Factors Influencing Daily Food-Intake Patterns in Birds

Abstract

Abstract. Avian foraging activity during daytime peaks after dawn and before dusk. The relative importance of each period of intensive foraging on the accumulated intake varies by species, individual, and day. We studied the relative importance of each period from direct observation of radio-tagged Common Cranes (Grus grus) during winter at a site of stopover and wintering in Spain. After a mathematical model was fitted, accumulated intake showed a typical anti-sigmoid shape, with greatest increases of intake after dawn and before dusk. The rise of accumulated intake decelerated until 50% of the day length, when the trajectory inflected and accelerated according to the fitted model. The trajectory of accumulated intake in territorial families that foraged in small home ranges with food predictably available but the cost of vigilance high decelerated until 20% of the day length, then accelerated for the rest of the day. In flocking nonterritorial cranes the inflection point was delayed until 60% of the day length, as expected since flocking cranes foraged in larger home ranges with food less predictable and the cost of vigilance lower. The inflection point was delayed in early winter and advanced in late winter. The changes in the inflection points of the functions for accumulated food intake may be straightforwardly applied to daily foraging routines of other species whose rates of intake may be recorded.

Learning and Reciprocity in Coal Tits Playing the Prisoner’s Dilemma Game

“…We thus conclude that coal tits were not physiologically stressed by a smaller food intake. Another index of physiological stress is low body mass, which changes as a consequence of food deprivation (Bautista & Alonso, 2013;Bautista, Tinbergen, & Kacelnik, 2001;Bautista, Tinbergen, Wiersma, & Kacelnik, 1998). Our birds did not undergo decreased body mass and activity rates (which also suggest there was no energy loss during the Game condition).…”

Food Availability But Not Sex Determines Morning Foraging Area Size in the Great Bustard Otis tarda, the Most Sexually Size-Dimorphic Bird Species

“…In this study we did field observations during the morning foraging period, which is usually the longest and most intensive one in diurnal birds (Polo & Bautista, 2006 and references therein; Bautista & Alonso, 2013). Our results therefore apply to this short period of the day; longer periods might deliver different results.…”

“…The proportion of feeding birds in a flock does not only vary with daytime, but is also determined by food availability (ducks: Maxson & Oring, 1980;shorebirds: Sedinger & Raveling, 1988;Common Cranes: Alonso et al, 1997;Bautista & Alonso, 2013). Food availability also determines the size of the foraging area (Schoener, 1968;Brown & Orians, 1970).…”

The potential impacts of changes in ecological networks, land use and climate on the Eurasian crane population in Estonia

“…The distance between the overnight sites and feeding areas varied between stopover locations in different landscape types, and with food availability. The maximum distance between the overnight site and feeding area was 20-34 km on the West-European Flyway in Estonia (Matsalu, Meelva) (Keskpaik et al 1986;Leito et al 1987), 20-40 km in Germany (Rügen-Bock, Rhin-Havelluch) (Albrecht et al 2010;Nowald et al 2010), and 25-40 km in Spain (Gallocanta, Orellana) (Alonso et al 1997;Guzmán et al 1999;Alonso et al 2004;Bautista and Alonso 2013). The average maximum distance between overnight resting places and feeding areas, both on stopover and wintering sites on flyways, was estimated to be 30 km.…”