The average incubation period for the Dalmatian pelican is 31-32 days. We have many indications that we may have prolongation of the incubation period in large numbers of these birds in Prespa National Park. We know it may happen for example when eggs are left un-incubated for some reasons, but it is not clear to us under which exactly conditions it may take place and how longer it can become. For example can it be 40 or 45 days? Have similar cases been observed in other birds and could you suggest literature for this?