Birding in Costa Rica: Relationships of species identified, habitat observed and feed

This topic submitted by Nathan Moyer ( moyerna@yahoo.com) at 9:52 AM on 7/18/02.

Larry is all smiles in the Bahamas

Tropical Field Courses -Western Program-Miami University

INTRODUCTION
The neotropics house around 3751 species of birds throughout the year, with Costa Rica hosting roughly 830 of them. Although it is only the size of West Virginia, Costa Rica houses more bird species than the entire United States (Janzen, 1995). Costa Rica is full of diverse habitats, such as highland and lowland forests, rain and dry forests, and Atlantic and Pacific coastal forests, all of which provide habitat for diverse communities of birds.
The avifauna of Costa Rica are important to the countryÕs culture and economy. Birding is a major component of ecotourism, which is Costa RicaÕs primary foreign revenue generator. Therefore, the conservation and protection bird is very important to the country. Eco-tourists spend money to see some of the most beautiful birds in the world. Rare birds, only found in areas with large tracts of undisturbed forest cover, also bring birders and their money to Costa Rica.
Human pressures on the land, especially forests, have been escalating in tropical regions around the world. The destruction of avifauna habitat ultimately leads to a decrease in bird species diversity and with it, birders and their money. It is essential that we develop an understanding and appreciation of these birds and their habitats to ensure species survival.
In this study we compared bird species located at two locations in Costa Rica, a highland forest (Monteverde region) and a lowland forest (Osa Peninsula region). We first tested JanzenÕs (1995) abundance classification of all the birds of Monteverde. We hypothesize the species considered abundant or common will have a higher representation in the study sample than the total known species in Monteverde. We also looked at the habitat locations of the sampled birds between the two sites and hypothesis they would be correlated.
The feeding guilds were compared between species sampled at Monteverde and the total known species of Monteverde as well as species sampled at Monteverde and species sampled at Osa Peninsula. It is hypothesized that both relationships are correlated. Finally our study compares the rank order of species present per feeding guild between habitat location and study site. We hypothesize that feeding guilds are represented differently among habitat locations and sampling site and therefore the rank orders are independent.
METHODOLOGY
Guided tours at the Monteverde preserve and Osa peninsula were undertaken, and birds were identified based on sight and calls. A list of the bird species and its habitat location were created for each region. Additional observations made during the 3-4 day stay at each study region were added to the list.
A database was created of the total species known to exist within the Monteverde region and their abundance rating from JanzenÕ (1995) Costa Rica Natural History. The list of bird observations and their habitat locations were added to the database. All bird species sampled and bird species known to exist within the Monteverde region were placed in seven feeding guilds based on StilesÕ (1989) A Guide to the Birds of Costa Rica (Table 1). Statistical analyses including Chi-square tests and Spearman correlation were run to verify the hypotheses.

Table 1. List of seven feeding guilds of birds
Fruit/Seed 11
Fruit/Seed and Insect 11
Fruit/Seed and Nectar 1
Insect 19
Insect and Vertebrate 8
Vertebrate 10
Nectar 4

RESULTS AND DISCUSSION
More species were observed at Osa Peninsula, but a higher percentage of total species (according to JanzenÕs (1995) list of species for each site) occurred in Monteverde (Table 2). This is possibly due to a larger size of Osa Peninsula and more time would be needed to view the same percentage of species as Monteverde.

Table 2. Comparison of total species and species observed between two sites
Monteverde Osa Peninsula
Total Species 168 367
Observed 27 38
Percent % 16.07% 10.35%

More than eighty-five percent of the birds observed at Monteverde were classified as abundant or common according to Janzen (1995) (Fig. 1 (a)). Our short duration sampling event found a disproportional number of abundant and common species. There is a statistical difference (p-value=0.0112) in the abundance classification between the birds sampled and total birds known to exist at Monteverde.
Monteverde site has a higher ratio of birds that are fruit/seedivore, insectivore, and nectavore than Osa Peninsula (Fig. 1 (b)). There is a statistical difference (p-value=0.0035) between the ratio of species feeding guilds at Monteverde and Osa Peninsula. This difference was not hypothesized to occur and is possibly explained because of different ecological settings supplying many diverse habitats and niches.
The feeding guild relationship between Monteverde total and observed species appears very similar (Fig. 1 (c)). Although there is a statistical difference (p-value=0.0015) between feeding guild ratios. This difference is likely caused by a large difference in the insect and vertebrate feeding guild (almost 12 percent observed of 3 percent total).
The habitat location of the bird species at the time of sampling ratio for each site is similar (Fig. 1 (d)). There is no statistical difference (p-value = 0.3945) between the relationship of ratio and habitat location. Both Monteverde and Osa Peninsula have similar ratios of the habitat location where birds were sampled.
Table 3 shows the data used to compare the rank order of feeding guilds both between sampling sites and habitat location among each site. We fail to reject that the rank order of guilds in the sites are independent at each location level (p-value < 0.05). This relationship was hypothesized and again possibly explained because of differing ecology of a highland and lowland forest.

Table 3. Data to compare rank order of feeding guilds
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

When comparing rank order of feeding guild among habitat location for each site, we fail to reject independence except in one comparison. The only correlation among rank orders of guilds occurred between sub canopy and undergrowth levels at Monteverde (p-value = 0.0409, Rho = 0.914, df = 5). The rank order is dependant for feeding guilds at Monteverde sub canopy and Monteverde undergrowth. It was not hypothesized that this relationship would occur because of the dissimilar habitats of undergrowth and sub canopy. However, all other comparisons fail to reject independence.

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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