Seasonal differences in energy expenditure, flight characteristics and spatial utilization of Dalmatian Pelicans Pelecanus crispus in Greece

Abstract

Animals typically adjust their behaviour to their changing environment throughout the annual cycle, modulating key processes such as the timing of breeding and the onset of migration. Such behavioural changes are commonly manifested in the movements and the energetic balance of individuals in relation to their species-specific physiological characteristics, habitat attributes and the environmental properties of their distribution ranges. We used GPS and acceleration data collected using transmitters on free-ranging birds to quantify annual movement patterns and estimate energy expenditure of the Dalmatian Pelican Pelecanus crispus, a large, soaring avian species which performs short-distance migration and spends its entire annual cycle in mid-latitudes. To assess the representativeness of our results, the transmitter effect was also tested. We found that daily trends in the overall dynamic body acceleration (ODBA; a proxy for energy expenditure) differed among seasons, with the highest values occurring during spring and the lowest during winter. Long inter-lake flights were very rare in winter, and the number of flights and ODBA during spring was higher than during summer, suggesting greater motivation to move in spring. Although transmitters may have affected the birds, as none of the tagged birds bred, we found seasonal differences in behaviour and activity level. The observed patterns in differences in activity levels, long-distance flights and flight characteristics between seasons suggest an annual rhythm of energy expenditure. These findings allow a better understanding of bird phenology, specifically regarding adaptations to wintering in a cold climate by reducing movement-driven energy expenditure. Finally, the identification of periods with high and low energy expenditure may guide future conservation efforts by adjusting conservation plans in accordance with changing needs during the annual cycle.

Landscape‐dependent time versus energy optimizations in pelicans migrating through a large ecological barrier

“…The finding that pelicans exhibit different behaviours over different parts of the migration route corresponds to previous results from other soaring birds (Klaassen, Strandberg, Hake, & Alerstam, ; Mellone et al, ; Vansteelant et al, ). Furthermore, our findings on the decisive role of atmospheric conditions in shaping flight characteristics of migrating birds are in general agreement with previous studies of other soaring birds, including other pelican species (Efrat, Harel, Alexandrou, Catsadorakis, & Nathan, ; Gutierrez Illan, Wang, Cunningham, & King, ). However, our results show how the interaction between landscape and atmospheric conditions modulates migratory optimization considerations, suggesting that the landscape over which birds migrate can affect their migratory behaviour and response to atmospheric conditions, even without landscape‐induced changes in the atmospheric conditions.…”

Overland and oversea migration of white storks through the water barriers of the straits of Gibraltar

“…In fact, when we compared complete itineraries, oversea tracks displayed an overall 108% rise in ODBA compared to overland. Given the tight links previously established between ODBA levels and movement-related energy expenditure, including avian flight [31][32][33][34][35][36] , our results empirically support the idea that migrating across sea straits imposes physiological burdens to white storks, reinforcing the view of water bodies as movement barriers and supporting the water barrier hypothesis 7,13,23,24,37,38 . Considering that overwater movements lasted half the time recorded in overland flights of similar lengths, the ODBA per distance was actually similar across itineraries, which nonetheless differed in ODBA per time unit thus revealing the higher power displayed overwater.…”

Using a Homeogram to Detect Sleep in Free-living Animals

“…In red squirrels, day length and mean ambient temperature are positively correlated with overall activity levels, however, we do not have granular data regarding the light at, or temperature inside a given nest (but see Studd et al, 2016). Therefore, we cannot exclude the possibility that microclimates (e.g., the rise and fall of ambient temperature, winter snowfall, cloud cover, nest orientation) could also serve as a strong gate of wakefulness, although, we suspect ambient temperature is a proxy for behavioral requirements of a particular season for red squirrels (Efrat et al, 2019;V. Y. Zhang et al, 2019).…”