High Prevalence of Hematozoa in Nestlings of a Passerine Species, the Pied Flycatcher (Ficedula Hypoleuca)

While this may be true in many passerines, mainly ground-nesting species with short fledgling periods, we show here that prevalences may be detected as early as 13 days of age in a cavity-nesting passerine. Prevalences and intensities of hematozoa in nestling birds may merit further study, as both parameters are relatively easy to quantify in smears of peripheral blood in bird species such as the Pied Flycatcher (Ficedula hypoleuca, Muscicapidae), which has a relatively extended fledgling period. In 1993, an intensively studied population of Pied Flycatchers in central Spain (Potti 1993) was sampled for presence of hematozoa. Adult birds were captured while incubating (females) or feeding nestling (males); a drop of blood was obtained from the brachial vein, smeared, air dried, and fixed with 100% ethanol. Slides were later stained with Giemsa for 45 min. In addi-