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

Purger J., Muzinić J., Purger D.

Polish Journal of Ecology

2012

Vol. 60, nr 1

207-212

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.

Forest fragment size affects edge effect in nest predation . experiment with artificial nests

Mazgajski T., Rejt Ł.

Polish Journal of Ecology

2005

Vol. 53, nr 2

233-242

Many species react negatively to forest fragmentation. If this process also decreases the abundance of forest predators we expect that birds. broods in small forest patches would be preyed upon only by predators that penetrate from the matrix while broods in larger patches would be also attacked by predators specifically associated with forests. We tested the hypothesis that an increase in forest patch size leads to an increase in predator pressure on nests. Studies were conducted in Central Poland, in an agriculturally dominant area with 6% forest cover and highly fragmented woodlot. Three patch sizes were chosen for the experiment: small (< 20 ha), medium (30 - 50 ha) and large (> 120 ha). One quail egg was placed in each nest. All transects were checked after 13 - 14 days. The highest predation level was found in medium-sized patches, the lowest . in the largest patches. We found a reverse edge effect on nest predation in the largest patches, i.e. a decreased predation risk closer to the forest/matrix border. When comparing our results with other studies, it seems that the manner of classifying forest size significantly affects the results obtained. This may explain the differences in the results of many authors studying this phenomenon.