Ticks (Acari: Ixodida) on birds (Aves) migrating through the Polish Baltic coast

Seasonal bird (Aves) migration between breeding and wintering areas, often located on different continents, can facilitate the spreading of tick species (Acari: Ixodida) and of tick-borne pathogens. The aim of the study was to analyse the occurrence of ticks dispersed by birds migrating along the Polish Baltic coast during spring and autumn migration. Field research was conducted at the bird ringing station in Wicie, located on the middle of the Polish Baltic coast, in 2011 and 2012 during spring and autumn migration. A total of 2657 birds from 45 species was examined. The most common species inspected were European robin (Erithacus rubecula) (63.3%), song thrush (Turdus philomelos) (5.13%), and goldcrest (Regulus regulus) (4.5%). Overall, 3129 ticks belonging to six species were collected: Ixodes ricinus (1650 larvae, 1390 nymphs and 1 male), Ixodes frontalis (20 larvae, 20 nymphs), Ixodes arboricola (35 larvae), Dermacentor reticulatus (1 larva), and Haemaphysalis punctata (1 nymph). Ten larvae and one nymph could only be identified to the genus level Ixodes. Ticks were located on various parts of the head: on the corner of the beak (75.0%), near the eyes (14.6%), on the chin (4.4%), near the ears (4.4%), on the neck (1.1%), and in the beak (0.5%). The overall tick prevalence was 40.5%. The highest prevalence was for bird species feeding on the ground, covering a medium distance to wintering grounds and migrating at night. Statistically significant differences between the number of ticks and the sex of the host species were detected in blackbirds: males carried more parasites than females, both, during spring and autumn migration. The fact that I. ricinus and other ticks parasitize birds migrating through Poland extends the possibility of the spread of tick-borne diseases.