Coccidial infection does not influence preening behavior in American goldfinches
Adrian Surmacki
Geoffrey E. Hill
0
) Department of Avian Biology and Ecology, Faculty of Biology, Adam Mickiewicz University
, Umultowska 89, 61-614 Pozna,
Poland
Preening behavior in birds is important for the maintenance of thermoregulatory and ornamental functions of plumage. It has been repeatedly demonstrated that birds trade off time between plumage maintenance and other activities. However, the condition-dependent constraints of preening remain virtually unstudied. Here, we present the first experimental test of the hypothesis that intestinal parasite infection impairs preening activity. We studied male American goldfinches (Spinus tristis ), a species with carotenoid-based plumage coloration. Following pre-alternate (spring) molt, we manipulated the health of males by infecting some birds with Isospora spp. coccidia and keeping others free of the infection. Although the goldfinches increased preening throughout the captive period, we found no significant effect of coccidial treatment on preening behavior. The effect of coccidia on plumage maintenance may be more pronounced under natural conditions where birds have limited access to food and engage in more activities that might limit time available for preening.
-
Plumage maintenance is an important behavior among birds,
accounting for about 9 % of the daily time budged (Cotgreave
and Clayton 1994; Walther and Clayton 2005). The primary
functions of preening include: controlling ectoparasites load
(Clayton et al. 2010), removing dirt and detritus (Lenouvel
et al. 2009; Griggio et al. 2010), spreading preen wax over the
surface of feathers (Moyer et al. 2003), and keeping feathers
properly positioned. All of these activities are crucial for the
maintenance of thermoregulatory function of plumage, which
might be altered if the physical condition of feathers is
disturbed either by soiling load, keratin-eating parasites, or
disorder. Plumage maintenance can also help maintain plumage
coloration. In many bird species, females use male coloration
as a cue during mate choice (reviewed in Hill 2006).
Ornamental plumage coloration can be compromised by soiling
(e.g., Surmacki and Nowakowski 2007; Lenouvel et al. 2009;
Griggio et al. 2010), and ectoparasites (Moreno-Rueda 2005) or
enhanced by preen oil (e.g., Lpez-Rull et al. 2010).
Feather maintenance is believed to be a time- and
energyconsuming behavior (Cotgreave and Clayton 1994; Walther
and Clayton 2005). Birds must trade off time and energy
between preening and other behaviors such as foraging or
scanning for predators (Redpath 1988; Cucco and Malacarne
1997; Randler 2005). Consequently, we may expect that any
alteration of physiological condition may impose negative
effects on preening activity. Surprisingly, this idea has been
tested only once, using juvenile apapanes (Himatione
sanguinea , Yorinks and Atkinson 2000). Individuals
experimentally infected with malaria spent significantly less time
preening than did healthy birds. Infected individuals also
showed a reduction in activity, body mass, and fat stores
(Yorinks and Atkinson 2000).
Here, we experimentally tested the hypothesis that parasite
infection affects preening behavior in male American
goldfinches (Spinus tristis ), a sexually dichromatic songbird. Male
goldfinches have bright-yellow carotenoid-based plumage
coloration (McGraw et al. 2001) that females assess during
mate choice (Johnson et al. 1993). We manipulated parasite
infection status of birds by either infecting them with coccidia
(Isospora sp.) or by curing them of coccidiosis with medicine.
Coccidia are common intestinal parasite of many songbirds
including house finches, Carpodacus mexicanus (Brawner
et al. 2000). Their sporozoites feed on the epithelium of the
small intestine, leading to significant impairment of
absorption of various components of food (Hrak et al. 2004). To
date, the effect of coccidia infection on preening has not been
tested but coccidiosis is known to affect sexual display
behavior in birds (e.g., Costa and Macedo 2005; Aguilar et al. 2008)
and anti-predator behavior in mammals (Voek et al. 1998).
Consequently, we predicted that infected individuals would
spend less time preening.
Material and methods
We captured 57 wild male American goldfinches on the
campus of the Auburn University in April 2010 using wire
mesh traps baited with thistle seeds (see Hill (2002) for
trapping method details). We registered standard biometric
measurements: body mass (0.1 g), tarsus (0.01 mm), bill
(0.01 mm), wing (0.5 mm), and tail length (1 mm).
Additionally, we collected 1015 breast feathers from each
bird before coccidia treatment and at the end of the experiment
for ectoparasite examination. We estimated the age of birds as
after second year (ASY) or second year (SY) based on
plumage characters (Pyle 1997). We randomly divided the
birds into four groups of 13, 16, 14, and 14 birds. The
proportions of the two age classes (ASY/SY) in each cage
were as follows: 11/2 (...truncated)