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Predation on Artificial Nests Imitating the Broods of Two Rallid Species: The Influence of Habitat Features

Chibowski P., Brzeziński M., Jedlikowski J.

Polish Journal of Ecology

2015

Vol. 63, nr 4

573--584

We tested the influence of nest concealment (vegetation type, density and height), water depth and nest distance from the bank on predation rates upon simulated nests of the water rail (Rallus aquaticus) and the little crake (Porzana parva). Broods of both rallids were simulated by real and wax-filled quail (Coturnix coturnix) eggs coloured typically for each species. Three grades of nest concealment were used: uncovered nests located on wooden floating boards, nests hidden in littoral vegetation and nests hidden under a plastic mesh covered with plants, which made them invisible from the air. Concealment proved to have a stronger impact on the fate of artificial nests than water depth; 95% of the nests on boards were depredated after one week of exposure. Nests attached to a peg at water level and hidden in vegetation had survival rates of 18 and 22%, after three weeks of exposure in two experiment repetitions. In 2012, we found significant differences between survival rates of nests located in different types of vegetation after the first week of the experiment: nests in bulrush (Typha spp.) had a higher survival rate than nests in sedge (Carex spp.) and common reed (Phragmites australis), and nests in sedge had a better survival rate than nests in reed. Those differences disappeared after the end of the experiment. In 2013, nests located in sedge (Carex spp.) had a better survival rate than nests located in bulrush (Typha spp.) or the common reed (Phragmites australis). Covering nests with plastic mesh and plants increased nest survival up to 38% after a three-week-long exposure period. Potential nest predators were monitored: mammals (mustelids and rodents) using live traps and birds by observation of their hunting activity. Filling quail eggshells with wax allowed us to identify the marsh harrier (Circus aeruginosus) as the main nest predator — in 67% of depredated nests, wax eggs carried marks of a raptor beak. American mink (Neovison vison) and the water vole (Arvicola amhibius), though abundant in the study area, were not important nest predators, as only a few bite marks of these mammals were recorded.

Effect of parental care on depredation of Blackcap Sylvia atricapilla L. nests: an experiment with artificial clutches

Zieliński J., Lik M.

Polish Journal of Ecology

2014

Vol. 62, nr 4

761--769

Small solitary open nesting passerines, such is the Blackcap Sylvia atricapilla that builds nest in the undergrowth, have little chance of successfully scaring off a predator to defend a nest. The aim of our study was to determine if parental care by Blackcaps can reduce the risk of depredation of its nests. We compared the survival of natural clutches with artificial clutches (plasticine and independently both plasticine & quail eggs). The artificial clutch was placed in a nest after the natural clutch had been concluded, and the results were analysed as matched pairs of data. We assumed that significantly higher survival rates of natural clutches than of artificial clutches deprived of parental care, might indicate a significant positive effect of parental care on reducing depredation risk of Blackcap clutches. Losses caused by birds, rodents and larger mammals were 49%, 41% and 9%, respectively. The differences in survival rates of artificial clutches (plasticine as well as quail & plasticine) and natural clutches were not statistically significant. This might show that parental care is not strong enough to significantly reduce depredation risk of Blackcap clutches. Although this conclusion should be treated cautiously because it was difficult to assess the influence of using artificial clutches on our results.