Altitudinal migration of birds in the Uluguru mountains, Tanzania: effects of forest fragmentation, altitude, fire, arthropod food and habitat structure

A study was conducted to assess the effects of forest fragmentation, altitude, seasons, fire, vegetation structure and distance from the source habitat on altitudinal migration of birds at the lower altitude forest fragments and forest edges between 180 – 1300 m above sea level in the Uluguru Mountains, Tanzania. This was conducted using mist netting augmented by audio-visual observations during the cold and hot seasons between 2010 and 2013. Twenty one species, all of them forest dependent had higher abundances during the cold season than in the hot season at most of the study sites. There was no significant relationship between area of the forest fragement and the number of species of altitudinal migrants. The abundances and species diversities of altitudinal migrants were higher during the cold season than in the hot season. Forest fragments located at relatively higher altitudes close to the source habitat, the Uluguru Nature Reserve, had more species, higher abundances and diversities of altitudinal migrants than in the relatively lower altitude forest fragments. Density of trees was positively correlated with the number of species and diversity of altitudinal migrants. Fire negatively affected the abundance of the migrants suggesting that burning of forests can lead to loss of some bird species and restricted use of lower altitude forests by some altitudinal migrants. Due to the isolation of the forest fragments studied and possible inhibition of movements of some of the altitudinal migrants at forest edges, the results of this study have implications for conservation; corridors linking higher with lower altitude forests are needed and further threats to the forest such as fragmentation, creation of forest edges and fires should be reduced