Data from: House sparrows offset the physiological trade-off between immune response and feather growth by adjusting foraging behavior

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.