 Some of the same factors that have promoted adaptive radiation of island avifauna over evolutionary time appear to promote vulnerability to non @-@ native species in modern time . The susceptibility of many island birds is undoubtedly due to evolution in the absence of mainland predators , competitors , diseases , and parasites , in addition to lower reproductive rates and extended incubation periods . The loss of flight , or reduced flying ability is also characteristic of many island endemics . These biological aspects have increased vulnerability to extinction in the presence of introduced species , such as the domestic cat . Equally , behavioral traits exhibited by island species , such as " predatory naivety " and ground @-@ nesting , have also contributed to their susceptibility . 
