Introduction Predation On Birds Nests example essay topic

The effects of Nest predation with reference to open and vegetated environments Abstract The predation of nest in vegetated and open areas was studied in a broad area around the Illawarra region from 13/3/03 to the 23/3/03. Experimental nests were used made from halved tennis balls and modeling plasticine was used to make eggs. The result of 36 nests were collaborated. Each nest had three eggs, the type of predator that attached the nest was recorded. 58% of the 36 nests were attacked with 57% of the nests attacked being in the open. The highest amount of predation came from other birds with 42% of the eggs attacked in the open and 33% in vegetation.

Accounting for 40% of all nests attacked. Our studies concluded that nests in the open are more likely to encounter predation than those in the thick vegetation. Introduction Predation on birds nests is commonly coincided as a major factor reducing the population of young (Angelstan. P 1986) Many different predators have been found to prey upon bird eggs, some of the predators of nests include rats, cats, other birds such as Currawongs, crows, Kookaburra, snakes and other reptiles as well as a range of other species. In this report a comparison was made between open nesting sites to vegetated nesting sites in urban environments comparison of total predation as well as types of predation on each type of nest. However most studies dealing with nest predation have however found it extremely difficult to tell which predators had been responsible (Angelstan.

P 1986). This was also found in this experiment with most nests showing no signs of which predator being responsible with the eggs just missing or in some cases the whole nest. Despite this difficulty bests effects were made to correctly identify predator by identifying teeth or beak marks in eggs left behind. The hypothesis of the experiment was that nests in the open area would be attacked by predators more often then those in the thick vegetation as they were more easily found. The null hypothesis was that the position of the had no effect on the amount of predation. The experimental independent variable was the location of the nest over a number of different sites around the Illawarra region the standardized variable were the number of eggs used, nest size, plasticine used to make the eggs.

The choice of sites for nesting has shown to be important part in survival of offspring. The choice can be determined either genetically or some by some form of learning process, or by a combination of both of these features. Methods and Material The experiment was set so that a group of 18 students each took two nests each, with three eggs in each and placed them in there back yard. One in a highly vegetated area the other in a more open area. There was a number of variables with this practice that were not looked at such as height of nest as well as specific area localities. All nest and eggs were kept constant with the nests being made out of 1/2 tennis ball that was covered with coconut fiber on both the outside and the inside to make it look like as much like a real nest as possible.

Plasticine was used to model small eggs that were placed in the nest. Predator were identified mainly by the process of looking at teeth or beak marks that were in eggs that were left or spat out. Some were identified visually but this was not common thought out the group. Group data was collaborated into nests attacked in the open and vegetated.

And also into eggs attacked by the type of predator, predators were broken up into Rodents, Cats, Birds, Snakes, and unidentified, specific species were not looked at. Results The result showed that nests in the open were more vanuble to attack against all predators. 58% of the total nests were attacked. Of that 57% of the nests attacked were in the open. Although this figure only shows marginally higher attack rates of nests. The number of eggs attacked varies greatly with 21 out of the 30 eggs attacked being in the open.

The highest amount of predation came from other bird species with 43% of the nest being attacked in the open, and 33% of the nest being attacked in the dense vegetation. Which amounted to 40% of the total eggs attacked were by birds. The next highest amount of predation shown was in the unknown with the eggs be entirely taken or in some cases the entire nest, proper judgement could not be made to the predator responsible. 33% of open nests and 44% of vegetated nests were attacked by unknown predators. Cats attributed to 14% of nests attacked in the open and 11% of those attacked in the vegetated areas. Rodents were the only other predator recorded with 9% of attaches in the open and 11% of the vegetated.

The graph below shows the proportion of eggs taken by each predator. The only variable that can be looked at being inconsistent was the position of the nest and definition of dense vegetation. Also the height the nests were placed of the ground was also not monitored. Discussion The observation of the nests over a two week period was in agreement with the hypothesis that nests in vegetated area are more protected against predation then those in the open.

Although the degree to which artificial nests are attacked to natural nests is largely untested (Major R.E. et. al 1996) For example some important mammalian predators of natural nest are under represented while others such as birds can be over represented. Even though the identity of the nests predator is largely not documented. It is likely that many of the predators recorded could not gain access to natural nest. Especially if the nest is protected by the parents of the eggs such as magpies or willie wagtails. Given that most previous artificial experiments have no independent identification on the identity of nest predators, it is likely that animals that do not prey on natural have preyed upon affecting nests (Major R.E. et al 1996) the data gathered by this experiment The effect of the height of the nest on predation was not measured in this experiment, in other experiments Major R.E. et al Nest predation incidences increased with nest height, despite there only being a narrow range of height variation. Other features such as the amount of trees and other vegetation was also not looked at but could affect the results gathered.

The amount of vegetation in this environment was also not measured. Although the conclusion can be made that nest predation is lower in vegetated areas then in the open. The highest amount of predation came from other birds, the conclusion can be drawn that the thicker the vegetation the lest likely a nest is to be found. Nest site location to forest also has been shown to play an important role in nest per dation in experiments carried out by A.P. Moller showed that nest predation on open nesting sites were much lower far from the edge of any woodland, were bird species with open nests were more abundant, while the pacifically covered nests experienced a consistently low level of nest ped dation across the ecotone. The hypothesis from the experiment can be found correct as the open area nests experienced much higher amounts of predation then did the vegetated areas.

Although results could have been affected by a number of variables such as the artificial nest used may have been attack's may have increased and others may have decreased. Also in real life natural nests often protect by there parents, which means there a great variation between different bird species to the success of young.