Environmental effects on reproduction in a managed population of the harvested and Endangered Saker Falcon Falco cherrug

We report how artificial nests can be utilised at scale in nest site-limited areas of Mongolia to create a managed population of Saker Falcons (Falco cherrug), an "Endangered" species that is harvested for international trade. The provision of 5,000 artificial nests created an average annual saker population of 602 (SE +/- 59) breeding pairs, producing an estimated 1,735 (SE +/- 272) fledglings per annum over the period 2013-2015. Our regular monitoring enabled us to identify the effects of climate and vegetation on breeding performance. A warm and dry climate prior to breeding was associated with earlier egg-laying dates, while warmer conditions during the breeding season increased fledging success. Greater vegetation biomass in the previous growth season was positively related to breeding density and earlier clutch initiation, which was associated with larger clutch size and larger fledged brood size. Furthermore, using small mammal remains from saker pellets collected at artificial nest sites, we found that higher breeding density, earlier egg laying, larger clutch size, and increased nest survival were associated with areas with a higher proportion of small mammal prey in the diet. Our results provided evidence of the role of temporal and spatial variation in climate and prey availability on breeding performance, demonstrating the requirement for dynamic modelling of variable demographic parameters to be incorporated within an adaptive management framework for the sustainable management of the Saker Falcon.