ISLAND EXTINCTION RATES FROM REGULAR CENSUSES

Regular censuses conducted over a long time allow the calculation of b oth extinction and immigration rates. We present formulae for estimati on of those rates. We use them on bird censuses of three British islan ds. These formulae mulae improve on previous estimators of extinction but reaffirm that smaller populations have a higher probability of bec oming extinct. On the other hand, they suggest no correlation between extinction rate and either body size or migratory status among birds.