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Thread: Why did Birds Survive Dinosaur Mass Extinction?

  1. #1 Why did Birds Survive Dinosaur Mass Extinction? 
    Time Lord zinjanthropos's Avatar
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    Going on the asteroid impact 65 mya. I kind of figure birds had the most valuable asset required to survive the extinction event and by that I mean being able to fly to whatever survivable habitat was left in the aftermath. Turns out there are other factors, one being a part of the brain I’ve never heard of…the wulst.

    Only bringing this up after a thought occurred to me that at some point after the impact there must have been some areas completely filled with surviving birds. I wonder if such areas should they have existed, might be hinted at in the fossil record.

    https://www.zmescience.com/science/n...%20extinction.


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    Quote Originally Posted by zinjanthropos View Post
    Going on the asteroid impact 65 mya. I kind of figure birds had the most valuable asset required to survive the extinction event and by that I mean being able to fly to whatever survivable habitat was left in the aftermath. Turns out there are other factors, one being a part of the brain I’ve never heard of…the wulst.

    Only bringing this up after a thought occurred to me that at some point after the impact there must have been some areas completely filled with surviving birds. I wonder if such areas should they have existed, might be hinted at in the fossil record.
    Good question, z.

    An article in CNN* might have some answers for you.

    Doubtless there is a lot of speculation about survivors, and for all those which were lost.


    "These were the unlikely survivors after dinosaurs went extinct"

    * https://www.cnn.com/2018/05/24/world...udy/index.html


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    ox
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    Did only small birds survive?
    The spherules that came raining down might have been more likely to hit the slower bigger ones.

    https://www.bbc.co.uk/news/science-environment-60495951
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    Quote Originally Posted by ox View Post
    Did only small birds survive?
    The spherules that came raining down might have been more likely to hit the slower bigger ones.
    It appears to have a lot to due with habitat destruction, and food sources for the survivors. Not any different than the current mass extinction, just a different cause.

    Since many birds were arboreal, most of the trees were destroyed in fires and acid rain. Eliminating habitat eliminates the animals which live there.

    Also an issue is food source. Bigger animals need more food. With so many sources of food disappearing, the largest animals were doomed. It makes sense if you consider that little animals could survive on slim pickings from seeds and insects. The bigger ones, and many of them carnivores, could not be sustained.
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    Time Lord zinjanthropos's Avatar
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    Don’t smaller birds use more energy than the large? If so wouldn’t the small birds require more food? The larger birds I assume ate larger prey which wasn’t overabundantly available?

    From internet:

    Birds have high basal metabolic rates & so use energy at high rates. Among birds, songbirds (passerines) tend to have higher basal metabolic rates than nonpasserines. And, of course, the smallest birds, hummingbirds, have the highest basal metabolic rates of all birds. In general, basal metabolic rate (or BMR) is related to mass, with larger birds expending less energy per unit weight than smaller birds.

    Species Mass (gms) Kcal/kg/day



    Trumpeter Swan 8900 47
    Brown Pelican 3500 75
    Common Raven 850 108
    American Kestrel 110 157
    White-crowned Sparrow 27 324
    House Wren 11 589
    Rufous Hummingbird 3.5 1600
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    Quote Originally Posted by zinjanthropos View Post
    Don’t smaller birds use more energy than the large? If so wouldn’t the small birds require more food? The larger birds I assume ate larger prey which wasn’t overabundantly available?
    You have it right on the big animals having a problem getting food. This is all about survival of enough breeding animals to avoid extinction. Small animals would likely have a much shorter maturation time, so they could more easily multiply with limited food. And while they have a high metabolic rate, their small size makes up for this by availability of food.

    Think of the food chain. A large number at the bottom, a progressively smaller number of "predators", depending what they are eating. In a mass extinction like this one, the survivors have the advantage of small size, and the metabolic rate may have helped some of them, depending on their local environment and temperatures. But it stands to reason that smaller animals would be more able to adapt, and begin the evolutionary radiation of entirely new animals, with the dubious distinction of starting the "Age of Mammals".
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    Quote Originally Posted by Double Helix View Post
    Quote Originally Posted by zinjanthropos View Post
    Don’t smaller birds use more energy than the large? If so wouldn’t the small birds require more food? The larger birds I assume ate larger prey which wasn’t overabundantly available?
    You have it right on the big animals having a problem getting food. This is all about survival of enough breeding animals to avoid extinction. Small animals would likely have a much shorter maturation time, so they could more easily multiply with limited food. And while they have a high metabolic rate, their small size makes up for this by availability of food.

    Think of the food chain. A large number at the bottom, a progressively smaller number of "predators", depending what they are eating. In a mass extinction like this one, the survivors have the advantage of small size, and the metabolic rate may have helped some of them, depending on their local environment and temperatures. But it stands to reason that smaller animals would be more able to adapt, and begin the evolutionary radiation of entirely new animals, with the dubious distinction of starting the "Age of Mammals".
    So basically, in a large extinction event, smaller animals stand the best chance of survival. Would that mean at some point a small animal such as a bird became the largest surviving predator? No doubt there were pockets where large animals did survive but in an area predominantly filled with birds, seems a certain equilibrium is reached and the non survivors were those that didn’t quite have enough to survive on. My original question still stands….does the fossil record reveal huge concentrations of birds in the few remaining habitable zones after the asteroid hit?
    All that belongs to human understanding, in this deep ignorance and obscurity, is to be skeptical, or at least cautious; and not to admit of any hypothesis, whatsoever; much less, of any which is supported by no appearance of probability...Hume
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    Quote Originally Posted by zinjanthropos View Post
    So basically, in a large extinction event, smaller animals stand the best chance of survival. Would that mean at some point a small animal such as a bird became the largest surviving predator? No doubt there were pockets where large animals did survive but in an area predominantly filled with birds, seems a certain equilibrium is reached and the non survivors were those that didn’t quite have enough to survive on. My original question still stands….does the fossil record reveal huge concentrations of birds in the few remaining habitable zones after the asteroid hit?
    According to wiki*, the impact 66 million years ago most likely caused an "impact winter", which would have global consequences and left no areas habitable for larger animals. This "winter" simply lasted too long for large animals to survive. Quoting from wiki:

    "With the exception of some ectothermic species such as sea turtles and crocodilians, no tetrapods weighing more than 25 kilograms (55 pounds) survived."

    So it seems that no matter where on the planet life was, it was exposed to harsh cooling temperatures, bad news for large endotherms. Have never heard about "huge concentrations of birds in the few remaining habitable zones". The wiki article indicates that a "mass extinction of archaic birds took place" at that time. From what is presented in this wiki treatment, the largest surviving terrestrial predators likely would have been reptiles, such as the precursors of crocodiles and alligators.


    "Cretaceous–Paleogene extinction event"

    * https://en.wikipedia.org/wiki/Cretac...tinction_event
    Last edited by Double Helix; February 25th, 2022 at 07:13 PM.
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  10. #9  
    Time Lord zinjanthropos's Avatar
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    Crocodilian survivors have also been mentioned in this thread so here’s some thoughts as to why they didn’t perish…

    https://www.thoughtco.com/why-did-cr...nction-1092137
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