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Dr Rob Pople
Email: rob.pople
at cantab.net
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From:
Pople,
R. G. (2003)
The ecology and conservation of the White-winged Nightjar
Caprimulgus candicans.
University of Cambridge, UK (Ph.D. dissertation). |
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THESIS
SUMMARY
[PDF version
available in English (download),
in Portuguese (download)
and Spanish
(download)]
In the tradition
of previous studies of threatened species, this thesis was undertaken
with the aim of improving our understanding of the ecology of the
White-winged Nightjar Caprimulgus candicans [= Eleothreptus
candicans], and providing the information necessary to facilitate
conservation efforts on its behalf. In 1998-2001, I studied a population
of White-winged Nightjars at Aguará Ñu, an area of
cerrado habitats within the Reserva Natural del Bosque Mbaracayú,
eastern Paraguay. Over the course of three fieldwork seasons, I
captured and ringed a total of 49 nightjars (34 adults and 15 young
birds). Young females first bred at approximately one year old,
while still in pre-definitive plumage. Young males exhibited a form
of delayed plumage maturation, whereby they only attained definitive
plumage following a prolonged moult spanning much of their first
potential breeding season. No evidence was obtained to suggest that
they succeeded in breeding while in this conspicuously intermediate
state of moult. Considerable variation was noted in the plumage
whiteness of definitive males, but no clear evidence was found for
consistent age-related increases in white. During the breeding season,
males defended small aggregated display territories, at which they
conducted nuptial display flights between late August and early
January. Female nightjars were responsible for all the parental
care, and apparently visited male display arenas solely to obtain
copulations. Chick paternity data confirmed that the study population
was polygynous, with patterns of male aggregation suggestive of
an exploded lek or ‘landmark’ mating system.
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Radio-telemetry
studies showed that nightjars utilised home ranges of at least
20 to 40 hectares during the eight to ten months for which they
were monitored. Home ranges contained a disproportionately large
amount of young campo cerrado vegetation, but no forest or old
campo cerrado habitats. When selecting foraging sites within
their ranges, nightjars preferred younger and avoided older
campo cerrado vegetation; wet grassland was utilised roughly
in proportion to its availability. Observed patterns of habitat
selection were potentially explained by the greater abundance
of insect prey in younger habitats. When selecting daytime roost
sites, nightjars preferred vegetation of intermediate age, reflecting
their need for a balance between cover and ease of access. A
more general analysis of patterns of sexual dimorphism within
the Caprimulgidae showed that, although almost 80% of nightjar
species exhibit some dimorphism of plumage whiteness, the study
species was by far the most extreme case. The striking plumage
of the male was partly explained by a strong positive relationship
between wing white and openness of breeding habitats within
the family. However, this failed to explain the complete absence
of white in the female plumage, or the extent of white dimorphism
shown by the species. The most likely explanation would appear
to be that extreme
plumage dimorphism occurred in conjunction with the evolution
of polygyny and female-only care in this open-country species.
The implications of these findings for the conservation of the
White-winged Nightjar are highlighted, and recommendations are
proposed for future work and conservation action.
To download a PDF of the full thesis, please visit DSpace@Cambridge. |
Cerrado
habitat of the White-winged Nightjar
Displaying male White-winged Nightjar
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Publications |
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- Cordeiro
NJ, Seddon N, Capper DR, Ekstrom JMM, Howell KM, Isherwood IS,
Msuya CAM, Mushi JT, Perkin AW, Pople RG and Stanley WT (2005)
Notes on the ecology and status of some forest mammals in four
Eastern Arc Mountains, Tanzania. Journal of East African Natural
History 94, 175–189.
- Capper DR,
Clay RP, Madroño Ñieto A, Mazar Barnett J, Burfield
IJ, Esquivel EZ, Kennedy CP, Perrens M & Pople RG (2001) First
records, noteworthy observations and new distributional data for
birds in Paraguay. Bulletin of the British Ornithologists'
Club 121: 23-37.
- Seddon N,
Ekstrom JMM, Capper DR, Isherwood IS, Muna R, Pople RG, Tarimo
E, Timothy J 1999 Notes on the ecology and conservation status
of key bird species in Nilo and Nguu North Forest Reserves, Tanzania.
Bird Conservation International 9: 9-28.
- Seddon N,
Ekstrom JMM, Capper DR, Isherwood I, Muna R, Pople RG, Tarimo
E, Timothy J 1999 The importance of the Nilo and Nguu North Forest
Reserves for the conservation of montane forest birds in Tanzania.
Biological Conservation 87: 59-72.
- Clay RP,
Capper DR, Mazar Barnett J, Burfield IJ, Esquivel EZ, Fariña
R, Kennedy CP, Perrens M & Pople RG (1998) White-winged Nightjars
Caprimulgus candicans and cerrado conservation: the key
findings of Project Aguará Ñu (1997) Cotinga
9: 52-56.
- Pople RG,
Burfield IJ, Clay RP, Cope DR, Kennedy CP, López-Lanús
B and Warren B (1997) Project Ortalis '96: interesting and important
results of bird surveys in western Ecuador. Cotinga 8,
59–63.
- Pople RG,
Burfield IJ, Clay RP, Cope DR, Kennedy CP, López-Lanús
B, Reyes J, Warren B & Yagual E (1997) Bird surveys and conservation
status of three sites in western Ecuador: final report of Project
Ortalis '96. Cambridge, UK: CSB Conservation Publications.
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