Nesting behavior of the female and male Resplendent Quetzal Pharomachrus mocinno Jennifer Heller Department of Environmental, Population, Organismal Biology, University of Colorado Boulder ___________________________________________________________________ ABSTRACT Knowledge of nesting behaviors of tropical birds, even for the magnificent Resplendent Quetzal, comes from few records of observations outside the nest. However, the popularity of the bird in the Monteverde Cloud Forest Preserve inspired the Tropical Science Center to place a camera inside one of the box nests just before the 2000 nesting season. I studied the images taken during the entire nesting period. Upon analysis of the data, I found that parental care and behavior changed significantly as the chick aged. Additionally, only females slept in the nest, and although both the male and female brooded and attended to the young, the female spent significantly more time in the nest than the male p < 0.05. As the chick aged, the time that the parents spent in the nest decreased significantly p < 0.0001. Observations recorded by others from outside the nest concur with this data. Nest predation is high in tropical environments; thus, having both parents alternating care in the nest may increase the chances of a successful brood. However, in my study of the quetzal, the duties were not necessarily equally sha red, leaving the female more vulnerable to predation. RESUMEN Existen pocos registros sobre el perÃodo de anidaciÃ³n para los quetzales y las observaciones son del exterior del nido. Pero la popularidad de los quetzales en el Bosque Nuboso Monteverde causo que Centro CientÃfico Tropical pusiera una camara en el nido d espuÃ©s del periodo 2000 de anidaciÃ³n. Yo estudie las fotos que se tomaron durante el entero periodo de anidaciÃ³n. DespuÃ©s de anÃ¡lisis, yo encontrÃ© que los padres no estuvieron en la madriguera mucho como el pollito, tambiÃ©n que solamente la madre dormÃa en el nido. Aunque los dos padres empollaron y atendieron al pollito, la madre pasaba mas tiempo en la madriguera que el padre p < 0.05. El tiempo que los padres pasaron en el nido disminuyo significatoriamente conforme el pollito creciÃ³ p < 0.0001. Observaciones del exterior de la madriguera concuerda con los datos. EI riesgo de predacion esta en crecimiento en los trÃ³picos. Entonces teniendo los dos pa dres se puede aumentar la probabilidad de tener una nidada exitosa. Pero en esta investigaciÃ³n del quetzal las obligaciones entre los padres no fueron equivalentes. INTRODUCTION Many differences in nesting behavior exist between temperate and tropical bird species. There are differences in clutch sizes, parental care, and nest protection. For example, temperate birds on average have larger clutch sizes than their tropical counterparts Ghalambor and Martin 2001. Ghalambor and Martin 2001 also studied the different nest defense strategies between temperate and tropical bird species. Using playbacks of potential nest
predator calls, they found that Northern Hemisphere birds decreased their rate of visits, thereby decreasing attention called to the nest. On the contrary, tropical birds only decreased their rate of visits when the call was from a predator of the adult bird. These results indicate that temperate birds may accept a greater risk to themselves in defense of their nests, as they have a larger inves tment in the each nest and the probability of surviving to produce another clutch is low. Therefore the fitness value of the young is high. The opposite is true for tropical birds in that they produce smaller clutches, but have an increased likelihood of s urviving to reproduce again. Therefore, they invest less in the protection of their nests and more in their own survival Ghalambor and Martin 2001. The clutch size, often reflecting the current investment that parents will place on a nest, is correlated with adult survival Ghalambor and Martin 2001. There exist other behavioral differences in birds that may correlate with species survival. For example, most tropical birds tend to be insectivorous, as well as monogamous Hilty 1994. Hilty 1994 noted t hat these two trends may be correlated. Fruit and nectar are usually easy to find and harvest. Insects, however, are harder to find, and therefore foraging occupies more time and energy. This leaves no extra time for courting displays, leading to monogamy. Additionally, because the foraging requires nearly 60 70% of the day, during nesting season, it is essential to have both sexes to help guard the nest and forage Hilty 2001. Alcock 1984 also suggested that monogamy may benefit the male as well becau se males can then provide for the young, increasing the chance of survival of the nestling and therefore the fitness of the male. Although pairs may be monogamous, the male and female often devote different amounts of time to the nest. Triver 1972 argued that as females invest more in their eggs initially than the males do in their sperm, the females will invest more in the clutch itself. One example of a tropical bird that shares nesting responsibilities is the Resplendent Quetzal Pharomachrus mocinno. Although they are often difficult to see, once a nesting site has been found, it is easy to identify the male and female quetzal. The male quetzal is recognized by its shimmering, metallic green back, bright red belly, a crest of feathers atop its head, a nd two 30 cm, green/blue, streamer like tail feathers. The female, though lacking the long streamers, is also green with a red underside Stiles and Skutch 1989. The quetzal is found at elevations of 1200 3000 meters in montane to premontane life zones fr om Mexico to western Panama Norman 1993. Their breeding season is from March to June and sometimes into July. After courtship displays, the quetzal pair begins to build their nests in holes of dead trees Norman 1993, Fogden and Fogden 1996. The opening of the nest is approximately 12 cm in diameter, the cavity 10 30 cm in depth, and the hole averages about nine meters above the ground Norman 1993. The clutch size is usually two pale blue eggs, and they are often lay two clutches per season Norman 199 3. The incubation period lasts about 18 19 days Norman 1993, Fogden and Fogden 1996. After hatching the chicks spend approximately 25 days in the nest, and are fed insects, land snails, small lizards, frogs, and fruits Norman 1993. The quetzals often share parental responsibilities. Wheelwright 1988 observed three nests during the first 12 days after the nestling hatched. At the first nest, he found that the male spent nearly three times as much time brooding as the female. However, in the
next two n ests, the time was divided fairly equally Wheelwright 1988. Skutch 1944 also found data similar in that the nesting time was equally divided at his observation site. Thanks to recent efforts by the Tropical Science Center, new information is available from inside a Quetzal nest. This flood of new information provides insight c a relative parental care in a Tropical bird species over an entire nesting period. METHODS I observed an occupied quetzal nest box located in the Monteverde Cloud Forest Preserve MCFP, Puntarenas, Costa Rica. The MCFP, managed by the Tropical Science Center TSC is located in the TilarÃ¡n Mountain Range at 1520 1600 meters Norman 1993, in th e lower montane wet forest life zone Haber 2000. The box nest is posted on a dead tree in secondary forest at 1530 meters. The tree is located approximately 80 meters west of the lower laboratory owned by the TSC. The nest box has two electric fences, on e above and one below, for protection against arboreal and terrestrial predators. In order to increase awareness of the Mesoamerican Biological Corridor Initiative, The World Bank and associates started an internet based environmental project. They chose to focus on an artificial nesting site for the quetzal in the MCFP, Costa Rica. The efforts resulted in the Quetzal Cam, the first camera placed inside a nest. The public can view the images on the Cloud Forest Alive website www.cloudf orestalive.com. I analyzed photographs taken by the Quetzal Cam positioned in the ceiling of the nest box from April 5, 2000 until the chick fledged on May 16, 2000. Although official data collection began on the fifth, the eggs were laid on April 4. Th e Quetzal Cam takes one photo, labeled with date and time, every minute over the entire nesting period. After Brian Schwartz downloaded all of last year's nesting season data onto CD's, I was able to view each photo in sequential order. I was able to recor d the length of time the parents slept in the nest, the time each spent in the nest awake, including feeding and the time the egg or chick was alone. I also recorded any additional observations regarding feeding, and the habits, physical characteristic s and the developing attributes of the chick. During the 2001 nesting season, I made field observations at the nest site on May 1, May 2, May 3, and May 6. Though the birds are not banded, it is believed to be the same pair of quetzals as the previous year Brian Schwartz, personal communication. I spent three hours each of four days observing the nest from approximately ten meters uphill. I observed perch spots, length of time a female or male spent perched at a specific spot, and what type of food was br ought to the two chicks inside. RESULTS General Observations of Major Nesting Events Around March 22, 2000, the quetzals began investigating several of the nest boxes in the MCFP. Volunteers reported that the quetzal pair tested several sites, including nest boxes, before deciding on the box studied here. On April 2, the male and female alternated going inside the box, occasionally removing wood shavings wvvw.cloudforestalive .com. Two eggs were laid on April 3, 2000. One of the eggs hatched on Day 18 of the nesting period. The second egg never hatched, and
was removed from the nest by the male on Day 27. On Day 34, the nestling's eyes opened. By the next day, they remained wi de open all day. It was during this time Days 34 36 that the nestling took on a more adult like appearance. There was considerably less fluff, and the feathers became more prominent. The nestling became very active in the nest with lots of movement, wing stretching, and preening. The metallic green color of the parents also appeared on the head and back of the nestling. At this point, I determined the chick to be in its pre fl edgling stage. Finally, on Day 43, the chick fledged. Differential Parental Care During the initial part of the nesting, the parents focused on incubating the eggs. Both parents spent long periods of time in the nest during this period Figure 1. The long incubation time is also apparent in the short periods of time the eggs were left unattended Fig. 4. Although both parents tended to the eggs, the female spent noticeably larger periods of time brooding than males Sign test, 15+, 0 , p < 0.05. On average, females spent twice as long brooding as males avg. female = .3915, Â± 10.13; avg. male = .1570, Â± 4.32. After the eggs hatched, the female continued to tend to the nest for a longer period of time than the male Fig. 3. There is a significant difference between the male and female's time spent in the nest after the egg hatched Sign test, 26+, 0 , p < 0.05 Changes in Behavior over Nesting Period As the nestling ages, there are gradual and abrupt changes in parental roles Fig. 5. The total time the male is inside the nest remains fairly constant during brooding. However, after the eggs hatch, there is a gradual decrease in male attendance to the nest. By Day 42, the male no longer frequents the inside of the nest. The change in the amount of time the female spends in attendance, as well as the time she spends sleeping in the ne st decline abruptly. The female stops sleeping in the nest on Day 36, and stops visiting the inside of the nest on Day 37. The lack of parental attendance attributes to the increasing time that the nestling spends alone Fig. 5. In order to account for si gnificant changes in behavior, the nesting period was divided into three stages of development. The first is the egg stage, the second is the nestling stage, and the third is the pre fledgling stage. Day 18 is the day the egg hatched, introducing the nestl ing stage. In the first subsection of results, I describe the characteristics that led me to justify the pre fledge stage. This stage began on Day 36. The average percent of a day that a parent was in the nest, the female was sleeping, or the egg/chick was alone was tabulated for each stage of development Table 1. There was significant difference between the three stages in the time the female spent in the nest H = 18.93, tied p < 0.0001, the time the male spent in the nest H = 21.18, tied p < 0.000 1, and the time that the chick was alone H = 21.39, tied p < 0.0001. There was also significant difference between the three stages in the time that the female spent sleeping in the nest H = 17.20, tied p < 0, 0002.
Observations Made Outside the Nest The female and male quetzals were in and out of the nest frequently during the observation period. I noticed that if one of the pair was out foraging, the other was usually somewhere near the nest. If I could not see the male, I could usually hear him chirping nearby. The male and female spent little time in the nest and often fed the chick from the outside of the nest. From my observations, the female brought in one caterpillar, one insect, one fruit, and one unknown food item. The male brought in three fruits, one insect, and one caterpillar. Due to the low sample size of food items identified, no statistical analyses were done. On the forth day of observation, I noticed a different type of bird chasing both the male and female quetzal around the f orest canopy. Often it followed them off perches and farther into forest. I also observed the male and female share preferential perching spots near the nest. Both usually perched for a brief period of time before ever entering the nest. They often turned their heads from side to side as if surveying the area first. The times the male and female were away from the nest varied, but never lasting much longer than an hour at a time. Discussion I found that both quetzal parents invest a large amount of time i n the care of their clutch. However, Ghalambor and Martin 2001 found that tropical birds produce smaller clutches and are more willing to protect themselves instead of their young. Because quetzals produce smaller clutches and are able to reproduce again if the first clutch fails Fogden and Fogden 1996, it may be inferred that they may also follow this same trend. However, my data seems to contradict this trend; the quetzal parents invest large amounts of time in their nestling, but there are fluctuatio ns in the data. These sudden short times of parental care could be an indicator of an outside predator. When looking only at the inside nest information, a crucial key to behavior may be missing when outside activity is unknown. Most tropical bir ds are monogamous because they are insectivorous. Foraging for insects requires 60 70% of the day. This increase in time spent foraging leaves little time for additional courting displays and searching for a new mate Hilty 1994. Although adult quetzals a re mainly frugivorous, they feed their young insects and small vertebrates. Nestlings that are fed solely fruit grow slowly. Slow growth results in an increase in the time the nestling is in the nest, thereby increasing the risk of being preyed upon Hilty 1994. The monogamous relationship of the quetzal also benefits in that it affords more time for nestling care, increasing the amount of protein brought to the nest, and greater protection of the nest. These explanations may provide insight into why the quetzal parents invest more time in the clutch; however, it does not explain why the female tends to spend more time in the nest. Although Wheelwright 1988 found that, in one nest, males spent nearly three times the amount of time brooding as th e female. In two other nests he found that
the male and female spent equal amounts of t ime in th e nest Wheelwright 1988. Skutc h 1944 also found that the parental care was equal. My data contradicts both of these previous findings. I found that the fema le spent nearly twice as much time attending to the nest as the male, and this did not include sleeping time Fig. 1 and 3. Previous studies do not go into depth regarding the exact length of time the female spends sleeping with her eggs and nestlings, wh ich is important because it accounts for a large period of time that the female spends in the nest Fig. 2. This increased time in the nest makes the female more vulne rable to predators; a risk the male never takes. Triver 1972 attributes increased female investment to the female's greater initial investment in her eggs versus the male's smaller investment in his sperm. Even though the inside data show that the female spends more time in the nest, from my outside observations of the nest bo x, it may be the male is investing just as much time by watching outside of the nest. Became the female has invested so much, she is more willing to increase her vulnerability, again contradicting the traditional role of tropical birds' preference for self preservation. Another reason that may affect the quetzal's nes ting behavior is elevation. Hilt y 1994 observed that cot ingas usually practice polygyny and have small clutche s. However, in the higher elevations of t he Andes Mountains, the birds tended to be monogamous and clutch size increased to th ree eggs. This change may be attribut ed to fewer predators in higher elevations and the birds may be less dependent on fruits Hilt y 1994. Addit ionally, Hilty 1994 observed that increased thermal demands may require increased parental care at night. These same explanations for parental investment may be applied to the quetzal's behavior, as they are also located at higher elevations as well Fogden and Fogden 1996. Studies done on quetzals not only benefit sc ience but also eco tourism and conservation. Because of the birds' beauty in its natural habitat, it often attracts many tourists. The Monteverde Cloud Forest Preserve offer many incredible aspects of nature, but the Resplendent Quetzal is always piques the interest of the tourist. Thanks to the investment in nest boxes, it may be possible to compare nesting activity between natur al nesting sites versus box nest s. This data could demonstrate the positive effects of conservation efforts by the Monteverde C loud Forest Preserve. Another factor that could possible affect the nesting behavior of the quetzal is global warming. Pounds XXXX has found that global warming ha s caused the cloud in Mont everde to rise. These cloud forests are prime nesting spots for t he quetzal s, and as the climate changes, the quet zal may exhibit changes in nest ing behavior accordingly. Comparing information found in 1944 by Alexander Skutc h with da ta found today may show interesting t rends. From this on e study, I was able to show t hat the female invested more time in the nest , contradicting what Skutch found. With such little information on the quet zal it is often difficult to make definite co rrelations between nests. However, if studies on t he Resplendent Quetzal cont inue, eventual l y enough data may be collected t o note possible trends in nest ing behavior due lo altitude and unnatural environmental factors such as deforestation and global warming.
ACKNOWLEDGEMENTS This study would not have been possible without the contributions of The World Bank, The Tropical Science Center, and the Monteverde Cloud Forest Preserve. Thank you for initiating and providing such a valuable resource of data. Additionally, thank you to the many people along the way who have kept the project going and have also helped me personally in providing the data: Jason Roberts, Brian Schwartz, Julio Caloo, and Rafa BolaÃ±os. I would like to thank Alan Masters for his patience with many bird project s doomed from the start Â€ but yet in the end finding one that was truly enjoyable. I would also like to thank Andrew Rodstrom for wrestling whenever I needed to get out some frustration and most of all for his never ending help. Thank you to Tim Kuhman for his creative thinking in getting the images from the CD into the computer program. And of course a thank you to Karen and Mauricio for their oh so lovely sense of humor and sarcasm. And one last thanks you to Ali for helping me at the very, very last minu te in correcting this paper! LITERATURE CITED Alcock, John. 1984. Animal Behavior an evolutionary approach. Sinauer Associations, Inc., Sunderland, Massachusetts. Fogden, Michael and P. Fogden. 1996. The Resplendent Quetzal. Green Mountain Publishing, Mont everde, Costa Rica. Ghalambor, Cameron K. and Martin, Thomas E. 2001. Fecundity survival trade offs and parental risk taking in birds. Science 292: 494 497. Haber, William A. 2000. Plants and Vegetation. In: Monteverde ecology and conservation of a tropica l cloud forest, Nalini M. Nadkarni and Nathaniel T. Wheelwright, eds. Oxford University Press, New York, New York. Hilty, Steven. 1994. Birds of tropical America a watcherÂs introduction to behavior, breeding and diversity. Chapters Publishing Ltd., Shelbo urne, Vermont Norman, David. 1993. Costa RicaÂs Resplendent Quetzals. Heredia, Costa Rica. Skutch, A.F. 1944. Life History of the Quetzal. Condor 46: 213 235. In: Fruits and Ecology of Resplendent Quetzals. 1983. N. Wheelwright. Auk 100: 286 Â€ 301. Stiles, F. Gary and Skutch, A.F. 1989. A guide to the birds of Costa Rica. Cornell University Press, Utica, New York. Trive.s, R.L. 1972. Parental investment and sexual selection. In: Sexual selection and the descent of man. B. Campbell ed.. Aldine, Chicago. In : Animal Behavior and Evolutionary Approach. J. Alcock. Sunderland, Massachusetts. Wheelwright, Nathaniel. 1988. Fruit eating birds and bird dispersed plants in the tropics and temperate zone trends. Ecology and Evolution 3: 270 274 In: G.F. Stiles and A.F . 1989. A guide to the birds of Costa Rica. Cornell University press, Utica, New York.