Gone with the wind: Seasonal trends in foraging movement directions for a central-place forager

Abstract

Lesser kestrels Falco naumanni are migratory central-place foragers that breed in dynamic arable landscapes. After arriving from migration, kestrels have no knowledge of the distribution of crops, and consequently prey, around their colony. The energy demand of pairs increases as breeding season progresses, but at the same time prey abundance, and their knowledge on prey distribution, also increases. Wind can have a strong influence on flight cost and kestrels should try to reduce energy expenditure when possible. When prey abundance is low, kestrels have little knowledge of prey distribution, and pairs have no chicks, they could reduce foraging flight cost by leaving the colony with tailwinds. When prey is abundant, knowledge on prey distribution has increased, and chick demand is high, kestrels should fly to the most favorable foraging patches. We analyzed foraging trips directions in a lesser kestrel colony along the breeding season and in relation to wind speed and direction. We recorded 664 foraging trips from 19 individuals using GPS-dataloggers. We found that outward flights direction changed from uniform to a concentrated distribution along the season, as prey abundance and individual experience increased. We also found a temporal trend in the angular difference between outward flights and wind directions, with low values early in the season and then increasing as expected, but again low values at the end, contrary to expectation. Results suggest changes in kestrels foraging strategy along the season in relation to wind. Kestrels depart more with tailwinds in exploratory flights early in the season, while there is a spurious coincidence in direction to preferred foraging patches and dominant wind direction at the end.

Taking a trip to the shelf: Behavioral decisions are mediated by the proximity to foraging habitats in the black‐legged kittiwake

“…Animals encounter a hierarchy of decisions when optimizing their foraging efforts (Stephens, ). Within a heterogeneous environment, seabirds therefore have to be able to adapt their foraging behavior (Hernández‐Pliego, Rodríguez, & Bustamante, ) and balance the allocation of resources for reproduction and self‐maintenance (Erikstad et al., ).…”

Seasonal trend in movement directions at dawn and dusk: a study on crow and white herons

“…Differential selection of directions could be the consequence of photoperiodic changes, food availability, wind direction/ speed or ecology of the nearby area (Alerstam 1979;Liechti 2006;hernández-Pliego et al 2014). Flying with or against wind may result in different flight costs; therefore, the animals adopt different strategies to optimize their flight efficiency (Chapman et al 2011).…”

Optimal central place foraging flights in relation to wind

“…Whether birds vary their CPF distance in relation to wind speed has not been strictly analysed in any of the available detailed field studies of CPF flights in relation to wind (Weimerskirch et al 2000(Weimerskirch et al , 2012Grémillet et al 2004;Wakefield et al 2009;Hernández-Pliego et al 2014). There are some studies that indirectly suggest that CPF distance could be reduced under stronger winds.…”

“…The preference for following sidewinds may be assigned to their complex dynamic soaring behaviour in the wind speed gradient above the sea surface reaching an optimal performance level in such winds (Alerstam et al 1993;Weimerskirch et al 2000;Richardson 2011Richardson , 2015. CPF flights in crosswinds were regular among Cape Gannets Morus capensis in South Africa (Grémillet et al 2004), as well as among Lesser Kestrels Falco naumanni in Spain (Hernández-Pliego et al 2014). However, other patterns have also been reported, with Northern Gannets primarily having a cross-to tail-wind component on outward flights and a head-to cross-wind component on inward flights (Amélineau et al 2014) and Common Guillemots primarily having tailwinds on outward flights and headwinds on inward flights (Evans et al 2013).…”

“…Field observations of CPF flights under different wind conditions have been analysed in some detail for seabirds like Albatrosses (Weimerskirch et al 2000(Weimerskirch et al , 2012Wakefield et al 2009), Shearwaters (Raymond et al 2010;Gibb et al 2017) and Gannets (Grémillet et al 2004) as well as for insect-eating falcons breeding in farmland (Hernández-Pliego et al 2014) and for bats (Sapir et al 2014). These studies indicate that wind indeed is a factor of major importance, in addition to the distribution of food resources, for the directions and trajectories of CPF flights.…”