Droevendaalsesteeg 10
6708 PB Wageningen
The Netherlands
Bart Nolet is a movement ecologist with a particular interest in linking foraging and migration theory. Most of his work is on waterfowl like geese and swans, scaling up from individual behaviour to population dynamics and distribution. His is also working on herbivory, with research on goose-grass, swan-pondweed and beaver-willow interactions.
Bart Nolet leads two scientific consortia, investigating Arctic bird migration and adaptive goose management. He is NIOO representative in the steering committee of the Centre for Avian Population Studies, and is a national expert in bodies from the European Goose Management Platform. He holds a special chair in Waterfowl Movement Ecology at the University of Amsterdam.
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. 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. 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. 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° N), 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. 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.
The Russian breeding population of barnacle geese Branta leucopsis has shown a rapid increase in numbers since 1980, which has coincided with a southwest-wards breeding range expansion within the Russian Arctic. Here barnacle geese also started to occupy coastal and marsh land habitats, in which they were not know to nest on their traditional breeding grounds. While these changes have been well documented by studies and observations throughout the new breeding range of barnacle geese, observations are lacking from the traditional breeding grounds on Novaya Zemlya, as this area is remote and difficult to access. This is especially relevant given rapid climate warming in this area, which may impact local distribution and population size. We used GPS-tracking and behavioural biologging data from 46 individual barnacle geese captured on their wintering grounds to locate nest sites in the Russian Arctic and study nesting distribution in 2008–2010 and 2018–2020. Extrapolating from nest counts on Kolguev Island, we estimate the breeding population on Novaya Zemlya in 2018–2020 to range around 75,250 pairs although the confidence interval around this estimate was large. A comparison with the historical size of the barnacle goose population suggests an increase in the breeding population on Novaya Zemlya, corresponding with changes in other areas of the breeding range. Our results show that many barnacle geese on Novaya Zemlya currently nest on lowland tundra on Gusinaya Zemlya Peninsula. This region has been occupied by barnacle geese only since 1990 and appears to be mainly available for nesting in years with early spring. Tracking data are a valuable tool to increase our knowledge of remote locations, but counts of breeding individuals or nests are needed to further corroborate estimates of breeding populations based on tracking data.