Abstract

BackgroundThe 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.ResultsResident 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.ConclusionsThe 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.

Highlights

  • 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

  • Seasonal foraging habitat, landfill and nest use The percentage of total global positioning system (GPS) fixes on non-landfill habitat was similar in the breeding and nonbreeding seasons (Fig. 2a, paired t-test, t(16) = 1.465, p = 0.162)

  • During the non-breeding season, a large percentage of total GPS fixes were spent on the nest with 25 % of the birds spending up to 49.7 % of GPS fixes within 20 m of the nest. Individuals of both sexes were found on their nests throughout the day and there was no significant difference in the hour of nest attendance between seasons (Fig. 2b), 22.6 % ± 2.24 of non-breeding GPS fixes on the nest occurring at midday (Fig. 2b)

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Summary

Introduction

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. Many previously wholly migratory bird species that used to winter in sub-Saharan Africa are forming resident populations in their southern European breeding grounds [4, 5]. The migratory strategy an individual adopts may impact on subsequent survival and lead to different population dynamics between migrant and resident individuals. Understanding the role of food availability in driving changes in resident bird distribution and movement behaviour will improve our ability to predict how partially migratory species may respond to future climate and environmental change and assist in designing effective conservation strategies

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