Advanced

Changes in immunocompetence and other physiological measures during molt in brown-headed cowbirds (Molothrus ater)

Ellis, Vincenzo A. LU ; Merrill, Loren; Wingfield, John C; O'Loghlen, Adrian L. and Rothstein, Stephen I. (2012) In Auk 129(2). p.231-238
Abstract

We tested one of the foundational hypotheses of the field of ecological immunology: that it is difficult for animals to simultaneously carry out two or more especially demanding physiological processes at optimal levels because of energy needs or other factors that cause tradeoffs among competing components of life history. We investigated possible effects of molt (a costly life-history stage that all birds share) on three physiological parameters in 32 male and female Brown-headed Cowbirds (Molothrus ater). We measured hematocrit, corticosterone levels (CORT), and the bactericidal competence (BC) of blood plasma by drawing blood from the birds before, twice during, and twice after their molt from late July to early September 2009. In... (More)

We tested one of the foundational hypotheses of the field of ecological immunology: that it is difficult for animals to simultaneously carry out two or more especially demanding physiological processes at optimal levels because of energy needs or other factors that cause tradeoffs among competing components of life history. We investigated possible effects of molt (a costly life-history stage that all birds share) on three physiological parameters in 32 male and female Brown-headed Cowbirds (Molothrus ater). We measured hematocrit, corticosterone levels (CORT), and the bactericidal competence (BC) of blood plasma by drawing blood from the birds before, twice during, and twice after their molt from late July to early September 2009. In accordance with our predictions, BC dropped during molt for both males and females. Interestingly, BC recovered faster after molt ended in males, and female BC remained depressed for the rest of our sampling period. Hematocrit also dropped during the molt but returned to initial levels after molt in both males and females. CORT dropped during molt, but the change was significant only for males. Our results highlight possible physiological consequences of molt in Brown-headed Cowbirds even when the birds are maintained in optimal conditions (i.e., shelter, ad libitum food and water, relatively low-stress environment). Furthermore, we suggest that the slower recovery of female immune function following molt may be related to higher female mortality resulting in the ubiquitous phenomenon of male-biased sex ratios in Brown-headed Cowbird populations.

(Less)
Please use this url to cite or link to this publication:
author
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Corticosterone, Cowbird, Ecological immunology, Hematocrit, Life history, Molt, Sex ratios, Tradeoff
in
Auk
volume
129
issue
2
pages
8 pages
publisher
BioOne
external identifiers
  • scopus:84861379891
ISSN
0004-8038
DOI
10.1525/auk.2012.11215
language
English
LU publication?
no
id
6f6d4eed-1c07-4e8b-a7a0-6e5186c474e4
date added to LUP
2017-05-09 17:19:25
date last changed
2017-05-30 14:05:08
@article{6f6d4eed-1c07-4e8b-a7a0-6e5186c474e4,
  abstract     = {<p>We tested one of the foundational hypotheses of the field of ecological immunology: that it is difficult for animals to simultaneously carry out two or more especially demanding physiological processes at optimal levels because of energy needs or other factors that cause tradeoffs among competing components of life history. We investigated possible effects of molt (a costly life-history stage that all birds share) on three physiological parameters in 32 male and female Brown-headed Cowbirds (Molothrus ater). We measured hematocrit, corticosterone levels (CORT), and the bactericidal competence (BC) of blood plasma by drawing blood from the birds before, twice during, and twice after their molt from late July to early September 2009. In accordance with our predictions, BC dropped during molt for both males and females. Interestingly, BC recovered faster after molt ended in males, and female BC remained depressed for the rest of our sampling period. Hematocrit also dropped during the molt but returned to initial levels after molt in both males and females. CORT dropped during molt, but the change was significant only for males. Our results highlight possible physiological consequences of molt in Brown-headed Cowbirds even when the birds are maintained in optimal conditions (i.e., shelter, ad libitum food and water, relatively low-stress environment). Furthermore, we suggest that the slower recovery of female immune function following molt may be related to higher female mortality resulting in the ubiquitous phenomenon of male-biased sex ratios in Brown-headed Cowbird populations.</p>},
  author       = {Ellis, Vincenzo A. and Merrill, Loren and Wingfield, John C and O'Loghlen, Adrian L. and Rothstein, Stephen I.},
  issn         = {0004-8038},
  keyword      = {Corticosterone,Cowbird,Ecological immunology,Hematocrit,Life history,Molt,Sex ratios,Tradeoff},
  language     = {eng},
  number       = {2},
  pages        = {231--238},
  publisher    = {BioOne},
  series       = {Auk},
  title        = {Changes in immunocompetence and other physiological measures during molt in brown-headed cowbirds (Molothrus ater)},
  url          = {http://dx.doi.org/10.1525/auk.2012.11215},
  volume       = {129},
  year         = {2012},
}