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Cambios en el comportamiento de la reinita (Myioborus miniatus) y la reinita (Myioborus toquatus) a lo largo de un gradiente altitudinal en la Reserva de Monteverde
Behavioral changes of the Slate-throated Redstart (Myioborus miniatus) and the Collared Redstart (Myioborus toquatus) along an altitudinal gradient in the Monteverde Cloud Forest Preserve
Climate change has been found to affect the distribution of bird species in Monteverde, Costa Rica (Holmes 2000). In this study, the Slate-throated Redstart (Myioborus miniatus) and the Collared Redstart (Myioborus toquatus) were observed in the Monteverde Cloud Forest Preserve. Both altitudinal distribution and behavior were observed for both species. It was found that the Slate-throated Redstart has moved up in altitude. Further, observations for both species were compared using a chi square test, and there were significant differences between the two species, and also within the same species. This study shows that climate change is possibly responsible for the migration up hill, which in turn may impact the future behavior of bird species, competition and may cause extinction.
Se ha encontrado que el cambio climtico afecta la distribucin de las especies de aves en Monteverde, Costa Rica (Holmes 2000). En este estudio, la especie de reinita Myoborus miniatus y Myoborus toquatus fueron observados en la Reserva del Bosque Nuboso de Monteverde.
Text in English.
Birds--Behavior--Costa Rica--Puntarenas--Monteverde Zone
Aves--Comportamiento--Costa Rica--Puntarenas--Zona de Monteverde
Tropical Ecology 2006
Ecologa Tropical 2006
t Monteverde Institute : Tropical Ecology
Behavioral changes of the Slate-throated Redstart (Myioborus miniatus ) and the Collared Redstart (Myioborus toquatus) along an altitudinal gradient in the Monteverde Cloud Forest Preserve Emma Gabrielsson Department of Biological Sciences, The George Washington University Abstract: Climate change has been found to affect the distribution of bird species in Monteverde, Costa Rica (Holmes 2000). In this study, the Slate-throated Redstart ( Myioborus miniatus ) and the Collared Redstart ( Myioborus toquatus ) were observed in the Monteverde Cloud Forest Preserve. Both altitudinal distribution and behavior were observed for both species. It was found that the Slate-throated Redstart has moved up in altitude. Further, observations for both species were compared using a chi square test, and there were significant differences between the two species, and also within the same species. This study shows that climat e change is possibly responsible for the migration up hill, which in turn may impact the future behavior of bird species, competition and may cause extinction. Resumen El cambio climtico ha sido un factor que ha influido en el cambio en la distribucin de la especie de aves en Monteverde, Costa Rica (Holmes 2000). En este estudio, la especie de reinita Myoborus miniatus y Myoborus toquatus fueron observados en la Reserva del Bosque Nuboso de Monteverde. Observe la distribucin de altitudinal y el comportamiento para ambas especie. Encontr que Myoborus miniatus ha incrementado su distribucin altitudinal. A un mas, las observaciones para ambas especie fueron comparadas utilizando una prueba de Chicuadrado encontr la diferencia significativas entre la do s especie, y tambin dentro de la misma especie. Este estudio muestra que el cambio climtico es posiblemente responsable de la migracin cuesta arriba de Myoborus miniatus cambio en esto puede causaron la conducta futura del las especies de aves, la competencia y la extincin posible. Introduction There is natural variation in abiotic factors such as altitude that impact the abundance of species. As altitude increases, avian species diversity declines (Tramer 1974). There is also a difference in abundance and amount of species in the tropics when compared to temperate areas. When compared to the temperate zone, the bird species communities in the tropics are complex and many variable components influence comp osition and abundance (Loiselle et al 1992). These variable components can be such things as habitat, altitude, and p opulation variation, all of which could also be affected by many factors (Loiselle et al 1992). Such factors could be deforestation and global climate change. It has been found that hum an impacts including deforestation have resulted in species loss (Kessler et al 2001). Global climate change has already been found to affect dist ribution in range, loss of amount of species, and the changing of ecosystems (McCarty 2001). As birds altitudina l ranges increase due to climate change they may be taking over habitats of other birds pos sibly causing competition and eventually possible extinction. This is of immediate concern in trop ical montane areas, such as Monteverde, Costa Rica, where the affects of climate cha nge is felt the hardest (Holmes 2000). Unfortunately, Monteverde has already felt th e affects of climate change. There have been studies that show correlation between climat e change and extinction of certain frog species in the Monteverde area (Pounds 1999). Additionally, other species have also been affected by climate change. One example is the Keel-bi lled Toucan which non migrates up to altitudes
where the Resplendent Quetzal is found (Holme s 2000). Now both of these species are found to be competing for the same food resources. This is thought to be a di rect result of global warming (Holmes 2000). Other birds may also be moving up in elevation because of climate changes. Two species of birds that are found in the Monteverde area are the Slate-throated Redstart and the Collared Redstart. Interesti ngly, these two species, even though similar in behavior and prey preference, ar e found at different altitudes. The Slate-throated Redstart is found at lower altitudes usually below 1,600 m, and the Collared Re dstart is usually found above 1,600 m. The purpose of this study was to observe both the Slate-throated Redstart and the Collared Redstart in their natura l habitat in the Monteverde Cl oud Forest Preserve. I studied these species because in previous studies there ha ve been no observations of altitudinal migration (Mahan 1998, Fogden 1993). Furthermore, I also want ed to observe behavior for each species to see if their behavior changes with an increase or decrease in altitude. If the Slate-throated Redstart was found at higher altitudes this may be due to affects of climate change. Furthermore, it will be interesting to note behavior of these species, and if these beha vioral observations differ at different altitudes. If so, these behavioral changes could po ssibly be the affects of habitat change, and they could affect foraging, and compet ition for prey or ultim ately survival of the species. Materials and Methods Description of habitat and study species: The Monteverde Cloud Forest Pres erve is divided into 6 different Holdridge life zones. Holdridge life zones are based on precipitation, altitude, and biotemperature. The two zones of interest in this study are z one 3, ranging from about 1,500 1,600 m but sometimes lower, and zone 4, ranging from 1,600 m and above (Fogden 1993). At about 1,500 m the forest is dense with tall trees. Some common tree species found here are Psychotria jimenezii in the Rubiaceae family as well as Ardisia compressa in the Myrsinaceae family (Haber et al 2000). At higher elevations increasing towards the timber line, there are strong wi nds and the tree species are much more exposed. Common tree species found here are Elaeagia auriculata in the Rubiaceae family and Clusia spp. in the family Clusiaceae (Haber et al 2000). The Slate-throated Redstart ( Myioborus miniatus ) and the Collared Redstart ( Myioborus toquatus) are common in zones 3 and zones 4 of the MCFP. These insectivorous birds are both approximately 12 cm long, weighing about 10 g. They are in the genus Myioborus which is known to use unique animated behavior, as well as flashing or flushing of their tail feathers in order to pursue prey which are usually ho mopterans (Galatowitsch and Mumme 2004). The Slate-throated is known to occupy zone 3, and th e Collared Redstart has historically been found in zone 4 and at times in zone 3 (Fogden 1993). Study Site I conducted in the Monteverde Cloud Forest Preserve, for 17 days from October 21, 2006 November 15, 2006. The trails walked incl uded: Bosque Nuboso, El Camino, Wilford Guindon, El Roble, Chomogo, Pantanoso, and La Vent ana (Figure 1). These trails were walked in the early morning from approximately 6: 30am to 12pm each day of data collection. Methods Each day I choose a different starting point for data collection, in order to survey as much area of the preserve as possible. I alternated randomly between the Camino, Nuboso or Wilford Guindon trails. When a trail was chosen, the calls and sounds of the Slat e-Throated Redstart were played continuously for 5 minutes, while walking, looking, and actively listening for this
species. This was then followed by 5 minutes of silence. In the following 5 minutes the calls and sounds of the Collared Redstart were played. Th ese calls and sounds were played on a Panasonic mini cassette player (model number RQ-L3G). A bird of either species could be observed anytime during these 15 minute periods (which we re then repeated continuously while in the MCFP). If a bird was found, a stop watch was acti vated. At every 30 second interval, the exact behavior at that time was noted. The activities that were obs erved included: chasing, flashing, sitting, flying, fidgeting, and hopping. See Table 1 for a description of each. The observation time depended upon the activity of the bird, and ho w difficult it was to observe. These birds were difficult to observe when at a far distance, or they were moving too quickly. When a bird could no longer be seen, the observation was finished. At this time, the altitude and time of observation were recorded. The trails were walked at a pace of about 12-14 meters per minute, with 2-3 hours required to walk one trail. Total obser vation time was affected by how many birds were found, how long the species could be observed an d the weather conditions (during extremely sunny and rainy days almost no birds were observed). After assessing the data it was decided that altitudes above 1580 m would be considered zone 4 and altitudes below 1580 m would be considered zone 3. Bo th new altitude markers and Fogdens method of separating the reserve into these zones according to vegetation were considered while making this decision (Fogden 1993) Finally a Chi Square test was used to assess all comparisons. I used this test because I was constantly only comparing two factors Results I observed a total of 87 birds during this study. The Slate-throated Redstart (S.T.) and the Collared Redstart (C.R.) were pr esent in both zones 3 and zones 4. Thirty S.T. were found in zone 3, and 18 were found in zone 4. Nine C.R. were found in zone 3 and 30 were found in zone 4 (Table 2). S.T. were found chasing, and flashi ng more frequently than C.R. in zone 4 (Chi Square test, X2 >3.84, p < .05) (Table 3). C.R. were found sitting and chirping more frequently than S.T. in zone 4 (Chi Square test, X2 >3.84, p < .05) (Table 3). Ac tivities that were not significantly different include: fl ying, fidgeting, and hopping (Table 3). Between the two species when in zone 3, S.T. were found chasing, flashing, hopping and flying more frequently than C.R. in zone 3 (Chi Square test, X2 >3.84, p < .05). Behavior that was not significant include sitting, chirping and fidgeting, meaning that there was no noted change in behavior between these two species (Table 3). Behavior was also compared between the same species in different zones. The S.R. were found fidgeting more in zone 4 than in zone 3, while all other behaviors were not different from each other (Chi Square test, X2 >3.84, p < .05) (Table 4). Additionally, the C.R. behaviors of flashing, sitting, chirping, fidgeti ng and hopping were all were observed more in zone 4 than in zone 3, while all other behaviors were not (C hi Square test, X2 > 3.84, p < .05) (Table 5). Lastly, activity budgets between the Collared Redstart and Slate-throated Redstart were also made by comparing average activity for each species in each zone (Figure 2). Discussion: It was interesting to find that some Slate-th roated Redstarts (S.T.) were indeed found in zone 4, where in past years they had never b een seen before (Fogden 1993). This elevational migration could bring competition with the Collar ed Redstart (C.R.) as well as other zone 4 species. Another implication of this movement uphill may be the future development of interspecific aggression between the S.T. and the C.R. which has been found in other species in the Amazonian rainforest (Robinson and Terborgh 1995).
Also, these birds are not likel y altitudinal migrants (Loisell e et al 1992). This further supports the hypothesis that S.T. are moving up in altitude possibly because of the affects of global warming. These two species may begin to co mpete with each other for prey, which may in turn cause the amount of prey ava ilable to decline. Lastly, I al so observed the C.R. in zone 3, where they have been found vagrantly in past studies (Mahan 1998, Fogden 1993). To study behavior in each species relative to its life zone, I co mpared all behaviors between the S.T. and the C.R. in both zone 3 and zone 4. Overall I observed more S.T. than C.R. in zone 3. I observed that the S.T. flashed its tail far more frequently than the C.R. in both zones. This flashing is usually to flush insects out of th e trees, or out of their ta il if caught in the pursuit (Galatowitsch and Mumme 2004). I also noticed that the S.T. would chase insects or other S.T. that were in pursuit of insects more than C.R. This is important because these two species are known to have the same prey. So if the S.T. is found actively foraging more, when compared to the C.R., this may cause a reduction in food resour ces thus future competition for prey between these two species. Also in zone 3, the S.T. s eemed to be more active in flying and hopping behaviors, when compared to the C.R. This is important because this type of animated behavior is also used to catch prey (Galatowitsch and Mumme 2004). In zone 4 there was a unique difference in be havior between the C.R. and S.T. The C.R. behavior was found sitting and chirping more than th e S.T. and therefore calmer in zone 4. This may be because the C.R. is commonly found at higher elevations and is adapted for these lower temperatures (Stiles 1989). This may also show th at compared to the S.T., the C.R. is a more passive bird at hi gher elevations. Comparisons between the same species in di fferent zones were then assessed. The only observed behavior that wa s significantly different for the S. T. between zone 3 and zone 4 was fidgeting. Instead of hopping or chas ing insects, these S.T. would fidget and seem overall more anxious in zone 4 when compared to zone 3 birds. This was interesting to note, since they are not commonly found in zone 4. This behavior may be their way of adjusting to a new altitude and habitat type. C.R. behavior also differed from zone 3 to zone 4. I noticed that as altitude increased, the C.R. seemed to be acting more cal mly. This species would sit still longer, and would respond to playback more often. This behavior may mean that these birds are more passive because they did not evolve with high levels of competi tion, compared to the S.T. which displays more active behavior because of the pos sibility that it did evolve with competition. Additionally, migrant birds are us ually found in lower elevations of the MCFP, so this supports that possibly the S.T. does deal with more co mpetition than the C.R. (Terborgh 1989). This behavior could affect the foraging success of the C.R. because the S.T. has moved up in altitude causing there to be a new introduced competitor. Further, since both species are part of the genus Myioborus, which are explicitly know n to use their different colored plumage and active behavior to startle prey in order to capture them, this calm behavi or may have to change in order to possibly compete with the S.T. (Galatowitsch and Mumme 2004). This study has shown that the Slate-throated Redstart has migrated into higher areas. Although this difference is only about 10 m, this difference is significant because now this species is found in a different zone type and ultimately a new habitat. This migration may eventually cause competition between other species historically found at higher elevations. Also, behavior of both species differs depending on the zones and species present. This study further emphasizes how all types of species are being a ffected by global warmi ng, and that action must be taken in order preserve species and habitats that are being lo st. Future study should include a larger sample of both species in each zone, with a greater emphasis on zone 4 areas, and
behavior shown by birds in that zone. Further, a longer study time will allow for a greater data set to be analyzed, and will help to emphasize these results. Additionally, the separation between zone 3 and zone 4 areas of the reserve should be made more de finite. Finally, it would be interesting to conduct this study in the dry season to s ee if the behavior of the birds changes. Acknowledgements : I would like to thank the Monteverde Cloud Forest Preser ve for allowing me to use the amazing trail system, and the guides that helped me find the best areas of the reserve to observe my species Thank you Tania Chavarria Pizzaro for helping me understand my findings, and helpin g me through everything, and thank you Alan and Karen Masters for being wonderful professors and helping me all along the way this semester and with this project. I would like to thank my tico family for giving me breakfas t everyday so early so I was possible to arrive at the preserve at a decent hour. Lastly, I would like to th ank my classmates, Cam and Tom for making this semester abroad the most amazing time ever, one that I will never forget. Pura Vida. Literature Cited : Fogden, M. 1993. Wood Warblers. An Annotated Checklist of the Birds of Monteverde and Penas Blancas. Published by Michael Fogden. Monteverde, Costa Rica, 54-55. Galatowitsch, M. L. and R. L. Mumme. 2004. Es cape Behavior of Neotropical Homopterans in Response to a Flush-Pursuit Pred ator. Biotropica 36: 586-595. Haber, W.A., W. Zuchowski, and E. Bello. 2000. An Introduction to Cloud Forest Trees: Monteverde, Costa Rica Mountain Gem Publications: M onteverde, Costa Rica, 11-13, Holmes, B.2000. Case of the dwindling cloud forest. Internati onal Wildlife 30: 20. Kessler, M., S. K. Herzog, J. F. and K. Bach. 2001. Species richness and endemism of plant and bird communities along two gradients of elevat ion, humidity and land use in the Bolivian Andes. Diversity and Di stributions 7: 61-77. Loiselle, B. A. and J.G. Blake. 1992. Popula tion Variation in a Tr opical Bird Community. BioScience 42: 838-845. Mahan, J. S. Altitudinal Abundance of Collared Redstarts and Slat e-Throated Redstarts in the Monteverde Cloud Fore st Preserve in Tropical Ecology and Conservation: Fall 1998, CIEE, Monteverde, Costa Rica. McCarty, J. P. 2001. Ecological Consequences of Recent Climate Change. Conservation Biology 15: 320-333. Pounds, J.A., M.P.L. Fogden, and J.H Campbell. 1999. Biological response to climate change on a tropical mountain. Nature 398: 611-615. Powell, George V.N. 1979. Structure and Dynamics of Interspecific Flocks in a Neotropical Mid-Elevation Forest. The Auk 96: pp 375-390. Robinson, S. K. and J. Terborgh. 1995. Inters pecific Aggression and Habitat Selection by Amazonian Birds. The Journal of Animal Ecology 64: 1-11. Sanatana-Castellon, E. 2000. Dynamics of unders tory birds along a cloud forest successional gradient. The University of Wisconsin-Madison; Dissertation: AAT 9972863 Stiles, F.G. and A.F. Skutch. 1989. A Guide to the Birds of Costa Rica. Cornell University Press, Ithaca, New York: 382, 401402. Terborgh, J. 1989. Where Have All the Birds Gone? Essays on the Biology and Conservation of Birds that Migrate to the American Tropics Princeton University Press, New Jersey: 149155. Tramer, E. J. 1974. On Latitudinal Gradient s in Avian Diversity. The Condor 76: 123-130.