Data to test for the early learning of the foraging niche hypothesis in Great Tits

This is the data set for the paper “Did you learn what to eat from your parents? A test of the early learning of the foraging niche hypothesis in Great Tits Parus major”, published in Journal of Avian Biology. 

We collected information on foraging preferences of breeding Great Tits during twelve years (2011-2022) in the field station of Can Catà, within Collserola Natural Park (Cerdanyola, Barcelona, NE Iberian Peninsula, 45º 27' N, 2º 8' E). To obtain data about nestlings’ diet, we attached infra-red Micro-D cameras (Mini Colour Sony IR Camera SK-C170IR) to the nest top inside the nest-box and focused on the entrance, thus allowing us to identify delivered prey. Nests were recorded from 07:00-13:00h (five hours).

Prey were classified into three categories -caterpillars, spiders and others- because caterpillars and spiders are the most important prey types for Mediterranean populations of Great Tits. The size of each prey item was determined according to a semi-quantitative scale in relation to beak size of the Great Tit, which has an average size of 9 mm. Size categories were: 1=small (smaller than beak size), 2 = medium (similar to beak size), 3 = large (larger than beak size).

Data refers to percentage of caterpillars, percentage of spiders, percentage of ‘other prey’ and mean prey size (of all prey categories). To perform the analyses the percentage of each type of prey (caterpillars, spiders and ‘other prey’) were square-root transformed to approximate normality. Since the diet of individuals may vary across years due to changing weather conditions and environmental factors affecting prey availability, before comparing an individual’s diet across different years, data was standardised for different variables using a generalised linear mixed-effects model fitted by restricted maximum likelihood. Variables included were ‘year’, ‘sex’, ‘age’ (to distinguish if the breeding individual was yearling or adult), ‘brood size’, ‘brood age’, ‘date of recording’ (taken as the number of days from 1st April to control for phenology), and the proportion of oak trees in relation to Aleppo Pines within 25m of the nest-box. Analysis allowed to extracte residuals for further analysis, which appear in the four provided tables.  

For each individual we provide prey data corresponding to the chick stage and the data from the adult stage. Data is divided in four different sheets, using different variants of the diet data that individuals received as a chick: (1) using exclusively the father’s data (referred to as Father Data), (2) using only the mother’s data (referred to as Mother Data), (3) using the mean of both parents’ prey data (referred to as Mean Data), and (4) using weighted parents data depending on the number of provisioning trips (giving more importance to the prey delivered by the most actively feeding parent, referred to as Weighted Data).