Environmental complexity: A buffer against stress in the domestic chick.

Birds kept in commercial production systems can be exposed to multiple stressors from early life and this alters the development of different morphological, immunological and behavioural indicators. We explore the hypothesis that provision of a complex environment during early life, better prepares birds to cope with stressful events as well as buffers them against future unpredictable stressful episodes. In this study, 96 one day old pullets were randomly distributed in eight pens (12 birds/pen).

The looks matter; aggression escalation from changes on phenotypic appearance in the domestic fowl.

Domestic fowl in small groups are assumed to establish hierarchical systems based on individual recognition. Conversely, interactions in large groups are modulated by badges of status. Previous studies suggested that birds differing in phenotypic appearance (PA) became targets for aggression, possibly mistaking altered PA for badges of status.

Excretion patterns of coccidian oocysts and nematode eggs during the reproductive season in Northern Bald Ibis ().

Individual reproductive success largely depends on the ability to optimize behaviour, immune function and the physiological stress response. We have investigated correlations between behaviour, faecal steroid metabolites, immune parameters, parasite excretion patterns and reproductive output in a critically endangered avian species, the Northern Bald Ibis (). In particular, we related haematocrit, heterophil/lymphocyte ratio, excreted immune-reactive corticosterone metabolites and social behaviour with parasite excretion and two individual fitness parameters, namely, number of eggs laid and number of fledglings.

Manipulation of the phenotypic appearance of individuals in groups of laying hens: effects on stress and immune-related variables.

This study evaluated whether phenotypic appearance (PA) alteration during two developmental phases in laying hens, reared in two different group sizes, affects stress and immune responses. After hatching, 750 chicks were randomly assigned to 30 pens at a group size of either 10 or 40 birds. Then, the appearance of 0, 30, 50, 70 or 100% of the chicks in each pen was altered by blackdyeing their head feathers (marked); remaining chicks were unmarked.