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Survival chances of ground nests in a meadow habitat : a case study in Vrana Lake Nature Park (Mediterranean region, Croatia)

100%

Purger J. , Muzinić J. , Purger D.

Polish Journal of Ecology

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2012

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tom Vol. 60, nr 1

207-212

EN

The number of ground-nesting bird species in meadows, one of the most vulnerable habitats in the ornithological reserve of Vrana Lake Nature Park has decreased in recent decades. Nest survival rates were investigated in meadows and reed beds using nest predation experiments in late March and in May 2005. Predators damaged 18% of the 50 artificial nests placed in the pasture meadow habitat in March and 22% in May. Daily survival rate of nests were found to be similar in March (97%) and May (96%). In May, 64% of 25 nests located in the reed bed were discovered by the predators, with the daily survival rate of nests (90%) being significantly lower than that of nests in the nearby meadow. The results suggest that the reasons for the decreasing number of nesting bird species may be - instead of the pronounced presence and activity of predators in the area - the shrinkage of meadow area, the lack of buffer zone, the proximity of agricultural lands, and disturbance caused by intensive grazing.

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Survival chances of ground nests in a meadow habitat: a case study in Vrana Lake Nature Park (Mediterranean region, Croatia)

100%

Purger J. J. , Muzinic J. , Purger D.

Polish Journal of Ecology

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2012

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tom 60

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nr 1

EN

The number of ground-nesting bird species in meadows, one of the most vulnerable habitats in the ornithological reserve of Vrana Lake Nature Park has decreased in recent decades. Nest survival rates were investigated in meadows and reed beds using nest predation experiments in late March and in May 2005. Predators damaged 18% of the 50 artificial nests placed in the pasture meadow habitat in March and 22% in May. Daily survival rate of nests were found to be similar in March (97%) and May (96%). In May, 64% of 25 nests located in the reed bed were discovered by the predators, with the daily survival rate of nests (90%) being significantly lower than that of nests in the nearby meadow. The results suggest that the reasons for the decreasing number of nesting bird species may be – instead of the pronounced presence and activity of predators in the area – the shrinkage of meadow area, the lack of buffer zone, the proximity of agricultural lands, and disturbance caused by intensive grazing.

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Ground nesting in recultivated forest habitats - a study with artificial nests

100%

Purger J. J. , Meszaros L. A. , Purger D.

Acta Ornithologica

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2004

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tom 39

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nr 2

EN

The study was carried out in the outskirts of the town of Pécs (southern Hungary) in a recultivated former coal mine. Bordered by Turkey Oak forests, this open area forms a wedge-shaped clearing in that woodland. Since trees and taller shrubs are rare in the area, it is mainly ground nesting bird species that occur in the clearing. In order to discover whether it is more advantageous to nest in the recultivated area (clearing) than in the nearby forest or at its edges, 150 artificial ground nests were constructed. On 7 May 2002, one quail egg and a plasticine egg of similar size were placed in each of the artificial nests. After a week it was found that 24% of nests in the clearing, 30% of those in the forest edge, and 44% of the ones inside the forest had suffered depredation. The proportions of damaged plasticine and quail eggs inside the forest and at the forest edge were similar, whereas the quail eggs in the clearings were significantly less damaged than plasticine eggs. Of all the experimental eggs, significantly more plasticine eggs (29%) were damaged than quail eggs (17%), which suggests that small-bodied predators are unable to break the quail eggs. 18% of the plasticine eggs attacked, and 72% of the quail eggs attacked were removed from the nest by the predator. Among the predators, small mammals were dominant in the clearing and inside the forest, and birds at the forest edge. Based on the predation of quail eggs, the survival chances of ground nests in the clearing are greater than at the forest edge or inside the forest.

PL

Badania prowadzono na części terenu kopalni węgla objętym rekultywacją. Teren ten otoczony jest drzewostanem liściastym, z dominacją dębów, porośnięty jest roślinnością zielną. Badania miały na celu ocenę czy gniazdowanie na terenie poddanym rekultywacji jest bezpieczniejsze niż w otaczającym lesie lub na jego skraju. W każdym z wyróżnionych środowisk: wnętrzu lasu, skraju lasu i na terenie otwartym wyłożono po 50 sztucznych gniazd. Gniazda w każdym transekcie oddalone były od siebie o ok. 20 m, do każdego wyłożono do nich po jednym jaju przepiórczym i jednym wykonanym z plasteliny. Po tygodniu od wyłożenia jaj stwierdzono, że udział gniazd znalezionych przez drapieżniki był podobny w każdym z transektów (Fig. 1). Jednakże rozpatrując wyłącznie drapieżnictwo na wyłożonych jajach przepiórczych, stwierdzono istotnie mniejsze drapieżnictwo na terenie otwartym niż w lesie i na jego skraju (Fig. 1). Ślady pozostawiane na jajach wykonanych z plasteliny sugerują, że głównymi drapieżnikami skraju lasu były ptaki, natomiast na terenie otwartym i w głębi lasu — ssaki (Fig. 2). Analizując wyniki z wszystkich gniazd znacząco więcej jaj plastelinowych nosiło ślady drapieżników (29%), niż zostało zniszczonych jaj przepiórczych (17%), co wskazuje, że drobne ssaki nie są zdolne do przebicia skorupy jaj tej wielkości. Uzyskane wyniki wskazują, że w przypadku większych ptaków (bażant, lelek), presja drapieżników na lęgi może być mniejsza na terenach otwartych, niż w otaczającym tereny rekultywowane lesie.