Vega Rivera et al. • FLAMMULATED FLYCTACHER ECOLOGY 
763 
Description of Nest and Eggs .—JHVR found an 
empty Flammulated Flycatcher nest on 29 June 
2010 at the Chamela Biological Station (19 30' 
17" M. 105 02' 26" W, 94 m asl). The nest was 
along the Ardilla Trail on a hillside covered by 
primary deciduous forest; the canopy height was 
"8 m. The nest was inside a cavity of a dead tree 
(Croton spp.. Euphorbiaceae), which was 6 m tall 
with a DBH of 17 cm (Pig. 2A). The cavity 
entrance was 2.1 m above ground and measured 
8.3 cm wide X 18.2 cm in length. The nest cavity 
was 7.8 cm wide and 15 cm in length. The nest 
was lined mostly with thin dark fibers of Spanish 
moss (Tillandsia usnenides) and rachises (< 1 min 
in diam) of pinnate leaves (Leguminosae), 
accompanied by small fragments of dry leaves, 
shredded bark, an insect wing, small twigs, fungal 
mycelia, and fragments of snake skin. Man-made 
materials were absent (Fig. 2B). 
The nest had four eggs on 10 and 15 July. There 
were three nearly fully grown chicks on 27 July 
and part of the skeleton of the fourth young was 
still in the nest. The nest was empty and 
undisturbed on 30 July. Neither eggs nor chicks 
were visible from the entrance of the nest. We 
observed a single bird entering or leaving the nest 
on three occasions. Egg color and shape were 
similar to those of members of the genus 
Myiarchus : creamy white with brown circular 
spots at the wider end of the egg and turning into 
irregular streaks toward the narrow end. One egg 
measured 19.41 X 15.84 cm (Fig. 2C). 
DISCUSSION 
Previous authors (e.g., Schaldach 1963, Binford 
•989) described die Flammulated Flycatcher as an 
uncommon to rare endemic resident along the 
Mexican Pacific Slope as well as on our specific 
study area (Hutto 1989. Ornelas et al. 1993). Our 
data document this species is common during the 
breeding season and uncommon for the rest of the 
a pattern reported for other species in the 
Chamela region (Vega Rivera et al. 2003. 2004). 
This seasonal pattern of occurrence suggests the 
birds are wary of mist nets, or that at least part of the 
population undergoes local migrations to habitats 
not sampled in this study (e.g., secondary forests). 
Hutto (1989) during his surveys on 18-28 February 
1985 did not find this flycatcher in his study sites 
outside the Reserve; he reported this flycatcher 
occurring only in the “undisturbed forest ol the 
protected area. Ornelas ct al. (1993) suggested the 
low detection of D. flammulatus and other species 
in Chamela was either because they were rare or 
because they preferred more humid habitats. Our 
data suggest this hypothesis may be true as more 
birds were captured in the semi-deciduous forest 
during the dr)' season than in the wet season. It is 
evident that long-term studies and simultaneous 
sampling of a variety of habitats will be necessary 
to understand the spatial and temporal distribution 
of birds historically regarded as sedentary. 
The end of the dry season seems to mark the 
beginning of the breeding season for this species 
and other passerines (Ornelas et al. 1993; Vega 
Rivera 2003, 2004). We captured 38 birds in 
breeding condition. However, only 15 females 
had well-developed brood patches and two males 
had cloacal protuberances and a partially devel¬ 
oped brood patch. These birds were captured 
between 27 June and 24 July, which corresponds 
with the beginning of the rainy season and the first 
annual peak in insect production in Chamela 
(Lister and Garcia 1992). The only other record 
for comparison is that of Lanyon (1982) who 
reported a nesting pair with three eggs on 18 June. 
Myiarchus flycatchers are also cavity nesters, 
and they incorporate feathers, fur, and shed 
reptilian skin in the nest lining (Lanyon 1978). 
Traylor (1977 in Lanyon 1978:414), regarding the 
relationship of Myiarchus and Deltarhynchus, 
wrote: “Unfortunately nothing has been published 
on the anatomy or behavior of flammulatus. If it is 
found to be a hole nester using a few scraps of 
snake skin for decoration, it should certainly be 
merged in Myiarchus." Lanyon (1982) provided 
the first record of nest and eggs of this species and, 
to our knowledge, the single published study on 
this species. Lanyon (1982:421) concluded, “there 
is nothing in the external morphology, foraging 
behavior, vocalizations, coloration of the eggs, or 
the use of a cavity for nesting that would justify 
generic separation of Deltarhynchus. However, 
based on the characteristic of the nest, which 
•“being located in a comparatively shallow cavity 
and in lacking fur. feathers, and shed reptilian skin 
or substitutes in its conservationhe cautiously 
concluded that "Deltarhynchus should be consid¬ 
ered a close relative of the Myiarchus assemblage 
of tyrant flycatchers but merits separate generic 
status.” Our observations regarding the nest of the 
Flammulated Flycatcher add evidence against this 
conclusion. The nest's lining included small pieces 
of skin of an unknown reptilian species and the nest 
was as deep (15 cm) as those described for 
Myiarchus flycatchers. 
