Inter-species bird calls

I’ve often noticed when I step out of my apartment waiting for a carpool (Mid-atlantic; Maryland), the bird chirp seems to go up into high gear for about five minutes and then dies off to basal levels.

Are birds of different species warning each other that there’s a human on the scene? Here, we have ravens/crows, blue jays, robins, doves, cardinals, and who knows what else.

If so, how are they doing that and why? I imagine there is a specific warning chirp/species call/tone/chirp that within species other species recognize? But why would one species of bird practically care for another? Better the other species is tracked?

Actual altruism?

Maybe **Colbri **has some insight?

Because they all benefit? here’s one example:

The alarm calls are probably mainly directed to others of the same species, which may include mates, offspring, or other relatives. However, other species learn to recognize the alarm calls of other species so that all end up benefiting. Here’sa good discussion.

Many species of birds go about in what are called mixed-species flocks. Why they do so has been the subject of research. However the general consensus is that the main reason is for predator defense. All the birds in a flock benefit from having so many eyes on the lookout. There actually has been a convergence in warning calls so those of many species are quite similar.

As the article mentions, small birds engage in mobbing of predators such as owls and hawks when they find them roosting to drive them out of the area.