Biomass, abundances, and abundance and geographical range size relationship of birds along a rainforest elevational gradient in Papua New Guinea.

Although, studies reporting a positive trend ( Theuerkauf et al., 2017 ) or no trend ( Freeman, 2018 ) in the tropics also exist.

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However, the relationship of the three bird groups with different elevational weighted mean points showed a variable pattern, as the trend changed from a positive relationship in the lowland group of species, to no trend for middle species, and a negative trend for montane species ( Fig.

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