The Wilson Journal of Ornithology 124( 3):547—557, 2012 
NESTING BIOLOGY OF THE YELLOW-OLIVE FLATBILL 
(TYRANNIDAE. ELANINAE) IN ATLANTIC FOREST FRAGMENTS 
IN BRAZIL 
MARINA ANCIAES,' 43 THAIS MAYA AGUILAR,' LEMUEL OL1VIO LEITE, 2,3 RENATA 
DORNELAS ANDRADE, 1 AND MIGUEL ANGELO MARINE 
ABSTRACT.—The Yellow-olive Fiatbill (Tolmomyias sulphurescens) is a small insectivorous passerine inhabiting 
Ncoiropic forests. Us breeding biology is poorly know n despite its abundance and conspicuousness. We describe the nesting 
biology of Yellow-olive Flatbills from Atlantic Forest fragments in Belo liori/ontc County. Minas Gerais State, 
southeastern Brazil. Eighty nests were monitored every 2-5 days from August to January between 1995 and 2000. Active 
nests were found front mid-September through late December with a peak from mid October through late November. First 
dutches were usually laid during the first rains, but prior to the main peak in annual rainfall- The Yellow-olive Fiatbill 
builds closed, pencile nests oil tree branches along streams or rouds. principally of dark fungal (Marastnius sp.) fibers. 
Clutch size ranged from two to four white eggs. Incubation was irregular and hatching was asynchronous. Incubation and 
nestling periods were 20 and 23 days, respeemcly. Nesting success across all 5 y ears w as 29- r (i nean among years — 31%, 
Cl 25-37%). and nest predation was the main cause of nest failure (49% I. Mayfield estimates of nest survival were low 
imean = 26%. Cl = 17-36%). and the probability ol an egg to produce a fledgling was only 10%. Fledging success was 
0.8 fledglings per breeding pair, and chicks fledged at 107% (Cl = 106-108%) of mean adult body mass. Our results do not 
'upport the purported pattern of long breeding seasons for tropical birds. The Yellow-olive Fiatbill laid unusually large 
clutches, had lower nest survival, and greater fledgling productivity compared with other tropical passerines. Received 26 
April 2009. Accepted 23 March 2012. 
Studies of avian nesting biology are crucial for 
understanding many concepts in population biol¬ 
ogy. are relevant to evolutionary theory, and have 
many applications in conservation biology (Reed 
ei al. 1998, Duca et ul. 2009). Most studies of 
avian reproduction focus on temperate species 
(Stutchbury and Morton 2001). and studies on the 
reproductive ecology of tropical passerines are 
fewer (but see Marini 1992; Marini et al. 1997; 
Aguilar et al. 1999, 2000; Almeida and Macedo 
-901; Marini and Duraes 2001; Aguilar and 
Marini 2007; Duca and Marini 2004. 2005; Marini 
al. 2007). Nest architecture, brood size, and 
incubation time are all life history baits that 
impact individual fitness, and are subject to 
''election from environmental conditions such as 
Curso de Pos-Graduayiio cm Ecologia. Conservayao e 
Manejo da Vida Silvestre, t'FMG. Belo Horizonte, MG 
30161-970 Brasil. 
Departinento de Zoologia. 1CB, L'niversidadc de 
Brasilia. Brasilia. DF 70910-900 Brasil. 
Centro de Cicncias bioldgicas e da Saude. I niversidade 
Federal dc Montes Glares, Montes Cluros. MG 39401-089 
Brasil 
; Current address: Coordenayao de Biodiversidade e 
Programa de Coleyoes c Aeervos Cientificos. Instituto 
National dc Pesquisas da Ama/6nia-!NPA. Avenida Andre 
Araujo. 2936. Aleixo. Manaus. AM 69011-970 CP 478 
Brasil. 
'Corresponding author; 
e-maiI: marina.anciaes@gmai 1 .com 
food availability and predation (Mason 1985). 
Accumulating results on the breeding biology of 
tropical birds is crucial for testing hypotheses 
about the evolution of breeding strategies and the 
selective forces acting on populations nesting in 
different environments. For example, breeding 
cycles are influenced by changes in light levels 
and precipitation (Hau ct al. 2008, Wikelski el al. 
2008). Furthermore, few studies provide detailed 
information about the breeding biology of species 
based on large sample sizes, and frequently lack 
sufficient evidence for hypothesis testing (re¬ 
viewed by Ricklefs 2000). 
The Yellow-olive Fiatbill (Tolmomyias sul- 
plntrescem) is a common suboscine inhabiting 
neotropical forests throughout Central and South 
America (Ridgely and Tudor 1994). Virtually no 
information is available on its breeding biology, 
despite being relatively ubiquitous. The few data 
reported in the literature indicate the species lays 
an utypicallv large clutch for tropical passerines 
(3-4 eggs) (Sick 1997). Yom-Tov et al. (1994) 
reported an average clutch size of 2.7 for tyrant 
flycatchers in the tropics, and most species of 
tropical passerines lay only two eggs in contrast to 
the larger clutches of temperate species (Ricklefs 
1969. Stutchbury and Morton 2001). The Yellow- 
olive Fiatbill offers an exceptional opportunity for 
testing theories about evolution ol life history 
traits in tropical systems. 
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