DOI: 10.5061/dryad.1zcrjdfz1
title: Consequences of cross-season demographic correlations for population viability

description: Demographic correlations are pervasive in wildlife populations and can
 represent important secondary drivers of population growth. Empirical
 evidence suggests that correlations are in general positive for long-lived
 species, but little is known about the degree of variation among spatially
 segregated populations of the same species in relation to environmental
 conditions. We assessed the relative importance of two cross-season
 correlations in survival and productivity, for three Atlantic puffin
 (Fratercula arctica) populations with contrasting population trajectories
 and non-overlapping year-round distributions. The two correlations
 reflected either a relationship between adult survival prior to breeding
 on productivity or a relationship between productivity and adult survival
 in the subsequent year. Demographic rates and their correlations were
 estimated with an integrated population model, and their respective
 contributions to variation in population growth were calculated using a
 transient life table response experiment. For all three populations,
 demographic correlations were positive at both time lags, although their
 strength differed. Given the difference in year-round distributions of
 these populations, this variation in the strength of population-level
 demographic correlations points to environmental conditions as an
 important driver of demographic variation through life-history
 constraints. Consequently, the contributions of variances and correlations
 in demographic rates to population growth rates differed among puffin
 populations, which has implications for – particularly small –
 populations’ viability under environmental change as positive correlations
 tend to reduce the stochastic population growth rate.
description: Mark-recapture histories of adult puffins were
 available for 699 individuals at Isle of May (1984–2019), 572 individuals
 at Røst (1990–2019), and 952 individuals at Hornøya (1990–2019). Breeding
 puffins were caught and marked with individually coded colour-rings or a
 unique colour ring combination. Birds were captured either in the nest
 burrow (Isle of May, Hornøya), with noose traps (Hornøya) or in mist nets
 erected on the colony surface (Røst). Visual resightings of ringed birds
 were conducted in subsequent years, predominantly in the areas where
 puffins had been ringed. Productivity data consisted of annual numbers of
 fledged chicks (F<sub>t</sub>) from a sample of monitored
 pairs (E<sub>t</sub>) that made a breeding attempt (defined as
 egg laid on Isle of May and Hornøya and egg hatched on Røst). Island-wide
 population counts (C<sub>t</sub>) of adult breeding pairs were
 conducted at each colony. For Røst and Hornøya, the number of breeding
 pairs (based on the number of apparently occupied burrows) was up-scaled
 from counts in study plots made every year during the study period
 (1990–2019) (see Anker-Nilssen & Røstad 1993 for methodological
 details for Røst). At the Isle of May, total population counts of occupied
 burrows were made in 1984, 1989, 1992, 1998, 2003, 2008, 2013, and
 2017.