1 Kayla Smith and Sarah Hayden Professor Carlos Guindon Environmental Sustainability 14 April 2014 Bird Visitation in Native vs. Non Native Windbreaks in Monteverde, Costa Rica Abstract: Reforestation in Monteverde, Costa Rica began in the 1980Â€s and 1990Â€s and initially used non native tree species to form windbreaks. In our study we examined bird preferences between native versus non native trees in windbreaks. We examined three different sites with both native and non native windbreak tree spec ies. We found that the average bird visitation for windbreaks with native trees 4.17 birds was not statistically different from visitation in windbreaks with non native trees 3.50 birds T test p= 0.6. This is not what we expected or other studies wou ld suggest. Future studies should include a larger sample size with more homogeneous ages between the native and exotic windbreaks. Resumen: Reforestaci Ã³n en Montevede, Costa Rica, empezÃ³ en los aÃ±os 1980's y 1990's. Al principio, se usÃ³ Ã¡rboles no nativas para formar rompevientos. En nuestro estudio, examinamos las preferencias de aves entre Ã¡rboles nativos versus Ã¡rboles no nativos en rompevientos Estudiamos tres sitios diferentes con ambos Ã¡rboles nativos y no nativos rompevientos. El promedio visitaciÃ³n de aves rompevientos con los Ã¡rboles nativos 4,17 aves no fue significativamente diferente del promedio visitaciÃ³n de aves en rompevientos con los Ã¡rboles no nativos 3,50 aves p=0,6. Esto no es que esper Ã¡bamos o que otros estudios sugerirÃ an. En el futuro, estudios deben incluir tamaÃ±os de la muestra mÃ¡s grande y edades mÃ¡s homogÃ©neo entre los rompevientos nativos y exÃ³ticos. Introduction: The Monteverde Conservation League MCL began its reforestation program in Monteverde, Costa Rica i n the late 1980's and early 1990's Burlingame 2000. At first, exotic species, such as whistling pine Casuarina equisetifolia and cypress Cupressus lusitanica , were used because they were being promoted by the governmentÂ€s reforestation program Burli ngame 2000. The MCL then began an initiative to use native tree species so as to retain
2 local biodiversity and avoid some diseases and pests that exotic species were susceptible to. Certain naturalized exotics, such as Colpachi Croton niveus , were also used. The most widely used native species became TubÃº Montanoa guatemalensis , which grows extensively on the Pacific slope and it has thick leaf coverage that creates an effective wind barrier Burlingame 2000. Reforestation, especially of native specie s, is important because it provides windbreaks for agroecosystems, protecting them from soil erosion and wind damage. Reforestation is also vital because it provides habitats for forest species, also providing corridors for many bird species in temperate a reas. Burlingame 2000. The forested area of Monteverde is a concern not only because the area has such rich biodiversity but because it is part of the biological corridor for certain species, such as the Three Wattled Bellbird, which is considered a thre atened species ÂvulnerableÂ‚Cornell 2010. Monteverde reforestation is also important because it provides biological corridors for altitudinal migrant species, such as the Resplendent Quetzal, that use the corridors to move between elevations on the Paci fic Slope Powell et al. 2000. Reforestation of these biological corridors maintains pathways between zones, therefore preserving species population and diversity. Our objective was to examine how and if the reforestation efforts affect patterns of where birds decide to perch. Specifically, we observed birds to see if they have preferential tendencies towards native trees versus exotic trees in windbreak corridors. We hypothesized that there will be more bird observations in the windbreaks with native tree s versus windbreaks with exotic trees.
3 Materials and Methods: The windbreak sites which were chosen bordered peopleÂ€s properties near the Bajo del Tigre reserve in Monteverde. We selected three different plots to observe, all of which contained native an d exotic tree species. Site one contained two windbreaks, one consisting of native and the other of exotic trees, running parallel to one another. The exotic species were primarily cypress Cupressus lusitanica native to Guatemala. The native species at t his site was primarily Cirri Tapirira brenesii , Anacardiaceae. Sites two and three were windbreaks running perpendicular to each other. At each site, the two windbreaks being compared were relatively equidistant from forests and fields. They shared the s ame exotic cypress species as site one, but the native tree species were Tubu Montanoa guatemalensis , Asteraceae. We ensured that none of the native tree species were fruiting, since that could potentially influence bird visitation. The exotic cypress wa s fruiting; however they do not produce bird dispersed fruit so it did not likely influence bird visitation. Our observations were conducted between March 24 th and April 5 th . Each observation was for one hour during the morning from a fixed point along a 2 0 meter section of windbreak which was marked. Within this 20 meter transect we recorded all of the birds which we saw perching or interacting. Bird identification was done using ÂBirds of Costa RicaÂ‚ by Richard Garrigues and Robert Dean 2007. Birds were identified visually and by their calls. We each conducted one observation per site to equalize effort between observers and compensate for any observer bias. We used a t test to compare the number of individuals observed between native and exotic windbre aks.
4 Results: We completed two observations at each site, for twelve observations total: six observations of 60 minutes each for native species and six observations of 60 minutes each for exotic species. For all three native windbreak plots, a total of s ix different species were observed. Six different species were also observed for the exotic windbreak plots. A total of eight bird species were observed, six of which are resident species and two of which are migratory species. There were also five uniden tified birds that were observed in the native windbreaks and three unidentified birds that were observed in the exotic windbreaks. The number of visitations for each specie in both the native and exotic plots can be found in Table 1. The total number of ob servations for each site, including the native and exotic windbreak, can be found in Table 2. There were eighteen observations of resident species in the native windbreaks and fifteen observations of resident species in the exotic windbreaks, for a total of 33 observations of resident species. There were two observations of migratory species in the native windbreaks, and three observations of migratory species in the exotic windbreaks, for a total of five observations of migratory species Table 3. Over all, 25 birds were observed in the native tree species and 21 birds were observed in the exotic tree species Table 1, with an average of 4.17 birds in the native tree species and 3.5 birds in the exotic tree species Figure 1. This difference was not fo und to be statistically significant t test: p = 0.6, N = 6.
5 Discussion: As we did not find a significant difference between the numbers of birds observed in native windbreaks versus exotic windbreaks, we reject our alternative hypothesis and accept th e null that there is no difference between bird use of the native versus exotic windbreaks that we observed. Furthermore, this data analysis only examined the overall number of bird individuals and not species, so the statistical analysis only compares the number of bird observations, and not the type of species. Additionally, although the difference is not significantly different, we did observe a slightly higher number of birds on average in native tree species than in the exotic tree species. In the plot s that we examined except for Site One, the native trees were much younger than the exotic trees, and were therefore shorter and less developed. This could influence which trees the birds chose for shelter and protection. As seen in Table 2, site one was the site with the highest number of bird observations in the native windbreak; there were twelve observations in the native windbreak and five in the exotic windbreak, for a difference of seven observations between the two types of windbreaks. For site tw o, there were nine observations in the native windbreak and seven in the exotic, for a difference of two observations in favor of the native windbreak. For site three, there were four observations in the native windbreak and nine in the exotic, for a diffe rence of five observations in favor of the exotic species. There is the largest difference in observation in favor of the native species in site one, where the native trees are the oldest. Therefore, judging from the data, it is possible that the age of th e native trees plays a role in bird visitation, and the data may have been statistically significant if the native trees in the windbreaks of sites two and three were as old as the exotic species. It would be interesting to further examine how the age of t he trees influence bird visitation. As our results show a possible
6 trend in the direction we were predicting, maybe a larger sample size over a longer period of time would allow us to make a stronger comparison. There are many potential sources of error w ithin this experiment. There was animal interference at many of the sites; there were dogs near site one and horses near sites two and three. The barking of the dogs and the movement of the horses may have deterred birds from perching or flying by the site s. Additionally, due to the large size of the plots and the dense coverage of the exotic trees, we may have missed certain birds if they were not highly visible or if we could not hear their calls. If these birds were visible to us, it is possible it could have added strength to our results. Furthermore, because we used calls to identify certain birds, we may have counted the same bird multiple times accidentally. Additional studies could examine the visitation patterns of migratory versus resident birds to see which, if any, type of windbreak they prefer. Literature Cited : Burlingame, L.J. Conservation in the Monteverde zone: contributions of conservation organizations. Monteverde: Ecology and Conservation of a Tropical Cloud Forest. 2000. Garrigues, R., R. Dean. The Birds of Costa Rica . Zona Tropical Publications. 2007. Powell, G.N.V, R.D. Bjork, S. Barrios, and V. Espinoza. Elevational migrants and Habitat Linkages: using the Resplendent Quetzal as an indicator for evaluating the design of the Monteverde Reserve complex. Monteverde: Ecology and Conservation of a Tropical Cloud Forest. 2000.
7 Schulenberg, T.S. Three wattled Bellbird Procnias tricarunculatus , Neotropical Birds Online. Ithaca: Cornell Lab of Ornithology; retrieved from Neotropical Birds Onl ine. 2010.
8 Tables and Figures: Table 1: Bird species and number of observations for native and exotic windbreaks ÂMÂ‚ indicates migratory species and ÂRÂ‚ indicates resident species Table 2: Number of bird observations in native and exotic windbreaks fo r each site Table 3: Number of observations for migratory vs. resident birds in native vs. exotic windbreaks observations of unidentified species not included Species Native Observations Exotic Observations Black and White Warbler M 1 0 Black Vulture R 0 2 Brown Jay R 6 9 Great-tailed Grackle R 9 1 Keel-Billed Toucan R 2 0 Plain Wren R 1 1 Rufous-collared Sparrow R 0 2 Warbler M 1 3 Unidentified 5 3 Total Observations: 25 21 Site 1 Native: 12 Exotic: 5 Site 2 Native: 9 Exotic 7 Site 3 Native: 4 Exotic: 9
9 Figure 1: Comparison between bird use of three native versus three exotic windbreaks i n Monteverde, Costa Rica. Results are based on six one hour observations in each p = 0.6 . Standard Error bars shown. Native Observations Exotic Observations Total Observations Residents: 18 15 33 Migrants: 2 3 5