Endoparasite Infection Has Both Short- and Long-Term Negative Effects on Reproductive Success of Female House Sparrows, as Revealed by Faecal Parasitic Egg Counts

<div><p>Parasites have the potential to severely reduce host reproductive success. However, the effects of endoparasites on reproductive success have not received the same amount of attention as the effects of parasites on host survival. We investigated the relationship between an avian endoparasite (gapeworm, <i>Syngamus trachea</i>) and both current and future reproductive success of female house sparrows (<i>Passer domesticus</i>) in a population on the coast of Helgeland, northern Norway. We found that the proportion of eggs in a nest that failed to develop into fledglings increased as the faecal parasitic egg count of the mothers increased. We also found that juvenile females with high numbers of parasitic eggs in their faeces had lower lifetime reproductive success as adults. However, we did not find a relationship between maternal parasite infection and clutch size or recruitment rate of offspring. To our knowledge this is the first study to find a relationship between reproductive success of an avian host and faecal egg count of an endoparasite. The present study indicates that infection by an endoparasite may be associated with lower individual reproductive success in both the short-term and long-term in a wild population of hosts.</p></div

Fledgling failure and maternal infection.

<p>The relationship between fledgling failure (i.e. probability that eggs fail to develop into fledglings) over a 11-day interval with maternal faecal egg count (FEC) of the parasite <i>Syngamus trachea</i> in house sparrows on the island of Hestmannøy, northern Norway. The solid line indicates predicted values from the highest ranked generalized linear mixed model as judged by AIC_C (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0125773#pone.0125773.s003" target="_blank">S2 Table</a>). The model included individual identity as a random factor, and maternal tarsus length and hatch day as fixed covariates. Dotted lines indicate lower and upper limits of the 95% confidence interval of predicted values. “Sunflower” points indicate sample size of observed values.</p

Lifetime reproductive success and juvenile infection.

<p>The predicted relationship between faecal egg count (FEC) of the parasite <i>Syngamus trachea</i> and individual lifetime reproductive success of juvenile female house sparrows on the island of Hestmannøy, northern Norway, measured as the number of recruits produced in an individual’s lifetime. The solid line indicates predicted values from the highest ranked generalized linear mixed model as judged by AIC_C (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0125773#pone.0125773.s005" target="_blank">S4 Table</a>). Dotted lines indicate lower and upper limits of the 95% confidence interval of predicted values. “Sunflower” points indicate sample size of observed values (one observation omitted to improve clarity).</p

DemographicNe-Datafile

DemographicNe-Datafil

BaalsrudEtA-GeneticNe-SingleSampleNeData

Genetic single-sample Ne-estimates and corresponding population characteristic

BaalsrudEtAl-GeneticNe-MolecularData

Microsatellite genotypes for all individuals included in the stud

BaalsrudEtAl-GeneticNe-TemporalSamplesNeData

Genetic temporal samples Ne-estimates and corresponding population characteristic

Pedigree control

Pedigree for a house sparrow population at the island Hestmannøy in Norway. Includes phenotyped individuals alive in the years 2002-2012

Pedigree high

Pedigree for a house sparrow population on the island Leka in Norway, subjected to artificial selection to increase tarsus length (high). Includes phenotyped individuals alive in the years 2002-2012