Effects of climate change on clutch size of Tyrannus (Aves, Tyrannidae) species

Reproductive strategies vary geographically as result of environmental variables but may also vary temporally due to climate change. Global temperature increased about 0.6ºC and land precipitation increased by about 2% over the last century. To date, few studies have evaluated its impacts on Neotropical species. We tested if clutch size of species pertaining to the genus Tyrannus varies temporally across the New World as result of temperature and land precipitation anomalies (difference between variable value in a specific year and its historical mean). We gathered breeding and climatic (temperature and precipitation) data from 1901 to 2016. We tested the relationship of clutch size with anomalies on minimum temperature (AnTmin), minimum land precipitation (AnPmin), temperature isothermality (AnIsot), and precipitation seasonality (AnPseas) using mixed models and model selection by AICc. Clutch size was positively related to AnTmin (0.006, w=0.40) and negatively related to AnPseas (-0.001, w=0.21). The responses to climatic variables indicate that individuals increase breeding investment after years with higher AnTmin and lower AnPseas, probably due to better condition of individuals after milder or less seasonal years. Impacts of climate change on clutch size may affect population dynamics through adaptive value of the individuals and, thus, represent a challenge to species persistence.