1) For many species there is evidence that breeding performance changes as an individual ages. In iteroparous species, breeding performance often increases through early-life and is expected to level out or even decline (senesce) later in life. Furthermore, an individual’s sex and conditions experienced in early-life can affect breeding performance and how this changes with age.
2) Long-term monitoring of individuals from reintroduced populations can provide unique opportunities to explore age-related trends in breeding performance that might otherwise be logistically challenging.
3) We used a unique dataset from a reintroduced population of white-tailed eagles Haliaeetus albicilla in Scotland, which has been intensively monitored since their initial reintroduction in 1975, to study age- and sex-specific trends in two measures of breeding performance. This monitoring provided data on breeding performance of known individuals ranging in age from 3 to 26 years old. We also explored changes in breeding performance in relation to early-life experience (i.e. whether they were released or fledged in the wild).
4) Breeding performance increased with age in early-life in a similar manner for both sexes. We found stronger evidence for senescence in breeding performance in males than females. However, late-life female breeding success was associated with early-life experience, while male senescent trends were not apparently impacted by conditions experienced during early-life.
5) Sexual differences in senescence mean that older males are less likely to breed successfully compared to older females and this may influence females’ mate changes later in life. This difference may suggest a linked sexual difference in survival rates or the possibility of proactive partner change by females in later life in this typically monogamous bi-parental species.
white_tailed_eagle_female
This dataset includes all breeding attempts by known age female white-tailed eagles between 3 – 26 years old and the associated information of the partner if known.
FemaleID = individual code for female identity
MaleID = individual code for male identity
OriginF = Origin of female
OriginM = Origin of male (if known)
Origin categories: R1 = release phase 1, R2 = release phase 2, W= wild bred
Territory = individual code for breeding territory
Year = year of breeding attempt
FAge = The age of the female
Mage = The age of the male (if known)
Fexp = The number of breeding year / experience of the female
Mexp = The number of breeding year / experience of the male (if known)
Success = 0/1 if any chicks were fledged or not
Fledged = 0/1/2 the number of chicks fledged
white_tailed_eagle_male
This dataset includes all breeding attempts by known age male white-tailed eagles between 3 – 26 years old and the associated information of the partner if known.
MaleID = individual code for male identity
FemaleID = individual code for female identity
OriginF = Origin of female (if known)
OriginM = Origin of male
Origin categories: R1 = release phase 1, R2 = release phase 2, W= wild bred
Territory = individual code for breeding territory
Year = year of breeding attempt
FAge = The age of the female (if known)
Mage = The age of the male
Fexp = The number of breeding year / experience of the female (if known)
Mexp = The number of breeding year / experience of the male
Success = 0/1 if any chicks were fledged or not
Fledged = 0/1/2 the number of chicks fledged
young_success
This data set includes data from female white-tailed eagles aged 3 – 15 and male white-tailed eagles aged 3 – 18 years to examine breeding success.
ID = Individual identity
Territory = individual code for breeding territory
Year = year of breeding attempt
Origin = Origin of individual
Origin categories: R1 = release phase 1, R2 = release phase 2, W= wild bred
Sex = Male / Female
First_age = age at individuals first breeding attempt
Age = age at breeding attempt
Success = 0/1 if any chicks were fledged or not
young_productivity
This data set includes data from female white-tailed eagles aged 3 – 13 and male white-tailed eagles aged 3 – 18 years to examine breeding productivty.
ID = Individual identity
Territory = individual code for breeding territory
Year = year of breeding attempt
Origin = Origin of individual
Origin categories: R1 = release phase 1, R2 = release phase 2, W= wild bred
Sex = Male / Female
First_age = age at individuals first breeding attempt
Age = age at breeding attempt
Fledged = 0/1/2 the number of chicks fledged
old_success
This data set includes data from female white-tailed eagles aged 16 – 23 and male white-tailed eagles aged 19 – 23 years to examine breeding success.
ID = Individual identity
Territory = individual code for breeding territory
Year = year of breeding attempt
Origin = Origin of individual
Origin categories: R1 = release phase 1, R2 = release phase 2, W= wild bred
Sex = Male / Female
Last_age = age at individuals last breeding attempt NB. Many were still alive and breeding while monitoring was on going. Therefore year of last recorded breeding attempt also given (Last_year).
Age = age at breeding attempt
Success = 0/1 if any chicks were fledged or not
old_productivity
This data set includes data from female white-tailed eagles aged 14 – 23 and male white-tailed eagles aged 19 – 23 years to examine breeding productivity.
ID = Individual identity
Territory = individual code for breeding territory
Year = year of breeding attempt
Origin = Origin of individual
Origin categories: R1 = release phase 1, R2 = release phase 2, W= wild bred
Sex = Male / Female
Last_age = age at individuals last breeding attempt NB. Many were still alive and breeding while monitoring was on going. Therefore year of last recorded breeding attempt also given (Last_year).
Age = age at breeding attempt
Fledged = 0/1/2 the number of chicks fledged
