There's been some suggestion food source quality drives aggression /defense
of that food patch
https://academic.oup.com/condor/article-abstract/89/1/103/5188898
-Stephen

On Fri, Nov 26, 2021 at 7:19 AM Mike Wagenbach <wagen at uw.edu> wrote:


> I haven't noticed highly docile/sociable Anna's this year, but I saw one

> unusual event last year: It was during a cold snap when I had to bring the

> feeders in at night to prevent freezing. One morning I put them out at

> dawn and almost immediately saw all four perches of the feeder filled with

> birds, who drank more or less continuously for what seemed like a long time

> (a minute or two) with almost no interaction between them. This tolerance

> didn't last long, and within a few minutes, certainly less than ten,t there

> was a lot of chasing and defending the feeder, as usual. My assumption was

> that after an unusually cold night, they were desperate to feed and didn't

> have the energy for the typical chases right at first.

>

> This comment thread makes me wonder if there could be some evolution of

> behavior occurring as a result of consistent feeder maintenance around our

> homes. While needlessly defending an almost limitless resource

> (particularly during the non-breeding season) seems like a waste of energy,

> no doubt it promotes differential survival for the bird doing the

> defending. However, if that reduces the survival through the winter of

> that bird's sons and daughters, and even siblings, cousins and

> nieces/nephews, which seems likely, particularly if they have site-fidelity

> to where they spend successive winters, that would set up a potential

> kin-selection benefit to not defending the feeder.

>

> Has territoriality in Anna's been studied carefully enough to detect

> changes in the behavior?

>

> Mike Wagenbach

> Seattle (Ballard)

>

>

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