I have read that while certain animals (elephants, turtles, etc) live much long lives in terms of years as compared to other animals (rodents, etc), their lifespans are fairly equal in terms of number of heartbeats, with the smaller animals running on faster metabolisms “using up” their ultimate “allotment” of heartbeats faster than the larger animals with slower metabolisms. All of this makes perfect sense to me.
My main question is this: I thought that birds have relatively fast metabolisms, with rapid heartbeats. If this is true, though, how do certain types of birds, like the large breeds of parrots and macaws, often live for well over 50 years? How does their metabolic rate compare to that of a small mammal, and if it is similar, why do they not follow the pattern of heart rate being inversely proportional to lifespan?
The only thing I could come up with is that maybe you can only make comparisons within classification (mammals, birds, reptiles, etc), for example elephants live longer than dogs which live longer than mice and macaws live longer than sea gulls which life longer than sparrows, etc etc. So I guess the second part of my question is if the heart rate theory is all inclusive in the animal kingdom or if it is relative to each separate classification.
I’m sorry if this is a dumb question, it’s not for a school assignment or anything, just my own curiosity/confusion.