Within-brood body size and immunological differences in Blue Tit (Cyanistes caeruleus) nestlings relative to ectoparasitism

Several ectoparasites parasitise nestlings decreasing their body condition, growth and survival. To minimise any loss of fitness due to ectoparasites, birds have developed a wide variety defence mechanisms, potentially including hatching asynchrony. According the Tasty Chick Hypothesis (TCH), cost parasitism would be reduced if tend eat on less immunocompetent nestlings, typically last-hatched chick in asynchronously hatched broods, as they are poor condition. Two predictions TCH that immune capacity is lower smaller than larger ones parasites should provoke more negative effect nestlings. Here, we test these population Blue Tits (Cyanistes caeruleus) whose broods parasitised by Hen Fleas (Ceratophyllus gallinae) Blowflies (Protocalliphora azurea). We recorded presence both analysed immunocompetence (number leucocytes per 10,000 erythrocytes cutaneous response phytohaemagglutinin) condition within individual broods. The leucocyte count was higher ones, whereas did not differ between Smaller but had mass when fleas were present. Blowflies, contrast, no detectable Overall, our findings provide partial support TCH. Lower supported, seemed negatively impact ones.