Title
Leucocyte profiles and body condition in breeding brown boobies and red-tailed tropicbirds : effects of breeding stage and sex Leucocyte profiles and body condition in breeding brown boobies and red-tailed tropicbirds : effects of breeding stage and sex
Author
Faculty/Department
Faculty of Sciences. Biology
Publication type
article
Publication
Melbourne ,
Subject
Biology
Source (journal)
Australian journal of zoology. - Melbourne
Volume/pages
61(2013) :2 , p. 178-185
ISSN
0004-959X
ISI
000321628400009
Carrier
E
Target language
English (eng)
Full text (Publishers DOI)
Abstract
Foraging in a habitat with highly unpredictable availability of prey, breeding seabirds have to balance their investment in reproduction with their own energetic requirements, including their immune system. This study aimed to investigate the influence of breeding stage (incubation and chick rearing) and sex on body condition and leucocyte profiles in two sympatrically breeding tropical seabird species on Christmas Island, Indian Ocean: the strongly size-dimorphic, inshore-foraging brown booby (Sula leucogaster) and the monomorphic offshore-foraging red-tailed tropicbird (Phaethon rubricauda). Brown booby males were in poorer body condition than females. Male brown boobies had a higher heterophil/lymphocyte (H/L) ratio (indicating higher stress levels), and higher eosinophil numbers (suggesting higher intestinal parasite loads) than females, and sex differences in H/L ratio and body condition were more pronounced during chick rearing. The results suggest that in brown boobies, incubation was energetically less demanding for males than chick rearing, but that the smaller males were energetically more challenged than females during both breeding stages. In the monomorphic red-tailed tropicbird, there were no differences in body condition between sexes and breeding stage, and there was no influence of sex or breeding stage on the leucocyte profiles. The results suggest that incubation and chick rearing are equally demanding for males and females, and that the increased energetic demands of chick rearing are likely to be buffered by a bimodal foraging strategy by both sexes. Our results show that breeding stage as well as sex- and species-specific foraging behaviour can affect leucocyte profiles and particularly the H/L ratio differentially in sympatrically breeding seabird species.
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