Low prevalence of blood parasites in a long-distance migratory raptor: the importance of host habitat

Abstract

BackgroundThe low prevalence of blood parasites in some bird species may be related to the habitats they frequent, the inexistence of the right host-parasite assemblage or the immunological capacity of the host. Here, we assess the parasite load of breeding populations of Eleonora’s falcon (Falco eleonorae), a medium-sized long-distance migratory raptor that breeds on small isolated islets throughout the Mediterranean basin and overwinters in inland Madagascar.MethodsWe examined the prevalence and genetic diversity of the blood parasites belonging to the genera Plasmodium, Haemoproteus and Leucocytozoon in Eleonora’s falcon nestlings from five colonies and in adults from two colonies from nesting sites distributed throughout most of the species’ breeding range.ResultsNone of the 282 nestlings analysed were infected by blood parasites; on the other hand, the lineages of Plasmodium, Haemoproteus and Leucocytozoon were all found to infect adults. Our results support the idea of no local transmission of vector-borne parasites in marine habitats. Adult Eleonora’s falcons thus may be infected by parasites when on migration or in their wintering areas.ConclusionThe characteristics of marine environments with a lack of appropriate vectors may thus be the key factor determining the absence of local transmission of blood parasites. By comparing the parasite lineages isolated in this species with those previously found in other birds we were able to infer the most likely areas for the transmission of the various parasite lineages.

Ecological determinants of avian malaria infections: An integrative analysis at landscape, mosquito and vertebrate community levels

“…Strong relationships between landscape use and the prevalence of blood parasites infecting birds have previously been shown (Fourcade et al., ; Patz et al., ), which may be due to the effect of landscape features on the vector community (Norris, ). For instance, the scarcity of suitable vectors has been identified as the most likely reason of the low prevalence or absence of Plasmodium in birds from marine and saline environments (Figuerola, ; Gutiérrez‐López et al., b; Martínez‐de la Puente et al., ; Mendes, Piersma, Lecoq, Spaans, & Ricklefs, ) and deserts (Merino, Barbosa, Moreno, & Potti, ). Indeed, environmental characteristics strongly determined the mosquito abundance and community composition in the study area (Ferraguti et al., ).…”

Genetic colour polymorphism is associated with avian malarial infections

“…The lineage LK6 was recently isolated from passerines from Macaronesian archipelagoes, the Iberian Peninsula and Morocco (electronic supplementary material, table S1). Although the transmission areas remain unclear, it has been proposed that migratory birds such as Eleonora's falcon could spread blood parasites to resident birds on the main islands, where insect vectors are present [16]. It has been suggested that darker colours are more attractive to mosquitoes than light colours and so entirely dark plumages could increase host-vector contact rates.…”

“…In feral pigeons (Columba livia), alternative morphs were distributed non-randomly across an urban gradient and had different parasite risks [15]. However, the different Eleonora's falcon morphs inhabit small islands sympatrically during the breeding season and local transmission of blood parasites at breeding grounds is absent, owing to the lack of suitable vectors [16]. Therefore, differences in the exposure to vectors must occur during migration and/or in their wintering quarters, where rsbl.royalsocietypublishing.org Biol.…”

Louse flies of Eleonora’s falcons that also feed on their prey are evolutionary dead‐end hosts for blood parasites

“…To identify the avian hosts of the blood parasites that were isolated from the louse flies, blood samples from both adult and nestling Eleonora's falcons and bird prey were obtained. Blood parasites infecting Eleonora´s falcons that were sampled from 2006 to 2014 ( N = 173 nestlings and 209 samples from 183 adults) had been previously analyzed (Gangoso et al, ; Gutiérrez‐López, Gangoso et al, ). In addition, in September 2013 we sampled 90 recent kills of 12 bird species belonging to seven different families.…”

“…The Eleonora's falcon ( Falco eleonorae ) is a medium‐sized long‐distance migratory raptor that breeds on islands in the Mediterranean basin and winters in Madagascar (Kassara et al, ; Walter, ). Adult Eleonora's falcons are commonly infected by Plasmodium and Haemoproteus parasites (Gangoso, Gutiérrez‐López, Martínez‐de la Puente, & Figuerola, ; Gutiérrez‐López, Gangoso et al, ). In addition, both adults and nestlings are heavily parasitized by the louse fly Ornithophila gestroi (Gangoso et al, ), which has only been reported on Eleonora's falcon and the closely related common and lesser kestrels ( Falco tinnunculus and Falco naumanni ) (Beaucournu, Beaucournu‐Saguez, & Guiguen, ; Gangoso et al, ; Walter, ).…”