Habitat use and population dynamics of the Azure-winged Magpie, Cyanopica cyanus, and their response to fire in Northern Mongolia

Abstract

Fires are natural distubances in many ecosystems, but humans have altered fire regimes throughout the world. The effect of fire on organisms, particularly birds, depend on the extent and regime of the fire and the species’ ecology. The Azure-winged Magpie, Cyanopica cyanus is a cooperative breeder, and occurs in a disjunct distribution across much of Asia and in Iberia (Portugal and Spain). I conducted my study on the Northern Mongolian subspecies of Cyanopica cyanus in West Khentii, Northern Mongolia in 2009 and 2010. An anthropogenic fire that broke out in 2009 in the study area provided an opportunity to document the habitat use of the C. cyanus during the breeding seasons of 2009 and 2010, and to investigate the impacts of fire on the population dynamics of C. cyanus. The home range of this colony of C. cyanus is ca. 1.233 km² and the colony utilises six main areas (ca. 0.532 km²) in their home range. C. cyanus utilises an area which has the densest Padus asiatica shrub stands within their home range, and which is also the richest in species utilised by the C. cyanus. This area was also the least affected by the fire amongst all six areas in 2009. C. cyanus seemed to have expanded their home range compared to pre-fire years, and a change in social structure was observed. To address questions on population dynamics, four years worth of data was obtained from a previous study of the breeding biology of the same colony of C. cyanus. I found that over the four years: (1) colony size at the beginning of the breeding season did not change; (2) the number of hatched and fledged chicks declined significantly; (3) juvenile survival was constant, but adult survival declined slightly after the year of the major fire and following severe winter; (4) variable proportions of banded adults and juvenile were re-sighted from year to year, suggesting an open population; (5) between 26-67% of adults breed each year; (6) divorce rates in this colony of C. cyanus can be as high as 25%, and females still obtained new mates even though they had bred successfully the previous years; and (7) there was no association between breeding success and likelihood of returning in subsequent years. At this stage, no conclusions can be made about the long-term impacts of fire on this colony. A longer-term study must be conducted in order to understand the population dynamics and ecology of the Northern Mongolian population of Cyanopica cyanus. The presence of cooperative breeding behaviour is expected to affect population structure and how this species reacts to environmental stochasticity and catastrophies.