Is it possible that pelicans (https://www.inaturalist.org/observations?place_id=any&taxon_id=4323&view=species) routinely use a benign form of family abuse to train the growth of their super-light skeletons and air-sacs (https://en.wikipedia.org/wiki/Air_sac)?
At first sight, it might seem that
However, the situation is odder than this.
Please see:
https://www.dnr.sc.gov/wildlife/species/coastalbirds/files/Publications/Sachs2009BehaviorofParentandNestlingBrownPelicansDuringEarlyBroodrearing.pdf
https://brill.com/view/journals/beh/102/1-2/article-p119_7.xml
https://books.google.com.au/books?id=OUderEB-8UkC&pg=PA117&lpg=PA117&dq=Pelican+throwing+a+fit&source=bl&ots=5JY0q-R5Pu&sig=ACfU3U0875nB0d09uFIfajHHf3E4B1CHNg&hl=en&sa=X&ved=2ahUKEwiLgeruz_f_AhWPTmwGHUAuBEYQ6AF6BAg8EAM#v=onepage&q=Pelican%20throwing%20a%20fit&f=false
https://www.pbs.org/wnet/nature/outback-pelicans-video-pelican-tantrums/6451/
https://www.facebook.com/watch/?v=1069970860274746
https://www.youtube.com/watch?v=HLI8Dlx_2Ns
Scroll through https://www.flickr.com/photos/dougbeckers/5042779690/in/photostream/
Please consider the Australian pelican (Pelecanus conspicillatus, https://www.inaturalist.org/observations/22603013).
Juveniles, after and not before being fed, convulse in what looks like a mad rage, throwing themselves around for a minute, and then collapsing to the ground, before snapping out of it - as if nothing has happened - and settling down to their normal snooze.
Parents of the African white pelican (Pelecanus onocrotalus, https://www.inaturalist.org/taxa/4327-Pelecanus-onocrotalus) seize their half-grown juveniles, and shake them brutally, like a terrier killing a rat, before feeding them.
Later, as if to prove that this is not punishment, the workout becomes self-inflicted as the nearly-fledged juvenile of the African white pelican struggles to withdraw its head from its parent's throat. This is an excruciating ritual to watch, because the beak seems to jam, half-open, in the parent's stomach, and both individuals risk being flailed like rag dolls.
The violence of these fits seems at odds with
Pelicans are among the lightest of living birds for their bulk (https://www.lf2.cuni.cz/en/articles/the-legend-of-the-pelican). Consequently, their bones need to have particular resilience.
The hectic experiences of the juveniles of pelicans may therefore be a method of strengthening their growing skeletons and membrane-bound air-sacs.
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https://www.youtube.com/watch?v=des8gJP2aTE
https://www.youtube.com/watch?v=vU_Yc1hrSac
https://birdfact.com/articles/baby-pelicans
https://www.researchgate.net/figure/arious-ways-of-feeding-the-chicks-by-Spot-billed-Pelican-a-feeding-pre-digested_fig5_263922368
https://www.youtube.com/watch?v=p-q3c-hZNQc
https://www.youtube.com/watch?v=bFdAcG485NA
https://www.youtube.com/watch?v=CjDalFNg5nI
https://www.dnr.sc.gov/wildlife/species/coastalbirds/files/Publications/Sachs2009BehaviorofParentandNestlingBrownPelicansDuringEarlyBroodrearing.pdf
https://www.jstor.org/stable/1365232
https://bioone.org/journals/Waterbirds/volume-32/issue-2/063.032.0207/Behavior-of-Parent-and-Nestling-Brown-Pelicans-During-Early-Brood/10.1675/063.032.0207.short
https://www.jstor.org/stable/40166741
https://link.springer.com/article/10.1007/BF00164043
https://www.jstor.org/stable/1521225
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