No abstract

In an ecological community, groups of species may or may not have a nested structure. Furthermore, any nested structure detected could have several causes, each of which would have to be identified, since they may have important theoretical and management implications. In this paper, I assessed the nested structure of bird communities using cloud forest fragments in eastern Mexico to identify bird species and groups of species sensitive to cloud forest fragmentation. Sensitive species were expected to have a nested arrangement highly correlated with forest fragmentation intensity. Analysis identified the following groups of birds as showing a nested structure highly correlated with cloud forest fragmentation: birds with a body mass between 100 and 300 g and larger than 600 g, some trophic behavioural guilds (terrestrial granivore, terrestrial granivore–frugivore, understory granivore–frugivore, arboreal granivore–frugivore, gleaning terrestrial insectivore, gleaning understory insectivore, cliff gleaning insectivore, nocturnal aerial insectivore, diurnal raptor, nocturnal raptor, terrestrial omnivore, scavenger), forest interior and generalist birds, species restricted to cloud forest, and threatened species. This study shows that the analysis of the nested species assemblage can be considered a useful tool to identify species sensitivity to ecological or landscape patterns and processes, in this case, species or groups of species affected by a fragmented landscape pattern.

No abstract

We assessed the current conservation status and population trends of Cozumel Curassows (Crax rubra griscomi), a critically endangered and endemic cracid of Cozumel Island, Mexico. Distance sampling was used to estimate the population size in 2005 and compare it with a previous estimate in 1995. Population viability analysis (PVA) was used to model population trends, considering ecological and environmental conditions prevailing in 1995 and 2005. Additional PVA models were constructed using different hypothetical scenarios to assess the effects of particular factors and management strategies on population trends. We estimated a population size of 372 ± 155 curassows in the island's tropical semideciduous forest, before two hurricanes hit Cozumel Island in 2005. PVA modeling predicted a steep decline in population size in the ensuing decades as a result of an increased frequency and intensity of hurricanes related to global climate change, and an observed female bias in the sex ratio likely caused by a higher mortality rate for adult males. We recommend urgent management actions for the long‐term conservation of Cozumel Curassows, including a ban on hunting, eradication of the feral fauna, particularly dogs, and implementation of a captive‐breeding program to supplement the wild population.