Failure to adapt migration timing to changes in environmental conditions along migration routes and at breeding locations can result in mismatches across trophic levels, as occurs between the brood parasitic common cuckoo Cuculus canorus and its hosts. Using satellite tracking data from 87 male cuckoos across 11 years, we evaluate why the cuckoo has not advanced its arrival to the UK. Across years, breeding ground arrival was primarily determined by timing of departure from stopover in West Africa before northward crossing of the Sahara. Together with high population synchrony and low apparent endogenous control of this event, this suggests that a seasonal ecological constraint operating here limits overall variation in breeding grounds arrival, although this event was itself influenced by carry-over from timing of arrival into tropical Africa. Between-year variation within individuals was, in contrast, mostly determined by northward migration through Europe, likely due to weather conditions. We find evidence of increased mortality risk for a) early birds following migration periods positively impacting breeding grounds arrival, and b) late birds, possibly suffering energy limitation, after departure from the breeding grounds. These results help identify areas where demands of responding to global change can potentially be alleviated by improving stopover quality.

These datasets were constructed as described in the Methods of the paper. mig_timing_df.csv is the cleaned Julian date of each migratory milestone, with associated covariates, by PTT and year. mig_timing_df_uncertainty.csv is the uncertainty associated with each milestone.

The data files are in comma-separated value format and are designed to be analysed using the script analyse_cuckoo_mig_milestones.R.