Towhee species, Blue Jay, Finch species, Carolina Chickadee, Tufted Titmouse, Carolina Wren, Catbird, Mockingbird, and more.

There were also many thousands of Crows in the area, in massive roosts.  I would have hundreds of Crows streaming over my house daily as they flew to/from their roosts.  Most days they staged in the woods for a while and there could be 50 or more in the trees before flying on to their roosts.  There were also nesting Crows in the woods.  Sometimes I got lucky and I could watch their nest from my living room window. 

However, the Corvid scene changed when people who lived near the large roosts started complaining about them.  After public hearings, at which I spoke against exterminating the Crows, the people in charge voted to go ahead with poisoning the Crows coming to the roosts.  Not long after that, West Nile disease hit that area.  Between the poisoning and West Nile, Crows disappeared.  I had zero Crows in or over my yard for more than two years.  My many Blue Jays also disappeared, I assume because West Nile disease killed them. 

During those Corvid-less years I didn’t notice any dramatic difference in numbers of Robins or other nesting birds and their offspring that frequented my yard, and I watched birds in my yard pretty closely.  Not scientific, I know, but it is what I observed in my little patch, sort of how you are going by an observation in your little patch.  Perhaps if West Nile disease had killed the squirrels too, there would have been a noticeable difference in numbers of nesting birds/offspring, I don’t know. 

Perhaps my experience means nothing regarding your patch, but thought that I would mention it, fwiw.” 

———-

My reply to that: Thanks for the insight and anecdote…robins were not native breeders at this low elevation and moved in when people changed the habitat and BEFORE chemicals were introduced or before housecats could reign because humans wiped out the natural predators–from foxes and weasels up to bears…I would almost always assume now when wildlife or habitat changes, our species is the root of the cause…nature will  prevail but now most of what happens with other species short-term is caused  by our species. Gravity, techtonics, the magnetic pole, and volcanoes seem to be about the only processes we have yet to alter…as far as we know, which sometimes is much too little and too late.

Let’s listen to Jane Goodall, click here for short lesson on hope: https://www.newyorker.com/magazine/2021/10/04/jane-goodalls-survival-guide

• *It was her brother, Hart Merriam, who pioneered the use of nomenclature for various habitat zones in describing where species lived.