The effect of migration strategy and food availability on White Stork Ciconia ciconia breeding success
TL;DR: In this article, the influence of bird status (resident vs. migrant) and food availability (control nests vs. nests that benefit from high food supply) on reproductive success of Ciconia ciconia was investigated.
Abstract: In the mid 1970s, the breeding populations of the migrant White Stork Ciconia ciconia were close to extinction in the northeastern region of France (Alsace). A re-introduction project was implemented, resulting in the year-round settlement of some individuals in the region, which rely on additional food supplied by humans during the winter. Today, both resident and migrant birds breed in the same areas and take food from rubbish dumps and humans (farmers). The effects of these anthropogenic influences, altering Stork behaviour, on Stork reproductive success are not known. The aim of this study was to test the influence of bird status (resident vs. migrant) and food availability (control nests vs. nests that benefit from high food supply) on reproductive success. In control nests, the mean laying date was earlier in resident than in migrant White Storks. There was also a clear seasonal decline in clutch size. For all nests, the numbers of eggs and hatchlings were higher in resident birds than in migrants, which can be attributed to the earlier breeding of resident Storks. The large broods of resident birds showed a high mortality rate, leading to the same fledgling success (fledglings/hatchlings) and number of fledglings as in migrants. Fledgling success and the number of fledglings were higher for nests close to a reliable food supply. In summary, although resident birds can breed earlier and produce more eggs than migrants, we found no advantage in terms of number of fledglings. The higher mortality rate of chicks found in pairs with a large brood could be caused by the deterioration of their habitat. Thus, the year-round settlement of Storks may not present a biological advantage if the quality of their habitat is not guaranteed by the conservation of their grasslands.
Citations
More filters
TL;DR: This study provides first confirmation of year-round nest use by resident white storks and is the first to quantify the extent and consistency of landfill attendance by individuals during the non-breeding and breeding seasons and the influence of landfill use on daily distances travelled, percentage of GPS fixes spent foraging and non-landfill foraging ranges.
Abstract: The migratory patterns of animals are changing in response to global environmental change with many species forming resident populations in areas where they were once migratory. The white stork (Ciconia ciconia) was wholly migratory in Europe but recently guaranteed, year-round food from landfill sites has facilitated the establishment of resident populations in Iberia. In this study 17 resident white storks were fitted with GPS/GSM data loggers (including accelerometer) and tracked for 9.1 ± 3.7 months to quantify the extent and consistency of landfill attendance by individuals during the non-breeding and breeding seasons and to assess the influence of landfill use on daily distances travelled, percentage of GPS fixes spent foraging and non-landfill foraging ranges. Resident white storks used landfill more during non-breeding (20.1 % ± 2.3 of foraging GPS fixes) than during breeding (14.9 % ± 2.2). Landfill attendance declined with increasing distance between nest and landfill in both seasons. During non-breeding a large percentage of GPS fixes occurred on the nest throughout the day (27 % ± 3.0 of fixes) in the majority of tagged storks. This study provides first confirmation of year-round nest use by resident white storks. The percentage of GPS fixes on the nest was not influenced by the distance between nest and the landfill site. Storks travelled up to 48.2 km to visit landfills during non-breeding and a maximum of 28.1 km during breeding, notably further than previous estimates. Storks nesting close to landfill sites used landfill more and had smaller foraging ranges in non-landfill habitat indicating higher reliance on landfill. The majority of non-landfill foraging occurred around the nest and long distance trips were made specifically to visit landfill. The continuous availability of food resources on landfill has facilitated year-round nest use in white storks and is influencing their home ranges and movement behaviour. White storks rely on landfill sites for foraging especially during the non-breeding season when other food resources are scarcer and this artificial food supplementation probably facilitated the establishment of resident populations. The closure of landfills, as required by EU Landfill Directives, will likely cause dramatic impacts on white stork populations.
138 citations
TL;DR: The large extent of variation in the lifetime migratory decisions of young white storks originating from eight populations is uncovered, finding that juvenile storks differ in their geographically distinct wintering locations, and their diverse migration patterns also affected the amount of energy individuals invested for locomotion during the first months of their life.
Abstract: Annual migratory movements can range from a few tens to thousands of kilometers, creating unique energetic requirements for each specific species and journey. Even within the same species, migration costs can vary largely because of flexible, opportunistic life history strategies. We uncover the large extent of variation in the lifetime migratory decisions of young white storks originating from eight populations. Not only did juvenile storks differ in their geographically distinct wintering locations, their diverse migration patterns also affected the amount of energy individuals invested for locomotion during the first months of their life. Overwintering in areas with higher human population reduced the stork’s overall energy expenditure because of shorter daily foraging trips, closer wintering grounds, or a complete suppression of migration. Because migrants can change ecological processes in several distinct communities simultaneously, understanding their life history decisions helps not only to protect migratory species but also to conserve stable ecosystems.
130 citations
TL;DR: It is argued that restocking is an emerging conservation and ecosystem resilience issue of global significance and guidelines are provided to practitioners in conservation, game management, fisheries, epidemiology and other fields involved in restocking of vertebrates, who are likely to benefit from merging their perspectives and adopting a more cross-taxonomical and interdisciplinary attitude.
129 citations
TL;DR: This study is the first to show empirical evidence for increased mortality during some long migrations, likely driven by the presence of a physical barrier (the Sahara desert) in combination with suboptimal fuelling and unfavourable weather conditions en route.
Abstract: Explanations for the wide variety of seasonal migration patterns of animals all carry the assumption that migration is costly and that this cost increases with migration distance. Although in some studies, the relationships between migration distance and breeding success or annual survival are established, none has investigated whether mortality during the actual migration increases with migration distance. Here, we compared seasonal survival between Eurasian spoonbills (Platalea leucorodia leucorodia) that breed in The Netherlands and migrate different distances (ca 1000, 2000 and 4500 km) to winter in France, Iberia and Mauritania, respectively. On the basis of resightings of individually marked birds throughout the year between 2005 and 2012, we show that summer, autumn and winter survival were very high and independent of migration distance, whereas mortality during spring migration was much higher (18%) for the birds that wintered in Mauritania, compared with those flying only as far as France (5%) or Iberia (6%). As such, this study is the first to show empirical evidence for increased mortality during some long migrations, likely driven by the presence of a physical barrier (the Sahara desert) in combination with suboptimal fuelling and unfavourable weather conditions en route.
103 citations
TL;DR: It is demonstrated that bird feeding is important for urban biodiversity conservation, community engagement, and in establishing personal connections with nature and their associated benefits.
Abstract: Intentional feeding of wild birds in gardens or backyards is one of the most popular forms of human-wildlife interactions in the developed world, especially in urban environments. Scale and intensity of bird feeding are enormous with mainly birdseed consumed daily by a range of species. This represents a subsidy to natural diets of birds attracted to the feeders and typically involves novel dietary components. Yet, relatively little is known about how it influences the behavior and ecology of the species visiting feeders. In part, research has been hampered by logistical difficulties of working in urban areas but studies have demonstrated powerful influences on behavior and phenology of avian breeding, the spread of disease, and the structure of avian communities. Here, we compare bird feeding between Northern and Southern Hemispheres as a means of exploring how similarities and differences in avian responses might inform knowledge of this global urban phenomenon. We start by tracing its origins to north-western Europe and how its expansion has occurred before considering how geographical differences in feeding practices and attitudes map onto bird feeding ‘on the ground’. We explore some of the major emerging themes of recent interest, including why citizens are motivated to feed birds, whether birds become fully dependent on food supplements, the role of feeding in avian disease transmission, and how feeding changes urban bird communities. By proposing that scientists work in collaboration with the public providing food to birds, we pose key research questions that need to be answered urgently and suggest accompanying experimental approaches to do so. These approaches are essential if we are to improve our understanding of how bird feeding shapes the behavior, ecology, movements, and community structure of urban birds. Our hope is that through such citizen science we will be able to provide advice as to location-relevant practices that should maximise benefits to both urban biodiversity and human wellbeing, and minimise potential adverse impacts. We demonstrate that bird feeding is important for urban biodiversity conservation, community engagement, and in establishing personal connections with nature and their associated benefits.
63 citations
References
More filters
TL;DR: In this paper, the parent adjusts its effort in relation to prevailing environmental conditions in order to maximize the output of young in its lifetime, rather than measurable in terms of adult survival and recruitment of young.
Abstract: 1. Energetics of reproduction in birds is reviewed with the question in mind how the parent adjusts its effort in relation to prevailing environmental conditions in order to maximize the output of young in its lifetime. Emphasis is on proximate controls, rather than ultimate factors measurable in terms of adult survival and recruitment of young. 2. The decision to breed or not to breed is clearly related to body condition of the female, presumably because of the implications this has for survival. 3. Laying date and clutch size are likewise under the influence of female condition and can hence be modified by experiments involving supplementary feeding. Natural variation in these features may often be related to territory quality. 4. How the bird decides whether or not to commence a second brood is not clear, but in the Great Tit the habitat-related difference in incidence of second broods is functionally understandable when survival probabilities of birds at different times are considered. 5. A distinction is made between a "capital" and "income" model for translatting rates of change of female body condition into appropriate decisions on laying date and clutch size and experiments are suggested that discriminate between the two. 6. Lack's view that brood size is in an evolutionary sense adjusted in order to balance food requirement and foraging capacity of the parents is accepted, and growth rates in nidicolous birds are analysed to ascertain if a finer adjustment exists superimposed on the integer steps of brood adjustment. Critical for this analysis are groups of birds where broods of one are common, since only in these circumstances is growth adjustment the only strategy open to the parents. In common with other animals, growth rate is related to mature body size but within a category of adult weight clear examples can be found for retardation of growth rate in pelecaniform and charadriiform species with singleton broods. 7. Since daily energy requirement is related to nestling size and growth rate, retardation of growth is explicable as a strategy only in terms of reducing the daily commitment of the parents, not reducing the total cost of producing a nestling. 8. An additional economy in growth is to reduce the contribution of fat to the nestling body. 9. Implied in Lack's view of brood size is a limitation of parental foraging capacity, and the last section of the paper is devoted to exploration of the proximate factors delimiting what Royama terms the optimal working capacity of parents feeding young. Observations of parent starlings confronted with manipulated brood size suggest a limit on the time that can be devoted to energetically extravagant flight activity, rather than a shortage of absolute time. Beyond the limit to which stressed parents can be made to fly, body weight declines. 10. Preliminary data on energy metabolized daily by parents confronted with large broods conforms to the simplified view that parental effort on a sustained basis equates to energy mobilization equivalent to 4 B.M.R. units and it is suggested that this level of energy expenditure represents a proximal decision substrate for determining the optimal working capacity of the parent. 11. The paper ends with a plea for more research on the proximate controls of avian reproduction, and calls attention to the central importance of the protein bank to parental body condition.
2,070 citations
TL;DR: Evidence for food limitation in the context of life history theory is reviewed because it provides a fundamental framework from which to interpret.
Abstract: Food limitation is an important issue in ecology because it can influence life history traits, population sizes, and community structure (through effects of competition). Work at the level of populations and communities has led to arguments that food limitation and competition are more important in winter than during the breeding season (e.g. 1, 2, 7, 8, 83, 85, 211, 234). In fact, it is commonly argued that food is superabundant during the breeding season (7, 8, 161, 213, 246, 250, 251, 308-311). However, such arguments are based on indirect rather than direct evidence of the effects of food on reproduction and survival (fitness) (149). Direct evidence for food limitation and competition in winter exists when survival is affected, and some experimental evidence suggests such effects (e.g. 75, 113, 122, 132). However, if current or future reproductive success is limited by food, then food limitation will also exist during the breeding season. Reproductive ecologists historically have argued that food limits reproductive success (e.g. 13, 297). Yet, even this school has included recent arguments against food limitation. For instance, Ettinger & King (77) think that perching time of birds commonly reflects loafing time because birds set their clutch and brood sizes based on years and periods of stringent (low food) conditions. However, perching time may not reflect loafing but rather an important time commitment to reproductive success (T. Martin, unpublished ms.) Thus, the status of food limitation in breeding birds is not clear. Here, I review evidence for food limitation in the context of life history theory because it provides a fundamental framework from which to interpret
1,453 citations
TL;DR: The typical population response to food supplementation was two- to three-fold increase in density, but no change in the pattern of population dynamics, which points to the need for researchers to conduct food supplementation experiments in tropical environments.
Abstract: I reviewed 138 cases in which terrestrial vertebrates received supplemental food under field conditions. These cases are strongly biased toward small-bodied herbivores in north temperate environmen...
832 citations