Why are there so few crows in San Francisco?

[spaceman98]

I recently traveled to San Francisco and I noticed that there were no crows, either downtown or in Golden Gate Park. This was especially weird because Golden Gate Park had a lot of ravens, but no crows. Looking at iNat there have only been 71 research grade observations of American Crow in SF this year https://www.inaturalist.org/observations?d1=2023-01-01&place_id=854&subview=map&taxon_id=8021 compared to 408 in Seattle https://www.inaturalist.org/observations?d1=2023-01-01&place_id=119121&subview=map&taxon_id=8021

Looking on Google I find articles saying there were a lot of crows in the bay area a few years ago and there were efforts to chase them away https://www.sfchronicle.com/bayarea/article/Sunnyvale-started-spooking-hundreds-of-crows-with-16801628.php

So is this manmade? Very curious.

[swampster]

@spaceman98

Looking at iNat there have only been 71 research grade observations of American Crow in SF this year

That’s actually not a small amount for that sized area for just this year on iNat. For comparison, Atlanta, GA has 25 observations and New York City has 67 observations.

Ebird is typically more useful for checking this kind of thing. Check out the eBird frequency graph for American Crows in San Francisco:

Looks like it’s just the wrong time of year for American Crows in San Francisco.

[spaceman98]

So do crows in that region have a seasonal migration? I’m used to them being year-round residents in the Seattle area.

[swampster]

Yeah, I think there is a seasonal influx of crows in the winter as northern birds move into the south. Crows are year-round residents in San Francisco as well; that low point at the 2nd week of August is ~25% frequency. So they are around, just much less prevalent than in the peaks of spring and fall.

[jnstuart]

In my area (north-central NM) there is seasonal movement of crows. They are common in urban and suburban areas from fall to spring, often in fairly large flocks, then most disappear during breeding season, typically heading to more forested areas at higher elevation or in riparian areas. Don’t know what seasonal movements are like elsewhere.

[rupertclayton]

I have a different theory: They’re all in Oakland.

We have a ton of crows here, and there were some very large crow “rookeries” on Grand Ave near Lake Merritt over the winter.

Actually, I recall regularly seeing hundreds of crows traveling west above the Golden Gate Park Panhandle in the early evenings a few months ago. I think what you’re seeing in the iNat data may just reflect observation biases (how many people want to upload crow sightings to iNat?)

Your personal experience of seeing ravens and not crows in GG Park may be more a reflection of the seasons. I’m guessing that the ravens in the park are resident, and stay there in pairs and family groups. I know someone who fed the same pair of ravens in GG Park for many years. In contrast, the crows tend to aggregate in bigger flocks over the winter and then disperse in the spring to nest outside San Francisco.

Our Oakland neighborhood currently has lots of loosely connected crow families, and I wouldn’t be surprised if many of the parent birds spent the winter in the big flocks at Lake Merritt.

[swampster]

Interestingly, the ravens show a similar frequency pattern as the crows in San Francisco. They are just more frequently detected/reported overall.

@rupertclayton

In contrast, the crows tend to aggregate in bigger flocks over the winter and then disperse in the spring to nest outside San Francisco.

Yep, the abundance graph seems to agree with you.

[tiwane]

There was quite a crow ruckous outside my place in Oakland a few hours ago.

[dlevitis]

In the park where I work north of San Francisco, I see American Crows almost every time I’m there. We had close to 20K iNat observations before we had a single American Crow observation. Most people ignore them. They are certainly at least as numerous as the ravens in the park, but we have 28 raven observations and only 7 American Crow observations (and most of those seven I took after realizing that I was leaving them out).