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  • 1
    Online Resource
    Online Resource
    Hungry or angry? Experimental evidence for the effects of food availability on two measures of stress in developing wild raptor nestlings
    The Company of Biologists ; 2022
    In:  Journal of Experimental Biology Vol. 225, No. 15 ( 2022-08-01)
    Details
    In: Journal of Experimental Biology, The Company of Biologists, Vol. 225, No. 15 ( 2022-08-01)
    Abstract: Food shortage challenges the development of nestlings; yet, to cope with this stressor, nestlings can induce stress responses to adjust metabolism or behaviour. Food shortage also enhances the antagonism between siblings, but it remains unclear whether the stress response induced by food shortage operates via the individual nutritional state or via the social environment experienced. In addition, the understanding of these processes is hindered by the fact that effects of food availability often co-vary with other environmental factors. We used a food supplementation experiment to test the effect of food availability on two complementary stress measures, feather corticosterone (CORTf) and heterophil/lymphocyte ratio (H/L) in developing red kite (Milvus milvus) nestlings, a species with competitive brood hierarchy. By statistically controlling for the effect of food supplementation on the nestlings' body condition, we disentangled the effects of food and ambient temperature on nestlings during development. Experimental food supplementation increased body condition, and both CORTf and H/L were reduced in nestlings of high body condition. Additionally, CORTf decreased with age in non-supplemented nestlings. H/L decreased with age in all nestlings and was lower in supplemented last-hatched nestlings compared with non-supplemented ones. Ambient temperature showed a negative effect on H/L. Our results indicate that food shortage increases the nestlings' stress levels through a reduced food intake affecting both their nutritional state and their social environment. Thus, food availability in conjunction with ambient temperature shapes between- and within-nest differences in stress load, which may have carry-over effects on behaviour and performance in further life-history stages.
    Type of Medium: Online Resource
    ISSN: 0022-0949 , 1477-9145
    URL: Article
    DOI: 10.1242/jeb.244102
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 2022
    detail.hit.zdb_id: 1482461-9
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    Determinants of departure to natal dispersal across an elevational gradient in a long‐lived raptor species
    Wiley ; 2023
    In:  Ecology and Evolution Vol. 13, No. 1 ( 2023-01)
    Details
    In: Ecology and Evolution, Wiley, Vol. 13, No. 1 ( 2023-01)
    Abstract: Attributes of natal habitat often affect early stages of natal dispersal. Thus, environmental gradients at mountain slopes are expected to result in gradients of dispersal behavior and to drive elevational differences in dispersal distances and settlement behavior. However, covariation of environmental factors across elevational gradients complicates the identification of mechanisms underlying the elevational patterns in dispersal behavior. Assuming a decreasing food availability with elevation, we conducted a food supplementation experiment of red kite ( Milvus milvus ) broods across an elevational gradient toward the upper range margin and we GPS‐tagged nestlings to assess their start of dispersal. While considering timing of breeding and breeding density across elevation, this allowed disentangling effects of elevational food gradients from co‐varying environmental gradients on the age at departure from the natal home range. We found an effect of food supplementation on age at departure, but no elevational gradient in the effect of food supplementation. Similarly, we found an effect of breeding density on departure age without an underlying elevational gradient. Supplementary‐fed juveniles and females in high breeding densities departed at younger age than control juveniles and males in low breeding densities. We only found an elevational gradient in the timing of breeding. Late hatched juveniles, and thus individuals at high elevation, departed at earlier age compared to early hatched juveniles. We conclude that favorable natal food conditions, allow for a young departure age of juvenile red kites. We show that the elevational delay in breeding is compensated by premature departure resulting in an elevational gradient in departure age. Thus, elevational differences in dispersal behaviour likely arise due to climatic factors affecting timing of breeding. However, the results also suggest that spatial differences in food availability and breeding density affect dispersal behavior and that their large‐scale gradients within the distributional range might result in differential natal dispersal patterns.
    Type of Medium: Online Resource
    ISSN: 2045-7758 , 2045-7758
    URL: Issue
    URL: Article
    DOI: 10.1002/ece3.v13.1
    DOI: 10.1002/ece3.9603
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2635675-2
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  • 3
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    Online Resource
    Weather and food availability additively affect reproductive output in an expanding raptor population
    Springer Science and Business Media LLC ; 2022
    In:  Oecologia Vol. 198, No. 1 ( 2022-01), p. 125-138
    Details
    In: Oecologia, Springer Science and Business Media LLC, Vol. 198, No. 1 ( 2022-01), p. 125-138
    Abstract: The joint effects of interacting environmental factors on key demographic parameters can exacerbate or mitigate the separate factors’ effects on population dynamics. Given ongoing changes in climate and land use, assessing interactions between weather and food availability on reproductive performance is crucial to understand and forecast population dynamics. By conducting a feeding experiment in 4 years with different weather conditions, we were able to disentangle the effects of weather, food availability and their interactions on reproductive parameters in an expanding population of the red kite ( Milvus milvus ), a conservation-relevant raptor known to be supported by anthropogenic feeding. Brood loss occurred mainly during the incubation phase, and was associated with rainfall and low food availability. In contrast, brood loss during the nestling phase occurred mostly due to low temperatures. Survival of last-hatched nestlings and nestling development was enhanced by food supplementation and reduced by adverse weather conditions. However, we found no support for interactive effects of weather and food availability, suggesting that these factors affect reproduction of red kites additively. The results not only suggest that food-weather interactions are prevented by parental life-history trade-offs, but that food availability and weather conditions are crucial separate determinants of reproductive output, and thus population productivity. Overall, our results suggest that the observed increase in spring temperatures and enhanced anthropogenic food resources have contributed to the elevational expansion and the growth of the study population during the last decades.
    Type of Medium: Online Resource
    ISSN: 0029-8549 , 1432-1939
    URL: Article
    DOI: 10.1007/s00442-021-05076-6
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2022
    detail.hit.zdb_id: 1462019-4
    detail.hit.zdb_id: 123369-5
    SSG: 12
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  • 4
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    Online Resource
    Natal legacies cause social and spatial marginalization during dispersal
    Wiley ; 2024
    In:  Ecology Letters Vol. 27, No. 2 ( 2024-02)
    Details
    In: Ecology Letters, Wiley, Vol. 27, No. 2 ( 2024-02)
    Abstract: Early‐life experiences can drive subsequent variation in social behaviours, but how differences among individuals emerge remains unknown. We combined experimental manipulations with GPS‐tracking to investigate the pathways through which developmental conditions affect social network position during the early dispersal of wild red kites ( Milvus milvus ). Across 211 juveniles from 140 broods, last‐hatched chicks—the least competitive—had the fewest number of peer encounters after fledging. However, when food supplemented, they had more encounters than all others. Using 4425 bird‐days of GPS data, we revealed that this was driven by differential responses to competition, with less competitive individuals naturally spreading out into marginal areas, and clustering in central foraging areas when food supplemented. Our results suggest that early‐life adversities can cause significant natal legacies on individual behaviour beyond independence, with potentially far‐reaching consequences on the social and spatial structure of animal populations.
    Type of Medium: Online Resource
    ISSN: 1461-023X , 1461-0248
    URL: Issue
    URL: Article
    DOI: 10.1111/ele.v27.2
    DOI: 10.1111/ele.14366
    Language: English
    Publisher: Wiley
    Publication Date: 2024
    detail.hit.zdb_id: 2020195-3
    SSG: 12
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  • 5
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    Online Resource
    Turning tables: food availability shapes dynamic aggressive behaviour among asynchronously hatching siblings in red kites Milvus milvus
    The Royal Society ; 2023
    In:  Royal Society Open Science Vol. 10, No. 7 ( 2023-07)
    Details
    In: Royal Society Open Science, The Royal Society, Vol. 10, No. 7 ( 2023-07)
    Abstract: Aggression represents the backbone of dominance acquisition in several animal societies, where the decision to interact is dictated by its relative cost. Among siblings, such costs are weighted in the light of inclusive fitness, but how this translates to aggression patterns in response to changing external and internal conditions remains unclear. Using a null-model-based approach, we investigate how day-to-day changes in food provisioning affect aggression networks and food allocation in growing red kite ( Milvus milvus ) nestlings, whose dominance rank is largely dictated by age. We show that older siblings, irrespective of age, change from targeting only close-aged peers (close-competitor pattern) when food provisioning is low, to uniformly attacking all other peers (downward heuristic pattern) as food conditions improve. While food allocation was generally skewed towards the older siblings, the youngest sibling in the nest increased its probability of accessing food as more was provisioned and as downward heuristic patterns became more prominent, suggesting that different aggression patterns allow for catch-up growth after periods of low food. Our results indicate that dynamic aggression patterns within the nest modulate environmental effects on juvenile development by influencing the process of dominance acquisition and potentially impacting the fledging body condition, with far-reaching fitness consequences.
    Type of Medium: Online Resource
    ISSN: 2054-5703
    URL: Article
    DOI: 10.1098/rsos.230328
    Language: English
    Publisher: The Royal Society
    Publication Date: 2023
    detail.hit.zdb_id: 2787755-3
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