Disease resistance often comes at a cost to other functions, meaning that even within the same species, immune activity can differ between the sexes or even between different life-history strategies within a sex. White-throated sparrows are unusual in having two colour morphs, white and tan. Within each sex, white birds are more aggressive and tan birds provide more parental care. When researchers tested disease resistance in the two morphs, they found that – contrary to expectations – parasite loads were higher in tan birds, indicating that morph-associated immunity differences in sparrows could reflect fundamental differences in life history, not sex differences.
Biology Letters
Published July 04, 2018 (Brief from the Royal Society)

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Corresponding author: Elizabeth MacDougall-Shackleton, University of Western Ontario – emacdoug@uwo.ca