NEST SUCCESS – DOES BUILDING HIGHER REDUCE PREDATION RATE?

NEST SUCCESS – DOES BUILDING HIGHER REDUCE PREDATION RATE? Mary Ledger, Leyla Yusuf and Joel Turner (Year 9) Science Faculty, The Illawarra Grammar School, Western Avenue, Mangerton, 2500

Abstract

In this study, artificial birds’ nests and eggs were created using coir and clay and were placed at different heights to test the hypothesis that the nests placed in elevated positions would experience similar levels of predation to those at lower levels. While improvements could be made to increase the reliability of the experiment, it was found that birds’ nests placed in higher elevated positions had a higher level of predation.

Introduction

Predation on nests has been identified as the primary cause of breeding failure in open and cavity-nesting birds (Matessi & Bogliani 1999). Several studies have been conducted with artificial bird nests to investigate the effect of nest site elevation on predation. Although the effect of nest site elevation has been contested, in 1993 T.E. Martin evaluated the findings of several studies and stated that when nest predation on both types of nests is assessed in the same plot, ground nests are less preyed upon than elevated nests. In this investigation, artificial nests were made and placed in elevated and ground-level sites to monitor predation activity. In this study, it was hypothesised that the artificial nests placed in elevated positions would experience similar levels of predation as to those at ground level.

Method

Using half a tennis ball, each student shaped a bird’s nest out of coir (coconut fibre) and glued it to the hemispherical shape. Two artificial eggs were made for each nest using a small ball of clay, then were placed inside the nests, and the nests were taken outside to the natural environment. Half of the nests were placed on the ground, and the other half were placed in trees to determine whether this affected whether or not the nests would be attacked. Every couple of days, each nest was checked for signs of predation, and if there were, the nests were removed and taken back to the classroom for further inspection. The number of attacked nests for each group was counted and recorded, and the predators responsible for the attacked nests were determined by analysing the scratches and marks left on the eggs.

Results

The number of bird nests that were attacked was greater than the number of bird nests that were not attacked. Of the nests which were attacked, the greater majority were placed at a larger height. Of the nests which were not attacked, it was found that each height had an equal number of nests that were not disturbed. From this, we can conclude that the higher a nest is built, the greater the chance it has to be attacked by a predator.

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Figure 1: The number of nests attacked and not attacked at different heights.

Discussion

In this study, it was hypothesized that the artificial nests placed in elevated positions would experience similar levels of predation as to those at ground level, however, this was not the case. Approximately 71% of the elevated nests were attacked, which was 21% higher than the ground level nests. This correlates with research completed by T.E. Martin in his report ‘Nest Predation Among Vegetation Layers and Habitat Types: Revising the Dogmas’, which concluded that when nest predation on both types of nests is assessed in the same plot, ground nests are less preyed upon than elevated nests.

This investigation utilized artificial bird nests since that was the simplest to apply approach; nonetheless, this methodology has certain limitations. The lack of a female to sit on the eggs is the most significant limitation of constructing artificial bird nests (Angelstam 1986). Furthermore, "predation rate is often higher on artificial nests than on natural nests and some important mammalian predators of natural nests are under-represented at artificial nests, compared with avian predators” (Major, Gowing & Kendal 1996:407). Both of these limitations must be considered in this investigation.

Future studies in this area might help to increase nest placement specificity in terms of ecological location and height. The comparison of predation rates and predators on manufactured and natural nests in elevated and ground-level sites would be valuable if natural bird nests could also be observed concurrently.

References

Matessi, G & Bogliani, G 1999, ‘Effects of nest features and surrounding landscape on predation rates of artificial nests’, Bird Study, vol. 46, no. 2, pp. 184–194.

Martin, TE 1993, ‘Nest Predation Among Vegetation Layers and Habitat Types: Revising the Dogmas’, The American Naturalist, vol. 141, [University of Chicago Press, American Society of Naturalists], no. 6, pp. 897–913, viewed 5 December 2021, Nest Predation Among Vegetation Layers and Habitat Types: Revising the Dogmas

Major, RE, Gowing, G & Kendal, CE 1996, ‘Nest predation in Australian urban environments and the role of the pied currawong, Strepera graculina’, Austral Ecology, vol. 21, no. 4, pp. 399–409, viewed 5 December 2021, Nest predation in Australian urban environments and the role of the pied currawong, Strepera graculina

Atkin, N 2021, ‘The effects of forest edge and nest height on nest predation in a U.K. deciduous forest fragment’, Authorea, viewed 5 December 2021, The effects of forest edge and nest height on nest predation in a U.K. deciduous forest fragment

Piper, SD & Catterall, CP 2004, ‘Effects of edge type and nest height on predation of artificial nests within subtropical Australian eucalypt forests’, Forest Ecology and Management, vol. 203, no. 13, pp. 361–372, viewed 5 December 2021, Effects of edge type and nest height on

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predation of artificial nests within subtropical Australian eucalypt forests Student Scientific Report n.d., ‘Nest Predation in Open and Vegetated Areas’, Nest Predation in Open and Vegetated Areas, vol. 1, no. 1.

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