Phenology, Habitat Use, and Nesting of the Red-Breasted Chat (Granatellus venustus)

2004·3.5 MB·English

by  Jorge H Vega Rivera

Wilson Bulletin, 1 16(1), 2004, pp. 89-93
PHENOLOGY, HABITAT USE, AND NESTING OF THE
RED-BREASTED CHAT {GRANATELLUS VENUSTUS)
JORGE H. VEGA RIVERA,' ^ EERNANDO ALVARADO,' J. MANUEL LOBATO,'
AND PATRICIA ESCALANTE^
—
ABSTRACT. From March 1999 to August 2000, we conducted monthly mist netting in the Chamela-Cuix-
mala Biosphere Reserve, Jalisco, Mexico to document the phenology and habitat use ofthe Red-breasted Chat
{Granatellus veniistiis). We collected information on its nesting biology during the breeding season of 2001.
Chats {n = 116) were caught throughout the 18 months of the study; however, far fewer captures occurred
during the dry season than during the wet season. Our capture data revealed that chats made greater use of
deciduous {n = 88) than semi-deciduous forest {n = 28); there were no interactions among forest type, season,
and gender. Birds in breeding condition were capturedJune-Septemberand moltingbirds werecapturedAugust-
October. We found 10 cup-shaped nests in June and July. Nests were 48-103 cm above ground in saplings <2
mhigh. Clutch sizewas3-4andonlythefemale incubated.The incubationperiodwas 14days, andweestimated
the nestling period to be approximately 8-10 days. Of eight nests found with eggs or young, three were dep-
redated during the egg stage, three during the nestling stage, and two were successful. Received29June 2003,
accepted 18 March 2004.
The New World genus Granatellus includes chats only twice during 2 years of work in the
three species that occur in southwestern Mex- region of Chamela, Jalisco. Its relatively lim-
ico (Red-breasted Chat, Granatellus venus- ited distribution, the lack ofinformation on its
tus), southern Mexico and northeastern Cen- basic biology, and the fact that it inhabits an
tral America (Gray-throated Chat, G. sallaei), endangered ecosystem (Janzen 1988, Lerdau
' and the Amazonian lowlands of South Amer- et al. 1991) made the Red-breasted Chat a pri-
I ica (Rose-breasted Chat, G. pelzelni) (Sibley ority species for study. Here, we report on its
and Monroe 1990). The conservation signifi- phenology and habitat use. We also provide
cance ofthese species is high because oftheir the first complete description ofnest and eggs,
relatively restricted range, but virtually no de- and some details on nesting biology.
tails of their life history are known. Also, the
systematic position of the genus is uncertain METHODS
(Lovette and Bermingham 2002). There is We conducted our study at the Chamela Bi-
only one description of a nest of thefrances-
ological Station (3,300 ha), which is part of
cae group ofG. venustus from the Tres Marias
the Chamela-Cuixmala Biosphere Reserve
Islands (Grant 1964), and a recent description
(hereafter, the Reserve), Jalisco, Mexico (19°
of two nests of Gray-throated Chats (Salgado- 22' to 19° 35' N and 104° 56' to 105° 03' W).
'1 OrtIi'zheetRaeld.-b2r0e0a1s)t.ed Chat is endemic to the tWienactthrearinyth(eJreuneistostOrcotngolbyer)seaasnodnadlrywsietahsodniss.-
tropical deciduous and semi-deciduous forest
1 of western Mexico from northern Sinaloa The Reserve (13,300 ha) is covered predom-
I inantly by undisturbed deciduous forest on
south to Chiapas (American Ornithologists’
II Union 1983). Schaldach (1963:81) included dforryeshtillesxidteesn,dwiintgh aplaotnchgesarorfoyseomif-ldoeocdipdluaoiunss
Red-breasted Chats “among the rarest birds of
(Lott et al. 1987). Within the Reserve, 24 bird
the Pacific slope of Mexico”; Alvarez del
species endemic to Mexico have been record-
I' TCohrioap(a1s98a0n)ddOerscnreilbaesdetthealm. a(s19u9n3)coombmsoernveidn eidc;o o(fArtihzomsee,nd2i0eatreal.en1d9e9m0i).c SteoeweVsetgearnRiM\eexr-a
I
I et al. (2003) for a detailed description of the
' F^.stacion dc Biologfa C’hamcla. Inst, do Biologfa. study area.
UNAM. Apt. 21 San Patricio, Jalisco. 48980. Mexico. From March 1999 to August 2000, we con-
’ Dcp. de Zoologfa. Inst, dc Biologfa. IINAM, Apt. ducted monthly mist netting along four 3-km-
70-'1C.oSr3,reMsepxoincdoi.ngHIa-ut0h4or.S;Ie1,-mMaeilx;ico. long trails, separated from each other by 1 km.
jhvcga(ohbiologia.unam.mx file tlominant vegetation types were decidu-
90 THE WILSON BULLETIN • Vol. 116, No. I, March 2004
OLis in = 2) and semi-deciduous {n = 2) for-
est. Every month for 3 consecutive days and
5 hr/day, we placed 12 mist nets (12 m X 2.5
m, 6-mm mesh) along each trail; nets were
separated by 100 m. Each chat we captured
was banded with numbered aluminum bands
and processed for body mass (to 0.1 g with a
50 g Pesola spring scale), bill and tarsus
mm
lengths (to 0.05 using dial calipers), and
mm
length of unflattened wing chord (to 0.5
using a flat-ended 15-cm ruler). We deter-
mined whether chats were in breeding condi-
tion by evaluating the presence ofcloacal pro-
tuberance or brood patch. Age was evaluated
by plumage and, for hatch-year birds, by the
presence of unpneumaticized areas in the
skull.
Erom May to August 2001, we walked
along trails looking for singing males. Once
we identified a male’s territory, we searched
intensively for the nest. Nest-building, food-
delivery, and alarm behaviors were used to
help us locate nests. Nests were visited every
3 days until clutch completion; nests with
complete clutches were visited every day until
hatching. We measured and weighed chicks 2
days after the last chick had hatched. Nests Month(1999-2000)
werWeemaesasseusrseedd ahfatbeirtaftleudsgeing(.deciduous versus RedF-IbGr.eaIs.tedMoCnhtahtsly(Ad)i,stprriobputoirotnioonfocfapbtiurrdessinofbraedeudl-t
semi-deciduous forest; dry versus rainy sea- ing condition (B), proportion ofbirds molting (C), and
sons) and quality by examining chat abun- precipitation (D) in the Chamela-Cuixmala Biosphere
dance, age ratio, yearly persistence, and body Reserve, Jalisco, Mexico, 1999-2000.
mass corrected for wing length. Yearly persis-
tence was calculated as the proportion ofchats
marked during the breeding season (June to mist netting. Of those, 21 were hatch-year
September) that were recaptured in the study (HY) birds and 95 were after-hatch-year birds
site during the dry months ofJanuary to April. (54 males and 41 females). Monthly captures
We used nonparametric Mann-Whitney U- (including recaptures) differed between sea-
tests (MINITAB, Inc. 1996) to compare cap- sons (Fig. lA). From May to September
tures between seasons and to determine gen- (breeding season), the average numberofcap-
der differences in mass and wing chord. We tures per month was 14.0 ± 10.0, whereas
tested the null hypothesis of mutual indepen- during the rest of the year (non-breeding sea-
dence among variables (forest type X season son) it was 3.0 ± 2.6 (Mann-Whitney f/-test,
X gender) by a chi-square three-way test of U = 46, P = 0.034). Chats in breeding con-
independence. Since the hypothesis was not dition were captured from June through Sep-
rejected, we did not test for partial indepen- tember in — 50), with the proportion of birds
dence (Zar 1996:507). Statistical significance in breeding condition peaking in July (Fig.
was set at a < 0.1. All values are reported as IB). Females tended to move longer distances
mean ± SD. between yearly recaptures (300 ± 386 m) than
males (1 15 ± 109 m; f/ = 860, df = 54, P -
RESULTS
0.092). Eight males and five females captured
—
Phenology. We captured 1 16 chats (first during the 1999 nesting season were recap-
captures only) during the 18-month period of tured in the same nets the following nesting
Rivera et al. • RED-BREASTED CHAT ECOLOGY 91
j cseeamsboenr(t2h0r0o0u)g.hAFllebrbiuradrsyc(anpt=uHreY8d) fwreorme DHeY=- andTAmBasLsE(g1). ofMo1r0p-hdoaly-ooglidcaRledm-beraesausrteemdenCthast(nmesmt)-
and second-year males, and all birds (/? lings (n = 6) and adults (n = 85) in the Chamela-
2 were captured September-December. Cuixmala Biosphere Reserve, Jalisco, Mexico, 1999-
1)
Based on 13 adult chats captured during 2000.
molt, a complete prebasic molt occurred from
' wAeurgeusctapttourOecdtoibnerS.epSteevmebnermaonldtiOncgtoHbYerb(iFridg.s WMaisnsg chor(j 349..N11est±±ling02s..74 5172..A11dul±±ts^21..30
f 1C); from four individuals recaptured after Tarsus 18.5 ± 0.8 19.8 ± 0.6
i their second prebasic molt, we confirmed that Culmen 4.2 ± 0.4 12.3 ± 1.9
immatures attain adult plumage by the second
\ prebasic molt. In May, we captured four chats (ma“leR;ed-1b2.r1e7as±te0d.8C2h;aftesmalseh:ow1e1d.75si±gn0i.f9i0ca;ntMagnenn-dWehritdnieffyerteesntc.eUs =in3,m0a2s1s.
jj with light molt—on the neck and head. d5f5.4=25±6,17.275,;PU<=02..011546).adfnd=w5i6n.g7c2.hoPrd<(m0a.l0e1:).58.30 ± 1.89; female;
Habitat use. Significantly more individu-
I;
als were captured in the deciduous forest {n
= 88) than the semi-deciduous forest {n = 28) and mean inner rim diameter was 5.2 ± 0.9
cm.
and there were no interactions among forest
type, season, and gender (y^ = 8.04, df = 4, We found one nest before egg laying, six
P > 0.10). Yearly persistence was lower in the during incubation, one with nestlings, and two
\ dfoerceisdtuo(u0.s14()0,.1b1u)ttshmaanllinstahmeplseemsii-zdeescidduuroiunsg w±it0h.2pimecmes(roafngeeg:gs1he7l-l2.0Emgmg)s abvyer1a4g.3ed±108..26
j the dry months (seven and three, respectively) (range: 13-17 mm); eggs were white with
precluded us from conducting a statistically smooth surfaces. Only females were observed
! meaningful analysis. No differences occurred incubating; males spent most ofthe time sing-
j in corrected body mass for individuals cap- ing nearby. Both females and males were ex-
tured in deciduous (0.21 ± 0.002) versus tremely wary and typically they departed
semi-deciduous forests (0.20 ± 0.003; U = when we approached the nest. Ba.sed on the
6,469, P = 0.63). Corrected body mass was nest found before egg laying, chats laid one
lower during the dry season (0.20 ± 0.001) egg per day until clutch completion (four
than in the rainy season (0.22 ± 0.002; U = eggs); the incubation period lasted 14 days.
3,353, P < 0.01). Just-hatched chicks were without feathers
Nesting biology.—We found 10 nests in and had their eyes closed. At 3 days of age,
July, in both deciduous (/? = 8) and semi-de- nestlings had visible pinfeathers on their dor-
ciduous (// == 2) forest. Nests were attached to sal and ventral tracts; rectrices and remiges
a horizontal fork formed by two or three twigs barely protruded at this stage. At 10 days,
(4.3 ± 0.2 mm diameter) in saplings 141 ± feathers in all regions were breaking sheaths;
26 cm high (range: 82-175 cm) and 16 ± 1.3 rectrices and remiges were almost entirely in
mm sheaths. Primaries and secondaries were
dbh of Euphorbiaceae {Croton piranii-
brown-gray, and primary and secondary co-
clalis), Myrsinaceae (Arc/isia spp.), Rubiaceae
verts were gray with pale-brown margins (see
{Ranclia spp.), Acanthaceae, and Cappareceae.
Table for measurements and weights).
Mean nest height above the ground was 73 ± I
Both males and females fed nestlings; dur-
19 cm (range: 48-103 cm).
The cup-shaped nests had very thin walls; siengnttehde ffiorostdfetwo dfaeymsaleosf,brwoohdoingt,hemnalfeesd prteh-e
eggs were visible through some areas of the young. Young fledged at 8-10 days ofage. but
walls. Primary materials used in nest con- this may be an underestimate of fledging age
struction were Spanish moss CPillandsia spp.).
thin (<l mm) tendrils ofCucurbitaceae, inflo- dfuoeundtowoiutrh eagctgis\aiitiuelsoantenwesittsh.neOsftlisieigvse.nyoneusntgs
rescences of Ixissiasis spp., thin dark libers,
fledgetl from only two; three nests with eggs
and spider silk; nests were lined with the finer and three with young were tleprcdatc(.i.
materials. Fiber-like epiphytes (Spanish moss)
hung 20-30 cm below the main nest cup, ob- DESCTi.SSION
scuring nest outlines and making nests t|uite .Survey tlata suggest that Rctl-breastcd
cryptic. Mean nest depth was 4.7 ± 0.3 c!ii C'hats are imcommon along the Pacific slope
92 THE WILSON BULLETIN • Vol. 116, No. 1, March 2004
(Schaldach 1963) and in our study area (Hutto Nests of the Red-breasted Chat resemble
e1t99al3.) 1985; Hutto 1989, 1994; Ornelas et al. those described for the insular subspecies, G.
. According to our data, chats are per- V. frcmcescae (Grant 1964), and the Gray-
manent residents in the Chamela-Cuixmala throated Chat (Salgado-Ortiz et al. 2001). Nest
Biosphere Reserve, where they were very dimensions and location are similar, but nei-
common during the breeding season and un- ther Grant (1964) nor Salgado-Ortiz et al.
common the rest of the year. We do not know (2001) mentioned material hanging from the
whether our data reveal real changes in the cup. Salgado-Ortiz et al. (2001) reported that
abundance of this species, or reflect the great- only females build the nest and incubate eggs;
er effort of this study. Nevertheless, it is puz- they also indicated that a complete clutch con-
zling that far fewer birds were captured during tains two eggs, whereas most ofour nests had
part of the dry season. This pattern suggests four eggs. We believe that this difference may
either that the birds may become less suscep- not be real, because they found only one nest
tible to trapping, or that at least part of the with a complete clutch.
population may migrate locally to higher el- Worldwide, tropical deciduous forest may
evations (American Ornithologists’ Union be the most endangered major tropical eco-
1983) or habitats not sampled during this system (Janzen 1988). In Mexico, only 21%
study (e.g., second-growth forest). Ornelas et ofthe original cover oftropical deciduous for-
al. (1993) suggested that the low detectability est remained in 1990, and less than 10% of
of this and other species in Chamela was ei- the area covered with deciduous forest is now
ther because they were rare or because they under some type of protection (Trejo and Dir-
preferred more humid habitats. However, as zo 2000). Stotz et al. (1996) stated that severe
we showed earlier, this species was neitherun- habitat disturbance in most dry-forest zones in
common, nor did it seem to prefer the more the Neotropics has greatly affected birds that
humid, semi-deciduous habitats. Low num- are deciduous-forest specialists. They identi-
bers recorded for this species could be due to fied the Red-breasted Chat as one of eight
its preference for second-growth habitats dur- “indicator” species for conserving tropical
ing the dry season. However, Hutto (1989, deciduous forest of the Pacific lowlands in
1994) did not find chats in his study sites out- Mexico. Currently, this forest type is only pro-
side the Reserve; he reported chats occurring tected in the Chamela-Cuixmala Biosphere
only in the “undisturbed” forest of the Re- Reserve. We hope the information we provide
serve. It is evident that long-term studies are here will aid in conservation efforts for this
necessary to understand the spatial and tem- species and its habitat.
poral distribution of birds historically regard-
ed as sedentary (Winker et al. 1997). ACKNOWLEDGMENTS
For the chat and other passerines, the end
Funding was provided by CONACYT, the Denver
ofthe dry season seems to mark the beginning
Zoological Foundation, and Instituto de Biologia.
of the breeding season (Ornelas et al. 1993; UNAM. Logistical support in the form of vehicles,
JHVR unpubl. data). Although the first chats equipment, and office space was provided by Estacion
in breeding condition were captured in June, de Biologia Chamela. Instituto de Biologia, UNAM.
other activities such as territory selection and We are indebted toT. Valdivia, D. Curiel, and I. Fariza
settlement, mate selection by females, nest- for assistance in the field. We thank A. Mehaan for
site selection, and construction of the nest, miamnpursocvriinpgt.thCeomEmneglnitssh firnomanR.eaHrluitetrovaenrdsiotnwoofantohni-s
may have been initiated earlier. The Yellow- ymous referees greatly improved our manuscript.
green Vireo {Vireoflavoviridis), a species that Partial funding for fieldworkwasprovided by Instituto
migrates from South America to breed in the de Biologia. UNAM and CONACYT (fellowship
Reserve, shows the same pattern; it arrives in # 167320 to FA).
the Reserve in May, but the first birds in
breeding condition appear in June (JHVR un- LITERATURE CITED
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