Zoodiversity

Abstract

Th e breeding phenology of Collared Flycatchers was studied over an 11-year period (2006‒2011 and 2013‒2017) in oak-maple-lime stands located in the Northern-East of Ukraine (in the National Park Homilshanski Lisy). In most years, egg laying began in the fi rst and second ten-day periods of May. Th e earliest recorded fi rst-egg date (368 broods) was 23 April, while the latest was 5 May. Th ese dates varied from year to year. Th e relationship between the fi rst-egg date and the date of daily average temperature transition through + 10 °C suggests that birds bred earlier due to warmer local temperatures. Th e clutch size was negatively correlated with the date of the average air temperature transition through + 5 °C. Th e earliest hatching date was 15 May, and the latest was 25 May. Fledging typically began in the fi rst half of June. Th e breeding season’s length ranged from 30 to 42 days, and the breeding cycle was positively correlated with the transition of the average daily temperature through +5 °C. To determine which factors explained the fi rst egg date and clutch size, Generalized Linear Models (GLMs) were conducted. GLMs suggest a correlation between the fi rst-egg date and the sum of eff ective temperatures (∑T150), arrival date temperature, migration route temperature, and average temperature of the third decade of April. Clutch size is determined by the sum of eff ective temperature accumulation (∑130) and migration route temperature. Reproductive success is negatively correlated with the average of 30 daily temperatures until the median date. Key words: Collared Flycatcher, Ficedula albicollis, weather conditions, temperature, laying date, clutch size.