Short Note

Body condition of Little Egret Egretta garzetta nestlings in relation to hatching order in a southern Tunisian breeding colony

DOI: 10.2989/00306525.2018.1536082
Author(s): Amel NebUnité de Recherche “Ecologie de la Faune Terrestre” (UR17ES44) – Faculté des Sciences de Gabès, Tunisia, Abdessalem HammoudaUnité de Recherche “Ecologie de la Faune Terrestre” (UR17ES44) – Faculté des Sciences de Gabès, Tunisia, Slaheddine SelmiUnité de Recherche “Ecologie de la Faune Terrestre” (UR17ES44) – Faculté des Sciences de Gabès, Tunisia

Abstract

The effect of asynchronous hatching on nestling health and condition in ardeids is still in need of empirical evidence from populations living in different environmental conditions. Using morphometric and hematologic data from Little Egret Egretta garzetta nestlings in a Tunisian breeding colony, we assessed the relationship between hatching order and nestling condition, while accounting for the effects of brood size, age and hatching date. Our results showed that the youngest nestlings had lower values of hematocrit and body condition index but higher levels of fluctuating asymmetry compared with their older siblings. These trends seem to stem from increased nutritional stress experienced by younger nestlings who would have received less food from their parents than their siblings due to their less competitive nature. Additional constraints during the rearing period, such as possible injuries resulting from conflicts with siblings and the energy cost of thermoregulation, may also have contributed to the deterioration of the condition of last nestlings. Overall, our findings provide empirical evidence of the short-term repercussions of asynchronous hatching in a North African population of Little Egrets. They also highlight the great complexity of mechanisms by which asynchronous hatching may affect body condition and health of bird nestlings.

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