Seabirds are sensitive indicators of changes in marine ecosystems and might integrate and/or amplify the effects of climate forcing on lower levels in food chains. Current knowledge on the impact of climate changes on penguins is primarily based on Antarctic birds identified by using flipper bands. Although flipper bands have helped to answer many questions about penguin biology, they were shown in some penguin species to have a detrimental effect. Here, we present for a Subantarctic species, king penguin ( Aptenodytes patagonicus ), reliable results on the effect of climate on survival and breeding based on unbanded birds but instead marked by subcutaneous electronic tags. We show that warm events negatively affect both breeding success and adult survival of this seabird. However, the observed effect is complex because it affects penguins at several spatio/temporal levels. Breeding reveals an immediate response to forcing during warm phases of El Niño Southern Oscillation affecting food availability close to the colony. Conversely, adult survival decreases with a remote sea-surface temperature forcing (i.e., a 2-year lag warming taking place at the northern boundary of pack ice, their winter foraging place). We suggest that this time lag may be explained by the delay between the recruitment and abundance of their prey, adjusted to the particular 1-year breeding cycle of the king penguin. The derived population dynamic model suggests a 9% decline in adult survival for a 0.26°C warming. Our findings suggest that king penguin populations are at heavy extinction risk under the current global warming predictions.

Changes in seabird populations, and particularly of penguins, offer a unique opportunity for investigating the impact of fisheries and climatic variations on marine resources. Such investigations often require large-scale banding to identify individual birds, but the significance of the data relies on the assumption that no bias is introduced in this type of long-term monitoring. After 5 years of using an automated system of identification of king penguins implanted with electronic tags (100 adult king penguins were implanted with a transponder tag, 50 of which were also flipper banded), we can report that banding results in later arrival at the colony for courtship in some years, lower breeding probability and lower chick production. We also found that the survival rate of unbanded, electronically tagged king penguin chicks after 2-3 years is approximately twice as large as that reported in the literature for banded chicks.

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.