DOI: 10.5061/dryad.qjq2bvqhc
title: Postnatal growth rate varies with latitude in range-expanding geese – the role of plasticity and day length

description: This dataset contains data from an analysis of differences in growth rate
 among three different barnacle populations breeding at different
 latitudes, described in the paper: Boom, Michiel P., van der Jeugd, H.P.,
 Steffani, B., Nolet, B.A., Larsson, K., & Eichhorn, G. (2021),
 Postnatal growth rate varies with latitude in range-expanding geese – the
 role of plasticity and day length. Journal of Animal Ecology. The
 postnatal growth period is a crucial life stage, with potential lifelong
 effects on an animal’s fitness. How fast animals grow depends on their
 life history strategy and rearing environment, and interspecific
 comparisons generally show higher growth rates at higher latitudes.
 However, to elucidate the mechanisms behind this gradient in growth rate,
 intraspecific comparisons are needed. Recently, barnacle geese expanded
 their Arctic breeding range from the Russian Barents Sea coast southwards,
 and now also breed along the Baltic and North Sea coasts. Baltic breeders
 shortened their migration, while barnacle geese breeding along the North
 Sea stopped migrating entirely. We collected cross-sectional data on
 gosling tarsus length, head length and body mass, and constructed
 population-specific growth curves to compare growth rates among three
 populations (Barents Sea, Baltic Sea and North Sea) spanning 17° in
 latitude. Growth rate was faster at higher latitudes, and the gradient
 resembled the latitudinal gradient previously observed in an interspecific
 comparison of precocial species. Differences in day length among the three
 breeding regions could largely explain the observed differences in growth
 rate. In the Baltic, and especially in the Arctic population, growth rate
 was slower later in the season, most likely because of the stronger
 seasonal decline in food quality. Our results suggest that differences in
 postnatal growth rate between the Arctic and temperate populations are
 mainly a plastic response to local environmental conditions. This
 plasticity can increase the individuals’ ability to cope with annual
 variation in local conditions, but can also increase the potential to
 re-distribute and adapt to new breeding environments. 
description: We collected biometric data
 on growing goslings during long-term studies in colonies from three
 study-populations: 1) A long-distance migratory population breeding in the
 Arctic in Kolokolkova Bay along the Barents Sea coast (68°35’N, 52°20’E),
 data collected in 6 years between 2003 and 2015; 2) A short-distance
 migratory population breeding on Gotland in the Baltic Sea (57°25’N,
 18°53’E) data collected in 15 years between 1986 and 2000; 3) A sedentary
 population breeding in the Netherlands along the North Sea (51°40’N,
 4°14’E) data collected in 5 years between 2004 and 2018 (Larsson
 <i>et al.</i>, 1988; Van der Jeugd <i>et al.</i>,
 2003, 2009; Eichhorn <i>et al.</i>, 2010).
 Our analysis is based on all measured goslings with known age
 (Sample sizes: Barents Sea = 392; Baltic Sea = 933; North Sea = 116). Sex
 was determined based on cloacal inspection. Goslings were weighed in a bag
 using a Pesola spring scale with an accuracy of ± 5 g (if &lt;600 g)
 or a digital hand scale or Pesola spring scale with an accuracy of ± 10 g
 (if &gt;600 g). A calliper (± 0.1 mm) was used to measure the outer
 length of the bent tarsus. Head length was measured using a ruler (± 1
 mm). The number of daylight hours that had accumulated
 between hatching and capture was calculated for each gosling. Daylight was
 determined as the period between dawn and dusk, and was calculated based
 on the coordinates of the three breeding colonies using the R package
 “Suncalc” (see associated manuscript referenced above).
 We calculated relative hatch dates by centralizing hatch dates
 within each cohort, because years can differ in onset of spring and
 consequently in timing of breeding and hatching. For the calculation of
 the relative hatch date for each gosling, we used the mean hatch date of
 the colonies (not only of the recaptured goslings), as established from
 nest monitoring (see associated manuscript referenced above for
 details).
description: In the ReadMe file, a description of the variables in the dataset
 can be found, including the data type and measurement unit. The
 explanation column includes a clarification of the variable.
 In general, all measurements were taken from each individual
 gosling. However, on rare occasions one measurement was overlooked,
 resulting in a few missing values (NA = value not available)