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Breeding biology of the White-winged Nightjar (Eleothreptus candicans) in eastern Paraguay

2014; Springer Science+Business Media; Volume: 22; Issue: 2 Linguagem: Inglês

10.1007/bf03544249

2178-7875

Robert G. Pople,

Plant and animal studies

Breeding biology of the White-winged Nightjar (Eleothreptus candicans) in eastern Paraguay. I present the first detailed description of the breeding biology of the White-winged Nightjar (Eleothreptus candicans), based on data collected over three breeding seasons during 1998-2001 at Aguará Ñu, Canindeyú, eastern Paraguay. Male nightjars defended small territories situated on the upper slopes of ridgelines. Each territory contained one or more “display arenas” at which the male performed nuptial display fights. Aggregation indices confirmed that the primary display arenas of males were significantly clustered within the survey area. Within their territories, males apparently selected display arenas on the basis of their structural characteristics: mounds used as arenas were significantly lower and broader than random mounds. Males engaged in display activity from late August to early January. On average, males performed 0.54 ± 0.04 display fights per minute during nocturnal focal watches, but there was considerable intra-male variation in display rate. Following a burst of activity immediately after their arrival at display arenas at dusk, male display rate was best explained by ambient levels of moonlight. Males produced a previously undescribed insect-like “tik tik” call when inactive on their territories. Females made two nesting attempts per season, using a different site (360 ± 31 m apart) for each attempt. The clutch of two eggs was laid directly on the ground, adjoining a small access “clearing”, in either campo cerrado or wet grassland vegetation. The first egg was laid within two days of a full moon for all seven clutches for which laying date was confirmed. Incubation, brooding and chick provisioning duties were carried out exclusively by the female. The incubation period was 19 days and the nestling period c. 19–20 days. Overall, my data are consistent with polygyny — and even an exploded lek or “landmark” mating system — in this population of White-winged Nightjars.