Sex-specific relationships between urbanization, parasitism, and plumage coloration in house finches

Abstract

Historically, studies of condition-dependent signals in animals have been male-centric, but recent work suggests that female ornaments can also communicate individual quality (e.g., disease state, fecundity). There also has been a surge of interest in how urbanization alters signaling traits, but we know little about if and how cities affect signal expression in female animals. We measured carotenoid-based plumage coloration and coccidian (Isospora spp.) parasite burden in desert and city populations of house finches Haemorhous mexicanus to examine links between urbanization, health state, and feather pigmentation in males and females. In earlier work, we showed that male house finches are less colorful and more parasitized in the city, and we again detected such patterns in this study for males; however, urban females were less colorful, but not more parasitized, than rural females. Moreover, contrary to rural populations, we found that urban birds (regardless of sex) with larger patches of carotenoid coloration were also more heavily infected with coccidia. These results show that urban environments can disrupt condition-dependent color expression and highlight the need for more studies on how cities affect disease and signaling traits in both male and female animals.

Variation in Hematological Indices, Oxidative Stress, and Immune Function Among Male Song Sparrows From Rural and Low-Density Urban Habitats

“…Song sparrows from suburban habitats exhibited slightly elevated heterophil counts compared to their rural counterparts, though the biological significance of this finding is somewhat unclear. Several previous studies have found birds inhabiting urban environments experience increased risk of infection from avian diseases (e.g., avian malaria, poxvirus, and coccidia) compared to rural dwelling birds (Bichet et al, 2013;Jiménez-Peñuela et al, 2019;Sykes et al, 2021). Consequently, birds inhabiting highdensity urban environments tend to have greater investment in innate immunity (Møller, 2009b;Audet et al, 2016).…”

“…Shifts in energy budgets and higher oxidative stress in urban birds also may be associated with altered immune function (Watson et al, 2017;Cummings et al, 2020a,b). Indeed, urban dwelling birds tend to exhibit infection more often than rural birds, which could cause or be the result of altered immune function (Hamer et al, 2012;Bichet et al, 2013;Giraudeau et al, 2014;Rouffaer et al, 2017;Jiménez-Peñuela et al, 2019;Sykes et al, 2021). Interspecific comparisons among urban and rural dwelling avifauna indicate urban birds cope with increased disease exposure by investing in a more robust immune system (Møller, 2009b).…”

Bird-feeder cleaning lowers disease severity in rural but not urban birds

“…In prior work on these finch populations, researchers have shown that males are consistently more colorful and healthier (including having less coccidiosis) in rural compared to urban areas 22 – 24 . However, it was recently found that urban female house finches are less severely infected by coccidia than rural females 42 . This opposing pattern between males and females suggests complex disease dynamics in urban areas (i.e.…”

United colours of the city: A review about urbanisation impact on animal colours

“…On the other hand, females can also use plumage colouration as a signal of individual quality (Sykes et al . 2020). However, Sykes et al .…”

“…However, Sykes et al . (2020) reported that females of the house finch ( Haemorhous mexicanus ) were less colourful and had a lower parasite load in urban than in rural areas. These authors suggested that urbanisation can disrupt condition‐dependent colour expression.…”