Peregrine Falcon (Falco peregrinus) eggshell thickness monitoring data Sweden 1864-2023

The Peregrine Falcon (Falco peregrinus) population in Sweden has been monitored since 1972. At visits to Peregrine Falcon nests, eggshell fragments from hatched eggs as well as unhatched addled (dead) eggs have been collected with the aim of monitoring the thickness of the eggshells as well as analysing the whole eggs for contaminants. The shell thickness serves as a proxy for the falcons’ exposure to certain persistent organic pollutants, in particular DDT and its breakdown products. The field samples have been compared to reference eggs from 1864-1965 in museum collections.

This dataset contains the raw data on eggshell thickness measurements (5084 individual measurements) analysed by Falk et al. (2025); the dataset includes measurements from:

1.    Whole eggs/clutches in museum collection in Sweden, collected 1864-1965

2.    Whole addled/dead eggs collected in nests 1972-2023

3.    Eggshell fragments collected in nests 1972-2023 from crushed or hatched eggs

The dataset contains a mix of measurements of shell thickness including or excluding the eggshell membranes. Membrane thickness varies between different studies; in our study the average membrane thickness determined in two different ways was 0.057 mm. This ’membrane constant’ can be added or subtracted to the measurements for comparisons with other data sets.

Further details regarding the sampling areas, measurement methods and the results of trends analyses of changes in shell thickness are provided in Falk et al. (2025).

The file named Peregrine_eggshell-thickness_data_Sweden_1864-2023.csv contains the raw measurements data, and the file Peregrine_eggshell-thickness_data_Sweden_1864-2023ReadMe.txt specifies the database content.