Importance of Juvenile Mortality in Birds' Population: Early Post-Fledging Mortality and Causes of Death in White StorkCiconia ciconia

Abstract

ABSTRACT: Early post-fledging mortality of White Stork during the period from the first flight to their autumn departure from natal area was described. Data from eight breeding seasons (2005–2012) about 56 cases of death of juvenile White Storks from a study area in Western Poland were collected. For a comparison the data of 55 cases of death from recoveries data deposited in Polish Bird Ringing Centre from entire Poland were included in analysis. Early post-fledgling mortality rate varied from 2 to 11% (mean 4.3%) of all fledglings per year. The main causes of death were collision with power lines and electrocution which in Western Poland constituted 60% and in entire Poland — 78% of death cases with known causes. Other anthropogenic causes constituted responsibly 25 and 13% and natural causes — 15 and 9%. Mean distance where dead storks were found was 183.3m from natal nests, while 73% were found closer than 100 m from their nests.