Füsti fecskék (Hirundo rustica) betörő hidegfront okozta tömeges elhullása 2024 szeptemberében Magyarországon

Abstract

ÖSSZEFOGLALÁS A szerzők szeptember közepén, egy erős hidegfronti hatás miatt jelentkező tömeges elhullást észleltek füsti fecskék (Hirundo rustica) vonulási időszakát megelőző napokban. A patológiai vizsgálatok során megállapították, hogy a madarak felélték teljes zsírraktáraikat és a mellizmaik is jelentősen sorvadtak volt. Az akut testtömegcsökkenés (12,0–13,0 g közötti testtömeg) mellett a májsejtek glikogénraktára teljesen kiürült és a mirigyes-, ill. a zúzógyomorban vérzéseket lehetett megfigyelni. Az elhullás hátterében a fecskék számára elfogható repülő rovar mint táplálékforrás, hideg, esős idő miatti hirtelen eltűnése okozta eléhezés állt. Az eset felhívja a figyelmet a globális klímaváltozás hirtelen jelentkező szélsőséges hatásainak veszélyeire egyes érzékenyebb állatpopulációk esetében. SUMMARY Background: The barn swallow (Hirundo rustica) is a migratory bird with a characteristic color, shiny black on the back, dirty white feathers on the belly, rust-red throat, weighing 17–20 g. This species mainly hunts flying insects, catching them in flight and the swallows are constantly hunting in the air between sunrise and sunset. As the food-scarce autumn season approaches, swallows gather in large flocks and when the daytime temperature drops permanently below 15 ºC, they leave for their wintering grounds in Africa. The birds are preparing for the migration, replenishing their body's fat depots. By the time of leaving, the birds reach a body weight of 22–25 g, which enables them to travel thousands of kilometers. The metabolism of birds is fast, which is especially noticeable in smaller species. Shortterm starvation is already associated with a significant deterioration in nutritional status. Objectives: The carcasses of the swallows that were still alive at the time of capture, but died during transport were examined to identify to cause of sudden death. Materials and Methods: On September 16, 2024, 34 immobile and flightless swallows were delivered to the Clinic of the Department of Exotic Animal and Wildlife Medicine from the beach in Csopak, Hungary (46° 58′ 10.4″ N, 17° 56′ 13.9″ E). Five randomly selected carcasses of swallows were examined according to the standard pathological methods (dissection, histopathology, special stainings, bacteriological examination, PCR). Results and Discussion: During the dissection the body weight of the swallows delivered to the clinic was 12.0–13.0 g (12.6 g on average) which is around half of the normal bodyweight of these birds before migration. The supplementary examinations were negative for known pathogens and histopathology showed extreme lack of glycogen. According to the weather data from 11th of September 2024, a cyclone with significant cooling and heavy rainfall hit Hungary. The reason behind the death of the swallows was starvation caused by the sudden disappearance of the population of flying insects that could be caught by swallows due to cold and rainy weather. This case draws attention to the dangers of sudden extreme effects of global climate change in the case of some sensitive animal populations.