Parrots of Sector Santa Rosa
and Adjacent ACG Regions
Jack Bradbury, Timothy Wright, and Kathryn Cortopassi
Parrots and Santa Rosa:
Parrots are one of the most conspicuous vertebrate species in the Sector Santa Rosa (SSR) portion of the Area Conservacion Guanacaste (ACG). Santa Rosa is one of the best places in the world to see and observe wild parrots. This accessibility to parrots arises for several reasons. Foremost is that parrots are protected in the ACG. They become used to visitors and they do not mind you watching them pursue their various activities as long as you do not try to approach too closely. A second reason is the type of habitat. The lowland ACG is made up of old farms and ranches interspersed with large patches of dry seasonal forest. This is a perfect habitat for a number of dry forest parrot species and densities of local parrot species are very high. The canopy of the seasonal dry forest also tends to be low and especially in the dry season, sparsely vegetated. Resident parrots thus are closer to the ground, where visitors will be looking for them, and more easily seen. They are also highly vocal and once heard, they are usually easily located and observed. Peak activity for many species is in the early morning and late afternoon. If you look for them at these times, you should have no problem seeing parrots during a visit to the SRR/ACG. It takes considerable effort to visit SSR/ACG and not see parrots!
Resident Parrot Species of SSR/ACG:
There are four species of parrots which visitors are most likely to encounter throughout the year in and around the SSR. In order of decreasing body size, these are the Yellow-Naped Amazon (Amazona auropalliata), the White-Fronted Amazon (Amazona albifrons), the Orange-fronted Conure (Aratinga canicularis), and the Orange-chinned Parakeet (Brotogeris jugularis). These four species can be found throughout the SSR and are commonly present together in the seasonal dry forests along the Pacific coast of Central America from Costa Rica to north-western Mexico.
The four species rarely form mixed flocks. Orange-fronted Conures and White-fronted Amazons tolerate each other while feeding in the same patch of food plants (such as Cordia in the dry season or Muntingia in either season). However, the two species typically go their own ways soon after exhausting the food patch. White-fronted and Yellow-naped Amazon congeners may form communal roosts near to each other, but we have never seen mixed roosts in the SSR.
In addition to the four parrot species resident in the SSR, a number of species that normally live on the higher western slopes or even the humid eastern side of the cordillera will invade the Pacific lowlands during the wet season. In July and August, the large Mealy Parrot (Amazona farinosa; length: 38 cm (15"); weight: 600 g) can often be seen in small flocks of 4-8 flying high over Pocosol towards the west in the early morning and back east again near sunset. Another large Amazon, the Red-lored Parrot (Amazona autumnalis; length: 34 cm (13.5"); weight: 420 g) also invades the Santa Rosa Sector during the rainy season. They can often be seen in the forest of the Park center and Bosque Humido, and large flocks of Mealy Parrots have been seen feeding on acorns in the oak forests on either side of the PanAmerican highway near the entrance to SSR.. For the last several years, a flock of 15-20 Brown-hooded Parrots (Pionopsitta haematotis; length: 21 cm (8.25"); weight: 165 g) have been observed in late July flying from the cordillera uplands at dawn and feeding silently in the oaks just west of the Pan American highway near Finca Jenny. These are extremely shy birds when feeding so advance quietly if you want to get a good look at them. The Crimson-fronted Conure (Aratinga finschi; length: 28 cm (11"); weight:150 g) is occasionally seen in the wet season in the southern parts of the SSR. It looks quite similar to the Orange-fronted Conure and emits similar flight calls, but is about twice as large. This is the same conure seen so frequently around San Jose. In the past, Scarlet Macaws (Ara macao; length: 84 cm (33"); weight: 900 g) were once common in the area surrounding the SSR. Barring recovery of this lovely species in Guanacaste, those days appear to be gone. Green Macaws (Ara ambigua) are occasionally seen on the lower slopes of Rincon de la Vieja in the rainy season.
Diet: Although they will eat fruit, flowers and nectar, and occasionally insects, parrots are largely seed predators. As a result, they have to work harder to find suitable food than do frugivores whose host plants actively recruit animals to visit them. Parrots must deal with diverse and complex protections that plants create to protect their seeds. These include hard capsules, spines, and toxic or distasteful chemicals in the seeds. The powerful hooked bill of parrots surely evolved as a tool for gaining access to seeds. Some parrots regularly eat clay or other earth deposits. It is thought that these materials help absorb toxins that were ingested with the seeds. This has not yet been observed in any ACG species. Parrots are exceedingly dextrous with their feet which they use one at a time to hold large fruits or seed pods while eating. Parrots tend to favor one foot just as humans favor one hand: many of our local species appear to be largely left-footed, although there are clearly exceptions as in humans.
Home Range: Another consequence of the seed-eating diets of parrots is that they have much larger home ranges than do birds in other groups but of similar body size. As a result, they do not defend territories like many sympatric insectivorous or nectarivorous birds. Radio-tracking of parrots in the SSR has shown that different flocks often have entirely overlapping home ranges. This means that one flock may harvest all new fruit or seeds in a site before another flock arrives to feed, thus forcing the second flock to range further still.
Predators: Most parrots are heavily muscled for their body size and this makes them favored prey of sympatric hawks. The ubiquitous green of ACG parrots is surely an adaptation to make them less conspicuous to visual predators when in the foliage. The typical dry season flocks of 15-30 birds in all but the large Yellow-naped Amazon are in part adaptations to reduce individual predation risks (since a hawk can take only one prey at a time). In addition to hawks, sleeping Orange-fronted Conures and Orange-chinned Parakeets are both favored prey of the large bat, Vampyrum spectrum. Barn owls and bat falcons have also been observed attempting to flush sleeping Parakeets from their night roosts in early dawn hours. During the nesting season, both adult and nestling parrots are vulnerable to the diverse guild of tropical nest predators including snakes, lizards, caracaras, jays, owls, coatis, and capuchin monkeys.
Breeding: Nearly all parrots are hole-nesters and all of the SSR parrots are ostensibly monogamous year around. Most rely on natural cavities in trees or palms for nest sites. A few, such as the Orange-fronted Conure and the Orange-chinned Parakeet, excavate cavities in arboreal termitaria for their nests. For many parrots, suitable nest sites may be a limiting resource resulting in competition between pairs for good nest sites and reuse of the same nesting site in successive years.. In most species, the female does all the incubation and is fed by the male at intervals during this period. Because eggs are incubated soon after the first is laid, eggs hatch asynchronously and chicks in the same nest may be at quite different developmental stages. Both parents feed the offspring with at least one parent insuring that the smaller less competitive chicks get their share. Where offspring fledge asynchronously, the parents dutifully feed the remaining chicks until they too can leave the nest. Fledged youngsters may remain with the parents in small family groups for a month or more, or they may be put in a creche with other youngsters while the adults spend increasing amounts of time away from them.
Night Roosting: Night is a dangerous time for any diurnal bird and parrots are no exception. All of the SSR species aggregate into staging congregations in late afternoon. Whereas the Yellow-naped Amazons use the same sleeping trees for generations, the other SSR species tend to move their sleeping sites at intervals that differ among the species. White-fronted Amazons move night roosts every few months, Orange-chinned Parakeets move roosts every few weeks, and Orange-fronted Conures typically move night roosts every night. Because the latter are the favored prey of carnivorous bats, this may be an adaptation to reduce predation. The species that move night roosts at intervals all vocalize loudly to attract conspecifics to the current staging area. The hours from 16:00-17:30 are a good time to hear parrots vocalizing and to see large aggregations in one place. Between 17:30 and 18:00, all but the Yellow-napes move from their conspicuous staging trees into dense foliage nearby. Once installed in the foliage, they usually become silent, but in all three species, the birds may suddenly decide they do not like that spot, burst with loud calls from the foliage, and move en masse to an adjacent tree. Finally, they settle down and are silent until dawn. Yellow-napes, in contrast, trickle into the traditional night roost in pairs and are often still arriving at the site as late as 18:30. They congregate in a few bare trees and vocalize extensively before settling down to sleep. They do not hide in the foliage.It may be that Yellow-naped Amazons are sufficiently large that they are not threatened by the same predators that attack smaller species of parrots.
Yellow-naped Amazons are often the first up in the morning. They can be seen flying in pairs from the communal night roost as early as 5:00. Orange-chinned Parakeets are usually the next species to arise. They typically burst en masse from their hiding spot about 5:15-5:20 AM and fly with loud calls to nearby trees to preen and divide up into smaller foraging flocks. The White-fronted Amazons are usually close behind with typical awakening about 5:20-5:30. They often play and vocalize for 15-20 minutes before flying off in smaller groups. Last up are the Orange-fronted Conures which usually emerge from their sleeping sites about 5:35-5:40.
Flock Dynamics: Except during the breeding season, the three smaller species of parrots within SSR are usually found in small foraging flocks during the day. All three species follow a similar diurnal cycle. Larger night roost associations break up after dawn into foraging flocks of 6-20 birds that radiate out from the night roost in all directions. During the next 2-3 hours, each flock ranges over large areas hitting a rapid succession of different foraging sites. In mid-morning, flocks that find themselves in the same area land at a common site and fuse into a larger aggregation. Here they preen, sleep, and play for several hours. Play is very common at this time: mates bite each other's feet, hang upside down, chew sticks and branches, and spar. Midday is usually a period of sleep and repose for our local parrots. In early afternoon, the sleeping and play associations break up again into smaller flocks for more foraging. By late afternoon, flocks are refusing again at nigh roost staging areas. The daily life of these species is thus a continuous succession of fission and fusion of social units. Radio-tracking has shown that pairs of Orange-fronted Conures can shift foraging groups during a fusion-fission sequence. However, the same pairs are often found back together weeks later.
Yellow-naped Amazons are an exception to these patterns. Birds are most typically seen in pairs in the early morning after leaving the night roosts. These pairs will often visit their nests and perform conspicous and acoustically complex pair duets in the area nearby, both during and outside of the nesting season. Pairs will often engage in counter-duets with neighboring pairs in interactions that are reminiscent of singing duels in territorial male songbirds. Pairs usually conclude duets by 9 am, after which time it is rare to hearing these birds calling until late in the afternoon. Limited radio-tracking data suggest that pairs may join other pairs and juvenile flocks feeding at fruiting trees. Feeding bouts are followed by long periods of midday rest punctuated by preening and play. In the afternoon this temporal pattern is reversed, with feeding followed by dispersal of pairs to their nests, loud calling near nests, and then a return to the night roost.
Vocalizations: We are just beginning to understand the vocal repertoires of wild parrots. However, we can already identify several broad categories of call types that are widespread in our resident species. These include:
Loud Contact Calls: These are among the loudest calls in our parrots' repertoires and are typically given when the birds are in flight, during vocal exchanges with other roosting or overflying pairs, or when members of a pair are separated. All four of the SSR species have a characteristic loud contact call. Those of the three smaller species appear to function as mechanisms to get the attention and establish a vocal link between birds. Thus one bird will give a contact call, another will answer immediately, the first will call again, and after several exchanges, it is clear the two have gotten each other's attention. The callers may then approach each other, or one may then give another call in the repertoire to coordinate some joint activity such as flight. Yellow-napes, which are less social than the other species, often do not reply to the contact calls of other pairs. But they invariably look up and listen when another pair flies over giving this call.
Soft Contact Calls: These are very soft sounds that parrots use to coordinate movements when foraging in dense vegetation. Unlike loud contact calls, they do not necessarily elicit a response by other group members. Instead, each bird emits these calls at regular intervals and flock members use this information to remain close even though they are moving and cannot see each other.
Preflight Calls: All four species have signals that they use to coordinate taking flight at the same time. These are often very loud and repetitive. In several species, soft contact calls grade continuously into preflight calls as a flock exhausts the food at a given foraging site. When enough birds are emitting the preflight call, they all fly off simultaneously.
Warbling: Warbling consist of long rambling strings of highly variable sounds. It is most often heard during breeding season around nests, but can also be heard during the non-breeding season during midday playtime and late afternoon night roost stating. It may serve to reinforce pair bonds, but is more likely a declaration of dominance or status. All of our four species have been observed to warble.
Duets: Duets are highly coordinated strings of vocalizations emitted by both members of a pair according to a defined syntax. Different pairs may have different duet motifs and in some species, each pair may have a number of different duet motifs. Duets are conspicuous parts of the repertoire of the SSR species except for Orange-fronted Conures. It remains possible, however, that some of the sounds assigned to warbling in the Conures are in fact coordinated duets by both members of a pair.
Other Sounds: Each species has a number of other sounds that are less likely to be heard by short term visitors. All have aggressive squawks that they emit when engaged in a physical conflict. The young of each species continue to beg from their parents for some time after fledging, and each species has its own characteristic begging call. White-fronted Amazons are reputed to have a call they give after copulation, and Conures make a soft repetitive sound before becoming quiet at night.
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firstname.lastname@example.org (Jack Bradbury)
email@example.com (Timothy Wright)
This research supported by the National Geographic Society, the
National Science Foundation of the United States (Grants IBN-94-06217 & IBN
99-74527, and the Area Conservacion de Guanacaste of Costa Rica.
Revised 22 Oct 2002