Temperature‐associated decreases in demographic rates of Afrotropical bird species over 30 years

Tropical mountains harbor globally significant levels of biodiversity and
endemism. Climate change threatens many tropical montane species, yet
little research has assessed the effects of climate change on the
demographic rates of tropical species, particularly in the Afrotropics.
Here, we report on the demographic rates of 21 Afrotropical bird species
over 30 years in montane forests in Tanzania. We used mark-recapture
analyses to model rates of population growth, recruitment, and apparent
survival as functions of annual mean temperature and annual precipitation.
For over one-half of focal species, decreasing population growth rates
were associated with increasing temperature. Due to the trend in
temperature over time, we substituted a time covariate for the temperature
covariate in top-ranked population growth rate models. Temperature was a
better explanatory covariate than time for 6 of the 12 species, or 29% of
all focal species. Population growth rates were also lower for species
found further below their elevational midpoint and for smaller-bodied
species. Changes in population growth rates were more closely tied to
changes in recruitment than to changes in apparent survival. There were no
consistent associations between demographic rates and precipitation. This
study demonstrates temperature-associated demographic impacts for 6 (29%)
of 21 focal species in an Afrotropical understory bird community and
highlights the need to incorporate the impacts of climate change on
demographic rates into conservation planning across the tropics.