Birding In Costa Rica [FINAL RESEARCH PAPER]

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BIRDING IN COSTA RICA

Introduction:
The Neotropics houses approximately 3751 species of birds, with Costa Rica hosting 830 species (Stiles 1989). This high rate of species diversity found in Costa Rica is fostered by its varied habitats. Costa Rica consists of highland, and lowland forests, cloud forests, temperate forests, marshes, and mangroves (Janzen. 1995). The avifauna found here brings natural and economic value to the country.
The birds in Costa Rica form an integral part of the ecosystem. They are among the primary pollinators helping spread and maintain the diverse flora found in the rainforests (Kricher 1999). This vital role they play, make them indispensable to the survival of Costa RicaÕs distinct ecosystems. Birds in this country also have high economic value. Birding has been a major component of ecotourism - Costa RicaÕs primary revenue generator. People from around the world come here to witness, and study the diverse avifauna. Numerous studies have been conducted to understand bird habitat behavior.
The future for survival of this diverse avifauna is under threat. Human pressures on the land have been mounting, leading to destruction of habitat, and decrease in the species diversity. This could have disastrous repercussions not only on the economy of the country, but to Costa RicaÕs biodiversity; for conservation of avifauna habitat ultimately aids in conservation of Costa RicaÕs entire diverse ecosystem. Hence it is extremely essential that we develop an understanding and appreciation of these birds and their habitat to ensure a healthy future for their survival.
Our research focused on identifying the number of diverse bird species found in two study areas Ð the Monteverde cloud forest preserve and the Osa Peninsula (lowland forest). We studied abundance of common species present, and their feeding guilds. This data was used to understand the relationship between bird species found in cloud forests and that in lowland forests, and to identify and similarities or differences across their habitat usage and feeding guilds.

Hypotheses:
We developed five hypotheses to test our data, covering all aspects of our study, including species abundance, location, habitat usage, and nature of feeding guilds. They are as follows:
1) The abundant and common species will have higher representation in the study sample compared to total known species in Monteverde.
2) The location of sampled birds at Monteverde and Osa peninsula are correlated.
3) The feeding guilds of study sample compared to total known species at Monteverde are correlated.
4) The feeding guilds of birds sampled at Monteverde and Osa peninsula are correlated.
5) The rank order of feeding guild to between location and sites are independent (i.e. the number of birds per feeding guild will be different between locations and sites).
Study Design:

Background data was collected from both Monteverde preserve and Osa peninsula through guided tours. The birds were identified based on sight and calls. The location of the birds was also noted, based on whether they were found in the undergrowth, sub canopy, canopy, and water. This method of observing recording birds had numerous limitations. Firstly the group was limited to high rates of dependency on the guides. This was due to lack of adequate bird sighting skills. And secondly, the weather differed in both the study areas. Rain in the Osa peninsula restricted the sighting of birds.
The second step was to review available literature to list total known species within the Monteverde preserve and the Osa peninsula (Stiles 1989). This information was entered into a database. Data on the feeding guilds and location levels of the birds was also included. Seven feeding guilds were recorded. They include fruit and seed; fruit, seed and insects; fruit, seeds and nectar; nectar; insects; insects and vertebrates; and vertebrates.
The birds that were sampled in the study areas were placed into these seven feeding guilds, and four location levels mentioned earlier. Statistical comparisons were run to observe any similarities or differences between the birds sampled and the birds found in existing literature. Statistical analyses including Chi-square tests and Spearman correlation were also run to verify the five hypotheses.

Results and Discussion:
Initial statistical comparisons displayed the following results.
(1) Of the total species recorded at Monteverde (168 species)
 16.1% recorded (27 species recorded).
 26-27 were permanent residents.
 22.7% excluding migrant species (119 species)

(2) Of the total species recorded at Osa Peninsula (367 species):
 10.4% recorded (38 species recorded).

Despite observing a higher number of species at the Osa peninsula, compared to Monteverde, we see that a lower percentage was recorded. This could be due to a higher rate of species that is expected to be present in the area.

The results on testing the five hypotheses are as follows:
Hypothesis 1:

Figure 1. Graph displaying abundance of birds in Monteverde

Figure 1 graphically represents total number of species compared to birds sampled in the Monteverde preserve. On running a chi-square test with a 95% confidence interval (p-value<0.05),, the results were:
 p-value =0.0112
 degrees of freedom = 4

We reject the null hypothesis as the p-value shows a significant difference between the total birds present and the birds sampled in Monteverde. This difference could be attributed to numerous factors including time limitations, weather limitations, and dependency on guides.

Hypothesis 2:

Figure 2. Graph displaying the location of sampled birds at Monteverde and Osa peninsula

Figure 2 graphically represents the location of sampled birds at Monteverde and Osa
peninsula. On running a chi-square test with a 95% confidence interval (p-value<0.05), the results were:
 p-value =0.3945
 degrees of freedom = 3
We fail reject the null hypothesis as the p-value does not show a significant difference
between the location of sampled birds at Monteverde and Osa peninsula. This implies a consistency between birds sighted found in the two study areas. But this study had numerous limitations and further research needs to be conducted before accurate conclusions can be drawn.
Hypothesis 3:

Figure 3. Graph displaying the feeding guilds of study sample compared to total known species at Monteverde.

Figure 3 graphically represents the feeding guilds of study sample compared to total known species at Monteverde. On running a chi-square test with a 95% confidence interval (p-value<0.05),, the results were:
 p-value =0.0015
 degrees of freedom = 6

We reject the null hypothesis as the p-value shows a significant difference between the feeding guilds of study sample compared to total known species at Monteverde. Some guilds are spotted more frequently than others, maybe because of difference in time and activity levels across guilds. This could again be attributed to time, and weather limitations that contained our sample study.
Hypothesis 4:

Figure 4. Graph displaying the feeding guilds of birds sampled at Monteverde and Osa peninsula.

Figure 4 graphically represents the feeding guilds of birds sampled at Monteverde and Osa peninsula. On running a chi-square test with a 95% confidence interval (p-value<0.05),, the results were:

 p-value =0.0035
 degrees of freedom = 6

We reject the null hypothesis as the p-value shows a significant difference between the feeding guilds of birds sampled at Monteverde and Osa peninsula. This difference could be attributed to the difference in the type of rainforest being studied. The Monteverde preserve is a cloud forest, whereas the Osa peninsula is a lowland, temperate forest.
Hypothesis 5:
A Spearmans rank correlation test was run to test this hypothesis (The rank order of feeding guild to between location and sites are independent, i.e. the number of birds per feeding guild will be different between locations and sites).
Table 1. The rank order of feeding guilds between location levels at Monteverde and Osa peninsula.
Number Canopy MV Canopy OSA Sub MV Sub OSA Under MV Under OSA Water MV Water OSA
F/S 6 4 0 1 0 0 0 0
F/S + I 2 3 1 3 0 3 0 0
F/S+N 0 1 0 0 0 0 0 0
I 4 1 5 5 3 1 0 0
I+V 2 1 1 0 0 3 0 1
V 0 5 0 1 0 3 0 1
N 0 1 2 0 1 0 0 0

Table 1 graphically displays the ranking of birds across their seven feeding guilds, and four location levels at both study sites.

The first spearmanÕs test was run to observe dependency between rank order of feeding guilds in Monteverde and Osa peninsula across location levels. There was no significant p-value (<0.005) in the rank order tests run to prove that the rank order of guilds in the sites were dependent at each location level. Hence we failed to reject the null hypothesis, which stated independence between rank order guilds at the two sites.
The second spearmanÕs test was run to observe dependency between rank order of guilds at each study area (Monteverde and Osa peninsula), across location levels. The only p-value that was adequately significant to reject the null hypothesis (p-value <0.05) stating independence between the location levels was for the rank orders of guilds that occurred between sub canopy and undergrowth levels at Monteverde. The values for this were as follows:
 p-value = 0.0409
 rho value = 0.914
 z value = 2.044
 degrees of freedom = 5

Hence the only correlation among rank orders of guilds occurred between sub canopy and undergrowth levels at Monteverde (p-value = 0.0409).

Conclusion:

Costa Rica is a continuously growing and changing ecosystem. Its rich natural heritage must be preserved, and this is possible only through continuous research that helps us understand how to best adapt to it. Our research is just a starting point for further research to help preserve Costa RicaÕs avifauna, an integral and irreplaceable part of its diverse ecosystem.

References:

Janzen. 1995. Costa Rica Natural History. University of Chicago Press.

Kricher, J. 1999. A Neotropical Companion. Princeton University Press

Stiles, G. 1989. A Guide to the Birds of Costa Rica. Comstock Press.

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