Date: 5/5/25 8:33 am From: <chucao...> Subject: RE: [MBBIRDS] This year's migration numbers/lateness
Pete et al.
I think that one has to step back and realize that there is variation year to year as you all mention and that is normal. But, what has been noted this year is far from the norm. People who have been birding for a long time, and have a good gut feel about bird arrivals and migration density suggest it is way, way off the norm this year. Both late and low volume. I have not been birding much this spring so it is what I am hearing from folks, more than what I am seeing. The suggestion is that very dry winter in parts of Mexico may have influenced overall numbers or health of birds down there. The suggestion is that many may have died. Of course with birds that only live 5-6 years, one good year can resupply the loss that can happen in a poor year. We shall see.
From: <mbbirds...> <mbbirds...> On Behalf Of Pete Sole
Sent: Monday, May 5, 2025 7:23 AM
To: Abram Fleishman <abfleishman...>; Carol Pecot <carol.pecot...>
Cc: MBB <mbbirds...>
Subject: Re: [MBBIRDS] This year's migration numbers/lateness
Hi Abram,
Thanks for the insight! Much appreciated.
I wonder though, given the variability over time, if the averages are even representative of the data. Not to get in the weeds on the math, but if the standard deviation is high, then looking at the average could easily lead to wrong expectations. One example, I wonder if El Niño, La Niña, and in-between years, lead to noticeably different migration patterns (numbers and timing), given their effect on weather (rainfall).
Many factors to ponder. Some quite complex with feedback loops and subtle downstream impacts. Yet somehow, the birds still manage to migrate. 🙂
Thanks again for sharing,
Pete
On 5/5/25 6:39 AM, Abram Fleishman wrote:
Hi Carol and Pete,
The historical lines on birdcast come from the 1995-2017 period. As with any average, there are high years and low years and the average draws the line through the middle. There may even be average years that the line represents really well. But I like to think about our rainfall in Santa Cruz county (or California in general) when thinking about this stuff. With our rainfall, we normally have wet years or dry years and both of which are quite far from the average rainfall. Only occasionally do we get years that hit the average.
I imagine the same thing is happening with bird migration. There are many contributing factors like the previous breeding season’s reproductive success, the fall migration and then winter survival rate, and then spring migratory corridor and survival. All these are affected by weather (storms can kill, but rains lead to strong food resources, winds and storms can push and pull birds during migration) along with a host of other factors. This is all just to say that averages are just one piece of info, to ask the question of how this year stacks up to past year we would need to seem more data. Specifically yearly values or trend lines.
Good thoughts, Pete, thanks. Thanks also for mentioning the 7 simple actions link, it is a good one! Jane Orbuch made some posters in a larger format, and we usually display them at birding events. On the topic of planting natives = more caterpillars = more baby bird food, Doug Tallamy’s Homegrown National Park park is awesome: https://homegrownnationalpark.org/.
By the way, this coming Saturday will be a small Migration event at Natural Bridges. If anyone is interested in helping in some way, please contact me.
Carol
> On May 4, 2025, at 9:59 PM, Pete Sole <pete...> <mailto:<pete...> > wrote:
>
> Hi Carol,
>
> I'm no expert. I don't know how far back the "historic" data goes. But my suspicion, is that data older than perhaps 10 or 20 years, reflects migration patterns that may no longer be present. That is why when I look at data on ebird to try to tease out trends, I try to limit the data to the last 10 years. If nothing else, we know that land use and climate patterns have changed significantly in the last 50 years. Not to mention the estimates, that we have lost some 2.9 billion birds in North America since 1970. (source: https://www.birds.cornell.edu/home/bring-birds-back)
>
> Regardless, here are 7 suggestions to help avian species:
>
> https://www.3billionbirds.org/7-simple-actions >
> My 2 cents,
>
> Pete
>
>
> On 5/4/25 8:57 PM, Carol Pecot wrote:
>> I was looking at the BirdCast dashboard ( https://dashboard.birdcast.info/region/US-CA-087) and saw that the graph of the “Total Birds Crossed” seems to show about 1/2 the number of birds compared to the historic amount for our county. Does that seem correct, or might that be a late migration that people have been mentioning? If late is the case, then maybe it will continue rising more steeply…?
>>
>> Does anyone have other information on this?
>>
>> Carol Pecot (We now have M & F BH Grosbeaks, and got a Wilson’s Warbler about a week ago)
>>
>
