Long-distance dispersal in the short-distance dispersing house sparrow (Passer domesticus).

The house sparrow (Passer domesticus) is a small passerine known to be highly sedentary. Throughout a 30-year capture-mark-recapture study, we have obtained occasional reports of recoveries far outside our main metapopulation study system, documenting unusually long dispersal distances. Our records constitute the highest occurrence of long-distance dispersal events recorded for this species in Scandinavia. Such long-distance dispersals radically change the predicted distribution of dispersal distances and connectedness for our study metapopulation. Moreover, it reveals a much greater potential for colonization than formerly recorded for the house sparrow, which is an invasive species across four continents. These rare and occasional long-distance dispersal events are challenging to document but may have important implications for the genetic composition of small and isolated populations and for our understanding of dispersal ecology and evolution.

Immune gene expression and epigenetic potential affect the consumption of risky food by female house sparrows.

When organisms move into new areas, they are likely to encounter novel food resources. Even if they are nutritious, these foods can also be risky, as they might be contaminated by parasites. The behavioural immune system of animals could help them avoid the negative effects of contaminated resources, but our understanding of behavioural immunity is limited, particularly whether and how behavioural immunity interacts with physiological immunity. Here, we asked about the potential for interplay between these two traits, specifically how the propensity of an individual house sparrow (Passer domesticus) to take foraging risks was related to its ability to regulate a key facet of its immune response to bacterial pathogens. Previously, we found that sparrows at expanding geographic range edges were more exploratory and less risk-averse to novel foods; in those same populations, birds tended to over-express Toll-like receptor 4 (TLR4), a pattern-recognition receptor that distinguishes cell-wall components of Gram-negative bacteria, making it the major sensor of potentially lethal gut microbial infections including salmonellosis. When we investigated how birds would respond to a typical diet (i.e., mixed seeds) spiked with domesticated chicken faeces, birds that expressed more TLR4 or had higher epigenetic potential for TLR4 (more CpG dinucleotides in the putative gene promoter) ate more food, spiked or not. Females expressing abundant TLR4 were also willing to take more foraging risks and ate more spiked food. In males, TLR4 expression was not associated with risk-taking. Altogether, our results indicate that behaviour and immunity covary among individual house sparrows, particularly in females where those birds that maintain more immune surveillance also are more disposed to take foraging risks.

The evolution of extra-pair paternity and paternal care in birds.

Extra-pair paternity (EPP) influences the relatedness between social parents and offspring. Therefore, one might expect the level of EPP to influence levels of paternal investment. Here, we investigated the effect of variation in EPP rates on male contributions to parental care within a phylogenetic framework of up to 271 primarily socially monogamous bird species representing 85 families. We used proportion of male provisioning and occurrence of male incubation and nestbuilding as measures of paternal care. We tested the relationship between EPP rates and different components of paternal care while controlling for various life-history traits, namely lifespan, clutch size, and body mass in a phylogenetic path analysis framework. EPP was significantly negatively associated with the occurrence (i.e., whether males participate or not) of male nestbuilding and incubation, but not with the relative amount (proportion) of nestbuilding or incubation performed by the male. Importantly, the proportion of provisioning and biomass delivery by males was clearly negatively associated with EPP. These analyses thus confirm that the effect of EPP on proportion of provisioning visits by males is similar to proportion of biomass delivery, an often assumed but rarely tested assumption. Analysing only Passerine species provided similar results, although only proportion of provisioning was significantly negatively associated with EPP. This study, therefore, provides the most comprehensive support to date of a negative relationship between EPP and paternal care across species. However, a causal relationship between EPP and paternal care cannot necessarily be concluded. We also identify key methodological improvements for future research within the topic.