Dataset: Annual seabird productivity at breeding colonies around the world from 1964 to 2023 (Stratification Impacts on Seabirds Project)

Breeding performance is measured similarly by seabird ecologists around the world (see Materials and Methods from Cury et al. 2011 for examples). In general, most seabird ecologists determine breeding success by selecting a random sample of nesting pairs (females), and monitoring egg laying, egg hatching, and chick fledging by conducting periodic nest checks every 3-5 days (e.g. Sydeman et al. 1991, 2001).  This enables calculation of measurements of central tendency (means, medians, etc.), as well as between-nest (female) variability in these metrics.  Individual nest site (female) data is then averaged to produce annual mean values, which is what we report in this dataset.  For this particular study, we requested updates on annual mean seabird breeding success and annual sample size from researchers across the globe, many of whom had previously contributed to our Global Seabird Breeding Success dataset (Sydeman et al. 2021, DOI:10.5281/zenodo.4667747). Almost all previous data contributors responded by updating their data time series for this new study (ideally to 2022). We requested new time series for species and locations not previously included in Sydeman et al. 2021, and many new researchers joined the Global Seabird Working Group (see Observing Seabirds, Understanding Oceans webstory, https://seabirds.faralloninstitute.org/). Cury et al. (2011, Supplemental Material) showed that 13 years of data are needed to demonstrate non-linear numerical responses of seabirds to prey abundance, and given our interest in similar seabird breeding success and climate/food web dynamics, we decided on this same minimum limit for time series length. We requested data in annual time series format of at least 13 years in duration, and ending no sooner than the 2014 boreal breeding season. However, some data contributors submitted data in bulk for their colonies, and included time series of shorter duration, or time series that ended before 2014. Seven time series did not fit the criterion of continuing until 2014: 1) black-footed and Laysan albatross at Tern Island, Hawaii (ended in 2008), 2) wedge-tailed shearwater from Varanus Island, Western Australia (ended in 2013), 3) macaroni and gentoo penguins at Bird Island (ended in 2013), and 4) Adélie and gentoo penguins at Admiralty Bay, King George Island (ended in 2012).