Re: Where are the hummingbirds? Disturbing declines....


Bill Bousman
 

Jim and others,

The Palo Alto CBC circle is on the border of Santa Clara and San Mateo County.  Data from this circle are continuous since about 1960.  A hundred years ago, Anna's withdrew from the Bay area in the winter, but with all the gardens in urban areas, it is not clear that many leave in our warming winters.  Hence, the CBC data should capture population trends over a 15-mile diameter circle.  If you normalize the bird counts by party-hours, then you can combine multiple CBCs and examine metadata trends.

We also have a Summer Bird Count in the Palo Alto circle and that data is continuous from 1981.  This evening I looked at the data for Anna's Hummingbird and, although the variance is noticeable, a calculation based on the years from 1981 to 2019 shows an increase of 2.5% per year.  From my experience that is quite good.  Two local high school students have set up a website to visualize these changes <https://www.pasbcstats.com/>.  Just recently they have added a linear regression log fit, but I think there is a bug they need to work out.

I encourage anyone with some spare time to take a look at regional CBC trend data in their own area.  The data are on the Audubon site, and the analyses I use are pretty simple and straightforward if you have some familiarity with Excel or an equivalent spreadsheet program.

Bill Bousman
Menlo Park

On 4/13/2021 6:10 PM, Jim Chiropolos wrote:
This year and last fall have been disturbing slow for hummingbirds numbers at the house. This is documented by the daily yard eBird reports I began in august of 2017. When I started recording numbers of Annas hummingbirds, I had 30 individuals at multiple days in the fall in 2017 and over 8 on multiple days in the spring of 2018.

Last fall, 2020, we never had a day of over 6 and usually less. I put it down to the fires. This spring, 2021, we have maybe highs of 3 individual birds except for one day of 6. Rufous and Allen numbers are very low and similar in trends. This is very disturbing. We have a big blooming sage patch plus feeders and no hummers at the sage this year. Every year, review of ebird lists at my house is showing declining numbers of hummers.

I spoke with a friend in the Diablo foothills and he reports very low numbers of hummers (all species) at his house this spring compared to previous years. I’m below Vollmer peak on the Orinda side.

It’s good to have data to back up what I thought was happening, but I wish the treads were showing increases - not decreases. The daily reports seem to be showing some very disturbing trends - at least at my house.

Jim Chiropolos, Orinda




Join EBB-Sightings@groups.io to automatically receive all group messages.