Data from: Earlier springs increase goose breeding propensity and nesting success at Arctic but not at temperature latitudes

1. Intermittent breeding is an important tactic in long-lived species that
trade off survival and reproduction to maximize lifetime reproductive
success. When breeding conditions are unfavourable, individuals are
expected to skip reproduction to ensure their own survival. 2.
Breeding propensity (i.e. the probability for a mature female to breed in
a given year) is an essential parameter in determining reproductive output
and population dynamics, but is not often studied in birds because it is
difficult to obtain unbiased estimates. Breeding conditions are especially
variable at high latitudes, potentially resulting in a large effect on
breeding propensity of Arctic-breeding migratory birds, such as geese. 3.
With a novel approach, we used GPS-tracking data to determine nest
locations, breeding propensity and nesting success of barnacle geese, and
studied how these varied with breeding latitude and timing of arrival on
the breeding grounds relative to local onset of spring. 4. Onset of spring
at the breeding grounds was a better predictor of breeding propensity and
nesting success than relative timing of arrival. At Arctic latitudes
(> 66°), breeding propensity decreased from 0.89 (95% CI:
0.65-0.97) in early springs to 0.22 (95% CI: 0.06-0.55) in late springs,
while at temperate latitudes it varied between 0.75 (95% CI: 0.38-0.93)
and 0.89 (95% CI:  0.41-0.99) regardless of spring phenology.
Nesting success followed a similar pattern, and was lower in later springs
at Arctic latitudes, but not at temperate latitudes.  In early
springs, a larger proportion of geese started breeding despite arriving
late relative to the onset of spring, possibly because the early spring
enabled them to use local resources to fuel egg laying and incubation. 5.
While earlier springs due to climate warming are considered to have mostly
negative repercussions on reproductive success through phenological
mismatches, our results suggest that these effects may partly be offset by
higher breeding propensity and nesting success.