Description of eggs, nest, and parental care of the Smoky Bush Tyrant (Myiotheretes fumigatus) from Ecuador.
Abstract: We report the first nest of the Smoky Bush Tyrant (Myiotheretes fumigatus) which was found on 11 October 2009 at the Yanayacu Biological Station, Napo Province in Ecuador. The nest was a shallow open cup, 2 m above ground on the side of a dead stump covered in epiphytes. The nest was 12 cm wide by 6.5 cm in height; internally, the cup was 7 cm wide by 4 cm deep and was lined predominantly with scales from the tree-fern (Cyathea spp.), but included a few small sticks and brightly colored feathers. Both eggs were predominantly white with a few small, widely dispersed, chocolate brown spots, predominantly around the fattest area. They measured 24.0 X 18 and 23.0 X 17.5 mm, and weighed 3.6 and 3.5 g, respectively. The first fully feathered fledgling left the nest on 2 November and the second on 3 November, for a nestling period of 16-17 days. We noted the presence of a third bird (besides the pair) which remained within the territory through the entire nesting period, at times in close association with the breeding pair.
Article Type: Report
Subject: Tyrant flycatchers (Research)
Birds (Eggs and nests)
Birds (Research)
Authors: Stawarczyk, Tadeusz
Borowiec, Marta
Greeney, Harold F.
Simbana, Jose T.
Pub Date: 03/01/2012
Publication: Name: The Wilson Journal of Ornithology Publisher: Wilson Ornithological Society Audience: Academic Format: Magazine/Journal Subject: Biological sciences Copyright: COPYRIGHT 2012 Wilson Ornithological Society ISSN: 1559-4491
Issue: Date: March, 2012 Source Volume: 124 Source Issue: 1
Topic: Event Code: 310 Science & research
Geographic: Geographic Scope: Ecuador Geographic Code: 3ECUD Ecuador
Accession Number: 285207259
Full Text: Bush tyrants are a group of four New World flycatchers (Tyrannidae) which, together with >20 other genera, belong to subfamily Fluvicolinae (Fitzpatrick 2004, Ohlson et al. 2008, Tello et al. 2009). The Smoky Bush Tyrant (Myiotheretes fumigatus) occurs on both slopes of the Andes from western Venezuela and northern Colombia to Peru. The nominate subspecies, fumigatus, occurs in northern Ecuador, while ssp. cajamarcae occurs in southern Ecuador and adjacent Peru, mostly from 2,000 to 3,200 m asl (Ridgely and Greenfield 2001, Fitzpatrick 2004).

Ridgely and Greenfield (2001:511) stated the Smoky Bush Tyrant "generally remains inside forest," but reported this species to be most frequent in the subcanopy of humid montane forest edges and shrubby slopes or grassy regions with scattered trees. We conducted our studies in the vicinity of the Yanayacu Biological Station and Center for Creative Studies, 5 km west of Cosanga, Napo Province, Ecuador, at an altitude of ~2,100 m asl. The habitat in the area is dominated by montane cloud forest, interspersed with several small, semi-open clearings. One pair of birds occupied a small natural clearing dominated by Chusquea bamboo surrounded by high trees; another pair was observed in a larger area of Chusquea bamboo with scattered low trees. A third pair, which was attending a nest, was in a pasture with scattered bushes and small trees.

OBSERVATIONS

We flushed an adult Smoky Bush Tyrant on the afternoon of 11 October 2009 from a dead stump in a pasture behind the Yanayacu Station. The adult gave alarm calls as it changed perches several times, and was soon joined by a second adult. Unexpectedly, a third adult appeared but seemed to elicit no reaction from the alreadypresent adults. We did not search for the nest that evening as darkness was approaching. We returned the following morning and observed an adult entering the nest in a dead stump.

Nest.--The nest was a shallow open cup, 2 m above ground on the side of a dead stump covered in epiphytic mosses, ferns, orchids, and bromeliads (Fig. 1A). The supporting trunk was 3 m tall in a re-growing pasture 30 m from the forest edge. The nest was sunk into naturally growing moss, and its exact outer dimensions were difficult to measure; it was ~12 cm wide by 6.5 cm in height. The egg cup measured 7 cm wide X 4 cm deep. The outer portion of the cup was constructed principally of moss intertwined with sparse rootlets. The cup was lined predominantly with scales from the tree-fern (Cyathea spp.), but included a few small sticks and brightly colored feathers (Fig. 1B).

Eggs.--The nest on first inspection (12 Oct), contained two well-incubated eggs. Both eggs were predominantly white with a few (~10) small, chocolate brown dots, widely dispersed and predominantly around the thickest part (Fig. 1C). They measured 24 X 18 and 23 X 17.5 mm and weighed 3.6 and 3.5 g, respectively. Both eggs hatched on 17 October.

Incubation.--A HOBO temperature logger was placed in the nest on 12 October. The logger recorded temperature, once every minute, in the nest lining below the eggs and simultaneously in a protected location within the epiphytes 1 m below the nest. We used the relative differences in temperature between these readings to record adult presence or absence from the nest. The nest was filmed most days from 15 October to 3 November with a tripod-mounted digital video camera placed ~15 m from the nest. We used video records of adult presence to help interpret changes in nest temperature and to identify daily incubation rhythms. Mean daily attendance was 69 [+ or -] 5% of daylight hours during the final 6 days of incubation (including day of hatching). Mean periods of adult absence during the entire observation period were 18 [+ or -] 9 min (n = 58), while mean periods of attendance were 41 [+ or -] 31 min (n = 53).

Nestlings.--We examined the nestlings on 17 October, the day of hatching. They had yellow pink skin, were blind and mainly naked but with quite dense, fawn-colored natal down ~10 mm long on the coronal, occipital, and dorsal tracts (pterylography follows Wetherbee 1957). The young weighed 5.0 and 3.6 g, respectively. We weighed the nestlings on 23 October, when they weighed 21.7 and 19.2 g, respectively and on 26 October when they weighed 27.7 and 24.4 g, respectively. The first fully feathered fledgling left the nest on 2 November and the second on 3 November, for a nestling period of 16-17 days.

[FIGURE 1 OMITTED]

Parental Care.--Adult Smoky Bush Tyrants do not show sexual dimorphism and were not individually marked; we were unable to describe the role of the male and female in parental care. However, two adults took part in incubation, as in three cases both birds were visible simultaneously while changing places at the nest. Similarly, both parents cared for the nestlings, occasionally arriving simultaneously at the nest with food. Adults did not fly straight into the nest when approaching but stopped at a few preferred perches for 10-30 sec, apparently surveying the area surrounding the nest. We saw adult Smoky Bush Tyrants aggressively pursuing a Tropical Kingbird (Tyrannus melancholicus) on three occasions and twice chasing a Pale-edged Flycatcher (Myiarchus cephalotes), when these species approached to within 15-20 m of the nest. The bush tyrants began calling on one occasion when two Inca Jays (Cyanocorax yncas) passed nearby. We observed no aggressive behavior towards other bird species passing through the Smoky Bush Tyrant territory.

The third bird, first seen on the day of the nest's discovery, was later observed on several other occasions. It was not seen closer than 15-20 m during incubation. The third bird was observed closer to the nest after nestlings hatched, but was not recorded carrying food or feeding nestlings. It visited the nesting site on one occasion when both parents were within 1.0-1.5 m of the nest. It was fully tolerated by both parents and was not chased as with other intruders.

An adult brooded for 70.3% of the observation period during the first 2 days after hatching (7.3 hrs of filming), remaining in the nest for an average of 34 min per brooding bout (n = 9, range = 14-74 min). An adult brooded for 62.9% in the next 3 days (16.7 hrs of filming) and stayed in the nest for an average of 11.8 min per brooding bout (n = 78, range = 2-39 min). The parents brooded for only 5% of daylight observation periods during the second week of observation and stopped brooding entirely in the third week.

Adults provisioned young at a rate of 0.6 times per nestling/hr (9 trips in 7.3 hrs), when the nestlings were 1-2 days of age but, during the next 3 days (nestlings = 3-5 days of age), they provisioned at a rate of 2.3 times per nestling/hr (n = 78 trips in 16.7 hrs). The provisioning rate increased to 4.0 times per nestling/hr (n = 167 trips in 21 hrs) during the second week, whereas in the third week the provisioning rate was 4.3 times per nestling/hr (n = 136 trips in 14.2 hrs). The parents delivered 415 food items during 59 hours of filming, across the entire observation period.

DISCUSSION

The breeding biology of Myiotheretes bush tyrants is poorly known. There is only one species, Streak-throated Bush Tyrant (M. striaticollis), for which the nest is described as "a messy cup under bridge or overhanging structure" (Fitzpatrick 2004: 389). The breeding period of this species was in January-June in Colombia and nestlings were reported in early March in Venezuela (Fitzpatrick 2004).

Some details of breeding biology of the Rufous-webbed Bush Tyrant (Polioxolmis rufipennis) are known, a species now placed in a separate genus but which is closely related to Myiotheretes (Ohlson et al. 2008, Tello et al. 2009). Vuilleumier (1994) originally described the nest as belonging to Myiotheretes rufipennis. The two described nests of this species were at elevations ~4,000 m asl in northern Peru. Both were in open areas near the top of the giant bromeliad (Puya raimondii) (Bromeliaceae), 2.5-2.8 m above the ground. These nests were open cups made of twigs and grass stems, and lined predominantly with pieces of Puya seed down and a few feathers (Vuilleumier 1994: 4-5). The nest of the Smoky Bush Tyrant was in similar open habitat, at a similar height above the ground, and was similarly constructed. The nest, however, was better concealed among epiphytes. Fjeldsa (1990: 27) described the nest of the Rufous-webbed Bush Tyrant as "a rather flimsy and open cup of stalks and thin twigs placed just below the top of 5 m tall Polylepis tree overhanging a stream". It remains to be learned how much variability of nest placement and structure occurs within this group of species. Both nests of the Rufous-webbed Bush Tyrant in Peru were found in late October, when young were nearly ready to fledge (Vuilleumier 1994). Thus, the nest we observed agrees more with an October-November breeding season for the Rufous-webbed Bush Tyrant than for the Streak-throated Bush Tyrant breeding from January to June. Nesting during the drier months in our area agrees with the breeding cycles of most high-Andean species in eastern Ecuador (Greeney et al. 2011) and with most tyrannids at our study site (e.g., Greeney et al. 2005, Greeney 2007). This includes other species nesting in similar habitat, e.g., Smoke-colored Pewee (Contopus fumigatus), (Dyrcz and Greeney 2010); Pale-edged Flycatcher (Dyrcz and Greeney 2011); and Cinnamon Flycatcher (Pyrrhomyias cinnamomeus) (H. F. Greeney, unpubl, data).

The described eggs correspond well to most fluvicoline flycatchers which have white eggs with scattered, small reddish to blackish spots (Schonwetter 1971). Allocation of the natal down of young seems to be typical as for some other open cup nesting tyrannids (Wetherbee 1957, Collins and Keane 1991).

The presence of a third adult which remained in close association with the breeding pair, throughout the entire nesting period is of interest. Most of our observations were through a camera, and we could not tell the birds apart. Thus, it cannot be excluded that eggs were incubated by the third bird, which would suggest helpers at the nest. Fitzpatrick (2004) reported that juveniles of tyrant flycatchers stay for many months with their parents. He mentions only one example, a Cliff Flycatcher (Hirundinea ferruginea), where three birds were observed attending a single nest in Argentina. More recently, Dyrcz and Greeney (2011) observed fledgling Pale-edged Flycatchers remaining with their parents for >3 months at our study site. This is one of the least-studied aspects of parental care for tropical tyrannids, and it is unknown if long post-fledging dependency periods are normal.

ACKNOWLEDGMENTS

We thank both reviewers and the editor for stimulating remarks which helped us improve this manuscript.

Received 4 March 2011. Accepted 15 July 2011.

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Tadeusz Stawarczyk, (1,3) Marta Borowiec, (1) Harold F. Greeney, (2) and Jose T. Simbana (2)

(1) Museum of Natural History, University of Wroclaw, Sienkiewicza 21, 50-335 Wroclaw, Poland.

(2) Yanayacu Biological Station and Center for Creative Studies, Napo Province, Cosanga, Ecuador, c/o Foch 721 y Amazonas, Quito, Ecuador.

(3) Corresponding author; e-mail: stawar@biol.uni.wroc.pl
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