Interspecific variation in avian blood parasites and haematology associated with urbanization in a desert habitat

Abstract

Many avian species are negatively impacted by urbanization, but other species survive and prosper in urbanized areas. One factor potentially contributing to the success of some species in urban areas is the reduced presence of predators or parasite vectors in urban compared to rural areas. In addition, urban areas may provide increased food and water resources, which can enhance immune capacity to resist infection and the ability to eliminate parasites. We determined patterns of blood parasitism, body condition, and immune cell profiles in urban and rural populations of five adult male songbird species that vary in their relative abundance within urban areas. Urban birds generally exhibited less blood parasitism than rural birds. This difference was particularly evident for the urban-adaptable Abert's towhee Pipilo aberti. In contrast, no difference in haemoparasitism was seen between urban and rural populations of the curve-billed thrasher Toxostoma curvirostre, a less-urban adaptable species. In two closely related species, the curve-billed thrasher and the northern mockingbird Mimus polyglottos, urban birds had a higher leukocyte count and a higher heterophil to lymphocyte ratio, which is often associated with chronic stress or current infection, than rural birds. Urban northern mockingbirds were in better condition than rural counterparts, but no habitat-related differences in condition were detected for other species. Parasitic infection was correlated with body condition in only one species, the canyon towhee Pipilo fuscus. Parasitic infection in most species was correlated with changes in leukocyte abundance and profile. The findings suggest that interspecific differences in parasitic infection cannot be attributed entirely to differences in vector abundance or body condition. Interactions between immune function, parasite infection risk, and resource availability may contribute to determining the relative ability of certain species to adapt to cities.

High prevalence of Leucocytozoon parasites in fresh water breeding gulls

“…Among seabirds, high prevalence of Leucocytozoon was previously recorded in penguins (73.7 %; Argilla et al 2013). One of hypotheses proposed to explain differences in blood parasite prevalence is the vector-density hypothesis (Bennett et al 1992;Tella et al 1996;Piersma 1997;Sol et al 2000;Jovani et al 2001;Martínez-Abraín and Urios 2002;Fokidis et al 2008). Bird species associated with inland environments are expected to be more exposed to the malaria-like parasites than similar bird species inhabiting marine environments as the former provide more suitable breeding areas for vectors (Piersma 1997;Sol et al 2000;Mendes et al 2005).…”

“…Several hypotheses have been proposed to explain why blood parasites are rare in some birds species. These include absence or low abundance of vectors in saline or arid habitats (Engström et al 2000;Sol et al 2000;Jovani et al 2001;Wojczulanis-Jakubas et al 2010), competitive exclusion by ectoparasites , specific host-parasite assemblage (Earle and Underhill 1993;González-Solís and Abella 1997;Jones and Shellam 1999;Martínez-Abraín and Urios 2002;Fokidis et al 2008) or host immune capabilities (Merino and Minguez 1998;Tella et al 1999).…”

Elevated Immune Gene Expression Is Associated with Poor Reproductive Success of Urban Blue Tits

“…Cities have been associated with altered parasite communities and altered infection dynamics (Fokidis et al, 2008;Evans et al, 2009;Giraudeau et al, 2014;Neiderud, 2015). For example, foraging behavior in cities is thought to enhance the prevalence of intestinal coccidians (Giraudeau et al, 2014), potentially driven by increasing contact rates at feeders (Becker et al, 2015).…”

Prevalencia parasitaria en el gorrión altiplanero (Spizella wortheni): especie endémica de México y en peligro de extinción

“…La relación heterófilo/linfocito (H/L) fue de 0.48. A pesar de la infección los valores se encuentran en el rango de media previamente reportado para otras especies de las familias Emberizidae y Passerellidae: Emberiza cirlus (L=56.29, H=37.4, E=5.59, M=0.59, H/L=0.66;Figuerola et al 1999), Zonotrichia capensis (L=71.4, H=20.2, E=2.3, B=3.1 M=2.9, H/L=0.30; Ruiz et al 2002), Pipilo aberti (L=39.8, H=51.3, E=7.5, B=0.6, M=1.4, H/L=0.91;Fokidis et al 2008) y Spizella breweri (L=55, H=37.25, E=2.25, B=1, M=4.5, H/L=0.88, datos obtenidos en un estudio paralelo al presente no publicados). La relación entre el conteo de los eosinófilos en aves con infecciones intestinales es ambigua; a pesar de que se ha se ha mostrado una asociación limitada entre nemátodos y el número de eosinófi-los, los estudios experimentales con antígenos parasitarios no indujeron esosinofilia, y en el caso de inoculación de coccidias los niveles de eosinófilos circulantes en sangre se mantuvieron bajos (revisado en Rose et al 1979y Mitchell et al 2008.…”