Nest survival is critical to breeding in birds and plays an important role in life‐history evolution and population dynamics. Studies evaluating the proximate factors involved in explaining nest survival and the resulting temporal patterns are biased in favor of temperate regions. Yet, such studies are especially pertinent to the tropics, where nest predation rates are typically high and environmental conditions often allow for year‐round breeding. To tease apart the effects of calendar month and year, population‐level breeding activity and environmental conditions, we studied nest survival over a 64‐month period in equatorial, year‐round breeding red‐capped larks Calandrella cinerea in Kenya. We show that daily nest survival rates varied with time, but not in a predictable seasonal fashion among months or consistently among years. We found negative influences of flying invertebrate biomass and rain on nest survival and higher survival of nests when nests were more abundant, which suggests that nest predation resulted from incidental predation. Although an increase in nest predation is often attributed to an increase in nest predators, we suggest that in our study, it may be caused by altered predator activity resulting from increased activity of the primary prey, invertebrates, rather than activity of the red‐capped larks. Our results emphasize the need to conduct more studies in Afro‐tropical regions because proximate mechanisms explaining nest predation can be different in the unpredictable and highly variable environments of the tropics compared with the relatively predictable seasonal changes found in temperate regions. Such studies will aid in better understanding of the environmental influences on life‐history variation and population dynamics in birds.
Understanding the habitat selection and structure of a species is critical for developing evidence-centered conservation actions. Sharpe’s Longclaw Macronyx sharpei, a passerine bird endemic to Kenya, is threatened by reductions in habitat size and quality that have left it inhabiting a small and highly fragmented range. From January to June 2016 we investigated the abundance and density of Sharpe’s Longclaw in Marania farm located in Meru county in the northern sector of Mt. Kenya, where no previous study had been done. Population abundance and density were determined using the flush and count method. We observed that these birds were exclusively found in grasslands, being most abundant in habitats of short grass with tussocks, and less so in areas with tall grass. This habitat specificity indicates a key requirement for survival of Sharpe’s Longclaw populations in this area. We recommend surveys in and around Marania farm to determine the distribution of suitable habitats for this species, and that the farm be designated an Important Bird Area. Further studies should also focus on determining the intensity of grazing that is compatible with conservation of Sharpe’s Longclaw populations.
Home‐range studies have received considerable attention from ecologists but are greatly skewed towards the north temperate areas. Tropical areas offer an ideal setting to tease apart hypotheses about weather, food availability and social interactions as important factors influencing home‐range. In this study, we investigated home‐range and movement patterns of the tropical Red‐capped Lark Callandrella cineria, a year‐round breeding bird with a dynamic social structure. We tracked 56 individuals using radiotransmitters and colour‐ring readings over a 23‐month period. Our objective was to understand year‐round variation in home‐range size in the context of the highly aseasonal and unpredictable variation in weather and resources typical of many equatorial habitats, in addition to the birds’ changing social structure and year‐round breeding. The mean composite monthly home‐range of Red‐capped Larks was 58.0 ha, and the mean individual home‐range size was 19.9 ha, but this varied considerably between individuals. The total number of nests found per month (breeding intensity) best predicted home‐range size of non‐breeding birds, and of breeding and non‐breeding birds combined. We show for the first time that breeding intensity decreases the home‐range size of non‐breeding individuals. Our study also underlines the relevance of conducting more studies in aseasonal tropical areas in order to disentangle effects of weather, food availability and breeding that vary in parallel, peaking simultaneously in most seasonal areas.
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