Many species have advanced the timing of annual reproductive cycles in response to climatic warming, sometimes leading to asynchrony between trophic levels, with negative population consequences. Long-distance migratory birds, reliant on short seasonal food pulses for breeding, are considered particularly susceptible to such disjunction because late arrival may preclude optimal timing of egg-laying. It is unknown whether the relative timing of arrival and egg-laying is sufficiently plastic, in time and space, to enable an adaptive response when arrival times change relative to local food resources. We used citizen science data, describing pied flycatcher Ficedula hypoleuca arrival and egg-laying dates, to explore temporal (2013-2016) and spatial (across Great Britain) variation in the phenology of arrival, laying and their difference. To assess the long-term trend in arrival and laying at a single location, we used data from a long-term field study. The arrival-laying interval was consistently shorter in the north, driven by the contrast between spatial variation in arrival date and spatial invariance in laying date. To understand whether a short arrival-laying interval may have consequences for productivity, we assessed the association between this interval and clutch size. We found no statistically significant correlation between these two variables. To examine long-term changes in arrival and laying dates, we focussed on a single location in southwestern England. Both dates of first male arrival and first egg laid in a season advanced since 1986, with no evidence of interval shortening. Together, our results demonstrate spatial and annual variation in the arrival-laying interval, with no detected effect on fecundity. Thus, the interval from arrival to laying is likely dictated by spatially and temporally varying local conditions, suggesting these migrant birds may have the ability to adapt this interval to align with local conditions and mitigate potential mismatch impacts.

This file contains the different analyses covering sections 2.1 to 2.6 of the original paper. 

This includes multiple datasets including:

- processed dataset from database BirdTrack (BTO), showcasing presence/absence of Pied Flycatcher on checklists across Great Britain between 2013-2016.

- raw and processed datasets from database Nest Record Scheme (BTO), showcasing nests of Pied Flycatcher for the same range and time.

- geolocator data collected in Devon, UK, with arrival and nesting dates, for 2015-2016.

- first arrival date and first nesting data collected in Devon, UK, from 1986-2018.

Details of processing are included in the manuscript whenever the code is not provided.

The code for all the statistical analyses is provided.

All the ReadMe files are inside of the respective folders with instructions of how to use the scripts and with metadata.