Introduction
As habitat loss and extinction become more common, and our knowledge of biogenetics and symbiotic relationships broaden the importance of biodiversity has increasingly come to our awareness. The 830 species of  Aves that are found in Costa Rica is more than found in all of North America.The 100 species of bats known to Costa Rica make up 10% of all the species worldwide. Both birds and bats fill a variety of vital niches in all habitats, therefore their populations should be monitored. Our study compared the species diversity of birds and bats found in a primary forest location at La Selva with the diversity on a banana plantation. The hypothesis is that diversity will be greater in the primary forest due to availability of natural habitat and lack of human influence. We were also interested in how the diversity of these flying animals had changed  over time given humans increasing demands on natural systems.
 

Methods
On July 19th at 5:30 AM, we helped OTS students net birds on the Camino Experimental Sur (CES) trail at approximately 750 meters at the La Selva Biological Station, Costa Rica.  There were four mist nets set in a disturbed old growth forest.  The nets were arranged at right angles with the first one intersecting the trail.  Note that mist nets have certain biases because they catch mostly small, understory volant vertebrates.  Also certain species may be able to detect the nets, thus avoiding capture.  Since the same methods were used at both locations, we feel these inadequacies will not skew our comparison.  The nets were checked at fifteen-minute intervals for three hours.  The birds were identified to species and food guild, then released.  The food guilds for birds included nectivores, frugivores, and insectivores.  Another team followed the same procedures at the El Gavilan Banana Plantation.

On the same date at 5:30 PM, we helped net bats at the same location.  The bats were identified and data was recorded on arm length, body weight, sex, life stage, and net location.  The food guilds for bats were the same as birds, but included two additional guilds, carnivores and sanguinivores.

We reviewed previous studies at La Selva to see if our results were consistent in regards to species diversity in old growth forest and agricultural areas.

Results
Eight birds representing five species were caught at the forest site.  Eight birds representing three species were netted at the plantation site.  Table 1 gives species and number of the birds encountered at each site.  Table 2 contains information regarding the 14 bats captured in the forest and the 21 individuals captured at the plantation.  Of the forest specimens, eight species were represented.  Eight different species were found at the plantation.

Discussion
We investigated the diversity of  birds and bats in a forest area and a banana plantation. Then we compared our results to a bird study by Paul Slud in 1960, a bat study in 1972 by an OTS class, and a study that looked at both birds and bats by Jose Manuel Mora and Vivian Mendez in 1997. We thought that the forest would have greater diversity because it was relatively undisturbed. The plantation had several agricultural factors which we thought would lead to lack of natural habitat, thus limiting diversity.

Our analysis of bird diversity in a forest and on the plantation showed that more species were found at the forest location.(Refer to Table 1) Five  bat species were found in the forest and only three were found at the plantation.  This data is consistant with our hypothesis.  A review of the Mora and Mendez survey in 1997 found 13 species in the forest and nine species at the banana plantation lending further support to our research. The 1960 survey by Slud had a slightly different design and therefore, our results did not directly correlate. However, of the birds we netted, only three species matched  the aforementioned survey.  While this document did not provide support for our hypothesis, we felt it suggested the effects of continual study of the Aves class.

Our analysis of the bat data did not show any significant differences. (Refer to Table 1)  Eight species total were found at each location. One possible explanation for this is that bats have a wide home range that covers 1.5 – 5 km.  A review of the Mora and Mendez study in 1997 found no significant differences. The 1972 survey correlated highly with the genus that we found.

While limited sampling made it difficult to draw definitive conclusions, the data shows that primary forests can support more species of birds than agricultural areas.  The variety of food resources and lack of human interference provide opportunity of growth for many species.  The bat data shows more similarities between the sample sites because food sources are available and human interference is less of a problem at night.  Overall, birds and bats have adapted readily to land changes, but we feel it is pertinent to continue assessing the situation.

References cited

Mora, J. M. and Mendez, V.  1997.  La fauna silvestre: comoindicador de interacciones entre un area de bosque natural y un agroecosistema.  OTS 97-7

Relevance to schools
This project could be repeated in our area with the help of instructors from the Nature Center located about ten miles from our school. We feel that this would be a great team building activity and increase the comfort level of our students. The students could check with the Nature Center or local parks to see if they do studies similar to this and how our results compare.The information gained could be shared with  the community through the school newspaper, local paper, or Nature Center Publication. Since students learn best from peers teaching peers,we thought our students would enjoy putting together a bat program for the lower grades around Halloween. This could include a myth versus fact game,slide presentation, student made video, play, craft, Stellaluna story, etc. When students have hands on experience with rarely seen birds and bats they get very excited and become better stewards of habitats to attract them.
We may also write several grant proposals to get funding for the equipment. This would include nets, binoculars, books, etc.