Development pattern of blood oxygen carrying capacity in rainbow bee-eater nestlings
Kylie Eklom A and Alan Lill A B CA Wildlife Ecology Research Group, School of Biological Sciences, Monash University, Clayton Campus, Vic. 3800, Australia.
B School of Psychology, Psychiatry and Psychological Medicine, Monash University, Clayton Campus, Vic. 3800, Australia.
C Corresponding author. Email: alan.lill@sci.monash.edu.au
Australian Journal of Zoology 54(1) 1-7 https://doi.org/10.1071/ZO05063
Submitted: 12 October 2005 Accepted: 18 January 2006 Published: 23 March 2006
Abstract
Growth profile variation among altricial bird species is reflected in variation in development patterns of parameters influencing blood oxygen carrying capacity (O2Cap). Rainbow bee-eater nestlings develop slowly and their asymptotic mass reaches or exceeds adult levels before undergoing prefledging recession (mass overshoot–recession profile, MOR). Erythrocyte count (RBC), blood hemoglobin content (Hb) and hematocrit (Hct) increased 2.5-fold during development. Hatchlings’ erythrocyte volume closely approximated adult levels and decreased by only 1% during development. Erythrocyte hemoglobin content and concentration also increased minimally. RBC and Hb increased throughout development, but Hct increase was restricted to early development, overlapping the mass-gain period by just 37%. Blood parameters influencing O2Cap did not exceed adult levels and then decline during the mass asymptote–recession development stage. Continuing increase in RBC and Hb at this stage contributed to attaining a fledging O2Cap of adult levels. Results were consistent with there being a common mechanism regulating developmental increase in O2Cap in altricial birds. However, features of this development in bee-eater nestlings variously conformed to the patterns of both species with MOR and species with standard growth profiles. Some features shared with other MOR species also differed in timing or pattern in bee-eater nestlings.
Acknowledgments
The study was approved by the Monash School of Biological Sciences Animal Ethics Committee (BSCI/2002/12). We thank Kate Breuer, Peter Fell, Ian Stewart, Evelyn Nicholson, Prue Simmons and Alistair Stewart for field and technical assistance. We are very grateful to George Merritt for facilitating access to several private properties and to the owners (Terry Hedt, John and Marilynne Pettit, Andrew and Lynne McNeill and David and Thelma Basselot-Hall) for allowing us to work on their land. We are also grateful to Craig Bray and Parks Victoria for facilitating access to the study area.
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