Saker Falcon (Falco cherrug milvipes Jerdon) mortality in CentralMongolia and population threats

Abstract

This study is important because Mongolia is the main reserve country for breeding saker falcons inthe world, where they play a key role in the steppe ecosystem as a predator of a rodent pest species. Thisis the first study to address factors influencing egg, chick and adult saker mortality in Central Mongolia.A total of 338 eggs, fresh remains and carcasses from 194 active nests in the study areas were collectedand examined. Egg, chick and adult mortality in the study areas did not differ significantly between 1998and 2004. Deserted clutches (35.1%) and infertile eggs (30.4%) were found to be the two main factorscausing reduced hatching success. Factors causing chick mortality were not significantly different eachyear. In 1998 - 2004, natural causes accounted for 61.1% of total mortality of Central Mongolian sakers.Human or anthropogenic factors explained 26.4% of all saker deaths. The main predator of chicks wasthe Eagle Owl (Bubo bubo). Chick mortality caused by cleaning raptor nests from poles and HPELpylons was 21.3%. No significant differences were found between factors influencing adult saker mortality.The highest percentage of total adult saker mortality was caused by electrocution (54%). Poisoning alsoreduced saker numbers. The number of exported sakers has dramatically increased over the last fouryears. saker numbers in Mongolia are relatively high and so trappers are increasingly concentrating onthis reserve. A harsh winter in 2002 caused decreased Brandt’s vole (Microtus brandti) numbers in twostudy areas. The number of saker breeding pairs decreased in these study areas in 2003. The results willprovide an important data source for planning saker falcon conservation strategies and activities inMongolia.