Meeting Abstract
Circadian rhythms: cyclical patterns of gene expression, physiology, or behaviour on a diel time scale (24 hours cycles) are ubiquitous. Recent research on “wild clocks” has suggested that biological rhythms and chronotype might be linked to an individual’s ecology and fitness. We used an automated radio telemetry system to determine patterns of activity and individual chronotype (onset/cessation of activity relative to civil twilight, CT) in female European starlings during parental care. Diurnal patterns of activity varied among breeding stages, e.g. females were relatively more active just prior to sunset (16.00-18.00) during incubation but were more active in the early morning (7.00-10.00) during chick-rearing. Females which failed during incubation were relatively less active between 16.00-18.00, compared with successful birds. Chronotype was highly individually-variable, e.g. chick-rearing females first became active 7-127 min after morning CT, with low- to moderate repeatability within breeding stages. Females that were active earlier in the morning were also active later in the evening during all breeding stages, contrary to the idea of “larks” and “night owls”. There was a weak relationship between a) onset of activity during incubation and a female’s laying date, and b) onset of activity during chick rearing and probability of initiating a second brood, i.e. timing components of phenotype. However, there were few effects of chronotype on current breeding productivity (number of chick fledged, provisioning rate); females that were active later than average produced chicks with higher mass. Furthermore, we found no relationship between chronotype and any measure of future fecundity and return rate (in year 2) or cumulative 2 year productivity.
