Data Zone
Click on any of the following for some background and an explanation of the technical terms used in the species factsheets and additional data tables:
Generation length
Generation length is the average age of parents of the current cohort (i.e. newborn individuals in the population). Generation length therefore reflects the turnover rate of breeding individuals in a population. It is greater than the age at first breeding and less than the age of the oldest breeding individual, except in taxa that breed only once.
Species’ generation lengths are necessary for scaling population declines for assessing extinction risk, and are required for IUCN Red List assessments. An approach to systematically estimate generation lengths for all bird species was published in 2020 (Bird et al. 2020), where compiled information on life history and trait data was used to impute missing life history data using Generalized Linear Mixed Models. Generation lengths for all bird species were then calculated using the modelled values of age at first breeding (F), maximum longevity (L) and annual adult survival (S).
We continue to update the life history and trait database underpinning this work, and periodically repeat the methodology to generate improved estimates of generation length for use in each comprehensive Red List reassessment cycle. The most recent results are from November 2020, after an extensive update to the underlying data set. For some species, a generation length based on life-history tables has been calculated, which is used in preference to the value from the model-based methodology.
A file containing the latest generation lengths of the world’s birds is available to download here.
The Bird et al. (2020) paper and associated data are available here: https://conbio.onlinelibrary.wiley.com/doi/10.1111/cobi.13486