Biology Bird Nest Report
Investigation on the effect of location on bird’s nest predation Abstract: Nest predation impacts the success of avian species. To test if the location of the nest impacted upon the amount and time the nest was predated upon, artificial nests with plastiscine eggs were placed in exposed and protected environments for two weeks in the greater Sydney region. It was hypothesized that those nests in exposed environments will be preyed upon more and in a shorter period of time then nests in a protected environment.
It was found that nests in an exposed environment were predation upon significantly more (X? = 17. 38, d. f. 1, critical value=3. 84 p;0.
05) than nests in a protected environment. A significant association was also found in the amount of time until the nest was attacked and the location of the nests. (t=2. 15, degrees of freedom=85, probability;5% therefore Ho is rejected) the results show that nests in exposed environments were attacked in a in a shorter space of time compared to the nests in protected environments. Introduction: The largest contribution to lack of nesting success in avian communities (Wiens 1989) and is said to be predation, and is thought to influence location of avian nest locations and reproduction.
Bosque and Bosque 1995) Predators are animals that rely on other animals as a source of nutrition. In an attempt of protecting nests and avian individuals from being attacked camouflage is used as a form of defense. For example, the nest being off the ground if not a ratite reduces predation from specific species such as dingoes as they are unable to reach the nest. Camouflage helps reduce predation from animals with poor eye sight such as snakes. However, for predators to survive, they are forced to evolve (adapt) to defensive mechanisms.
Knox 2010) To discover if the different habitats relate to different amount of predation, and the time of until predation occurs an experiment needs to be done. This study investigates whether artificial nests in an exposed environment will experience the same amount of predation and in the same amount of time until attacked as nests in protected environments. It is hypothesized that nests in exposed environments will be preyed upon more and in a shorter period of time then nests in a protected environment. Method:
To determine which nests, exposed or hidden would be attacked and times that the nest was attacked, an artificial nest predation experiment was used, determining whether or not nest location will affect the amount and time of predation to the nest. The experiment was conducted in March 2011 throughout the suburban coastal area of Wollongong. The artificial bird’s nests were constructed by cutting a tennis ball in half, then using craft glue to stick coconut bark on and around the two halves and let the two halves set.
To make the artificial eggs, use plasticine and roll in the palm of your hands until a small bird’s egg shape is achieved that is approximate 2 cm in height. One of the two artificial nests is to be placed in an exposed environment in the costal suburban area of Wollongong; the other is to be placed in a hidden environment. Exposed: an exposed environment is an area in which the nest can be clearly seen for example a tree which have lost a lot or don’t have much foliage.
Protected: a hidden environment is an area in which the artificial nest cannot be easily found (camouflaged) such as in thick foliaged plants like bushes, The nests need to be checked every 2 days to see if they have been attacked, observe and record any signs of attack. Such as damage to plasticine eggs, eggs missing completely, nest damage or nest missing completely.
This experiment is to be repeated 42 times. To determine the predator which attacked the bird’s nest, compare the markings on the attacked plasticine eggs to animal skulls.
After the information was recorded, a T-test was used to test the null hypothesis “artificial nests that are in an exposed environment will not be prey upon more than artificial nests in a hidden environment. ” And chi-squared test was used to test the null hypothesis “nests in an exposed environment will not be preyed upon before nests in a hidden environment. ” Results: The amount of times the artificial nest was attacked in a protected environment was significantly different to the amount of times the artificial nest was attacked in an exposed environment (t=2. 5, degrees of freedom=85, probability;5% therefore Ho is rejected).
The mean (± standard error) time until attack in a protected environment was 6. 40 (±0. 61) days contrasting to 4. 81 (±0. 42) days for artificial nests in an exposed environment.
Therefore it can be concluded that there is a significant association in location of the nests in an exposed or protected environment and the amount of times the nest is attacked. FIG 1: shows that nests in an exposed environment are attacked significantly more in a shorter period of time than nests in a protected environment.
FIG 1 the time until the nests were attacked in exposed and protected environments. Bars are ± one standard error, n= 87. There also was a significant association with the location of the bird’s nest, this either being exposed or protected environments, and the time until the nests were attacked. (X? = 17.
38, d. f. =1, critical value=3. 84) the FIG 2 and the results from the chai squared test show that on average nests in an exposed average we attacked before nests in a protected environment. FIG 2 the mean amount of time passed until the nest was attacked in exposed and protected environments.
The number of times each predator attacked the bird’s nests in both exposed and protected environments can be seen in FIG 3.
this shows he environments in which the predator are most likely to attack the birds’ nests. FIG 3: the number of times the bird’s nests were attacked by a specific predator in both exposed and protected environments. Discussion: This study gives evidence that the number of artificial bird’s nest in exposed in environments are attacked significantly more than bird’s nests in protected environments and in a shorter period of time, which is highlighted in FIG 1 and FIG 2.
These results support Moller’s (1989) findings of overall nest predation rate were higher in open nests than closed nests. Crabtree(1989) also supports my findings as Crabtree’s results concluded that “dense vegetation establishes visual and scent barriers between nests predators and nests, ” but did not protect the nests from all predators, hence nests were still attacked just a t a lower rate – nests in protected environments were less likely to be attacked.
From my experiment it is shown that the location of the nests effect the amount of predation, Angelstam (1986), found that nest predation was related to the habitat of the predator. Using this information it is suggested that birds which were the highest predator to the artificial nests live in exposed environments therefore are more likely to attack nests in exposed environments than nests which are located in protected ones. Crabtree (1989) From the results of the chai squared test result of 17. 379 is ; 3. 4 we reject the null hypothesis, which means nests being in an exposed environment will affect the amount of predation upon the nest positively.
This supports Moller (1991) report which concluded that “the frequency of nest predation decreased with increasing size of habitat patches in the open-nesting European Blackbird, Yellowhammer, Chaffinch, and Black-billed Magpie, but not in the hole- or the semi-hole nesters. ” (Frequency of predation decreased in protected and increased in exposed- semi-hole nesters) Burke (2004) found that “In general, rates of predation on artificial nests were significantly higher than on natural nests. This is an implication to this report as artificial nests were used, according to Burke this is the reason for increased predation. To solve this issue and receive results with greater accuracy in the measurement of which environment is most predated use of natural nests is suggested. To make the experimental results more accurate, cameras can be used to record biological evidence to identify the predator which attacked the nests, and allow a more specific time period before attack to be calculated.
Liebezeit, Steve Zack) successfully used this technique and received more accurate results using the video camera to “identify nest predators at active shorebird and passerine nests and conducted point count surveys separately to determine species richness and detection frequency of potential nest predators in the Prudhoe Bay region of Alaska. ” This is a more accurate way of identifying, the predators of the bird’s nest than the method of comparing mark on plasticine eggs to skeletal jaw and teeth shape due to having visual evidence of the attack in action.
Another future experiment may be to carry out the experiment, in different regions, such as suburbia, city, rural/remote regions, to see if the region location has an impact on the level of predation and time until predation/ The weather conditions that occurred during the experiment may have impacted the reliability of the results found as across the south coast (south part if the greater Sydney region in which the experiment occurred. heavy rain and severe weather warnings we in place, this impacted the nests placed in this region and in turn the accuracy of the reports results as it is predicted that some of the nests were destroyed and eggs missing not from predation but, from severe weather. As this type of weather, is uncommon for the area, it is suggested that the experiment should be repeated again so that more accurate result can be obtained.
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