Diet specialization in a generalist population: the case of breeding great tits Parus major in the Mediterranean area

Abstract

The analysis of diet specialization provides key information on how different individuals deal with similar food and habitat constraints within populations. Characterizing parental diet specialization at the moment of breeding, and the consistency of these preferences under different levels of effort, may help us to understand why parents exploit alternative resources. We investigated these questions in a species commonly considered a generalist: a breeding population of Mediterranean great tits Parus major. Our aim was to determine whether they are specialists or generalists at the pair level, and the consistency of this behaviour under different levels of effort. Using proportional similarity and mean pairwise overlap indices, we found that parents showed great variability in prey selection between territories. That is, they displayed a small niche overlap. Interestingly, the most specialized breeding pairs showed a tendency to have larger broods. Additionally, we experimentally manipulated brood size and found that parents showed high short-term consistency in their foraging behaviour. They precisely adjusted the number of provisioning trips to the number of nestlings, while they were unable to modify prey proportions or prey size after brood size was changed. We can therefore characterize their foraging strategies as highly consistent. Our results suggest that although the great tit may be considered a generalist at the species or population level, there was a tendency for trophic specialization among breeding pairs. This high inter- and intrapopulation plasticity could account for their great success and wide distribution.

Dynamics of Gut Microbiota Diversity During the Early Development of an Avian Host: Evidence From a Cross-Foster Experiment

“…Such vertical transmission through feeding seems less likely in our species, however, as preys are fed directly without parental ingestion or regurgitation as is the case in swallows. An indirect parental effect is still possible through variation in feeding investment or prey type for example ( Pagani-Núñez et al, 2015 ; Mathot et al, 2017 ), given the importance of diet in shaping the gut microbiota ( Wu et al, 2011 ) A second possible mechanism explaining the nest effect is horizontal transmission of bacteria between nestlings, leading to homogenization of their gut microbiota. Indeed the social environment has been found to shape the gut microbiota ( Tung et al, 2015 ).…”

The need for new categorizations of dietary specialism incorporating spatio‐temporal variability of individual diet specialization

“…Yet, closer inspection of their diet throughout their geographical range reveals that caterpillar specialization is restricted to northern and central Europe (Baňbura et al ., ; Naef‐Daenzer & Keller, ; Rytkönen & Krams, ; Sillanpää, Salminen & Eeva, ). Mediterranean populations of tits develop divergent foraging strategies depending on whether they live in deciduous or evergreen forests (Blondel et al ., , ; Ziane, Chabi & Lambrechts, ) and whether or not they are breeding (Baňbura et al ., ; Pagani‐Núñez et al ., ). In evergreen forests, where tits’ provisioning rates are lower (and they have larger home ranges), tits also bring a greater variety of food items to the nest to feed nestlings (Blondel et al ., , ; Baňbura et al ., ; Ziane et al ., ).…”

“…variety of food items to the nest to feed nestlings (Blondel et al, 1991(Blondel et al, , 2006Ba nbura et al, 1994;Ziane et al, 2006). In mixed Mediterranean forests, which are very heterogeneous habitats, it is possible to find a combination of individuals with generalist and specialist strategies (Pagani-N uñez et al, 2015). A breakdown of caterpillar specialization in other habitats has also been reported, such as in boreal forests (Rytk€ onen & Krams, 2003), in urban areas (Cowie & Hinsley, 1988;Solonen, 2001;Isaksson & Andersson, 2007;Whitehouse et al, 2013), agricultural areas (Redhead et al, 2013) and reforested lands (Massa et al, 2004).…”

How much is enough? Effects of technical and biological replication on metabarcoding dietary analysis

“…Likewise, the precision of frequency of occurrence estimates is low when biological replication is low, and it varies with the prevalence of the prey items, and thus, a poor description of diet may occur at low sample sizes as a mere consequence of binomial sampling (Trites & Joy, 2005). These problems are worse when there is high variation in diet composition among individuals according for instance to gender, age or individual preferences (e.g., Mata et al, 2016;Pagani-Núñez, Valls, & Senar, 2015;Pleguezuelos & Fahd, 2004), and there may also be intraindividual variations due for instance to temporal changes in prey availability (Burgar et al, 2014;Clare, Symondson, & Fenton, 2014b;Clare et al, 2014a).…”