The first shot shows one of the chicks fluttering its just emerging wings, just the way passerine chicks will beg. I presume the coot young are semi-precocial. They clearly leave the nest and swim soon after hatching, but perhaps are fed by the parent for a short period of time. Wonder if anyone has speculated about why the chicks have such bright head color - maybe the parents don't have good vision?!
Regarding the color of the American Coot chick, I found an interesting explanation on Wikipedia:
Much research has been done on the breeding habits of American Coots. Studies have found that mothers will preferentially feed offspring with the brightest plume feathers, a characteristic known as chick ornaments.[4]
Davies, Nicholas B.; John R. Krebs and Stuart A. West (2012). "8". Behavioural Ecology. West Sussex, UK: John Wiley and Sons.
[further]
Chick ornaments The first evidence for parental selection of exaggerated, ornamental traits in offspring was found in American Coots.[27] Black American Coot chicks have conspicuously orange-tipped ornamental plumescovering the front half of their body that are known as “chick ornaments” that eventually get bleached out after six days. This brightly colored, exaggerated trait makes Coot chicks more susceptible to predation and does not aid in thermoregulation, but remains selected for by parental choice. These plumes are not necessary for chick viability, but increased chick ornamentation increases the likelihood that a chick will be chosen as a favorite by the parents. Experimental manipulation of chick ornamentation by clipping the bright plumes have shown that parents show clear preferences for ornamented chicks over non-ornamented ones.[27]
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