Sexual differences in food preferences in the white stork: an experimental study

Abstract

Sex differences in the foraging ecology of monomorphic species are poorly understood, due to problems with gender identification in field studies. In the current study, we used experimental conditions to investigate the food preferences of the white stork Ciconia ciconia, an opportunistic species in terms of food, but characterised by a low level of sexual dimorphism. During a 10-day experiment, 29 individuals (20 females and 9 males) were studied by means of a ‘cafeteria test’ in which the storks’ diet consisted of mammals, birds, fish, amphibians, insects and earthworms. The storks preferred food characterised by high calorific and protein values such as mammals, birds and fish. Sexes differed strongly in their preferences; males preferred mammals, whereas females preferred birds. Moreover, females consumed insects and earthworms less often than males. Interestingly, males spent significantly less time foraging than females. We have demonstrated that the white stork exhibits clear sexual differences in food preferences which are mostly attributable to differences in parental duties, physiology and anatomy.Electronic supplementary materialThe online version of this article (doi:10.1007/s00114-017-1457-5) contains supplementary material, which is available to authorized users.

Community‐wide consequences of sexual dimorphism: evidence from nectar microbes in dioecious plants

“…, Kwieciński et al. ), plant–herbivore (Ågren et al. , Cole and Ashman , Cornelissen and Stiling , Vesakoski et al.…”

“…One pervasive and often dramatic form of intraspecific variation is sexual dimorphism in animals and plants. Due to their divergent traits, females and males can interact with heterospecific individuals differently, as demonstrated in competitive (Butler et al 2007, Wagner et al 2012, predator-prey (Schoener 1967, Ryan et al 1982, Sakashita 1992, Sommer 2000, Costantini et al 2007, Tobler et al 2008, Kwieci nski et al 2017, plant-herbivore ( Agren et al 1999, Cole and Ashman 2005, Cornelissen and Stiling 2005, Vesakoski et al 2008, Tsuji and Sota 2010, plant-pollinator (Temeles et al 2009, Zhang andHe 2017), and plant-pathogen ( Agren et al 1999) interactions. These studies suggest that sex-specific interactions have the potential to shape a range of communities within and across trophic levels.…”

Supplementing a grain diet with insects instead of fruits sustains the body condition of an omnivorous bird

“…In the absence of diet limitation, animals may still face specific nutrient limitations in nature due to changes in the quality of their preferred diet, the energetic demand of cold conditions, and the occurrence of other energy/nutrient‐demanding periods of the annual cycle such as breeding and molt, resulting in over‐exploitation of body reserves (Andersson et al, 2018; Bravo et al, 2019; Cherel et al, 1994; Murphy & Pearcy, 1993; Swanson, 2010). To maximize nutrient intake during periods of limited nutrient availability, animals may shift between diets or show preference for a given food type (Kwieciński et al, 2017; Lamperti et al, 2014; McWilliams et al, 2004). Such periodic shifts may also be sex‐specific, arising due to differences in morphology (Bravo et al, 2019; Walker et al, 2014), physiology, and breeding roles (Kwieciński et al, 2017; Treidel et al, 2021).…”

“…To maximize nutrient intake during periods of limited nutrient availability, animals may shift between diets or show preference for a given food type (Kwieciński et al, 2017; Lamperti et al, 2014; McWilliams et al, 2004). Such periodic shifts may also be sex‐specific, arising due to differences in morphology (Bravo et al, 2019; Walker et al, 2014), physiology, and breeding roles (Kwieciński et al, 2017; Treidel et al, 2021). In birds, body mass, pectoral muscle, and fat scores indicate physical condition in terms of energy and nutrient reserves (Milenkaya et al, 2013).…”

A large bird’s digestive tract has an opposite intersexual pattern than body size

“…The White Stork (WS; Ciconia Ciconia) is a large bird (body mass: 2.3-4.5 kg, wingspan: 155-215 cm) without any distinct sexual dimorphism, where males are ca 12% bigger than females [9,32,33] The WS is a migratory species that occurs across the whole of Europe, except Iceland and the northern regions of Russia and Scandinavia [19]. It builds large, open nests, very often on the top of man-made structures, less often on trees [31].…”