Family size dynamics in wintering geese

Gupte, Pratik Rajan; Koffijberg, Kees; Müskens, Gerard; Wikelski, Martin; Kölzsch, Andrea

doi:10.1007/s10336-018-1613-5

Cited by 10 publications

(8 citation statements)

References 33 publications

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“…In the two regional models for Denmark and the Netherlands, respectively, the effect of flock size was strongest in the beginning of the autumn period, whereas towards the end of the period the proportion of juveniles was independent of the flock size. This corresponds with findings by Gupte et al (2019) who showed that through the season the proportion of families in larger flocks increased, and the proportion of independent juveniles increased with flock size. Furthermore, as the interaction between Julian days and flock size was significant in the regional model for Denmark and not for the Netherlands, this could indicate that the interaction effect is stronger in areas with disturbance from hunting, resulting in breaking up of families and juveniles seeking safety in larger flock.…”

Section: Discussionsupporting

confidence: 92%

“…As a result, the proportion of juveniles declines with flock size. Gupte et al (2019) also showed that through the autumn season the proportion of families in flocks increased, and the proportion of independent juveniles increased with flock size. Thus, the proportion of juveniles is likely to be higher in small flocks than in larger flocks, but as time progresses this effect is expected to attenuate.…”

Section: Introductionmentioning

confidence: 94%

“…In autumn, it is often observed that goose families are overrepresented in small flocks (Gupte et al, 2019; Madsen, 2010), which may be an attempt to avoid food competition in the larger flocks. Non‐breeding geese, on the other hand, typically gather in larger flocks, possibly to access enhanced group‐living benefits such as increased anti‐predator vigilance (Roberts, 1996).…”

Section: Introductionmentioning

confidence: 99%

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Sources of variation in estimating breeding success of migratory birds from autumn counts

Jensen

Johnson

Madsen

2023

Ecol Sol and Evidence

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Understanding drivers of change in population sizes requires estimation of demographic rates such as survival and productivity. In migratory geese, productivity or breeding success is typically assessed at the autumn staging and wintering grounds by observing the number of young versus adults in flocks of geese—also called age counts. Such age counts are, however, likely to be affected by a number of factors as we are compelled to sample from an open population, in which the temporal and spatial age composition can vary due to differential migration, mortality and flocking behaviour. In this study we seek to provide guidance for the design of age counts, by identifying which factors need to be taken into account when collecting data. Identification of these factors will facilitate a more targeted data collection and enable better conservation and management recommendations. We use the long‐term age count dataset for the Svalbard population of the pink‐footed goose and focus on the following factors: May thaw days on Svalbard, region of sampling, flock size, time and cumulative harvest, calculated as the amount of shot individuals up to each observation of juveniles. We find that the temporal trend in goose productivity based on raw data will be affected by variation in how (which flock sizes), where (which region) and when (which Julian day) the data have been collected. The sources of variation in observations of goose productivity confound inference at the population level. Thus, if the goal is to follow changes in annual productivity, pooled totals of age counts are only useful if data are collected following a random design. We recommend adjusting for these effects using a demographic population model, particularly for hunted species where age counts are conducted during the hunting season and where annual population assessment work is used to recommend an optimal harvest strategy and allocation of hunting quotas. These considerations not only apply to geese, but more generally to migratory birds where breeding and non‐breeding segments or age groups partially segregate in time and space in autumn.

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Section: Discussionsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

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Sources of variation in estimating breeding success of migratory birds from autumn counts

Jensen

Johnson

Madsen

2023

Ecol Sol and Evidence

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“…Winter fidelity in pair-bonded geese is a male-driven trait, where males are believed to lead the female from breeding locations to wintering locations to which they are philopatric [ 65 ]. Here, 79 of 97 white-fronts used for movement analyses were female, and while we did not test for differences between sexes or pairing status, rates of movement among wintering regions were higher than expected regardless of this status, and may be greater for juvenile and unpaired individuals in the population [ 32 , 73 ]. Considering males initiate pairing with females during winter, we may expect unpaired males to make regional movements at even larger rates than observed in this study.…”

Section: Discussionmentioning

confidence: 99%

Winter fidelity, movements, and energy expenditure of Midcontinent Greater White-fronted Geese

et al. 2021

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Background Animal movement patterns are the result of both environmental and physiological effects, and the rates of movement and energy expenditure of given movement strategies are influenced by the physical environment an animal inhabits. Greater white-fronted geese in North America winter in ecologically distinct regions and have undergone a large-scale shift in wintering distribution over the past 20 years. White-fronts continue to winter in historical wintering areas in addition to contemporary areas, but the rates of movement among regions, and energetic consequences of those decisions, are unknown. Additionally, linkages between wintering and breeding regions are generally unknown, and may influence within-winter movement rates. Methods We used Global Positioning System and acceleration data from 97 white-fronts during two winters to elucidate movement characteristics, model regional transition probabilities using a multistate model in a Bayesian framework, estimate regional energy expenditure, and determine behavior time-allocation influences on energy expenditure using overall dynamic body acceleration and linear mixed-effects models. We assess the linkages between wintering and breeding regions by evaluating the winter distributions for each breeding region. Results White-fronts exhibited greater daily movement early in the winter period, and decreased movements as winter progressed. Transition probabilities were greatest towards contemporary winter regions and away from historical wintering regions. Energy expenditure was up to 55% greater, and white-fronts spent more time feeding and flying, in contemporary wintering regions compared to historical regions. White-fronts subsequently summered across their entire previously known breeding distribution, indicating substantial mixing of individuals of varying breeding provenance during winter. Conclusions White-fronts revealed extreme plasticity in their wintering strategy, including high immigration probability to contemporary wintering regions, high emigration from historical wintering regions, and high regional fidelity to western regions, but frequent movements among eastern regions. Given that movements of white-fronts trended toward contemporary wintering regions, we anticipate that a wintering distribution shift eastward will continue. Unexpectedly, greater energy expenditure in contemporary wintering regions revealed variable energetic consequences of choice in wintering region and shifting distribution. Because geese spent more time feeding in contemporary regions than historical regions, increased energy expenditure is likely balanced by increased energy acquisition in contemporary wintering areas.

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“…In autumn, such time‐pressure for an early arrival is (likely) to be absent, giving geese more time to wait for supportive winds (Kölzsch et al 2016). In addition, in autumn geese fly together with their juvenile brood (Gupte et al 2019), which may require them to select supportive winds and stop more often. Interestingly, while Greater and Eastern greater white‐fronted geese Anser albifrons and Bewick's swans Cygnus columbianus bewickii migrate faster over land in autumn than in spring due to longer stopovers (Nuijten et al 2014, Kölzsch et al 2016, Deng et al 2019), there was no seasonal difference in migration duration in light‐bellied brent geese Branta bernicla hrota migrating almost non‐stop over sea (Vissing et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Sea crossings of migratory pink‐footed geese: seasonal effects of winds on flying and stopping behaviour

Geisler

Madsen

Nolet

et al. 2022

Journal of Avian Biology

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Migratory birds may need to cross barriers such as seas, without opportunities to rest or refuel. Waterbirds, unlike land birds, can stop at sea to rest or wait for better winds and thus may be less selective for supportive winds at departure and tolerate larger drift. However, pay‐offs of waiting are likely to depend on circumstances (e.g. pressure for well‐timed arrival, wind availability and travelling with/without juvenile brood), thus migratory behaviour during barrier crossings is expected to differ between seasons. We studied pink‐footed geese Anser brachyrhynchus crossing the Barents Sea (ca 650 km), in spring and autumn during 2018–2020, using 94 GPS‐tracks of 38 individuals, with annotated ERA5 weather data. We found that 1) especially in autumn, geese selected supportive winds for departure; 2) in spring, geese experienced lower wind support and more crosswinds than in autumn, leading to 23% longer routes, 60% longer durations, 93% longer air distances and 45% higher ratios of air‐to‐ground distances; 3) in both seasons, geese had more tailwinds in the first part of crossings, and in spring when deviating more from the shortest route; 4) geese stopped at sea more often in spring (mean 11×) than autumn (3×), in spring during earlier stages of crossings, but in both seasons, spent half of the crossing time at sea, during which they still continued to approach their destination slowly; 5) stops at sea happened mostly in adverse winds, warmer air, higher air humidity and on calmer water and, in autumn, took longer without juvenile brood. We conclude that for migrating pink‐footed geese, Arctic capital breeders, the importance of time and energy can shift en route and that seasonal differences in wind support, flying and stopping behaviour and the pressure for a well‐timed arrival cause the Barents Sea to be a larger barrier in spring than in autumn.

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Family size dynamics in wintering geese

Cited by 10 publications

References 33 publications

Sources of variation in estimating breeding success of migratory birds from autumn counts

Sources of variation in estimating breeding success of migratory birds from autumn counts

Winter fidelity, movements, and energy expenditure of Midcontinent Greater White-fronted Geese

Sea crossings of migratory pink‐footed geese: seasonal effects of winds on flying and stopping behaviour

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