PT  - JOURNAL ARTICLE
AU  - Ivett Pipoly
AU  - Bálint Preiszner
AU  - Krisztina Sándor
AU  - Csenge Sinkovics
AU  - Gábor Seress
AU  - Ernő Vincze
AU  - Veronika Bókony
AU  - András Liker
TI  - Effects of extreme hot weather on the reproductive output of great tits (<em>Parus major</em>, L.) in urban and natural habitats
AID  - 10.1101/2020.01.29.924332
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.01.29.924332
4099  - http://biorxiv.org/content/early/2020/01/29/2020.01.29.924332.short
4100  - http://biorxiv.org/content/early/2020/01/29/2020.01.29.924332.full
AB  - Extreme weather events are rare, but can have high impact on human societies and biological systems. As the frequency of extreme events are increasing with current climate change, it is important to understand its effects on fitness of individuals and on long-term viability of populations. In this study, we investigated the effects of extreme high ambient temperatures on breeding success of great tits in two urban and two natural forest populations during six years. We found that the number of hot days had habitat-specific effects on nestlings during their development period (from hatching to 15-days age). Average body mass of broods decreased with increasing number of hot days in both forest populations and one city population. However, the negative effect of hot days on chick mass was significantly stronger in forest compared to urban populations, suggesting that forest populations are more vulnerable to extreme hot weather conditions. Unlike other study populations, average chick mass increased with the number of hot days in the hottest urban study site, suggesting adaptation in heat tolerance in this population. Tarsus length of chicks and their survival until fledging was not influenced significantly by hot weather. Hot weather conditions may affect the reproductive output of birds at least two ways: indirectly through food availability and directly through nestling physiology. As the tarsus size and survival of chicks were not affected by hot days in our study, we suggest that the negative effect of hot days on body mass may emerge more likely from the direct physiological effects of heat. These results are one of the first demonstrations that the effects of extreme weather events can differ between wild populations living in different environment.