Answer:
Anything living needs to have certain conditions, if for example a group of flightless birds who are adapted for warm weather had their environment get colder each year and more extreme the surrounding plants and other animals may have a difficult time surviving and this will cause the birds to have less food. The birds also will not be accustomed to these changes and will not be able to adapt their bodies fast enough. This also makes reproduction difficult and in turn further dwindles the population.
