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Pterosaurs and birds, was Re: birds and pterosaurs

Just to hijack the thread.

I learned that flight feathers of large soaring birds
grow slowly, ca. 1mm/day. This means that largest
flight-feathers of vultures and pelicans take 3-4
months to grow.

I suspect that feather length and not body mass is
limiting size of flying birds. 

Bird needs to replace flight feather by moult at least
every 2 years, cannot lose too many feathers without
becoming flightless, cannot feed while flightless (I
talk about specialised flying scavengers and
fisheaters) and thick base of feather means that
extending wing by growing the flesh part of wing
results in very heavy wing. Ergo - there is some limit
of bird wingspan. 

Possibly for very large flying animals, wing membranes
are more efficent than feathers, models of animal
flight based on largest birds are biased and
pterosaurs achieved true limit of size of flying

Jerzy Dyczkowski 

PS. I am aware that ornamental bird feathers are
longer and birds feeding on water plants can become
flightless during moult.

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