House sparrows offset the physiological trade‐off between immune response and feather growth by adjusting foraging behavior

Abstract

Growing feathers and mounting immune responses are both energetically costly for birds. According to the life history trade-off hypothesis, it has been posited that the costs of feather growth lead to temporal isolation between molt and other expensive activities, reproduction for example. In contrast to life cycle events, the need to mount an immune response can occur at any time, including during feather growth. Thus, we hypothesized that mounting an immune response during feather growth may divert energy and resources from feather growth and impair feather renewal. To test this hypothesis, we clipped or plucked the same feathers of male house sparrows Passer domesticus biblicus. In the clipped group (n  16), the feathers were absent with no regrowth; in the plucked group (n  14), feathers were absent and regrowth was initiated. We also had an intact control group of 15 sparrows. We then initiated an inflammatory immune response by subcutaneous injection over the left breast muscle of the birds with a lipopolysaccharide (LPS) and quantified behavioral and physiological responses. We predicted that sparrows with plucked feathers would incur the highest energetic costs while mounting an immune response, and would increase their foraging effort to offset this cost. We found no difference in body mass and resting metabolic rates among sparrows subjected to the different feather and immune treatments. However, we did find that while sparrows with plucked feathers increased foraging efficiency following the immune challenge by paying fewer but longer visits to the food tray, allowing them to maintain food consumption. Foraging efficiency in sparrows with clipped feathers was reduced. We also found that quality of newly grown feathers after the immune challenge was poorer in the plucked group, suggesting that mounting an immune response competes with feather growth for resources.

Patterns of annual and seasonal immune investment in a temporal reproductive opportunist

“…Although “costly” physiological processes such as reproduction and moult can affect immune investment [9, 11, 76–78], our data only weakly supported this prediction. While both plumage moult intensity and reproductive measures were included in RFMs and LMs predicting complement, total leukocytes, monocytes, lymphocytes, and natural antibodies, only flight feather moult displayed any strong relationship with interannual or seasonal variation.…”

Patterns of annual and seasonal immune investment in a temporal reproductive opportunist

“…Overall, we observed substantial changes in crossbill immune investments among summers across four years, with interannual variation driven largely by food resources, while seasonal variation was less pronounced and lacked a dominant predictor. Although 'costly' physiological processes such as reproduction and moult can affect immune investment [9,11,61], our data only weakly supported this prediction. Flight feather moult (Ff), plumage moult intensity (body.molt) and reproductive measures (CP/BP) were all selected by RFMs for further consideration (electronic supplementary material, figure S1), yet of these, only flight feather moult displayed a marginally significant, positive relationship with complement (electronic supplementary material, table S6).…”

No energetic cost of tuberculosis infection in European badgers (Meles meles)

“…During infection, energy may be reallocated from one part of the energy budget to another, potentially reducing the energy available for aspects such as growth (e.g. Ben‐Hamo, Downs, Burns, & Pinshow, ), reproduction or survival (Lochmiller & Deerenberg, ). Studies which have attempted to quantify the energetic costs of infection have found conflicting results, suggesting that any energetic effects of infection are likely to be host–pathogen specific (Robar, Murray, & Burness, ).…”