Dimorphism from an early age: sex differences in size and immune function in great tit nestlings

The dataset contains data on great tit nestlings morphometrics (mass, wing, and tarsus) and innate immune function (agglutination, lysis, haptoglobin concentration, and bacteria killing capability), and was collected in a nestbox population in southern Sweden during two consecutive breeding seasons (2022 and 2023). In both years, a brood size manipulation experiment was carried out.
Birds can show patterns of sexual size dimorphism as early as during the nestling stage. This raises the question of how the faster growing sex might reconcile the energetic and nutritional needs of a faster growth rate with resource allocation to other important life functions, such as the development of innate immune function. Innate immunity represents the main line of defence against diseases, and while some innate immune defences are already present at hatching, substantial development occurs throughout the nestling stage. Hence, this development may compete for resource allocation with growth, potentia..., , # Data from: Dimorphism from an early age: sex differences in size and immune function in great tit nestlings

Dataset DOI: [10.5061/dryad.vt4b8gv5k](https://doi.org/10.5061/dryad.vt4b8gv5k)

## Description of the data and file structure

On day 5 (in 2023) or 6 (in 2022) after hatching, we performed a brood size manipulation experiment by moving 4 (in 2022) or 5 nestlings (2023) in-between nestboxes. Thus, our experimental set-up included three groups, a reduced and enlarged treatment, and some unmanipulated boxes were included as controls. At this time, we also ringed most of the nestlings and measured their mass.

On day 14 after hatching, we measured mass, wing and tarsus. We blood sampled a subset of the nestlings. We used the blood pellet for molecular sexing and the plasma for innate immune function assays (haemolysis-hemagglutination, haptoglobin assay, and bacteria killing assay). Agglutination and bacteria killing assays are only available for the 2022 breeding season.

### Fi...,