People use imperfect analogies all the time. Also words can have multiple meanings, especially across different fields. No one is complaining that their electrical 'resistors' are confusing their understanding of non-violent resistance.
> Isn't the whole distinction between gender and sex is one is biological and the other societal?
In people. These are birds. See above about words having multiple meanings.
> If there is a hereditary biological indicator that determines this behavior, shouldn't it fall outside of the gender concept?
Why would it. A, applying the "gender concept" of humans to birds is silly. B, "hereditary biological indicators" and gender can overlap in humans too.
> it could be easily observed and discussed without the confusion
I don't see at all why it would be confusing, and no one else seems confused. The English language does this literally all the time.
I think that the distinction between "biological" and "cultural" is a bit of a non-issue for the professionals. They don't know if it's cultural or biological, but it does not matter, and in fact, the reality is probably that untangling cultural from biological is impossible (not in the sense that the culture is a direct result of the biology, but in the sense that biological development does not care to make the distinction if the conditions that shape its direction are biological or cultural, and that a final trait is therefore the result of a complicated mix of the two).
... But I have to ask: to what end? What political group is massively benefiting from this insidious ornithological analogy?
> Within each gender, white-striped birds are more aggressive while tan-striped birds are more nurturing. That seemingly simple generalization is based on a vast amount of research. For many years, Falls and his students at the University of Toronto carried out highly detailed studies of White-throated Sparrows, showing how behavioral differences between the morphs touched every aspect of these birds’ lives.
Why would you define this variation that's associated with behavior "gender"? Isn't the whole distinction between gender and sex is one is biological and the other societal? If there is a hereditary biological indicator that determines this behavior, shouldn't it fall outside of the gender concept? I don't know how useful it is to add these human constructs to the biological world when it could be easily observed and discussed without the confusion