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Haemoparasites prevalence in birds can vary among species, age and sex groups and ecological conditions. To comprehend the host—parasite assemblages, it is important to investigate physiological mechanisms underlying the interactions in wild bird species. Here, using blood smears we investigated how leukocyte profiles in reed warblers (Acrocephalus scirpaceus) and sedge warblers (Acrocephalus schoenobaenus) vary in relation to the heamoparasite presence with respect to the host's age and sex. We sampled the birds during their autumn migration in 2008 at a stopover site in northern Poland. We found a significant relationship between the leukocyte profiles and parasite infection. Parasite infection was associated with elevated relative number of heterophils with simultaneous lowered relative number of lymphocytes. These opposite pattern resulted in an elevated H/L ratio in infected birds. Total leukocytes, lymphocytes and heterophils counts were elevated in birds infected with blood parasites as compared wi...

A survey for antibodies to West Nile virus (WNV; genus ,Flavivirus) was carried out by plaque-re-duction neutralization microtesting in 78 horses, 20 domestic chickens, and 97 wild birds belonging to 10 species from different areas in Poland. Specific antibodies were detected in five juvenile (hatching-year) birds collected in 2006: three white storks (Ciconia ciconia) in a wildlife rehabilitation center (5.4% of all examined storks; the antibody titers in each bird were 1:320, 1:160, and 1:20), one free-living mute swan (Cygnus olor; the titer was 1:20), and one hooded crow (Corvus corone cornix; the titer 1:20) in a wildlife rehabilitation center; thus the overall seropositivity to WNV was 5.2% among all the birds sampled. These data do not rule out the presence of WNV activity in Poland with 100% certainty, but they indicate a significant trace that demands verification. In addition, one black-headed gull (Larus ridibundus) had neutralizing antibodies for the Usutu Flavivirus, the first case recorded in Poland.

Absence of blood parasites in birds occurring in polar regions is believed to be a common phenomenon but only few surveys have been conducted on truly polar bird species. We examined blood parasites in a seabird with an exclusively high-Arctic breeding distribution, the Little Auk (Alle alle). Polymerase chain reaction was used to detect haemosporidians and traditional optical microscopy was used to detect a wider range of haematozoans in birds breeding on Svalbard (Norway). No blood parasites were found among 100 birds examined. This finding confirms scarcity of haematozoa in polar regions and provides baseline data for the Little Auk.